I appreciate your time , never worked on a motorcycle engine just a car , brings back knowledge, its only been 55 years since my first overhaul thanks a million
Thanks a ton for the videos. Was gunna take my bike to the shop for a full top end rebuild, but now my 14 year old self is pretty confident. I took it apart today, being super careful to label and keep organized. Gunna do everything you did, not burning oil but the cylinder looks iffy. Honda oem parts and $200 parts on order, should be a good project.
Unless i missed it, one of the most critical steps in this procedure is setting up the timing chain critically it must be set so the crankshaft rotation and cam shaft rotation are perfectly synchronised. You have to have the chain positioned perfectly on the correct tooth of the timing chain sprocket when the crank is at top dead centre. IF YOU DONT DO THIS YOU WILL FUCK YOUR ENGINE COMPONENTS and least the motor will not function. How this step has been missed in such a video is remarkable. For any of you out there watching this be careful you get some guidance on this before you undertake this procedure if your new to this.
Wanted to follow up. This video is great for XR400R. It helped me so much and especially helped me to notice the correct orientation for the head studs. The long end goes into the cylinder! Thanks again! Onky thing it doesn't mention is setting the timing cog correctly and making sure the piston is in the correct position. But that's OK!
Thanks for the video. I was just going to replace the head gasket in my 2005 Yamaha Kodiak 450 and found cylinder damaged from the wrist pin sliding on it. I couldn't find any videos for my engine specifically but I learned some good stuff from this video that will help me get the job done.
if it wasn't for this very 3 part detailed video i would have been so lost very very helpful in the process right now of putting the cam sprocket back on thank you !
I actually own one of these machines and turn wrenches on the side. I took a 400 ex in for a customer it has a broken cylinder on timing chain side at base of the cylinder kinda between fins. Its leaking oil of course. I was actually starting to do a video series of a few my projects. First attempts at you tube. But this partszilla and this mechanic do such a great job idk if I will on this machine!
don't put your bike back together without putting solvent down your valves to see if they're leaking that they are you can lap valve with a compound and just seal them up good.
100% same as my XR400 engine. ( I've added an electric start from the TRX) I even order parts from my local farm quad dealer. Should take care with holding the cam chain under tension. When rebuilding mine it slipped off the sprocket at the bottom somehow and I had to dismantle the clutch to get it back on.
I'm just curious about how in the world are you putting those Campbell's into that camshaft for the timing sprocket without putting loctite like they recommend from the manufacturer
I see some aftermarket cylinders don’t have a groove cut for that big o ring that you put at the base. Is that still a requirement or is this something that was tweaked over time and found wasn’t really necessary that some kits don’t have them?
Okay so u turned the timing chain 180 degrees by the bolt on the side to take bolt out of timing chain sprocket? Do I leave it there when putting timing chain back on or do I rotate it around twice to bring it back to top dead center then put chain back on?
what parts from a TRX400ex will interchange with a TRX300ex cause im having to replace a mainshaft and counter shaft due to stripping in my 2000 trx300ex thank you for your time and any advice you can share with a DIY like myself
Rebuilt my 400ex last night with help from this video thanks! one problem i lost the plunger spring but still have the little pin that goes ontop or the spring. i heard you can use it without the plunger. but my quad will not start not. so im guessing i need that correct?
Typically you only remove that when you use a hotcam. Remember, that may not be why it's not starting...you may have to go back through what you did to confirm everything is right.
I'm just wondering why you're not doing it exactly how the recommended by the manufacturer you're supposed to put loctite threadlocker on the cam sprocket bolts
Looks like you may have forgot to install the crankcase breather tube on the intake. Do you think doing this could cause an idle issue? Im currently trying to track down an idle issue with my 400ex and this is one of the issues that I need to fix. Great series and thanks for all of the info.
I am not a mechanic, but the crankcase breather tube, I would leave it out (I carry it like this in my xr 400) the reason is that those gases / air is hot and "toxic" air that comes out of the crankcase, and the intake is what It needs fresh air, you can attach a piece of metal mesh so that nothing gets inside, but the gases are always outside ... there is more space than inside ;-) it is my opinion sorry for my english ... (google translate)
How much do you charge total for the same exact procedure on my 2007 400 ex? I have a new piston, rings, top block or jug, piston pin, & spark plugs. All cane in a kit I bought online. No gaskets or seals though. You are very professional & I love your work 👍 how much $ do you need to do this to my 400ex?
Ughhhh.. theres an o-ring on the bottom of the cylinder?? How import is it? I dont wanna tear it all down again.. do i have to? All new everything except that oring
Hey John, thanks for the video. I'm currently doing this job. I was wondering what your reason is for putting each valve back to its "home". I didn't do that, and never recorded where each valve came out of. I know the exhaust valves are a different size than the intake. Thanks
thank u so much for making these videos even though there so old now. im gonna be rebuilding the top end on my 2001xr400r and the engines from a 400ex are pretty much the same but there are no videos on xrs..
Nice videos. I have a question maybe you could answer. If you add after market exhaust and/or air filter on a fuel injected ATV without tuner...will it cause it to run lean? It seems to me that it shouldn't change anything ( as far as air/fuel ratio) but it seems like everyone else believes it will.
Great video! I have a question that I hope someone can answer.. I have 400ex and had some problems with the valves... I took off the manifold and looked inside and found that the cone shaped area where the valves ride were completely gone on one side. I found the pieces in my muffler... My question is... Is this major and is it possible to repair??
I have a 250EX has no timing chain how do you set the time and make it run 2003 Honda replace piston rings push rods valves seats springs set top dead center inspection hole there's more than one t in there and I said it on the top dead center combustion I think will not run have you ever seen one without a timing chain I see no videos on it
I love to watch your videos you have no idea how many times you have helped me and I work in a small engine shop. I was wondering why you face the lobes down on the camshaft I'm assuming it's to keep everything top dead center correct I am actually working on this same four-wheeler right now and I just got the head back from the Machine Shop and I was wondering that exact question because that's the only thing I'm waiting on to put it back together
I have a 110cc atv engine that was burning oil I have replaced piston rings and cylinder head gaskets do I need to replace cylinder head o-rings there's videos that don't even put any o-rings in ?
Am I right by thinking that you put the piston at tdc in the cylinder then install the head and put the cam in with lobes down and put the sprocket on the marks am I right?
so I did a rebuild and did it bye the.book and this video for reference as it was any first rebuild. I put an aftermarket cam in n I did a compression test at the end just to check it. it read 160-165. would taking the stock cam with the decompression mech out give me more or less compression? and should I worry about it?
and cam shaft rotation are perfectly synchronised. You have to have the chain positioned perfectly on the correct tooth of the timing chain sprocket when the crank is at top dead centre. IF YOU DONT DO THIS YOU WILL FUCK YOUR ENGINE COMPONENTS and least the motor will not function. How this step has been missed in such a video is remarkable. For any of you out there watching this be careful you get some guidance on this before you undertake this procedure if your new to this.
It's not unlikely that it will smoke a little here and there, but if it's really noticeable, you are still burning oil somewhere. Did you seat the valves by lapping them?
I just recently bought a 2000, trx400ex and there are holes in the cylinder head right beside the exaughst valve and it spews out oil and smoke what should I do? Replace? Or can I jb weld or something like that I'll definently replace gaskets and o rings and do a check on everything while I'm balls deep its just the holes in the head itself that got me in a stump.
Hey I'm rebuilding my 2005 400EX and I noticed when I got it there was a couple bolts the little hex head bolts in the valve cover that were missing and also stripped out inside the head so I'm buying all that brand new and putting a 440 kit but I'm having trouble finding the original replacement bowls that go into the valve cover where can I find them
I've got a 2001 400ex. Head gasket is leaking oil in the front. I don't see exhaust smoke from it. I haven't checked compression yet. I can tell someone has had it apart before. Do you think I should check the torque on the head bolts first? Maybe do a compression test first then do it again after?
Bottom. between the head and the jug. on the front. It doesn't really leak much. Always wet and after running it hard it leaks enough to start smoking. Smoking as in, hot Surface with oil on it
Hi mate my mlnames adam and im from newcastle australia and i would like to say thanks for your videos about the trx 400 rebuild its help alot ...BUT can i please ask you a question about the trx i have 2001 honda xr 400 and the motors are the same i have rebuilt the top end and same problem you had with o-ring on base gasket .will i need to use one or can i just use permatex soft gasket sealant and new gasket and seal it that way or will i need o ring theres no grove on the bottom of my barrel and i just got new one so i have 2 one 3.00mm over and the new one is standed can you please help me mate
Could be a great many things. Fuse blew, connections loose...something wasn't connected properly or something got pinched when you put it back together. You're going to have to run through it.
Ok thank you for all your help, do you have a email I would be able to contact you at and send you pictures of this Trx400 cylinder and piston, to see what you think. Thank you
I’d like a little better in-depth look at putting the timing chain on and making sure it’s at top dead center when doing so because I do not want to be 180° out
Having an issue on my 02 400ex, valves have been checked but during inspection i found that my entire cam moves side to side! The bearing on the left side of my cam is able to wiggle and looks like the dowel is scored...also have a hitting noise could it be the bearing or cam as it floats around?? Sorry for the long message just stuck! Any help is appreciated!
What do you do if it is needed to replace the head with a new one not used. I heard that you have to seat the valves in the head. Meaning you have to use a type of gritty paste on the valve and spin the valve in the head to form the head to the valve for a good seal.
are the sub rocker arms supposed to be really hard to move?? I put them in a torque specs of 20 ft lbs and when I do they are super right I can't move them at all.
Hello .i have a problem with my honda fourtrax 350 4x4 piston . i haven't a piston 78mm .can i replace it by piston 74 mm. thank you and sorry for my language .i am from algeria
@Partzilla normally I set the crosshatch on all my projects myself, and I've always wondered how much does it typically cost to have a cylinder bored out 1 size at one of those shops?
So ive just rebuilt my 400 ex to a 440 big bore. Ive done everything and checked multiple times on everything. Im getting 120 psi on the comprssion test and spark and gas and it still refuses to run. Any suggestions? Im so stuck and clueless at the moment...
Timing is good. I set the valves to factory standard and was getting 150 psi on compression test. So i tinkered eith them ubtil i got down to 120. Should i just try and leave it at 150 with the factory clearance?
Partzilla also ive read a few different oppinions on ket sizes for a 440 big bore. Some say go smaller to a 146 keihin and some say go bigger to 170-185 main. And what size should i jet the pilot to
120 is too low. The lash is likely too tight/non-existant. Even if the A/F ratio is way off, it should still start. I'd go with the 170 and go 2-1/2 turns out on the fuel mix screw.
start it let it warm up then check the oil... change the oil and start it again until its nice and warm... ride it like you stole it.. beat the hell out of it... this will seat the rings better than ever... babying it is the worst thing you can do. i can explain why.
Could you email me or give me a better guide on the piston ring installation, I’ve done 2 strokes but never done a 4 stroke on a 400. Just kinda confused on the angles for the rings to sit.
+Jack Defevers I would definitely suggest you invest in one. If the head bolts are not torqued equally and to the same correct amount it can warp the head, strip the threads, or cause the head gasket to fail.
This is way better than watching TV programs. Learned something to.
I appreciate your time , never worked on a motorcycle engine just a car , brings back knowledge, its only been 55 years since my first overhaul thanks a million
Thanks a ton for the videos. Was gunna take my bike to the shop for a full top end rebuild, but now my 14 year old self is pretty confident. I took it apart today, being super careful to label and keep organized. Gunna do everything you did, not burning oil but the cylinder looks iffy. Honda oem parts and $200 parts on order, should be a good project.
Unless i missed it, one of the most critical steps in this procedure is setting up the timing chain critically it must be set so the crankshaft rotation and cam shaft rotation are perfectly synchronised.
You have to have the chain positioned perfectly on the correct tooth of the timing chain sprocket when the crank is at top dead centre.
IF YOU DONT DO THIS YOU WILL FUCK YOUR ENGINE COMPONENTS and least the motor will not function.
How this step has been missed in such a video is remarkable.
For any of you out there watching this be careful you get some guidance on this before you undertake this procedure if your new to this.
guys smoking some hindu kush hashish i guess,,,
Missed steps,like the timing sprocket position and timing
Wanted to follow up. This video is great for XR400R. It helped me so much and especially helped me to notice the correct orientation for the head studs. The long end goes into the cylinder! Thanks again!
Onky thing it doesn't mention is setting the timing cog correctly and making sure the piston is in the correct position. But that's OK!
So when you set the timing chain the piston has to be at dead TOP center with the cam lobes DOWN?.?.?.? HELP!!!!
Thanks for the video. I was just going to replace the head gasket in my 2005 Yamaha Kodiak 450 and found cylinder damaged from the wrist pin sliding on it. I couldn't find any videos for my engine specifically but I learned some good stuff from this video that will help me get the job done.
This video works perfectly for 96 XR400. Thanks so much!
Going to do my 98 XR400 any tips? Thanks
Great how to video. Shop was going to charge me 300$ to replace the valve seals on my 03 XR400. I'll be doing it myself. Thx!!
My 99 xr4 is burning oil like a banshee. Thesw videos definitely gave me some confidence to do this for a winter project
No one teaches like you partzilla good job learned alot
if it wasn't for this very 3 part detailed video i would have been so lost very very helpful in the process right now of putting the cam sprocket back on thank you !
Nice work. Learned a lot, your a very good instructor, replaced piston, rings, head etc. on my 2002 400ex, runs like a champ
I'm getting ready to do my 300ex lol guys is awesome
I actually own one of these machines and turn wrenches on the side. I took a 400 ex in for a customer it has a broken cylinder on timing chain side at base of the cylinder kinda between fins. Its leaking oil of course. I was actually starting to do a video series of a few my projects. First attempts at you tube. But this partszilla and this mechanic do such a great job idk if I will on this machine!
wow ! you're a great Mechanic John :D
WoW..you sure make that look easy...lol...I can see the keepers bein ALOT harder than that
Keepers are annoying especialy when u compress your springs with vice grips lol
i love the 400ex series.
don't put your bike back together without putting solvent down your valves to see if they're leaking that they are you can lap valve with a compound and just seal them up good.
Great video John 👍
thanks a lot for your video i can now do it myself and save a lot of money :)
+js “honda racing” vallée You are welcome.
100% same as my XR400 engine. ( I've added an electric start from the TRX) I even order parts from my local farm quad dealer. Should take care with holding the cam chain under tension. When rebuilding mine it slipped off the sprocket at the bottom somehow and I had to dismantle the clutch to get it back on.
Thanks great video rebuilding two 400 exs helped alot
Also you got a facebook page or somthing so I can get some advice just gonna send you a video to ask if it sounds normal to you
Such a good channel. They should have way more than 11k subs
Great video, I would like to know why the 4 head bolt washers are not the same . Thanks for all the great helpful videos.Tom
I will check back in another year hopefully someone will have answer . Thanks In advance
They are all the same, why would you think they are not?
Awesome video
Thank you fpr this video, saw some videos of engine rebuild where they install a camshafts without auto decompression system, it works?
Did you Gap the rings??
Thank you part zilla
I love how all the Honda Atv parts are just like There Automotive Division.
I'm just curious about how in the world are you putting those Campbell's into that camshaft for the timing sprocket without putting loctite like they recommend from the manufacturer
Any bottom end rebuild videos coming for 400ex?
Awesome video gonna try this rebuild
Where can I find the little black rubber garment that covers the plunger pin and spring? Mines just happened to fall inside the motor.
Awesome job.
I see some aftermarket cylinders don’t have a groove cut for that big o ring that you put at the base. Is that still a requirement or is this something that was tweaked over time and found wasn’t really necessary that some kits don’t have them?
Maybe I missed it in the video(s) but how do you put the studs back in the cylinder block??? Thank you
Just installed stage 2 hot cam in my 2005 400ex
Readjusted the valves and they are now ticking loud
Any ideas ?
I did this exact procedure and I went to start my 400 and it won't start. Any suggestions? Or could the timing be off?
Could be anything. Does it turn over? Could be anything you did in the top end or it could be a simple spark/fuel issue that's unrelated.
Okay so u turned the timing chain 180 degrees by the bolt on the side to take bolt out of timing chain sprocket? Do I leave it there when putting timing chain back on or do I rotate it around twice to bring it back to top dead center then put chain back on?
Definitely helped me replace mine. Thx!!
what parts from a TRX400ex will interchange with a TRX300ex cause im having to replace a mainshaft and counter shaft due to stripping in my 2000 trx300ex thank you for your time and any advice you can share with a DIY like myself
Rebuilt my 400ex last night with help from this video thanks! one problem i lost the plunger spring but still have the little pin that goes ontop or the spring. i heard you can use it without the plunger. but my quad will not start not. so im guessing i need that correct?
Typically you only remove that when you use a hotcam. Remember, that may not be why it's not starting...you may have to go back through what you did to confirm everything is right.
If that o ring at the bottom is missing, will that cause oil to be on top of the piston?
I'm just wondering why you're not doing it exactly how the recommended by the manufacturer you're supposed to put loctite threadlocker on the cam sprocket bolts
Would a missing plate decompressor pin and spring make it not run mine doesn’t have it and only bump starts it’s doesn’t fire up on its own
love you man thanck you
Looks like you may have forgot to install the crankcase breather tube on the intake. Do you think doing this could cause an idle issue? Im currently trying to track down an idle issue with my 400ex and this is one of the issues that I need to fix. Great series and thanks for all of the info.
I am not a mechanic, but the crankcase breather tube, I would leave it out (I carry it like this in my xr 400) the reason is that those gases / air is hot and "toxic" air that comes out of the crankcase, and the intake is what It needs fresh air, you can attach a piece of metal mesh so that nothing gets inside, but the gases are always outside ... there is more space than inside ;-)
it is my opinion
sorry for my english ... (google translate)
Nice job!
How much do you charge total for the same exact procedure on my 2007 400 ex? I have a new piston, rings, top block or jug, piston pin, & spark plugs. All cane in a kit I bought online. No gaskets or seals though. You are very professional & I love your work 👍 how much $ do you need to do this to my 400ex?
We don't work on customer units. We do the videos so you can!
What about your ring gap unless machine shop they did everything for you to make sure the rings was right
thx for the vids, crucial for my rebuild!
Ughhhh.. theres an o-ring on the bottom of the cylinder?? How import is it? I dont wanna tear it all down again.. do i have to? All new everything except that oring
Hey John, thanks for the video. I'm currently doing this job. I was wondering what your reason is for putting each valve back to its "home". I didn't do that, and never recorded where each valve came out of. I know the exhaust valves are a different size than the intake. Thanks
It's more of a habit. After use, if there is any wear on the valves, they will seat better in their original "home."
I cannot get the cam cover back on feels like it's pivoting on the timing chain gear
Hey I got a 440 big bore and hot cam but now it seems not to want to turn over someone said I need a starter with a higher output
thank u so much for making these videos even though there so old now. im gonna be rebuilding the top end on my 2001xr400r and the engines from a 400ex are pretty much the same but there are no videos on xrs..
Replace the timing chain if you do!
Nice videos. I have a question maybe you could answer. If you add after market exhaust and/or air filter on a fuel injected ATV without tuner...will it cause it to run lean? It seems to me that it shouldn't change anything ( as far as air/fuel ratio) but it seems like everyone else believes it will.
Harper's Harper's in a carbourated ATV you would have to change the jetting in the carb but fuel injection they should equal out them selves
Harper's Harper's electronic fuel injection should adjust to the correct fuel and air mixture automatically by how the motor runs (idle rpm)
Thank you
Great video! I have a question that I hope someone can answer.. I have 400ex and had some problems with the valves... I took off the manifold and looked inside and found that the cone shaped area where the valves ride were completely gone on one side. I found the pieces in my muffler... My question is... Is this major and is it possible to repair??
Anything is repairable with enough time and money. Also, if parts of your motor end up in your muffler, I would consider it major.
I have a 250EX has no timing chain how do you set the time and make it run 2003 Honda replace piston rings push rods valves seats springs set top dead center inspection hole there's more than one t in there and I said it on the top dead center combustion I think will not run have you ever seen one without a timing chain I see no videos on it
I love to watch your videos you have no idea how many times you have helped me and I work in a small engine shop. I was wondering why you face the lobes down on the camshaft I'm assuming it's to keep everything top dead center correct I am actually working on this same four-wheeler right now and I just got the head back from the Machine Shop and I was wondering that exact question because that's the only thing I'm waiting on to put it back together
With the lobes down, it is not only TDC but on the compression stroke.
Were would I send my cylinder to be rebored? Also, it's the first time my 400EX is being rebuilt so what size of piston should I get?
You would need to find a local machine shop that could do it for you. Then measure to determine the right size piston.
I have a 110cc atv engine that was burning oil I have replaced piston rings and cylinder head gaskets do I need to replace cylinder head o-rings there's videos that don't even put any o-rings in ?
The o-rings will help with oil leaks.
Am I right by thinking that you put the piston at tdc in the cylinder then install the head and put the cam in with lobes down and put the sprocket on the marks am I right?
That's the basics!
so I did a rebuild and did it bye the.book and this video for reference as it was any first rebuild. I put an aftermarket cam in n I did a compression test at the end just to check it. it read 160-165. would taking the stock cam with the decompression mech out give me more or less compression? and should I worry about it?
I work on vehicles often first time with a 4 stroke engine. it's a 03 400ex sorry I didn't mention that.
also put in New kibble white valves n lightweight racing springs. n hardware.
and cam shaft rotation are perfectly synchronised.
You have to have the chain positioned perfectly on the correct tooth of the timing chain sprocket when the crank is at top dead centre.
IF YOU DONT DO THIS YOU WILL FUCK YOUR ENGINE COMPONENTS and least the motor will not function.
How this step has been missed in such a video is remarkable.
For any of you out there watching this be careful you get some guidance on this before you undertake this procedure if your new to this.
My 00 400ex was smoking like a freight train when I bought it. I replaced head,valves,jug and piston. Still smokes some. ???
It's not unlikely that it will smoke a little here and there, but if it's really noticeable, you are still burning oil somewhere. Did you seat the valves by lapping them?
Partzilla it says not to la OEM
How long have you ran the motor since all the upgrades?
I just recently bought a 2000, trx400ex and there are holes in the cylinder head right beside the exaughst valve and it spews out oil and smoke what should I do? Replace? Or can I jb weld or something like that I'll definently replace gaskets and o rings and do a check on everything while I'm balls deep its just the holes in the head itself that got me in a stump.
Don't jb weld! I recommend replacing the head or you can try to get it repaired. thumperracing.net/index.php?route=product/category&path=73_355
Hey I'm rebuilding my 2005 400EX and I noticed when I got it there was a couple bolts the little hex head bolts in the valve cover that were missing and also stripped out inside the head so I'm buying all that brand new and putting a 440 kit but I'm having trouble finding the original replacement bowls that go into the valve cover where can I find them
These guys?
www.partzilla.com/catalog/honda/atv/2005/trx400ex-a-sportrax-400ex/cylinder-head-cover
What do you mean by tapping the chain tensioner. Do you loosen the screw in the middle once it’s bolted back on so the piston can move out ?
It's spring loaded. Just need to literally tap it and it will spring out where it's tight.
I've got a 2001 400ex. Head gasket is leaking oil in the front. I don't see exhaust smoke from it. I haven't checked compression yet. I can tell someone has had it apart before. Do you think I should check the torque on the head bolts first? Maybe do a compression test first then do it again after?
That's a good plan, check compression, check torque, then check compression again. Worst case you'll have to tear down and address further issues.
Partzilla okay thanks for the input.
Partzilla okay I just did a compression check and it's 120 psi. I'm stumped on why it's leaking a little oil. Maybe leaking on the timing chain side?
Is it leaking on top of the head or the bottom of the head? You could just need a gasket swap.
Bottom. between the head and the jug. on the front. It doesn't really leak much. Always wet and after running it hard it leaks enough to start smoking. Smoking as in, hot Surface with oil on it
Hi mate my mlnames adam and im from newcastle australia and i would like to say thanks for your videos about the trx 400 rebuild its help alot ...BUT can i please ask you a question about the trx i have 2001 honda xr 400 and the motors are the same i have rebuilt the top end and same problem you had with o-ring on base gasket .will i need to use one or can i just use permatex soft gasket sealant and new gasket and seal it that way or will i need o ring theres no grove on the bottom of my barrel and i just got new one so i have 2 one 3.00mm over and the new one is standed can you please help me mate
I recently did a top end rebuild on my 2003 400ex, turns over. But no spark, replaced the coil still same result?
trace back to see where you are losing power.
I just did this and now my quad stays on for about 5 minutes and dies but starts right up again! What can it be?
Did you ever figure it out?
Can you put rings on backwards? Like upside down I don’t think it matters does it?
They can go either way.
I have the same quad and I replaced the valve cover gasket and did not touch anything else. Now it won’t start what could the problem be?
Could be a great many things. Fuse blew, connections loose...something wasn't connected properly or something got pinched when you put it back together. You're going to have to run through it.
Is it the same on a 91 250x as far as just piston replacing and timing?
what are the main differences between this rebuild and a 400ex Foreman block?
Can you put it together like you took it apart if you bord it to a 440?
No lleva ajuste de tiempo?
Thanks for the informative Post! Do you have any videos about upgrading the performance of these engines?
We don't right now. We focus more on maintenance and making them run again.
Ok thank you for all your help, do you have a email I would be able to contact you at and send you pictures of this Trx400 cylinder and piston, to see what you think.
Thank you
hey will the 400ex leake oil if u dont use the long valve cover bolts?
Great work. Will this rebuild be the same as my Honda XR400r? Thanks.
The process will be the same but I would not try to use the part numbers such as the head gasket. There are shown to be different part numbers.
Thank you.
I’d like a little better in-depth look at putting the timing chain on and making sure it’s at top dead center when doing so because I do not want to be 180° out
Where can I get a set of timing tools for a 400ex Honda?
Having an issue on my 02 400ex, valves have been checked but during inspection i found that my entire cam moves side to side! The bearing on the left side of my cam is able to wiggle and looks like the dowel is scored...also have a hitting noise could it be the bearing or cam as it floats around?? Sorry for the long message just stuck! Any help is appreciated!
The noise could definitely be the bearing and cam. Rebuild time! Hopefully this vid helps you get it done!
What do you do if it is needed to replace the head with a new one not used. I heard that you have to seat the valves in the head. Meaning you have to use a type of gritty paste on the valve and spin the valve in the head to form the head to the valve for a good seal.
That is exactly what needs to be done.
Dont Forget the loctite on the camshaft gear bolt if you dont Want to blow up
I did not see you re time it do you have to put it back in time after this
are the sub rocker arms supposed to be really hard to move?? I put them in a torque specs of 20 ft lbs and when I do they are super right I can't move them at all.
Put it to TDC and they should be loose.
Why did you pull off the inspection bolts on the crankcase cover, you said something about finding top center or something
it allows you to look for the TDC mark so you can set Top Dead Center
Hello .i have a problem with my honda fourtrax 350 4x4 piston . i haven't a piston 78mm .can i replace it by piston 74 mm. thank you and sorry for my language .i am from algeria
Generally, you can only go up in size.
No stock bore
@Partzilla normally I set the crosshatch on all my projects myself, and I've always wondered how much does it typically cost to have a cylinder bored out 1 size at one of those shops?
It really varies by shop. I wouldn't venture to guess individual rates.
I got a complete head cylinder for my 2007 Honda 400ex what is dat small hole beside the exhaust the old one didn't have a hole
So ive just rebuilt my 400 ex to a 440 big bore. Ive done everything and checked multiple times on everything. Im getting 120 psi on the comprssion test and spark and gas and it still refuses to run. Any suggestions? Im so stuck and clueless at the moment...
Could be a few things, re-jet, timing, valve clearance...
Timing is good. I set the valves to factory standard and was getting 150 psi on compression test. So i tinkered eith them ubtil i got down to 120. Should i just try and leave it at 150 with the factory clearance?
Partzilla also ive read a few different oppinions on ket sizes for a 440 big bore. Some say go smaller to a 146 keihin and some say go bigger to 170-185 main. And what size should i jet the pilot to
120 is too low. The lash is likely too tight/non-existant. Even if the A/F ratio is way off, it should still start. I'd go with the 170 and go 2-1/2 turns out on the fuel mix screw.
My timing chain is too tight to put the cam in is there a fix for that?
hey man whats your opinion on a good proper break in on a top end rebuild please and thanks
start it let it warm up then check the oil...
change the oil and start it again until its nice and warm...
ride it like you stole it.. beat the hell out of it... this will seat the rings better than ever... babying it is the worst thing you can do.
i can explain why.
Why's that?
Could you email me or give me a better guide on the piston ring installation, I’ve done 2 strokes but never done a 4 stroke on a 400. Just kinda confused on the angles for the rings to sit.
But I wonder what cause the uneven wear on the rings? Not changing engine oil?
I do not have a torque wrench so how much will it effect those bolts you're supposed to get 32 pounds on?
+Jack Defevers I would definitely suggest you invest in one. If the head bolts are not torqued equally and to the same correct amount it can warp the head, strip the threads, or cause the head gasket to fail.
+Partzilla.com okay thanks
Could you possibly show a pic of the feeler gauges that you used I can’t find the ones I need to adjust the values
ua-cam.com/video/AConzWtH8Fk/v-deo.html