Man, this is excellent! I ride an 03 yz250 and absolutely love it! I work on and restore bikes on the side and as a passion. Just bought a spare 5up head to modify like you did. I'd like to still just use 93 non ethanol so I'm considering making the squish band .050". Thanks for making such a solid guide for doing all this. Great work!
Very time consuming But very worth it in the end. Thank you I learned more here than from anywhere else about squish bands and compression and how it all comes together. I'm currently building a 79cc motorized bicycle pretty much from scratch. And your spot on about how too much compression hurts top end. I was wondering why my engine was struggling to rap out all the way. Too much compression!
just took off my head 2022yz250x squish was .084 i purchased an apex xc head am trying it tomorow i had a 2017250x i had it cut .040 and it was great everywhere
@@UpAllNight91 i tried it today it was excellent . low and mid a littlie up high but the the thing was like a different fuckin bike unreal big increase in power for 225 dollars cant be beat
hi buddy very good work, i have a 2004 honda cr125 i understood how you do the work of removing material i polish the head, but the sums of removing material i the amount of water is that i did not understand well thank you
Hello. Yes you want to measure the overall volume of the head by CC'ing it with water as I did in the video and taking note the heads overall volume before starting any material removal. After you shave the head down to get the squish band where you want it then you open up the dome to bring the overall volume closer back to stock. So you will CC the head again as you open the dome back up till it closely matches the same overall volume that it did before you started removing material
I would if you are currently running more timing advancement. Start with stock timing again and test from there. Usually once the head has a good profile the stock timing is about the best you will find
thanks for the video, learned a lot, I just bought a new 2023 yz250, will 100LL Aviation fuel work with that head at .40, I live close to a airport where I can get it
Hmm. Good question. Honestly I have no experience with av gas and don't really know how well it controls the burn. To be safe I wouldn't be scared to try like maybe 0.050" and near stock compression, start there and see how she handles that on av gas.
If I do this mod, Will I have to run a race gas mixture all the time. If not, would 92 non ethanol be acceptable.. You need to do more vids, you are very knowledgeable and also a good teacher...preciate ya
Even the 5UP head stock (US model 2003 to 2010) would ping on crack of the throttle with 93 pump. Its acceptable but hardly. With the head mod specs i showed it surely requires even more octane, at least 40/60 race/pump to be happy . But there are things that can be done, like tighter squish but lowrr compression by opening the dome more. Or if its being used at high elevations . That eases octane requirements too
Again, Appreciate all the info. One comment about the heat range of plugs really struck me. Back in 01 when racing/ riding my CR250. I always wondered why my motor lost its crisp feeling after about 10 minutes of riding. Felt it was always jetting related, since some of those CRs were finicky at higher elevations and a slide cut did improve it. But now that I choose to ride a 2018 YZ250 bone stock, How much better of a bike it is in every way with near perfect jetting and great suspension for weekend warriors at or near sea level ( where I live now in NC) Would like for you to share with us some more of your knowledge if you can...Thanks again..
Yeah the heat range, I was like you, scratching my head. When I tossed a colder plug in her I was surprised it fixed that issue (back in like 2009). Kawasaki sells a optimal 9 heat range plug for the kx250 2006 so guess it's not unheard of.
Great video! Say if I were to get the squish down to .40 and then open up the dome to around 23 or 24cc so I would be able to run straight pump gas still do you think it would be worth it? Even a 1hp gain and a crisper running motor I would be happy with. Here in canada race gas is around 25 or 30$ CAD per gallon so its just not an option for me right now lol. I also have my timing retarded a few degrees too for a bit more top end power and to eliminate intermittent mid range detonation I was having. TIA
Hello. If I was sticking with pump fuel I would not go any tighter than 0.050" on the squish. It would have to be a lower compression head, about the same CC's as the 2011 to current 5MW head. That should be a good pump gas head with sharper throttle response and a little more HP.
Hello. For 93 pump gas I suggest following the specs that Apex heads also use for their heads. 0.050" squish band clearance and lower than stock compression. I have two videos where towards the end I check the specs on all these heads and show them. Here are two links to them two videos... ua-cam.com/video/Ht5gb_DQ-3U/v-deo.html and ua-cam.com/video/Kn-7eG6E6jE/v-deo.html
How thick is the dome? I have a stock YZ125 head, looks like a crack in the dome but not sure, the dome may be thicker than I think and it’s just a ding
Hello. Not sure how thick it is but I have seen heads crack in the dome area and it usually leads to lose of coolant and hard to start up because of coolant getting in the combustion chamber
Yes you can. It bolts right on. I would use the 5WM head used from 2011 to current YZ250 if you want to run pump fuel. If you plan to run at least 50/50 pump/race fuel then the 5UP head used from 2003 to 2010 on the US models will make the best power out of all the OEM YZ250 heads out there.
On a 250cc it can be worth 2 to 3 HP. It can shorten the life of the motor if its tuned to the max. This is why I set them at a happy medium as I mentioned in this video.
After doing this mod is re jetting a must ? I run a 2022 yz 250 with a hgs pipe and a r304 shorty and think about making this mod ? Iam on stock jetting right now .
If you want to stick with unleaded fuel i would keep the compression rather low and keep the squish clearance around 0.050" . As far as jetting, having the head modified with a tighter squish clearance usually desires slightly leaner jetting, especially if you want to reep the full benefits of the head mod. At least a size or two leaner main and some mild fuel screw adjustments
If the head has a 5UP writen on the top of the head, you have the best stock head yamaha ever offered as far as performance. But if its a 5MW or some other head then its going to be a lower performing head. The 5UP is a good head but can be made to even a better head with a little work.
Not so much on the 2005 to recent YZ125s because they have a sharp turn in the middle of the squish that would be hard to do by hand. But I'm sure someone could. I would just send that head out for the job
I get satisfaction by doing myself. Been doing it for years and there's really no gamble except I have dailed in the ability to pretty much make any profile I want and with trail and error been able to produce better than any local shop can compare too. The satisfaction when the bike runs great and I know its from me is nice
@@panic-revv85 sure. However the man behind the machine is more important. Seen many heads done on a machine that the profile was not desirable. When i do them myself I can make small changes and get the profile right where I want it. With patience the end result is amazing
172 main Stock needle for the 18, second clip from the top. 50 pilot. Air screw at around 1 turn. Sea level here is Florida. In the winter when it's real cold I usually have to run a 175 main and turn the air screw in a hair
For sure. Head gasket fully torqued down. And be sure to use the same brand and type of gasket every time you replace it to keep the same results, as different brands can come out thicker or thinner. I would just use the OEM gasket since you can always buy on of them and consistency
@@UpAllNight91 huge thanks, I stumbled across your videos and they have motivated me to start wrenching on my bikes again. I'll be relocating from about 600' elevation, up to 4500' so I will have my work cut out for me to get the KX jetted as well as adjust the compression. Any info for baseline head volumes (I noticed you were shooting for around 21.5cc) and their correlation to 91, 50/50, or full race 103-110 would be greatly appreciated as well!
@@joeydacey6591 Thats awesome man! Honestly I dont know where to start as every bike is different. But what I would do is start by seeing what the stock head CCs too and setup your modified head to that. Then test that out. From there if you want more bottom thrust put another head together the same but with more compression (less CCs) and if you desire more top end then put together another head or take the current modified head and remove the CCs (by removing more from the dome) for lower comp. Thats how I did it. It can be a trial and error thing but the end results pay well.
@@joeydacey6591 Hello. The 21.5cc is for the YZ. It will surely be different with a different bike like the KX because head dome can be a different profile and also how far the piston comes up can be slightly different on the KX. I mainly use CCing the head for reference. I would first CC the head stock and see what it comes out too. Then knowing you will be going higher in elevation I would setup a head with about maybe a 0.5cc to 1 full CC less and get the squish band down to 0.040" to 0.050" and start there. Test that out and then I would expect to have to either go back in and make a few changes to that head or even put together another head to make a few changes after the test ride. Sometimes it takes a few trials and errors towards your aim to hit the bull eye you are looking for.
Man, this is excellent! I ride an 03 yz250 and absolutely love it! I work on and restore bikes on the side and as a passion. Just bought a spare 5up head to modify like you did. I'd like to still just use 93 non ethanol so I'm considering making the squish band .050". Thanks for making such a solid guide for doing all this. Great work!
Right on! Thanks for watching!
Very time consuming But very worth it in the end. Thank you I learned more here than from anywhere else about squish bands and compression and how it all comes together. I'm currently building a 79cc motorized bicycle pretty much from scratch. And your spot on about how too much compression hurts top end. I was wondering why my engine was struggling to rap out all the way. Too much compression!
Yeah too much compression surely hurts top end. I too found that out the hard way lol
I do enjoy your videos. Even the long form vids.
Thanks! Glad to hear that!
Did it this way for years .... then picked up a cheap OLD lathe ... seriously DO THAT, you will not regret it.
I do plan to when I finally move and have more room.
Great informative videos . Thanks for sharing and educating us.
Your welcome. Thanks for watching!
Excellent info! Thanks for posting.
just took off my head 2022yz250x squish was .084 i purchased an apex xc head am trying it tomorow i had a 2017250x i had it cut .040 and it was great everywhere
Interested in what you find with the Apex head
@@UpAllNight91 im gonna try some mods to the stock head also
@@UpAllNight91 i tried it today it was excellent . low and mid a littlie up high but the the thing was like a different fuckin bike unreal big increase in power for 225 dollars cant be beat
I know man! The head is surely the big game changer. What squish did that head end up giving you? Any jetting?
Thank you for that cool DIY tech video! 👍 Best regards from germany. 🙂
Your welcome! Thanks for reaching out from Germany!😎
hi buddy very good work, i have a 2004 honda cr125 i understood how you do the work of removing material i polish the head, but the sums of removing material i the amount of water is that i did not understand well thank you
Hello. Yes you want to measure the overall volume of the head by CC'ing it with water as I did in the video and taking note the heads overall volume before starting any material removal. After you shave the head down to get the squish band where you want it then you open up the dome to bring the overall volume closer back to stock. So you will CC the head again as you open the dome back up till it closely matches the same overall volume that it did before you started removing material
Another great video!!!
Thanks man!
Top tutorial, full marks
Thanks!
Hey there awesome info, just like to know. After taking material off the head do i need to reset my my timing on on the fly wheel back to stock
I would if you are currently running more timing advancement. Start with stock timing again and test from there. Usually once the head has a good profile the stock timing is about the best you will find
thanks for the video, learned a lot, I just bought a new 2023 yz250, will 100LL Aviation fuel work with that head at .40, I live close to a airport where I can get it
Hmm. Good question. Honestly I have no experience with av gas and don't really know how well it controls the burn. To be safe I wouldn't be scared to try like maybe 0.050" and near stock compression, start there and see how she handles that on av gas.
If I do this mod, Will I have to run a race gas mixture all the time. If not, would 92 non ethanol be acceptable.. You need to do more vids, you are very knowledgeable and also a good teacher...preciate ya
Thanks brother!
Even the 5UP head stock (US model 2003 to 2010) would ping on crack of the throttle with 93 pump. Its acceptable but hardly. With the head mod specs i showed it surely requires even more octane, at least 40/60 race/pump to be happy . But there are things that can be done, like tighter squish but lowrr compression by opening the dome more. Or if its being used at high elevations . That eases octane requirements too
Again, Appreciate all the info. One comment about the heat range of plugs really struck me. Back in 01 when racing/ riding my CR250. I always wondered why my motor lost its crisp feeling after about 10 minutes of riding. Felt it was always jetting related, since some of those CRs were finicky at higher elevations and a slide cut did improve it. But now that I choose to ride a 2018 YZ250 bone stock, How much better of a bike it is in every way with near perfect jetting and great suspension for weekend warriors at or near sea level ( where I live now in NC) Would like for you to share with us some more of your knowledge if you can...Thanks again..
Yeah the heat range, I was like you, scratching my head. When I tossed a colder plug in her I was surprised it fixed that issue (back in like 2009). Kawasaki sells a optimal 9 heat range plug for the kx250 2006 so guess it's not unheard of.
Can I use this same process on a domed head and piston? 91 CR 125R
Hello. Yes you can. This was done on a domed piston YZ250. Its the same thing.
Great video! Say if I were to get the squish down to .40 and then open up the dome to around 23 or 24cc so I would be able to run straight pump gas still do you think it would be worth it? Even a 1hp gain and a crisper running motor I would be happy with. Here in canada race gas is around 25 or 30$ CAD per gallon so its just not an option for me right now lol. I also have my timing retarded a few degrees too for a bit more top end power and to eliminate intermittent mid range detonation I was having. TIA
Hello. If I was sticking with pump fuel I would not go any tighter than 0.050" on the squish. It would have to be a lower compression head, about the same CC's as the 2011 to current 5MW head. That should be a good pump gas head with sharper throttle response and a little more HP.
@@UpAllNight91 thanks!
Yes sir!
Great idea 🙌👍
So, to run pump gas, I need a tighter squish and bigger dome (less compression)? How much squish clearance and how much volume in the dome?
Hello. For 93 pump gas I suggest following the specs that Apex heads also use for their heads. 0.050" squish band clearance and lower than stock compression. I have two videos where towards the end I check the specs on all these heads and show them. Here are two links to them two videos... ua-cam.com/video/Ht5gb_DQ-3U/v-deo.html and ua-cam.com/video/Kn-7eG6E6jE/v-deo.html
Was that bike previously detonating by the look of the head
Yes it was for sure.
Have you experimented with the athena heads for yz,250
I have installed them for customers. They are good OEM copies.
How thick is the dome? I have a stock YZ125 head, looks like a crack in the dome but not sure, the dome may be thicker than I think and it’s just a ding
Hello. Not sure how thick it is but I have seen heads crack in the dome area and it usually leads to lose of coolant and hard to start up because of coolant getting in the combustion chamber
By the way excellent vidieos
Thanks man! Are you riding again?
After changing the squish how do you know how much dome you have to shave out?
You measure the cylinders head CC volume before you start shaving down the head. I think part 1 of this video is where I show that.
I have a 23 YZ250X trail bike. Can I just swap heads with the YZ250 race bike?
Yes you can. It bolts right on. I would use the 5WM head used from 2011 to current YZ250 if you want to run pump fuel. If you plan to run at least 50/50 pump/race fuel then the 5UP head used from 2003 to 2010 on the US models will make the best power out of all the OEM YZ250 heads out there.
how much does this affect the power of the engine and how many Kw are added by this work and is it harmful during the life of the engine
On a 250cc it can be worth 2 to 3 HP. It can shorten the life of the motor if its tuned to the max. This is why I set them at a happy medium as I mentioned in this video.
After doing this mod is re jetting a must ? I run a 2022 yz 250 with a hgs pipe and a r304 shorty and think about making this mod ? Iam on stock jetting right now .
And i run 98 pump gas. Sweden. Still need race fuel ?
If you want to stick with unleaded fuel i would keep the compression rather low and keep the squish clearance around 0.050" . As far as jetting, having the head modified with a tighter squish clearance usually desires slightly leaner jetting, especially if you want to reep the full benefits of the head mod. At least a size or two leaner main and some mild fuel screw adjustments
I have a 02 yz250 are these good heads or should I do this to it?
If the head has a 5UP writen on the top of the head, you have the best stock head yamaha ever offered as far as performance. But if its a 5MW or some other head then its going to be a lower performing head. The 5UP is a good head but can be made to even a better head with a little work.
Sorry i’m french
What i must have to do , if i only run 98 pump gas ?
Please its dificult to enderstand the video for me
250 yz
Dont want suprcross style off throtle,just want smooth and longduty power
Would this work on yz125 🤙🏻
Not so much on the 2005 to recent YZ125s because they have a sharp turn in the middle of the squish that would be hard to do by hand. But I'm sure someone could. I would just send that head out for the job
What fuel was it detonating with?
I don't know what fuel was used that caused this damage. But from this point on he started using race fuel mixed with pump fuel.
what elevation do you ride
I should have mentioned that. Sea level here in Florida.
Will this set up work on methanol ?
I honestly have no experience with methanol. I don't know really.
Can I do this to a 08 kx100?
Yes it can be done on a KX100 as well.
$80 and your local shop can spec it out. Why gamble?
I get satisfaction by doing myself. Been doing it for years and there's really no gamble except I have dailed in the ability to pretty much make any profile I want and with trail and error been able to produce better than any local shop can compare too. The satisfaction when the bike runs great and I know its from me is nice
@@UpAllNight91 I get the dyi stuff, but you'll never match the precision of a tool and lathe with sand paper and a drill. To each their own.
@@panic-revv85 sure. However the man behind the machine is more important. Seen many heads done on a machine that the profile was not desirable. When i do them myself I can make small changes and get the profile right where I want it. With patience the end result is amazing
What jetting are you running?
172 main
Stock needle for the 18, second clip from the top. 50 pilot. Air screw at around 1 turn. Sea level here is Florida. In the winter when it's real cold I usually have to run a 175 main and turn the air screw in a hair
thats pronounced mating , like your mate or wife. time you learn. cheers.
I have a kx250, and they have head gasket instead of o-rings. Would I have to install the head gasket when I perform the squish test?
For sure. Head gasket fully torqued down. And be sure to use the same brand and type of gasket every time you replace it to keep the same results, as different brands can come out thicker or thinner. I would just use the OEM gasket since you can always buy on of them and consistency
@@UpAllNight91 huge thanks, I stumbled across your videos and they have motivated me to start wrenching on my bikes again. I'll be relocating from about 600' elevation, up to 4500' so I will have my work cut out for me to get the KX jetted as well as adjust the compression. Any info for baseline head volumes (I noticed you were shooting for around 21.5cc) and their correlation to 91, 50/50, or full race 103-110 would be greatly appreciated as well!
@@joeydacey6591 Thats awesome man! Honestly I dont know where to start as every bike is different. But what I would do is start by seeing what the stock head CCs too and setup your modified head to that. Then test that out. From there if you want more bottom thrust put another head together the same but with more compression (less CCs) and if you desire more top end then put together another head or take the current modified head and remove the CCs (by removing more from the dome)
for lower comp. Thats how I did it. It can be a trial and error thing but the end results pay well.
@@joeydacey6591 Hello. The 21.5cc is for the YZ. It will surely be different with a different bike like the KX because head dome can be a different profile and also how far the piston comes up can be slightly different on the KX. I mainly use CCing the head for reference. I would first CC the head stock and see what it comes out too. Then knowing you will be going higher in elevation I would setup a head with about maybe a 0.5cc to 1 full CC less and get the squish band down to 0.040" to 0.050" and start there. Test that out and then I would expect to have to either go back in and make a few changes to that head or even put together another head to make a few changes after the test ride. Sometimes it takes a few trials and errors towards your aim to hit the bull eye you are looking for.