HOW TO Check The Valve Clearance On A 4 Cycle Flat Head Engine
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- Опубліковано 25 лис 2012
- In this video tutorial I show you how to check the valve clearance on a 4 Cycle Flat Head Engine.
Set Intake at .008 and Exhaust at .012
The same procedure can be used in many different engines with a flathead.
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Great video, even an 79 year old like myself could understand. I didn't know where or how to adjust the valve lash until your video. Thanks a bunch. Everett
It 2024 and thanks for all the videos and advice over the years
Hoping your wife is doing better ❤
You’re a skilled mechanic and these videos are all very well shot. Nice explanations!!
This video was a life saver. I had this exact problem with my craftsman snowblower and following your procedure I was able to fix it. Now my blower starts up strong and actual blows slushy snow without any problem. Thanks again!!
Great videos Donny. I have learned a lot by watching.Never too late to learn even at 71 years old.Keep up the good work.
I found a free snowblower that had 80psi compression. I shaved the valve to spec and it was 150 psi after! Runs great now. This video explains the issue great.
Thank You. Not only for your quick responses to my questions but for everything you have taught me.
Dude, many thanks for this video, it has just saved an old 7hp B & S from being scrapped! Keep up the good work!
you're welcome man, make sure you are subbed
One thing you mite want to add is make sure your not on valve over lap. Just because your piston is all the way up. Don't mean your on compression stroke. The way I was taught - is when the intake valve is fully open- measure exhaust. When exhaust is fully open- measure intake. Makes simple.
EXACTLY. if its at T.D.C. its not always on the compression stroke. If you dont have the piston the correct way, you will get innacurate readings. Also, Briggs recommends that the piston be .25" below the cylinder when checking valve clearance.
If both valves are closed your on the compression stroke with the eng apart there both closed so really don’t matter
Thanks Donyboy. I love your videos and small engine repair.
Great video Don. It helped me diagnose a valve clearance issue on a craftsman lawnmower mower. The mower now runs! Thanks again.
Right on
Great video Dony, you have the most calming voice to listen to. I can listen to your videos all day long. Cheers
thanks lol
YES I DO, search for valve decompressor on my channel
All your videos are exellent'
Thank you you give me the information I needed I'm a mechanic myself and I just needed to look to see where the timing marks were and I do appreciate it god bless you and thank you very much keep on truckin brother I am Charles out Farland Albert Farland
Thank you soooo much for this vid!! You guided me enough to figure out what was wrong with my snowblower and I was able to fix it. Got a storm coming tomorrow too and it wouldn't stay running even after putting in a new carb.
I had to watch your video again thanks for sharing your video
Before Tecumseh went out of business, I ran into brand new engines that the valve stems were never ground. Very rare anymore unless it's very old, valve seats have been beaten to death from worn valve guides or at the very end of tecumseh's run with the worn out molds and dies. But only ever seen maybe 3 or 4 like that new.
Did just this on my Tecumseh 5 HP rebuild...even with 'new' valves I had to grind (shorten) the valve to obtain clearance. Compression is good!
Smashing tutorial :-)
All the power of the engine just vanishing down the exhaust, and distroying the mixture as well.
No wonder it wasnt happy.
Thank you for posting this I really appreciate it.
Great video donny I've always wondered how to do that
Don, I'd would love to see a video on guide replacement and seat and valve cutting. Thx
Thank you for the video. I own a 8hp Tecumseh and I had a red hot exhaust at the end of last season, I rebuilt the carb but it was still running very lean. I had to grind 40 thou off the exhaust valve stem. I cleaned all the carbon off the piston and valves and changed the head gasket and intake gasket. The exhaust valve is seating properly now. I picked up a valve spring compressor and feeler gauges at Napa.
+davidbrennan5 thanks for watching
Thanks for the demo. Very helpful.
Hi Dony - What if the valve has too much clearance causing too much compression? This video shows how to grind it to give more clearance, but if you need less clearance? Is that adjustable?
My well used Murray mower, with the B/S 16.5 HP I/C engine, pumps oil into the valve cover through a galley located just under the intake pushrod. This oil is milky as it is being pumped but allowed to set for 15 minutes goes back to its normal color and consistency. It looks to be full of small air bubbles. I removed the head and found the gasket to be intact, no indication of a leak on the block or the head or the gasket. I removed the breather valve assembly (the reed valve as well as all else) and found it to be in good condition also. Very clean.This all started with the engine being hard to turn over even with a fully charged good battery. I reset the valves and this helped to some degree. It then began again to be hard to turn over. I then removed the valve cover and found it to be 1/4 full of oil. The motor does start with 3-4 tries, it runs good and idles as it should. It does not smoke as it is running but will on occasion emit a large puff of grayish white smoke and then the smoke is gone... The oil consumption is not excessive. If you might have an idea as to what causes this issue I would appreciate your advice. Thank you, ........Tom PS...I enjoy and appreciate your videos. You speak clearly and slowly enough to be properly understood. Thanks again......Tom
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+Thomas Huckaby What a baffling set of symptoms! I'd be interested to know if you figured out the problem. Worn rings, maybe?
great video as usual ,, keep up the awesome work that you do,,, your very helpful my friend..
thanks
Very helpful, thank you!
Thanks Don.I've been doing a lot of research on how to adjust non-overhead valve engines for the past few hours.Now I think it's basically the same for adjusting 18 h.p. Briggs opposed engine.Good info on the part about spinning the valve for wear.
DesertDigger1 yes same procedure
how to fix a small lawnmower if no compression and valves seems coming out and stuck
thanks for sharing
Nicely done. Thank you.
Nicely done as always!!!!
Would of been nice to see how you ground the valve stem to the proper clearance and explained why the problem accrued.
Why did it happen, I still don't know . . .thank you
I fixed this same problem on a garage sale find, all I used was a pedestal grinder and a 10 buck digital caliper.
I find the best grinding results accrue when you use the side of the grinding wheel since most of the time that part of the wheel has not been abused and will run truer.
With nimble fingers and a 2 degree rake I gently rotate the stem against the side of the wheel, this will produce a crown in the center of the valve stem. I find this is much easier to controls then a flat grind, this way when you get close you can stone off 1 or 2 thousands with little effort for the final fit.
Thank you for your teachings donyboy73 . . .we all need to spread our knowledge ;)
FWIW the valve clearance likely gradually reduced as the face of the valve, and the valve seat wore over time.
@@JeffinTD DUDE THANK YOU. I was like, is it just build up on the cam journals? That didn't make sense. Valve wearing away does. Thanks
@@andrewchristiansen-Detroit Yeah on some engines the lifter, rocker, tip of the valve might wear faster and gap will increase- but on this old flathead there’s no rockers, nothing is sliding on the end of the valve so it’s just a matter of the (likely soft) valve seat wearing faster than the end of the tappet.
Dony what caused the valve to "stretch" like that? Overheating? I've never ran into this problem before.. Very interesting, thanks for showing this..much appreciated buddy..
Love your videos, I have learned a lot.
There seems to be much confusion all over the internet regarding the valve clearances of Tec. L head engines. Some say like yourself, .008 in. / .012. ex. and some say it's .008 min. for BOTH valves and .012 max. for BOTH valves.
Different years and versions of Tecumseh manuals have kind of confusing information. I have a 1978 Ariens 7/24 that backfires out of the muffler when working hard and quits. After it cools it runs good again untill you work it hard again. My exhaust valve clearance is about .006 or .007 I'm thinking it get less when good and hot and causing this problem. I don't want to remove too much material though.
Yes! That is the question I'm trying to figure out. I believe it looks as if it's just a minimum of, in my case a LAV35 L head, .04 min and .08 max for both valves. But it sure would be great to be 100% certain on this.
thank you!
Great video! All you videos are great. Is it possible that you could show how you take the valve out and the procedure for putting it back in? Thank you and keep up the great work!
Yeah..... that's the clincher. Removal, grinding, reinserting and readjustment.
thanks for watching steve
love the great videos and detail, keep up the great work
thanks
@@donyboy73 do you have any videos on how to do this in an opposed twin cylinder Briggs and Stratton or is there something around youtube I've searched and have come up empty hsnded thanks for all your helpful informative videos may you and your business be blessed at all times in JESUS name
excellent video!
Thank you for this video, very helpful. When you took the exhaust valve out to grind the stem, were there clues which indicated that the valve face did not need to be ground, or even lapped in?
THAK YOU SIR!
hey..i just put a little spot weld on the end of the valve and grounded it down to the right play. worked out fine for me...
yes exactly, i seldom have to lap the valves
he doesn't want to spend more than $200 to fix it so i told him i couldn't get a block, iston and rings and labor for that price
@DannyOktim,
Never grind on the side of a grinding wheel, they are more likely to disintegrate and throw pieces of the wheel towards you.
Thanks 🙏 for sharing.
you can use a 00 grease, lithium or white grease, i talked about it in a previous Q&A, check ebay for the filter
Good job... well done
hey! you have one of best video easy explained or easy understand. But I have one problem what I can't found out. Problem is when shut down engine it's explode in the end. what can be wrong? thx a lot for your videos I wish you all that best.
yes canadian, i have a linkage configuration video on one of these engines i think
very great videos!
Hi Don, I saw ICANDOIT20s’ comment & understand how that happened. What would have cause the valve to have to be ground down. Thanks again for the time & effort you spend doing these videos.
not always but it is recommended
Well Donyboy, looks like this is my next lil project. My generator has that annoying lil "poof poof" backfires in an otherwise perfect tuned machine. Kinda betting the exhaust valve is spinning like the one you show in this vid. Wish me luck here.. and as always young man,,,, thanks for the vid.
Hi thanks for this great video. What tool do you use to remove the valve??
thanks Don!
Great video Dony! Any chance on a video of replacing the valves in the future?
Great videos, I have a 5hp tech snowblower with an exhaust leak. What tool do i need to remove the valves?
In the states, Sears has a 25 leaf feeler gauge for sale at $5.09 right now. You could also get one from Ace Hardware.
Wouldn't it be a good idea to lap the valve and valve seat before adjusting the play? There could be carbon buildup on the valve seat that will prevent the valve from sealing perfectly even after you adjust the clearance. And if a piece of carbon comes off you might have too small valve clearance again.
You can't lap the valve and valve seat before adjusting the play because they don't touch when there's no valve clearance at all. The issue is the seat and valve face wearing making the lifter clearance non existent. I've done 5 valve jobs in a year with the Tecumseh flat heads.
No Goran you have to get clearance first as the seats will not mate up and grinding paste will not grind the seat of the valve or the block seat , get clearance first then grind and paste and adjust clearance as required it takes time as its imperitive the clearance is correct as the exhaust valve seat will burn out as theres high temps in there loke up around 1200 degrees c in the cumbustion chamber ,Dony boy 73 did a good demonstration there , he is a good chap at his job he will have it running right before it leaves his workshop
on the flat heads it's .008 for intake and .012 for exhaust, yes I use a flat chainsaw file
I got a flat head briggs that Im sure has valve issues on the mower. Its a 2013 flathead but it has electric start so i want to get it working. OHV is so much easier to adjust lol.
Just did this to a Briggs 281016. What a PITA to get the keeper back on.
another good vodeo thanks
Great video Don...any idea on intake and exhuast valve clearance on a Tecumseh hs50 67326k 5hp flat head? Thanks
thanks dony
1. I don't think the valve can be "stretched" by the srping. I think it is because the wear between the valve and head so the valve "seats" deeper into the head so they lose the gap.
2. About question #2. I understand it "touches" the valve to open it but not at TDC. If the valve is not tight at TDC, I don't see how you can make it tight just by grinding it down.
Thanks man!!
Hi Dony, how's it going? I just finished checking the valves on my 5hp flathead snowblower engine and found that my exhaust valve has no gap at all and my intake has a gap of .012. I realise I need to file down the exhaust a bit, but how do I make the intake gap smaller? would buying a new valve fix it?
That's a good review. I was expecting you to have to relap the valve seats, but it looks like that wasn't necessary. I suppose that if carbon was holding the valve up, the gap would have been too large.
At the shop I used to work at we would get Chinese scooters in all the time, 75% of the ones that came in the door had a stretched exchaust valve. Can be caused by running at high load for a long time, or just cheap metal, just my 2 cents and as always great vid Dony
I think, if you look at a spec sheet, you will see the min/max at the top of the column that tells you the gap. If it was 8 intake 12 exhaust there would be no need to put min/max in there at all. Are they saying 8 min/max and 12 min/max...I don't think so. 8-12 for both.
Great tip Don , thanks , did ya get much snow over there ? almost 8 inches here in the Sault .
Also is your Q&A coming out soon I enjoy them alot
It would have been a big help if you show how to remove the valve....and explain why you did not clean (lap) the valve seat
Would have been nice to see how to adjust the clearance if either gap was too big!
Hi,
Could you show how to remove the valve for grinding? Possibly how to grind the valve and seat to seal better?
Thanks
Tony
Port Hadlock, WA
Nice and short.
Dony, Thank you for your continued five star videos. Please explain at what point the automatic cam decompression system; starts, then stops to function. Also with the flywheel key checking out okay, what else normally affects "pull starter kickback?" Tim.
Valves no set properly try again.
it's a valve seal and yes it can be replaced
Because of a badly scored cylinder, I had to purchase a 'new old stock' block for my 5hp Tecumseh HSSK50-67403U Yard Machines snow blower. I also purchased a new piston, rings and wristpin. Also purchased two new valves and a complete gasket kit.
Short block is back together, crank & cam timed properly.
I lapped the new valves and checked valves at TDC...before I put the cam/crank cover on I could easily see the 'lifters' were on the heel/low spot of the cam.
Clearance on this engines valves are intake-.004 & exhaust.008
Intake is in spec however I have to grind the exhaust...I have a bench grinding wheel but wondering if a Dremel would work better > > > I'm a little concerned about removing too much metal.
Hi again Donny, as you suggested I checked the clearance on my B&S 11.5hp, and there was basically no clearance on either valve. After grinding and lapping I have 10 thousands on the intake. I know this is too much clearance, but will it make much difference on the inlet, and if so will further lapping be enough to reduce the clearance? Lapping seemed to be increasing the clearance and this is the opposite to what I expected....
if it has adjusting screw i would turn the L and H screws a bit in until it runs better
I may be wrong I'm not an expert but I think that on most flat heads since the is no compression relief mechanics, either the intake valve or exhaust valve will have some clearance to allow the engine to turn freely at startup. please correct me if I'm wrong
good vedio
Hey Dony what is the valve clearance on a 16.5 hp briggs and Stratton flat head engine your help would be greatly appreciated, Thanks
Hey dony, can you explain to me how a valve (say exhaust valve) which doesn’t have any adjustments on it, would fail to seat properly over time? Ie what changes that you need to grind the valve to increase the valve clearance??
That is my question also. I can see things wearing and having MORE or too much clearance but how does clearance disappear?
If the valve seat wears then the clearance between the pushrod and the valve stem will decrease
Hi Dony. I'm rebuilding the exact engine you show in this vid and I'm at the point where I'm putting the valves in. I'm not seeing any clearance in either the intake or exhaust valves with piston at TDC. Is there anything else I should check before I go grinding down the valve stems? Thanks!
Hi Dony, I've read sometimes to check the clearance at top dead center and others say to drop the piston 1/4th of the way. Which way is correct and why do they suggest lowering the piston? I have an HMSK100 engine Thank you!
Always interesting :D
BTW is the customer let you repair his engine with the some scoring on the bore?
nice thanks a lot!!!!
thanks for watching
Hi Donny - Great Videos. 1 Question. At TDC, the exhaust valve is fully seated on my engine and I can not spin it by hand. But... on the compression stroke, it seems the valve opens VERY slightly, like there is another small lobe on the cam. I can spin the valve during this slight opening, but it seats again just before TDC. Is this normal? Tecumseh HSSK50 engine.
i have a video that shows how to use the valve tool to remove them
Might mention prior to grinding down a perfectly good valve to rotate the engine again, there is such a thing as valve overlap between exhaust and intake strokes. Engine didn't have excessive valve lash when you finished and a bunch of ticking by chance!
he has a video called, HOW TO USE VALVE SPRING COMPRESSOR TOOL ON SMALL ENGINES FOR REMOVING VALVES . its very informative thats what you are looking for
Cam you use a compression tester and if so what would be a good compression?
i believe so and usually it's smaller