yamaha timing issues

[newfiebullet]

so i just replaced my rings but im having trouble getting the bike back on its timing...i had the piston tdc with play on the valves and the t on the flywheel aligned with the cam sprocket also aligned but no luck...on one stroke the exhaust valve is opening as the piston comes up and brings up solid. ( turning motor by hand)...i tired it a few times and no such luck. any help?:wondering also does anyone know off hand the nut sizes on the 2 clutches? i need to find a couple sockets.

[newfiebullet]

Anyone have Anything?

[barnett468]

Hello

I don't have much it should not lock up. Try putting timing marks and piston up again at tdc then your rockers should have play, look at each cam lobe, they should be pointing exactly 180 degrees opposite if where the rocker arm rides on the cam. If they are not that us your problem for some reason. If they are not then remove cam gear, center lobes as described, move chain on gear until it bolts to cam without moving cam then try by hand. Make sure timing stays on T. Sounds like the cam timing is retarded by at least 1-3 teeth. Can you take photos of cam gear and timing mark on head etc.

Hope this info helps.

[barnett468]

Hello

Did it run before, could the flywheel have spun on crank?

[dougspcs]

"comes up and brings up solid" confuses me a bit, but I assume you are saying the there is contact between the piston and valve that is stopping the engine.

Did you remove your piston to install the rings or just slip them on?

If you removed it and while reinstalling it you rotated it 180 then there might be your issue..since the piston has a indent for the valves to clear the piston on the up stroke. If you got it backwards you have the valve hitting the piston head on the opposite side of the piston..

Since the two valves are not the same size (generally the intake is bigger) then also the indent on the piston top is different.

It's likely your intake valve that is hitting.

I assume you used the manual while reinstalling your chain to get be sure where your marks should be?

[newfiebullet]

yes i mean the piston is hitting the valve, when the piston comes up the exhaust valve is opening ( going down) and they both hit.i did not take off the piston for the rings. so thats not an issue.i cant visibly see the cam as its inside the head, but with the piston at tdc both rocker arms have a little play indicating there is no strain on them. i align the t on the flywheel with the mark and the cam sprocket line with the indicator on the head, dead on with each other. rotate the engine a bit with a wrench and on the pistons up stoke during one of the revolutions it contacts the valve, the second stroke up i think...it ran before but not well,smoked like crazy and i can smell gas in the oil. so my first thought was rings.since the ring change the piston itself moves freely and smoothly in the head.

[dougspcs]

Not sure what you mean by this? "so my first thought was rings.since the ring change the piston itself moves freely and smoothly in the head"..

Rings won't change the piston stroke length..

How about the head gasket..is the replacement you put in thinner than the original?

[newfiebullet]

i only mentioned that because it was asked if it ran before....all i meant was because of the smoke issue i changed the rings first...then i said the piston was free and clear after the ring change(not relevant)...head gasket is same as oem....the exhaust valve is almost full open when contact is made with the piston...sorry if i am confusing you, i was just trying to cover as many bases a possible....im gonna try this again tomorrow hopefully and see if i can have any luck. the bike is currently completely stripped being refurbished so i have the motor out and its easy to work on.

[barnett468]

Hello Newfiebullet


Thanks for the new info, if your new info is accurate then your cam timing is definitely off as I mentioned in my original post or there is a loose nut/bolt in your cylinder.

Below is a free online manual download if you don’t have one. It takes 10 minutes to load sometimes.

Based upon your statement that your ex valve is opening into the piston then your cam timing is retarded as I previously mentioned. I would do the following.


1. Rotate crank as far as it will from stop to stop. Check valve clearance by hand every ¼ rotation. Does it ever become excessive, like ¼” or so?

2. Look at pg 3-39 in the manual below if you don’t have one. Notice the keyway visible in the cam. Is it still there?

3. Put flywheel T in window. The keyway amd 1” long mark on timing bear must face straight up, do they?

4 Remove bolt from flywheel stick small wire in keyway slot and feel for kwyway to insure flywheel has not spun on crank.

6. Providing all keyways are in place and everytrhing lines up as described your cam is propeerrly timed and your problem lies elsewhere however there’s more ypu can do.

7. Remove cam gear keyway if possible and reinstall gear with cam gear bolt loose. If you can not temove keyway easily then just remove cam gear and hold chain up to remove slack.

8. Slowly turn motor over, if it still stops them remove head and remove the nut that is inside the cylinder or crank, lol.

9. Turn motor over again if it still locks up remove cylinder if it stilk locks up remove clutch assy. It must turn freely at this point.


YTM 200 FACTORY MANUAL. – There is a small window near top of screen that will enlarge photo up to 400%. If needed

http://www.oscarmayer.net/atc/manuals/Yamaha/ytm200_yamaha_servicemanual.pdf


Hope this info helps

[newfiebullet]

good news all is well after some tinkering. realigned and adjusted everything, seems to have done the trick, also set the valve clearances accord to spec in the manual.after the paint drys i just have to refinish my rear fenders and its reassembly time. motor is done and painted. ill have a start/finish post coming soon :) thanks for all the help guys :)

[barnett468]

good news all is well after some tinkering. realigned and adjusted everything, seems to have done the trick, also set the valve clearances accord to spec in the manual.after the paint drys i just have to refinish my rear fenders and its reassembly time. motor is done and painted. ill have a start/finish post coming soon :) thanks for all the help guys :)

Hello

Good news glad it's fixed, just curious since we know the vakve adjustment wasn't causing the problem because you had valve clearance and your piston wasn't in backwards do you mind mentioning if it was cam timing as first suggested. This info might help others with a similar problem that view your post. If it was timing how many teeth was it off?

Thanks again for the update.

[newfiebullet]

i honestly have no idea i disassembled double checked everything and took my time a carefully adjusted the timeing and this time i got it. i think before i didnt have the tensioner in enough and the chain skipped on the crank....seems to be the only thing i can figure to happen to it.