110cc - Wierd TDC Issue

Pitbike Tuner · 11-13-2024, 09:03 PM

Trying to get my engine to top dead center and have the 2 covers off. Issue is when turning counterclockwise and looking thru the top hole for the "t", whenever the engine gets to it it turns quickly past it and I cant get it to hold there. I had the spark plug out as its threads are stripped and I'm going to change the head to fix that issue, but even putting the sparkplug in it does the same.

Crossbar · 11-13-2024, 09:30 PM

At TDC both valves should be closed and there should be no spring pressure on the cam. If you're sure it's at TDC and not in between then could it have jumped timing or valve adjustment too tight? Did the engine run ok before? Find a way to lock it down at TDC and check the valve adjustment.

TominMO · 11-14-2024, 11:28 AM

Use a wrench or breaker bar to turn it, not something with a ratchet. That gives you a lot more control.

Pitbike Tuner · 11-14-2024, 09:01 PM

Quote:

Originally Posted by Crossbar

At TDC both valves should be closed and there should be no spring pressure on the cam. If you're sure it's at TDC and not in between then could it have jumped timing or valve adjustment too tight? Did the engine run ok before? Find a way to lock it down at TDC and check the valve adjustment.

Not sure how it ran before, got it from someone who said it wasn't running and found out the spark plug threads were stripped. It turned over fine when trying to start, and came with a new complete head so think the guy new of the issue. The engine turns without much resistance at all, and then when it gets just to TDC it spins quickly about a half turn.

So to check the valve adjustment just pull the top and bottom caps after getting it at TDC correct?

**cheesy** · 11-15-2024, 06:10 PM

Pull the caps first. Set crank at TDC. Both valves should be closed as Crossbar said. If one valve is open, rotate the crank one revolution and line up with timing marks again for TDC. Both valves should then be closed. If still not, the engine has jumped time.

krat · 11-16-2024, 09:40 PM

Questions;
Are you installing the new head? If so you set TDC on the flywheel and install the new head and adjust the valves to match. That should also take care of any timing problem that might have existed. You will line up the cam and lifters to the new head with the timing chain in the proper position.

It also makes the spark plug issue a moot point.

Otherwise, why would you try to adjust the valves on a head that was trashed?

11-13-2024, 09:03 PM	#1
Pitbike Tuner Join Date: Oct 2021 Posts: 6	110cc - Wierd TDC Issue Trying to get my engine to top dead center and have the 2 covers off. Issue is when turning counterclockwise and looking thru the top hole for the "t", whenever the engine gets to it it turns quickly past it and I cant get it to hold there. I had the spark plug out as its threads are stripped and I'm going to change the head to fix that issue, but even putting the sparkplug in it does the same. __________________ 2010 ZheJiang YX110cc ATV 2008 ZMC125r Pit Bike 2007 Viper Z32 (X15) Super Pocket Bike
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11-14-2024, 11:28 AM	#3
TominMO Join Date: Sep 2021 Location: De Soto, MO Posts: 1,978	Use a wrench or breaker bar to turn it, not something with a ratchet. That gives you a lot more control. __________________ 2021 Lifan Xpect--sold 2022 Lifan KPX 1972 Honda CT90--The Carrot 1969 Honda CT90--The Tomahto Cheesy is the WDK (workplace drama king). Now retired. Nope, back in the saddle. Nope, finally retired. Climate: The Movie https://www.youtube.com/watch?v=A24fWmNA6lM How our government really works https://www.youtube.com/watch?v=QjadCd0VRBw Question all authority.....think for yourself
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11-15-2024, 06:10 PM	#5
cheesy Moderator Join Date: Jul 2010 Location: Elburn, IL Posts: 5,989	Pull the caps first. Set crank at TDC. Both valves should be closed as Crossbar said. If one valve is open, rotate the crank one revolution and line up with timing marks again for TDC. Both valves should then be closed. If still not, the engine has jumped time. __________________ Cheesy ______________________________________ 07 Hi Bird Enduro-Flown the Coop 07 Ural Gear Up 79 Honda CX500 77 VeloSolex 4600 V3 73 VeloSolex 3800 I'm making this up as I go.-Indiana Jones Telling me something 'is for my own good', is a fast way to a fat lip.-Me I don't even care about my own problems, why should I care about yours?-Quote on one of my favorite t-shirts
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11-16-2024, 09:40 PM	#6
krat Join Date: Nov 2019 Location: KY Posts: 278	Questions; Are you installing the new head? If so you set TDC on the flywheel and install the new head and adjust the valves to match. That should also take care of any timing problem that might have existed. You will line up the cam and lifters to the new head with the timing chain in the proper position. It also makes the spark plug issue a moot point. Otherwise, why would you try to adjust the valves on a head that was trashed? __________________ %90 of the Chinese motorbikes ever made are still on the road. The other %10 made it back home.
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11-13-2024, 09:30 PM	#2
Crossbar Join Date: Jun 2024 Posts: 85	At TDC both valves should be closed and there should be no spring pressure on the cam. If you're sure it's at TDC and not in between then could it have jumped timing or valve adjustment too tight? Did the engine run ok before? Find a way to lock it down at TDC and check the valve adjustment.
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