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Discussion Starter · #1 · (Edited)
Couple quick questions if I may.

Couple quick questions if I may?
Replacing timing chain on my 2006 Bruin YFM350.

Questions:

Timing marks...
1. As long as the cam and crank marks are lined up, (when installing chain). I don't need to worry about compression stroke, right? (It only needs to be on the compression stroke when setting valves, right?)
2. Use the single line mark on the flywheel for timing, (not the T or wide H) correct?
3. After I installed the tensioner, the cam gear timing mark is about 1/8th. inch off. Is this normal and acceptable?
4. I watched a few vids on YT and NO ONE mentioned ANYTHING about lining up the counter balancer marks. I did that before setting timing marks. This is correct, right?
5. On the tensioner, I just pushed the plunger in and bolted it down. There's no specific procedure for that, right?

Thank you all for your expert guidance,
Johnny
 

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Your questions are understood yet not easy to answer without a longggggg post.
The cam is in time when the valves are fully closed after the compression stoke, then with the chain installed on the proper teeth both top and bottom the piston will be at t.d.c. The rub comes with getting the cam lobes in the correct cycle.
Then when the chain tensioner is set both the valves are still closed and the piston is at t.d.c. (nothing moved). In your case it sounds like the cam turned slightly as the chain slack was removed.
I suggest getting a f.s.m. with more detail, look here for a free download;

I'm not a writer and doing is easier than explaining.
 

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Discussion Starter · #3 · (Edited)
Thanks Ridgeway...

What is an FSM? > Free Service Manual?

On the tensioner, I just pushed the plunger in and bolted it down. There's no specific procedure for that, right?

PS - can anyone tell me what ATV's have the same exact YFM350 motor as the 06 Bruin? I can't find a FSM for my Bruin.
 

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Factory Service Manual.....
When you install the tensioner and it takes up slack on one side of the cam, the cam can move/turn without the crank moving.
 

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Discussion Starter · #5 · (Edited)
The flywheel is dead on the straight mark. (Not the wide or H mark). Is this good, or should I move the chain over one? Or should I be using the H mark? in which case the timing mark would be pretty much right on. The intake valve is about 4-5k at this cam/crank position.

Well... after looking at the marks from this angle, I think maybe the gear is a tooth off. I'm gone move it over one and have another look-see.

Tire Wheel Automotive tire Locking hubs Tread
 

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I mentioned using the piston at t.d.c. as your guide for proper bottom end timing, don't go by the marks as you might not see the exact angle. What does the f.s.m. say?
 
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