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Discussion Starter #1
Installed a 88cc big bore kit on a trx70 that has been sitting in pieces for more than 20yrs. I noticed during installation that after i installed the tension push rod and spring, the chain still seemed loose. The bike fired right up but has crazy loud chain noise. I've ordered a fly wheel puller so I can get in there, but is there a way to inspect chain tension once i pull the flywheel & stator? I can't seem to find it in the book. I think it could be more than just a stretch chain bc of how loose it is, and i would of remembered this loud of chain slap 20yrs ago before it was disassembled. For some reason it just seems like the tensioner is not applying tension to it at all.
Is the spring against the pushrod tensioner the only thing that applies tension or does it work off oil pressure as well? There has to be some way to check the tension with the motor not running right.
With the timing sprocket cover off the head, you can bump the flywheel by hand back and forth and see how much slack is in the chain, Just a quick bump left then right will make the slack show up in the head, and its a lot. This should not be correct? I read in a post where someone said the chain can sometimes slip to the side of the tensioner roller or the roller can be off to one side or something. I won't know much i guess till i get in there.
For you guy with more experience with these, i should not be able to see all that slack right?
If i can figure out how to post pics i might try and do that.
Thanks
 

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Discussion Starter #4
So looking at it more today, it could be more than just loose timing chain. It's a pretty load knock/tick sounds more like on the clutch side to me but sound can really travel through the case i guess. It sounds more bottom end than top.
I know the history of the bike and it has very low hours on it even from new. I would think bottom end is good. I didn't replace chain as I knew it had low hours. I feel like i have the timing set right (see pic) I've attached some vids of the sound. I'm pretty good at following directions, so i felt good about doing the top end, but have some concerns about going into bottom
https://youtu.be/V15cxG5vjWg
https://youtu.be/rNSmiUyFp-Q
 

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Personally, I don't think the flywheel is indexed correctly, the "T" is supposed to be in line with the case notch at the 12 o'clock mark. I've never that "arrow" indicator stamped on a Honda flywheel to show TDC.
 

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Discussion Starter #8
I did question this, the book shows using the access hole in the cover to find "T" and that is tdc. The hole is slightly to the left of the tick mark in the case. I but a mark on the edge of the case where the sight holt was, then set by hand. When i lined up the T where the sight hole is, that little arrow lined up with tick mark in case. So I thought it was right.
Plus don't you feel when trying to hold it by hand, right at tdc that it is trying to spin left/right slightly on its own? It sure felt like tdc, maybe I need to get an extra hand and pull spark plug and check with light.
That access hole through me for a loop, but I thought maybe it all made sense after the fact, but again I'm not all that familiar with this.
 

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Can you post a pic of the left side engine cover, if you don't mind?

You should pull the plug when checking for TDC, it lessens the tendency for the flywheel to drift.
 

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Here see if this works, the red mark is the tick line on the case, here's a pic from book
Yes, that works fine, now I understand the offset. The main reason I never saw the arrow indicator is because every TRX70 engine I bought didn't include the flywheel or left side engine cover.
Thanks for posting that up
 

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Discussion Starter #13 (Edited)
Yes, that is the index line i went off of. Did you guys listen to the vids? Any ideas? I'm not sure what's the best way to go about diagnostics for this problem
 

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Discussion Starter #15
I did. I set them at . 002.
One thing that wasn't clear and I might call Spanglers about it, in their instructions it says to set valve lash, then turn flywheel by hand 2 full revolutions and then they should be tight no play.. This makes no sense to me, but mine is not tight after 2 revolutions, it's still .002, you can feel it in the rocker when you wigle it..
 

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1 revolution of the flywheel pulls the piston down to BDC and both valves are either opening or closing, and the rockers will be tight. 2 revolutions brings the piston back to TDC, and both valves are closed, and the rockers are loose.

Kurlon said:
...Minor correction for an earlier post, starting at TDC and turning the crank one full revolution brings you back to TDC, not BDC. You're on a different part of the four stroke cycle, but the piston is at TDC. Turn it again, TDC again...
Thank you, Josh, for bringing that to my attention, and clarifying it for everyone. Not sure what I was thinking when I posted that, but it certainly wasn't the right information.
 

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Discussion Starter #17
That's what I thought also, here this is from their instructions

Starting with the upper tappet, use a .05mm (.002) feeler gauge to set the valve clearance. Once the gap has been set, tighten the tappet bolt (9mm) to 80 in. lbs. Repeat the process for the lower tappet.

After the valve clearance has been set, grab the flywheel and turn the engine over counterclockwise TWICE and re check the valve clearance. If you have done everything correctly, there should be NO gap clearance. If there is a gap, you will need to repeat this step until no gap is present
 

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I'd have to guess that the wording should have been "...If you have done everything correctly, there should be NO gap difference...", meaning that you have set the jamnut correctly and the .002" gap hasn't changed. :dunno:
 
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