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Is my 2007 completely gone?

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Over the past few weeks I've noticed my bike losing compression. 2007 with a 290 kit. Still started 1st or 2nd even when hot, so I thought I'd be able to go until the winter before rebuilding the top. Last night I was riding with my dad - after about 20 mins of woods we stopped to take a break. I was in gear, engine off, just before kicking it I heard a faint "ching," didn't think anything of it, went to kick, and it felt like very very low compression. Then the kick would get stuck, very stuck, after a good lock it would become loose once more and would have no compression for several kicks. Then get very stuck again. Then tried to bump start down the hill to the road but no go.

I understand its very general but any indication as to what this may be?

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Big end bearing (or also referred to as lower rod bearing) is toast from what you've described. Kickstarter locks up at certain point but if you rock the bike in gear or really work at the kick starter you can get it to free up and it'll spin another revolution until it hits that spot again. 

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Could be, but it's a case of ruling things out now. Pull the valve cover to see what's up in there. Check to see if timing changed. If timing did jump, you'll need a new chain later. Then pull the head and take a look. I would think a bent or dropped valve may cause your symptoms, but hard to tell from here. You'll know in about 15 minutes of work. Let us know what you find.

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Bringing back the dead after finally finding time to do this project:

At TDC (line to the right centered in the eye hole) my valve clearances were:

Intake - between .102 and .127 (tight), and .152 would not fit.

Exhaust - between .127 and .152, and .178 would not fit.

HOWEVER, when I removed the ratchet on the bolt holding the flywheel/crank at "TDC" and let it "settle" (ended up being a few mm slightly to the left of the two lines), the clearances were:

Intake - between .127 (tight) and .152 (would not fit).

Exhaust - between .203 (tight) and .229 (would not fit).

Not sure what that indicates but those numbers seem closer to spec than the ones above, at "true TDC.."

I then removed the head. The cylinder looks good. The piston has, to me at least, a bit of residue on the top, not sure what that indicates. The plug looks good too, not too rich or lean. The valves don't look out of the ordinary, but I really have no idea what I'm talking about.

I felt the crank to test if the bearings are toast, but it felt tight side to side as well as "up and down," it wasn't mushy at all. Given, it doesn't feel like a new one, but it doesn't feel like its compromised... The crank spins smoothly, but I'm not sure if that crosses out the crank bearings. However, can crank "feel" necessarily cross out the problem being the big end bearing? Rather not do a new crank if I can help it obviously.

The only thing that I thought was strange is the cam chain. It felt like there were some stiff links, or not as smooth as it should be. Is this normal?

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Edited by doofer

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Did you take a pic from the left straight on so we can see the alignment of the timing marks on the cams?  It looks like it may be off (exhaust cam), but hard to tell from the pic.  What is that mark on the left exhaust valve?  Tight exhaust valve clearance + timing off may have caused the valve to touch the piston?

 

While you have the head off, turn it so the valves are facing down and fill each side with something less flammable than gas.  See how much they leak.  A little migration of fluid is not bad.  Drip, drip, drip indicates a problem.

 

The chain should be totally smooth with no binding.  You should get a new one.  Keep us posted on the leak test, and if you have a pic from the left side with the valve cover off at TDC it would be interesting to see.

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Did you take a pic from the left straight on so we can see the alignment of the timing marks on the cams?  It looks like it may be off (exhaust cam), but hard to tell from the pic.  What is that mark on the left exhaust valve?  Tight exhaust valve clearance + timing off may have caused the valve to touch the piston?

 

While you have the head off, turn it so the valves are facing down and fill each side with something less flammable than gas.  See how much they leak.  A little migration of fluid is not bad.  Drip, drip, drip indicates a problem.

 

The chain should be totally smooth with no binding.  You should get a new one.  Keep us posted on the leak test, and if you have a pic from the left side with the valve cover off at TDC it would be interesting to see.

Unfortunately I don't have a picture from that angle. From what I can remember it did look slightly off from the diagram in my manual.

Any recommendation as to what liquid I should use?

Will get a new cam chain upon reassembling! 

Thanks very much for your help

Edited by doofer

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Brake clean works great, its still flammable though.

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So I'm not 100% sure I did this right. BUT.. I turned the head so the valves face down. For each valve (one at a time), I sprayed the bejesus out of the top - where the "stick" end of the valve is visible. I checked for drippage on each valve. None had any drips. Brake cleaner came out of the other various holes on the bottom of the head, but not a single drip out of the valves. Indications?

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So you heard the sound before you kicked it? Have checked your jets. Sounds like one fell out. LoL!!

Edited by Brandt233

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Brandt, You have got to be joking....

Replace the cam chain. Check the gears on the kicker shaft, make sure all the teeth are there. Put it back together.

You should have done a leakdown before you took it apart.

Woods riding and 290s = a lot of heat. Do a comp check aswell, rings might be toast.

Edited by charper

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Brandt, You have got to be joking....

Replace the cam chain. Check the gears on the kicker shaft, make sure all the teeth are there. Put it back together.

You should have done a leakdown before you took it apart.

Woods riding and 290s = a lot of heat. Do a comp check aswell, rings might be toast.

Thanks a lot for the info! That is now the next check. So far I'm going to do a new cam chain, new piston and rings. I think the valves are ok for re-use, assuming I shim to spec.

I have a wiseco clutch basket on the bike, where installation required peening of 6 bolts that hold the primary gear on the basket. Thought its possible that one backed out... Just want to rule everything out before the motor goes back in and gets buttoned up.

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the bike is already apart, if it were me, I would replace valves and grind/cut seats before assembly. your already in that neck of the woods anyway, would be cheap insurance for the reliability of the bike.

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