Will it run with skipped tooth on cam chain?

[FloppyRunner]

Hi all,

Did my valve clearance check today. Still plan to change oil and sync the throttle bodies, but I've completed the valve clearance check and put in new spark plugs. When I started it to make sure all was OK, it seemed to idle lower than it used to. I believe it was 1100-1200 at normal operating temp before, now it's at about 900. I assumed I somehow changed the sync or idle RPM and that the problem would go away with they sync I'm doing tomorrow.

But then I did a quick test drive and discovered I could almost kill the bike by lugging the engine (unlike before), and it SEEMED a little down on power. It also seemed to idle a bit noisier (but again, maybe it's just in my head).

Anywho, thinking back on it, I'm wondering if I may have skipped a tooth on the main gear. I foolishly did NOT mark the chain and sprocket for the main gear. So both camshafts are where they were with respect to the chain, but the main sprocket may not be... So my question is...can the bike run with the main sprocket being one tooth of? Or would the results be much more disastrous and obvious?

 

[greg]

Did you take the timing chain off?

FWIW when I changed the belt on my car I had an issue with power loss and stalling, the air pipe was loose and so the MAF was sending incorrect data to the ECU. It might be worth checking your air box is on properly, and also check the TPS is reading correctly in the diagnostic menu.

 

[Marthy]

Skipping a tooth on a cam is roughly 12 degree, you will know! And naa... it won't run great and would most than likely hear some piston/valve banging noise.

Sent from my SAMSUNG-SGH-I337 using Tapatalk

 

[FloppyRunner]

I consider this all good news; other problems are likely less labor intensive than going back in to fix the timing chain...haha. I also now feel foolish because I remember how small the main sprocket was; of course one tooth change would be a rather huge difference.

No, I did not take the timing chain off. Here's what happened. I only took the exhaust camshaft off because for some reason only my exhaust valves were out of whack (and I suppose there lies another potential problem: me screwing up the shim job). I went to put the cam back in and made sure both cams were aligned with the marks I made on the chain. Then I went to turn the motor a couple times before checking clearances again as suggested in my manual, but the chain did not properly catch the intake cam and it became off one tooth (the tensioner was not in at this point which may have been my mistake). I, perhaps foolishly, turned the motor counter-clockwise just a bit at that point to give myself some slack to match up the two cams with respect to the chain. Now that I think about it, there should have been no skipped tooth...

I will check the airbox and things, and let you all know how it goes after that and the sync and oil change. Thanks again!

 

[FinalImpact]

As best I can tell, the cam gears have 34 teeth so the crank would have 17.

Cam off one:
360° / 34t = 10.58° per tooth

Crank off one:
360° / 17t = 21.17° per tooth

That said, if it were the crank drive gear being 21° off, you'd have a heck of time getting it started and the exhaust would sound horrible.
JWAG - w/the cam timing off at the crank:
- Advanced one tooth it may not collide piston to valves.
- Retarded one tooth and I'm pretty sure it would collide.

The crank being smaller its much easier to move it (skip) once the chain has slack. In short, if you don't find something obvious, you might have to pull the two covers and check it. On another note seeings how you've already ran it and ridden it, do a compression test on one hole (although it should sound very different when cranking) and see what the compression is.

When you made corrections to the exhaust, was it to add clearance or take it away?

 

[Motogiro]

I would go back to opening the bike and resetting the cam timing. The alternative could be a major failure.

 

[FloppyRunner]

I wanted to update you guys on this.

To answer FinalImpact's question, I added clearance (decreased shim height). I re-measured when the cam was put back in and everything should be good in that regard.

I had a terrible time trying to TB sync last night. The vacuum levels were all very low, although I did eventually get them all even. The bike still rides the same, with a stumbling on lugging (which wasn't there before).

I'm thinking I screwed up something putting it back together: knocked some vacuum hose somewhere, maybe didn't do one of the plugs correctly, etc... I probably won't be able to touch it until later this week or the weekend though. I'll know what kind of mileage I'm getting when I fill up tomorrow morning.

 

[Motogiro]

I wanted to update you guys on this.

To answer FinalImpact's question, I added clearance (decreased shim height). I re-measured when the cam was put back in and everything should be good in that regard.

I had a terrible time trying to TB sync last night. The vacuum levels were all very low, although I did eventually get them all even. The bike still rides the same, with a stumbling on lugging (which wasn't there before).

I'm thinking I screwed up something putting it back together: knocked some vacuum hose somewhere, maybe didn't do one of the plugs correctly, etc... I probably won't be able to touch it until later this week or the weekend though. I'll know what kind of mileage I'm getting when I fill up tomorrow morning.

Do a compression check! If you kissed a valve you'll see the loss. If compression is good check the cam alignment.

 

[FinalImpact]

I wanted to update you guys on this.

To answer FinalImpact's question, I added clearance (decreased shim height). I re-measured when the cam was put back in and everything should be good in that regard.

I had a terrible time trying to TB sync last night. The vacuum levels were all very low, although I did eventually get them all even. The bike still rides the same, with a stumbling on lugging (which wasn't there before).

I'm thinking I screwed up something putting it back together: knocked some vacuum hose somewhere, maybe didn't do one of the plugs correctly, etc... I probably won't be able to touch it until later this week or the weekend though. I'll know what kind of mileage I'm getting when I fill up tomorrow morning.

Excessive lash (too much clearance) will impact valve timing making it late on effected cylinders and be Noisy. Think of a sound like TAP TAP TAP TAP at 1/2 engine speed.

NO LASH (no or reduced clearance) , means the valve opens early and will burn. It WILL NOT make a TAP TAP TAP sound as it has no clearance.

With reference to running: The engine will run but the manifold vacuum (all 4 cylinders into one vacuum port) would be erratic. This would make the idle unstable and lumpy as well as making TB sync near impossible. It why lash is done before the TB sync.

 

[FloppyRunner]

Oh balls. Guess I likely won't be riding Devil's Highway this weekend... I'll update you guys when I get the time to dig that deep again. I thought I checked the final measurements, but maybe I screwed something up. It is afterall my first time doing valve clearances on a motor of any kind.

 

[markgm]

Perhaps it's too obvious, but did you try adjusting the idle speed?

 

[FloppyRunner]

Yup. Worth asking though, haha.

 

[FloppyRunner]

I'm stumped. I checked the clearances again and best as I can tell, they are good. But I THINK it still seems down on power. And I could only TB sync to about 12.5mm hg, which seems excessively low. I know that value is less important than the fact that they all have the SAME value, but still.

I might throw in the towel and take it to somebody to fix.

 

[FinalImpact]

I'm stumped. I checked the clearances again and best as I can tell, they are good. But I THINK it still seems down on power. And I could only TB sync to about 12.5mm hg, which seems excessively low. I know that value is less important than the fact that they all have the SAME value, but still.

I might throw in the towel and take it to somebody to fix.

Vacuum is idle speed dependent. What is it at now?
Also - what did you gap the new plugs at? Excessive gap is a NO GO! You must not exceed spec on this system or misfires, idle speed, acceleration will all be erratic.

Gap is 0.24 - 0.28"
See this thread for details: http://www.600riders.com/forum/fz6-...tion-cure-bad-vibrations-spark-plug-caps.html

 

[TownsendsFJR1300]

As noted above, pull the valve cover and the rt side chain cover and simply re-check the marks turning CLOCKWISE ONLY. Confirm all the marks are dead on.

On the FJR, someone had a tooth off(similar to your situation) and it still ran, (just crappy-like yours).

I strongly suspect the chain /cams/ crank is still off one.


If you have to move a tooth:

Plastic ZIP TIE the cam chain to the cam sprocket(s) so it CANNOT MOVE.

Re the crank, ZIP TIE thru the chain just atop the crank sprocket to keep it from moving off the sprocket. Now you can remove the CCT, and loosen the cam (thats off) and readjust it..

Once the marks are KNOWN to be correct, check valve clearances again. A bent valve will show a very large gap as it isn't closing fully..

We did recently have a member with an engine a tooth off, piss poor performance but it didn't hurt anything.

 

[FloppyRunner]

Alright, I'm a stubborn SOB, so I'll give it another shot this coming weekend, if not before.

First will be check the plug gap. After the first time I changed plugs, I haven't even been measuring gap; I've just assume they're correct from the factory (I know, I know, so much for "I'm stumped", sorry...).

Next I will take off BOTH the valve cover and timing chain gear cover...thing... This last go around I only took off the valve cover to avoid having to buy another gasket for the timing chain gear cover. But a cover with a leaky gasket is better than a bike that runs funny so I'll give it a try. After this weekend, if it's still the same I think it's off to a professional...

Right now, the idle somewhere around 1200 or so.

Thanks again guys, I'll dig up this thread from the dead after this weekend at the latest to document the resolution (or non-resolution...).

 

[TownsendsFJR1300]

If you didn't pull the side cover off last time, that check would have been useless (it could have been off down there). The mark on the crankshaft ignition rotor HAS TO BE LINED UP with the mark on the block

Also, IMPORTANT, make sure when setting marks, moving teeth, etc, the top run of the chain is taught and the front run is taught. All chain slop should be at the rear where the cam chain tensioner will take it up.

 

[FinalImpact]

If you didn't pull the side cover off last time, that check would have been useless (it could have been off down there). The mark on the crankshaft ignition rotor HAS TO BE LINED UP with the mark on the block

Also, IMPORTANT, make sure when setting marks, moving teeth, etc, the top run of the chain is taught and the front run is taught. All chain slop should be at the rear where the cam chain tensioner will take it up.

Not entirely true - the center plug and the side plug for checking the timing can be used. See the downward arrow by the pickup coil - that will do it. Shine a light in and take a look! Couple that with TDC and you're golden!
>>

 

[TownsendsFJR1300]

The aliignment mark on the engine is on the MATING surface (page 5-10, 07-09 Yamaha manual). The cover itself is over it.. Unless something else is sticking out, not shown in the manual, I'm not seeing it.

I just pulled that plug out on mine and I didn't see any definite mark to line up the rotor with. Maybe I'm missing it.

In the event he has to adjust the chain, he still CANNOT zip tie (if he chooses to go that route) the chain to the crankshaft sprocket with that cover on.


**With that said, the potential of being a tooth off, to save a $10.00 gasket, to see that the chain is taught in the correct positions, both cam marks dead on, etc, IMO, its just NOT worth chancing serious damage to the engine.

 

[FinalImpact]

The aliignment mark on the engine is on the MATING surface (page 5-10, 07-09 Yamaha manual). The cover itself is over it.. Unless something else is sticking out, not shown in the manual, I'm not seeing it.

I just pulled that plug out on mine and I didn't see any definite mark to line up the rotor with. Maybe I'm missing it.

In the event he has to adjust the chain, he still CANNOT zip tie (if he chooses to go that route) the chain to the crankshaft sprocket with that cover on.


**With that said, the potential of being a tooth off, to save a $10.00 gasket, to see that the chain is taught in the correct positions, both cam marks dead on, etc, IMO, its just NOT worth chancing serious damage to the engine.

We agree and I'd have the cover off too! Its cheap insurance that nothing is missed. However - if you drop a dial indicator into Cyl # 1 you get TDC. Granted not everyone has one but some of us do! :thumbup:

FWIW: timing cover has been off mine a couple times and I resealed it with no ill effects. I have new gasket for the "final time" when I'm done messing with the timing...