Trouble setting timing, exhaust cam lobe hits bucket and moves!

[burning1]

Edit: Dupe

[burning1]

By the way... I should clarify... It looks like your timing is off by 2 links, not one. I usually think of links in terms of side-plates. So... You need to rotate the camshaft forward by 2 teeth.

[utgunslinger13]

Burning1,

I think I'm following you now.  When I move the exhaust cam forward 2 links, I don't have to have the crankshaft at TDC so I could theoretically have it so neither lobes hit and when I move it forward 2 links it will still be in correct relation to the crank correct?

Am I on the same page now?


***EDIT*** Just out of curiosity, what effect would it have on the bike by riding it with the timing set like this?  I know nothing is hitting as I've rotated the engine as it sits multiple times, but I don't fully understand the effect of "retarding/advacncing" it like this?

Please note I'm not saying I am riding it as it is, I'm curious in a theoretical way!

[burning1]

Yes, exactly.

In fact, you're a little ahead of me. I hadn't even thought of the idea of rotating the crank so that the exhaust lobes were off the cams. That would have made things much easier when I did it.

[burning1]

***EDIT*** Just out of curiosity, what effect would it have on the bike by riding it with the timing set like this?  I know nothing is hitting as I've rotated the engine as it sits multiple times, but I don't fully understand the effect of "retarding/advacncing" it like this?

Your volumetric efficiency would go to shaZam!. Basically, your exhaust wouldn't be open during the first 15-20 degrees of the exhaust stroke, and it would stay open during the first 15-20 degrees of intake stroke... Then, the intake would stay open during part of the compression stroke.

So basically, exhaust wouldn't be pushed out very efficiently. Then, you'd be slow to start pulling in fresh air. And some of that air would be pushed back out through the carbs. It might be run, but your fueling would be all off, and you'd have horrible power.

On some cars, the timing is run off of the cams, so it could also cause the ignition timing to be too far advanced, or too far retarded, causing further problems.

[burning1]

Also... On an interference engine (a high compression engine, where the piston at top dead center will hit an open cam,) having the timing *too* far off could cause valve damage. The GS is fairly low compression and runs with a lot of clearance, so this is less likely to be an issue. Some engines are tuned with so much compression that the piston has small cutouts for the valves.

Another thing that could happen... If your intake and exhaust camshafts are badly misaligned, the valves could hit each other. In practice, I doubt that would happen on the GS unless you really messed up the timing (as a guess, by 45 degrees or more?)

[utgunslinger13]

I didn't pay much attention while disassembling them but I wonder if they were off before and this was the cause of it having a horrible time accelerating?  The Buddha and I were working on getting some slides with 1.5 holes plugged to slow the slide opening because it was falling on its face when I opened the throttle quickly.  It would eventually accelerate, but slowly.

Thanks for all your input and helping me walk through this in my head Burning1

[burning1]

It could be part of the problem. Bad valve timing would certainly affect fueling. With that said, I'm a FI guy, not a carb guy.

[the mole]

I'm trying to remember how it went when I did this...i don't remember having your problem.
I'm thinking that the trick might be to have the crank at the right position, then get the exhaust cam tightened down (don't worry about the intake), and turn it to the right position and then engage the chain on the sprocket. Now you've got the exhaust cam and the crank in the right relationship. Then you position the intake cam by counting 18 pins between the '2' mark on the EX cam and the '3' mark on the IN cam and engage the chain with it. Note that you count the pin at each mark, so there's only 17 'spaces' between them. Just checking, you have got the CC tensioner out haven't you?

TIP: Replacing the CC tensioner is a PITA if you try and hold the tensioner retracted with a screwdriver as the Haynes manual says. You need three hands and there isn't room for them all. What I did was cut a strip off a tin can that was just wide enough to engage with the slots in the CCT housing. Then, I wound the tensioner back with a screwdriver, held it in with one hand and removed the screwdriver. Then slid my strip of tin in the slot and engaged with the tensioner. It locked the tensioner in place, and then it was easy to install. once in and bolted, just pull the tin strip out!

And valve timing is critical to correct performance. I had a VW Kombi engine rebuilt years ago, and afterwards it ran smoothly but was (even more than usual!) lacking in power. It would start to lose speed if it caught sight of a hill a mile away. After spending hours tuning, rebuilding carb etc etc, the problem was the cam was installed one tooth retarded.

[burning1]

If you're going to pull the cams as part of a valve adjustment, your best bet is to align the crankshaft to the timing marks, and actually mark the alignment of the cam-chain and sprockets using white-out, or a similar marking agent.

[the mole]

What he said^, the Haynes manual mentions that too.

[utgunslinger13]

Well I got it set correctly last night!  I tried to move the sprocket in relation to the crank as Burnin1 mentioned but I turned it 2 links the wrong direction! lol  So I went ahead and took it off, and when I was lining the number "1" mark up I turned it about 5 degrees below parrallel.  What this did was take out the slack (what little there actually is) between the crank and the exhaust cam shaft and prevented the cam shaft from turning when I tightened it down!

After buttoning it back up and going for a ride, the hesitation problem is gone and she rides like a dream!  I'm guessing when I originally set the timing after the rebuild I had it off by a link or 2 and that was why it was running poorly.

Thanks for all your help!

[burning1]

I'm glad to hear you got it worked out, and resolved a performance problem in the process!

[the mole]

I'm glad to hear you got it worked out, and resolved a performance problem in the process!

+1

[Allen]

Good job, so being 1-2 tooth off it still ran and gave you power? Can you decribe how it feels being off by a tooth or two? thanks.

[utgunslinger13]

It would idle just ok, and when I would crack open the throttle quickly it would take a second or 2 before it would accelerate.  The acceleration was very week but I could still move the bike.  It was very similar to lean conditions.