Jumping time

Just added stage 2 cams. When pulling the stock cams out, both the intake and exhaust appeared to be out 180. The bike ran though(approx. 50 hours). When installing the new cams, we put them back per the Owners Manual. We adjusted the intake shims, as they we're off by .015. .145. The exhaust was ok at .160.

The first try and the bike ran rough, and jumped time after I tried to restart it. We had released the chain tensioner, so no reason to think it would do this.

We pulled the cover off, and found the timing was off tdc. Readjusted, assmbled., and kicked the bike. It ran sweet. I shut off the bike, and let it cool. Went to rekick, and it jumped time again (kick starter is very tight at the top, and then goes down smoothly).

Questions: Could a bike run if it was 180 degrees off (both cams). The assumption, at this point, is the Owners manual is wrong, b/c the bike ran for approx. 50 hours fine. So I'm thinking about putting them back. The question is, what is causing the bike to jump time. The chain seems tight after releasing the tensioner. I did check the tensioner (after the second jump, and there was approx. 1/8 to 1/4 more of a turn. Would that do it?

Just added stage 2 cams. When pulling the stock cams out, both the intake and exhaust appeared to be out 180. The bike ran though(approx. 50 hours). When installing the new cams, we put them back per the Owners Manual. We adjusted the intake shims, as they we're off by .015. .145. The exhaust was ok at .160.

The first try and the bike ran rough, and jumped time after I tried to restart it. We had released the chain tensioner, so no reason to think it would do this.

We pulled the cover off, and found the timing was off tdc. Readjusted, assmbled., and kicked the bike. It ran sweet. I shut off the bike, and let it cool. Went to rekick, and it jumped time again (kick starter is very tight at the top, and then goes down smoothly).

Questions: Could a bike run if it was 180 degrees off (both cams). The assumption, at this point, is the Owners manual is wrong, b/c the bike ran for approx. 50 hours fine. So I'm thinking about putting them back. The question is, what is causing the bike to jump time. The chain seems tight after releasing the tensioner. I did check the tensioner (after the second jump, and there was approx. 1/8 to 1/4 more of a turn. Would that do it?

Did you install a new timing chain with the new cams? I would replace the timeing chain if not. If the bike is jumping timing I would get a new timing chain tensioner as well though they rarley go bad. What year is the bike by the way? Take some pics of the timing marks so we can see exactly where you have the timing marks at. :ride:

Did you properly torque the cam caps to 7.2 ft. pounds? Before releasing the chain tensioner, did you try to twist the cams back and forth a little by hand to make sure they aren't binding?

No such thing as the cams being 180 degrees out of time. If you rotated the crank one rotation you would have found the cams at the correct timing since the cams rotate at half the speed of the crank. Since the ignition fires every rotation of the crank (called a wasted spark), you can set the cams correctly at TDC, or you can set them to be "180 degrees off" and it is still timed correctly.

As for it jumping time, which cam is it jumping time on? Make sure that you didn't over torque the cam caps and cause one (or both) of the cams to seize momentarily. Other than that, either your cam chain is kinked from old age, or you have a problem with the tensioner. How old is the cam chain?

No such thing as the cams being 180 degrees out of time. If you rotated the crank one rotation you would have found the cams at the correct timing since the cams rotate at half the speed of the crank. Since the ignition fires every rotation of the crank (called a wasted spark), you can set the cams correctly at TDC, or you can set them to be "180 degrees off" and it is still timed correctly.

Cool, thanks.

As for it jumping time, which cam is it jumping time on? Make sure that you didn't over torque the cam caps and cause one (or both) of the cams to seize momentarily. Other than that, either your cam chain is kinked from old age, or you have a problem with the tensioner. How old is the cam chain?

approx. 70 hours.

Did you properly torque the cam caps to 7.2 ft. pounds? Before releasing the chain tensioner, did you try to twist the cams back and forth a little by hand to make sure they aren't binding?

This is the leading suspect, I think they were overtightened. Didn't have a torque wrench for 7.2 lbs last night. Guessing the theory is after it heated up, and cooled down (expansion/contraction), the housing binded causing the timing jump. I'll post up later tonight.

This is the leading suspect, I think they were overtightened. Didn't have a torque wrench for 7.2 lbs last night. Guessing the theory is after it heated up, and cooled down (expansion/contraction), the housing binded causing the timing jump. I'll post up later tonight.

Pull off the cam caps, if there is scoring on the cam journals then you overtightened the cam caps. With 70 hours on the cam chain, you should probably get a new one. They stretch fast and a cheap to replace, especially when compared to the damage that is caused by running a stretched out cam chain over time.

This is the leading suspect, I think they were overtightened. Didn't have a torque wrench for 7.2 lbs last night. Guessing the theory is after it heated up, and cooled down (expansion/contraction), the housing binded causing the timing jump. I'll post up later tonight.

Ok, I got it. Forgot to scheck the torque on the intake, but the cam was off by a tooth. The exhaust was ok. I checked the torque setting on the exhaust and it was approx. 2 lbs. I retorquethe exhaust and intake. When I set the tensioner, I gave it the extra 1/8 turn (good to know on the replacment of the chain kj).

The bike started up. It started 5 times and didn't jump. So they were under torqued! Thanks for catching the torque setting as that seems to be the culpritt.

Ok, I got it. Forgot to scheck the torque on the intake, but the cam was off by a tooth. The exhaust was ok. I checked the torque setting on the exhaust and it was approx. 2 lbs. I retorquethe exhaust and intake. When I set the tensioner, I gave it the extra 1/8 turn (good to know on the replacment of the chain kj).

The bike started up. It started 5 times and didn't jump. So they were under torqued! Thanks for catching the torque setting as that seems to be the culpritt.

I would advise against going 1/8 turn past the proper torque setting. Personally I feel that the torque listed for those bolts is on the higher end, since Yamaha uses tighter cam journal tolerances than all of the other brands, I have seen many people screw up their heads without even overtightening them. I tend to run them at 7 lb-ft of torque instead of 7.2 lb-ft.

I would advise against going 1/8 turn past the proper torque setting. Personally I feel that the torque listed for those bolts is on the higher end, since Yamaha uses tighter cam journal tolerances than all of the other brands, I have seen many people screw up their heads without even overtightening them. I tend to run them at 7 lb-ft of torque instead of 7.2 lb-ft.

1/8th turn was on the chain tensioner, not the cam housing.

1/8th turn was on the chain tensioner, not the cam housing.

Oops, I'm an idiot, I miss read that.

You NEED a new cam chain...STAT.

Oops, I'm an idiot, I miss read that.

Yeaaah, I've read your posts, I dont think so! :ride:

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