skipping gear.

[GMP]

Pneumatic impact wrench for the clutch and crank pinions is eaisiest. A piece of aluminum or copper in the primary gears with a breaker bar works as well. On the 250/300 the crank pinion is a REVERSE thread, I assume the same on the 200 but never personally had one apart, anyone? The cases split fairly easy with gentle tapping on the crank and countershafts with a soft mallet.

[rupecopp]

Ok, I had to get a flywheel puller in the end. But it's all stripped down now and was fairly easy.

This is where the problem starts, as I can't see anything wrong with it. The gear set seems to be in good condition with no worn or damged teeth.

The shift forks are straight, although there is a very small mark that shouldn't be there near the end. But I can't see this a real problem here either. Altough if I look at where the forks run on the gears one as made an even wear mark around, but the other wear mark is thinner as if only a smaller part of the fork has been touching.

The crank bearings were a bit rough, but not sure if that would be anything to do with it.

[Loosenut]

Go ahead a replace the crank bearing and seals. The hard part is already done.

Mike

[blitz11]

If you have skipping, you need to look at the gear dogs (the protrusions from the side of the gears). If those are worn (i.e., not square with the gear, rounded corners), those gears need to be replaced, as well as the gear into which those dogs go. it doesn't take much wear to get the dogs to disengage. Polished surfaces on the ends of the dogs are an indication.

If you look at the shift forks, look for any wear on the sides of the shift fork which ride in the grooves in the gear. If you see any wear at all, then you know you have gears putting lateral loads on the shift forks. More likely than not, that is the problem.

The OTHER thing it could be would be worn pins on the shift forks (the pin rides in the grooves in the shift drum, see http://www.gofasters.com/index.php?m...ath=65_133_318) or a bad spring / ratchet mechanism on the shift drum itself. If the pins are worn, it could allow enough lateral movement of the shift fork to allow the popping out of gear. However, the reason the pins are worn is likely because the dogs are worn, putting lateral loads on the shift forks, and those pins on the shift forks react against the lateral loads on the fingers.

A weak ratchet mechanism would also allow the shift drum to rotate, allowing the gear dogs to disengage. I'd check that over, too.

[rupecopp]

Originally Posted by blitz11

If you have skipping, you need to look at the gear dogs (the protrusions from the side of the gears). If those are worn (i.e., not square with the gear, rounded corners), those gears need to be replaced, as well as the gear into which those dogs go. it doesn't take much wear to get the dogs to disengage. Polished surfaces on the ends of the dogs are an indication.

If you look at the shift forks, look for any wear on the sides of the shift fork which ride in the grooves in the gear. If you see any wear at all, then you know you have gears putting lateral loads on the shift forks. More likely than not, that is the problem.

The OTHER thing it could be would be worn pins on the shift forks (the pin rides in the grooves in the shift drum, see http://www.gofasters.com/index.php?m...ath=65_133_318) or a bad spring / ratchet mechanism on the shift drum itself. If the pins are worn, it could allow enough lateral movement of the shift fork to allow the popping out of gear. However, the reason the pins are worn is likely because the dogs are worn, putting lateral loads on the shift forks, and those pins on the shift forks react against the lateral loads on the fingers.

A weak ratchet mechanism would also allow the shift drum to rotate, allowing the gear dogs to disengage. I'd check that over, too.

Looking again today at the gears I can see the dogs on secoundary pinion V have worn/damaged corners. And secoundary pinion I that the dogs go into has damage. Am I right in guessing that pinion V is fith gear, and pinion I is first??

As When I got the problem of the horrible clunking, and felt the bike struggling to get in to gear when in third. I had to limp home, but had a few steep little hills to climb which ment I had to go hard in 2nd gear, which was fine. 1st also didn't have a problem, but don't know about fith as didn't want to try to push past 3rd and do more damage. Most of my riding is tight woods stuff so I would hardly ever use fith, mainly 2nd, 3rd, and 4th. So I'm not sure these pinions would cause a problem in 3rd????

As for the forks, yes they do have wear marks on either side of the flat large surface. Not sure what you mean by the gears putting lateral load on them, or how/why this is a problem?

Can't afford to spend loads of cash replacing parts if they are not the problem, but don't want to put it back together and still have the problem.

Thanks

[blitz11]

Uh Oh. I edited in the quotes. Sorry, i don't do much on forums. Hopefully, you can see my response.

Originally Posted by rupecopp

Looking again today at the gears I can see the dogs on secoundary pinion V have worn/damaged corners. And secoundary pinion I that the dogs go into has damage. Am I right in guessing that pinion V is fith gear, and pinion I is first??

Yes, gear V secondary controls the engagement of gear IV and gear I. Secondary gear IV and secondary gear I freewheel unless gear V engages either of them.

Gear VI on the secondary also controls the engagement of secondary Gear II and Gear III. The III/IV gear on the primary works engages the V gear and the VI gear as well.

If secondary gear V has damage, it wouldn't effect gear II. Pinion VI (and its shift fork) would affect gear II and Gear III. How do those pieces look?

If the bike is in gear III, the shift fork is neutral, meaning no load. In gear III, secondary gear VI engages gear III, and primary gear III/IV is held in it central position.

This doesn't look like the V pinion problem.

As When I got the problem of the horrible clunking, and felt the bike struggling to get in to gear when in third. I had to limp home, but had a few steep little hills to climb which ment I had to go hard in 2nd gear, which was fine. 1st also didn't have a problem, but don't know about fith as didn't want to try to push past 3rd and do more damage. Most of my riding is tight woods stuff so I would hardly ever use fith, mainly 2nd, 3rd, and 4th. So I'm not sure these pinions would cause a problem in 3rd????

Did you look at the mechanism which indexes the shift drum? If the shift drum rotates freely, it can cause the gear selector to move. I'd double check this. Things will clunk, but since the drum is controlling the position of the gears, nothing will bind up. slip, (false neutrals), but not bind. If that spring is bad, or the little wheel that rides on the shift star is bad, or the shift star itself is bad, it might explain what you experienced.

As for the forks, yes they do have wear marks on either side of the flat large surface. Not sure what you mean by the gears putting lateral load on them, or how/why this is a problem?

The fork is designed only to slide the gears so that the dogs can be engaged. The dogs are generally undercut a bit so that they stay engaged under load (the load on the chain actually pulls the gears together). If the undercut is gone, side loads from the gears "push" on the shift forks, putting a lateral load on them. This is how they wear or bend. The only lateral force on the shift forks should be when the fork slides the gear on the splined shaft.

Can't afford to spend loads of cash replacing parts if they are not the problem, but don't want to put it back together and still have the problem.

Another thought i had was the condition of the secondary shaft or the sprocket splines are at. Is it possible that the splines on either the shaft or sprocket are shot? if they are on their way out, it could be symptomatic of what you describe.

without seeing pictures, those are my best guesses. if you can post pictures, that might help a great deal.

Thanks

[rupecopp]

Ok to the gearset into a local bike shop and he said the one of the forks needed replacing, and the dogs on third had lost the sharp edge. So it was new third gear and the gear the dogs go into (expensive) or I could get the gears machined (any opinions on this?).

I took the secondary pinion gears off a min ago to look at third and all the dogs look the same to me. A bit of wear but nothing to bad, but the needle bearings on third have had it. 4 needles fell out, and are shattered, and 2 are completly missing? So is this something caused by skipping/clunking gear, or why it was skipping/clunking???

[blitz11]

Originally Posted by rupecopp

Ok to the gearset into a local bike shop and he said the one of the forks needed replacing, and the dogs on third had lost the sharp edge. So it was new third gear and the gear the dogs go into (expensive) or I could get the gears machined (any opinions on this?).

I took the secondary pinion gears off a min ago to look at third and all the dogs look the same to me. A bit of wear but nothing to bad, but the needle bearings on third have had it. 4 needles fell out, and are shattered, and 2 are completly missing? So is this something caused by skipping/clunking gear, or why it was skipping/clunking???

I think we're getting somewhere. I've had gear dogs machined (undercut) before in a "free" yamaha i was given. It worked fine, but I was always conscious of that issue, so i was careful when shifting with that gear combo.

If the pinion on the III gear secondary had bad bearings, the gear would not run perpendicular to the shaft, and this would cause lateral loading on the gear combination. This lateral loading would put force the shift fork to react against it, and thus wear the shift fork. How does the countershaft look? did the bearing failure ruin the shaft?

Also check the secondary pinion (pinion IV) which engages secondary pinion III to engage it. There is some reason that the bearing failed. Perhaps bad dogs on secondary pinion IV forced misalignment with secondary pinion III.

If the shift fork is just worn and not bent, you can build the ends of the shift fork up with some weldmet, and then grind the excess off. Use a good shift fork as a reference. Shift forks aren't that expensive, but if you have access to a welder, you can save yourself some dough. I've done this before, and it's worked fine. (I try to be a mechanic more than a parts replacer.) If it's bent, then you have to replace it.

Good luck.

blitz

[rupecopp]

here is some pics which might help

[blitz11]

Can you use a macro mode on the camera, and put a good shift fork next to a bad one? the focus is soft, and the glare makes it hard to see the shift fork.

thanks.

blitz