Transmission guru's please explain this ?????

Andy86
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Andy86 5/29/2016 4:01am
5/29/2016 4:01am
outbackmytrack wrote:
Have you looked at the thrust washer between pressure plate and clutch basket? Look for any scoring. You can move the shift drum by hand with...

Have you looked at the thrust washer between pressure plate and clutch basket? Look for any scoring.
You can move the shift drum by hand with the clutch removed, I would try duplicating the problem on the stand, turning the rear wheel to help engage the inner trans gears with the star, if you can get it to lock again the problem is inside, if not maybe clutch/thrust/primary gear?
Tricky problems suck, I've fixed many.
Yep the thrust washer behind the clutch basket and clutch hub boss both got replaced, i'll try what you said about trying to duplicate the problem on the bench

I know you signed up to the forum just to try and help me with my problem, so thank you very much bro its appreciated very kind of you indeed
triplex
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triplex 5/29/2016 11:24am
5/29/2016 11:24am
It sounds like you have a gear installed backwards. Most likely the first gear against either the right or left cases on the countershaft.
Andy86
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Andy86 5/29/2016 1:04pm
5/29/2016 1:04pm
triplex wrote:
It sounds like you have a gear installed backwards. Most likely the first gear against either the right or left cases on the countershaft.
Its physically impossible to install 1st gear on this transmission backwards
Andy86
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Andy86 5/29/2016 1:37pm
5/29/2016 1:37pm
outbackmytrack wrote:
Andy, I have built many of those engines working at a Yamaha dealership 1986-92. Currently going on 27 years experience and I've seen problems like this...

Andy, I have built many of those engines working at a Yamaha dealership 1986-92.
Currently going on 27 years experience and I've seen problems like this, were everyone in the shop gave up and I kept looking and figured it out.
Every time it was something assembled wrong. Your bike shifted fine before someone rebuilt transmission.
Very easy to make mistake with Trans if everything was removed and not replaced at the same time piece for piece.
Of course you want to check the parts behind the clutch assembly first, but the shift drum STAR does not come off on the 87 model so it can't be that it is misaligned.
My best guess with all your testing notes is that a washer in the trans is in the wrong place, or a gear you replaced has one tooth more from the wrong year, but you'll need all the old parts to compare what went sideways.
It's strange the clutch seems to make the problem happen, but your clue is it locks up the shift shaft, that is from the drum getting locked up inside the engine.
If any of the Trans end washers get mixed up it can cause your problem, also if the shift forks on the longer shaft are reversed this kind of problem can occur.
It is not a worn gear dog, worn parts slip, not usually lock up, don't buy any more parts until you disassemble engine, it takes 1 hour to have engine on bench, you spent way more that that already with research.
outback ? the bit you mentioned about the shift forks being reversed ?

When i first put the engine back together the transmission was binding the counter shaft would only turn so far so i took it apart and reversed the two shift forks on the same longer shaft shift fork 1 and 3

I have the picture i took before i put it back together in the picture i have shift fork number 3 installed like it should be according to the manual and parts diagram but when i added yamabond and put the cases together the transmission was binding, the countershaft would not spin freely

So i quickly took it back apart and flipped shift fork 1 and 3 around and put it back together and the transmission worked perfectly shifting through all gears on the bench and the countershaft spinning freely

So it looks like the shifts forks are reversed but why would the transmission be binding when i first installed the shift forks the right way according to the manual

I am only going to know once i split it and see which way the shift forks are installed, but even if they are in the wrong way now the tansmission was binding up real bad with forks installed the other way around

Pic below of how the forks were installed when the transmission was binding really bad ( forks the right way according to the manual )

Thoughts opinions anyone especially outback ?



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triplex
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triplex 5/29/2016 3:14pm
5/29/2016 3:14pm
Every transmission I've ever seen with the shift forks swapped locks up. If it shifts on the bench with the shift forks swapped, I would suggest a few things. Possibly the wrong shift fork(s)/gear(s) or a gear is put on the shaft incorrectly. Just because it's locking in first gear, don't assume it is only first gear that is the cause. It could be a different gear that is meshing incorrectly when shifted into 1st.
Underground 5/29/2016 3:49pm
5/29/2016 3:49pm
triplex wrote:
Every transmission I've ever seen with the shift forks swapped locks up. If it shifts on the bench with the shift forks swapped, I would suggest...
Every transmission I've ever seen with the shift forks swapped locks up. If it shifts on the bench with the shift forks swapped, I would suggest a few things. Possibly the wrong shift fork(s)/gear(s) or a gear is put on the shaft incorrectly. Just because it's locking in first gear, don't assume it is only first gear that is the cause. It could be a different gear that is meshing incorrectly when shifted into 1st.
This^^^^.
I had my 89 CR125 start jumping out of 1st when I was an apprentice and this being my 1st gearbox job I just ordered both new 1st gears, stripped and replaced them when they turned up. Was still jumping out of 1st and with no time left to get it apart and other parts ordered, I had to race my first SX with no 1st gear. No biggy except for when I crashed at base of the big table I couldn't ride up it cause it kept jumping out so had to go around. Stripped it after and had a good look this time and found rounded dogs on 3rd gears I think and a shift fork with rub marks and slightly bent when compared to the new one. Good lesson learned right there. Genuine manuals sometimes have pictures of gear flows or drive through the gear clusters to help with determining a gear problem as such.
Anyway by the sounds I think that you have issues with the shift forks incorrectly fitted. Possibly thrust washers also. The Clymer manuals are pretty good but they can be a bit vague on those key issues some times. If you can get a genuine fiche or parts diagram for your exact model, they generally have the dimensions of the washers next to the part number in description and sometimes markings for shift forks to help identify loose parts. Good luck and keep us posted on your fix. Sounds like there's a few minds grinding over the issue.
Underground 5/29/2016 3:58pm
5/29/2016 3:58pm
Here's a link to an online parts diagram (and not H Jacks) that lists a few dimensions. No marking for shift forks though. An older micro fiche might show extra information if you find one and a reader to view it.
Transmission exploded diagram
Shift drum and forks
Andy86
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Andy86 5/29/2016 4:33pm
5/29/2016 4:33pm
Cheers lads that does help but i won't know until i split, im waiting for the crankcase splitter tool

I'll be happy if it is the shift forks the wrong way round

I have also got the genuine yamaha service manual on the way

But then i have still got to figure out why the transmission was binding the first time i put it together with the shift forks the other way round as it meant to be (that's if the shift forks are the wrong way round when i take it apart otherwise it's back to square one)

Once i put it back together i'll do it without gasket cement just to make sure everything is right then take it back apart to apply the yamabond

Plus i still have to find two new shift forks because they are probably trashed if they was installed the wrong way and like most of the parts for my bike they are discontinued

I really appreciate everybody's help and input you guys at vital are all awesome thanks for everybody's time

And i will update the thread once i figure out the issue
Underground 5/29/2016 4:45pm
5/29/2016 4:45pm
Could be as simple as the shift drum wasn't sitting all the way home or the like the first time.
p.s. 4 strokes for da win!
Andy86
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Andy86 5/29/2016 5:10pm
5/29/2016 5:10pm
Underground wrote:
Could be as simple as the shift drum wasn't sitting all the way home or the like the first time.
p.s. 4 strokes for da win!
Imo they sound awful and they will never beat a 2 stroke for the smell but that's just my opinion 4 strokes are fast but they don't make you smile like the joker in the batman

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