Topic: 5th gear noise, not quite a grind

[Tim2005]

The inside of that oil pan is ultra clean... suggests to me that it has been apart very recently. I'd check all the gearbox parts against the diagram to see if whoever previously split it either left something out or put it together in the wrong order.

[beaniam]

That'd be the smart thing to do.  It really sucks not having a computer out in my shop, or a printer to print my pdf manual.  Makes things annoying.

Worn dogs. 





That definitely should not be...



Zoom

[beaniam]

http://s257.photobucket.com/albums/hh224/beaniamyota/1978%20cb750/?action=view&current=P1010290.mp4

[beaniam]

Comparing the transmission I got from ebay other than that gear and the dogs, everything else looks the same, the forks don't look bent.  They sit level on a flat surface.  However when I pulled my parts out of the case there was a washer like # 15 in between 14 and 4 on the bottom of this diagram.  http://www.hondachopper.com/engine/diagrams/images/tranny.diagram.gif
Looks like that's not supposed to be there? That's the only thing I've found out of place.

[mystic_1]

Nope, there should not be a thrust washer between gears 14 and 4.  Here's that diagram, posted here for clarity:



Attached below is the fiche for the K8-F3 transmission, you should have 3 x 25mm thrust washers, and 2 x 25x34 thrust washers, so 5 total.

Also attached is a diagram showing the movements of the various gears when you shift.

Hope this helps.

mystic_1

[beaniam]

Thanks.  I'll be dumbfounded if the only reason this thing has been wearing a gear away is because someone put an extra thrust washer in the wrong place.   I'm going to swap in all of the newer less worn transmission parts anyway.

[Old75_ratafe]

http://s257.photobucket.com/albums/hh224/beaniamyota/1978%20cb750/?action=view&current=P1010290.mp4

Ouch

[scottly]

Were all the snap-rings in their grooves properly?

[mystic_1]

http://s257.photobucket.com/albums/hh224/beaniamyota/1978%20cb750/?action=view&current=P1010290.mp4

Ouch

Indeed.  Methinks either your C1 gear or your final drive gear (1 above) is installed backwards, there shouldn't be any play between them, and your final drive gear doesn't seem to align with the final driven gear (2 above) properly.

mystic_1

[beaniam]

how does one know which way to install the c1 gear?  The final drive gear looks identical to me either way it's installed...

[beaniam]

I just realized all that play is probably because the bottom half doesn't have the half moon clips that align the gears where they need to be...  Anyway I replaced the worn gear, worn dogs, and shifter drum.  Kept my old shift forks because the newer ones felt like they were binding.  Put the case back together, ran through the gear while spinning the sprocket and they all seem there.  So basically all I did was remove the thrust washer that shouldn't between those gears and replace worn gears.  I sssuuuurrrreeeee hope that little washer was the source of my problems.

[mystic_1]

how does one know which way to install the c1 gear?  The final drive gear looks identical to me either way it's installed...

If I recall correctly the C1 gear has a more pronounced shoulder on one side than the other.  The higher shoulder should be towards the final drive gear.  If you install it backwards, the two gears will rub together, and I was thinking the mis-positioning could cause the sideways slop you had.

But sounds like this is irrelevant based on your latest post.

On the other hand, having an extra thrust washer between the gears is certainly wrong, any chance it was causing the teeth on the final drive gear to rub on the case or something?  That might account for you noise.

mystic_1

[beaniam]

No sign of rubbing on the case.  I'm pretty sure it was the dogs hitting the gear next to c1.  The holes were badly worn and rounded as well as the dogs.  Hoping that extra washer was pushing the gear just slighty into the dogs and causing it.

[mystic_1]

You know, you're probably right.  There SHOULD be a thrust washer on the other side of C1, between the C1's bushing and the snapring.  #16 in the above diagrams.  I don't see it in this pic:



Possible the thrust washer isn't an extra, but was installed in the wrong place?  That would certainly cause the condition you describe, and I've been trying to figure out how an extra thrust washer could even possibly fit.

mystic_1

[beaniam]

Now I'm going to have to split the case again because I'm not 100% positive I put that back between the bushing and snapring.  At least it's not back in the bike yet.
In the diagram every bushing is marked 15 except for that one which is 16.  Is that a different thickness? 

[mystic_1]

Well, they're different part numbers and different descriptions.  Going off of memory now since my bottom end is back together now, but I believe that the #16 thrust washers have a larger diameter.

Every snapring should have a thrust washer next to it.

BTW, when fitting the bushings, make sure that the oil holes align with the corresponding holes in the shaft.

mystic_1

[beaniam]

mystic it's a good thing you said something.  I split the cases again and sure enough I left that thrust washer out.  I had wondered why the oil hole in the bushing didn't really line up with the one in the shaft.  Now it's in and everything sounds pretty quiet and smooth while spinning and shifting by hand.  Hopefully this weekend I'll get time to get it back in the bike.  I'm really itching to ride this thing, I've owned it for almost a month and rode it for 2 days not being able to enjoy it because of the horrible grinding.

[mystic_1]

Sweet, glad you got it sorted.  Let us know how things turn out.

mystic_1

[beaniam]

Well the transmission and cases are back together with hopefully everything in their proper places this time around.  Still haven't got the engine back in the bike.  Today I did the fork seals (the old ones were in upside down  ), put on my drag bars, rewired the front end and spent some time making everything fit in the small space with the drag bars.







Still trying to figure out what I'm doing with the rear end.  Going solo seat but leaving the suspension alone as it has been lowered by the PO and I'm happy with it.  Some sort of short fender and losing the grab bars/giant marker turn signals.

[beaniam]

Just kinda sat my solo seat on it and bolted the taillight to the side to take a quick ride.  No more 4/5th grinding.  Running a bit rich, gotta adjust the carbs.  Guess I put it back together right!  Now to finish the bike.

I've gotta change that exhaust... it grinds bad when I lean to the right.  Really half to be careful making right turns.

[mystic_1]

No more 4/5th grinding. 

Great news!  Congrats.

mystic_1

[Old75_ratafe]

No more 4/5th grinding. 

Great news!  Congrats.

mystic_1

+1