Transmission issue

[madass140]

Hello gentlemen and ladies. advice needed. Assembled engine from parts. all good except changing
down usually from 3rd wont select 2nd . I replaced the following to no avail, Complete clutch,shift shaft, everything on the end of the shift drum. I've adjusted the eccentric spring stop bolt below so that the
ratchet arm which rotates the shift drum is correct. Yesterday went for a ride, when cold changing
gears was reasonably ok, but after 30 mins riding in hot weather I could not change gear at all. its as if
the shift drum was frozen. Let it cool down for 7 hrs and was good to go again.
I was thinking that through heat maybe the shift drum had lost any end float it had and locked up.
I havent checked that yet but if it looks like there is no end float then a sharp tap inwards or outwards
on the shift drum may help. Any clues?

 

[madass140]

well just some confirmation. with the engine dead cold, it would shift thru the gears perfectly.
Warmed the engine up by letting it idle for 15 mins to max engine temp. Now wont go thru
the gears.

 

[DogBunny]

Did you center the star wheel between the two pawls of the ratchet arm while in neutral?
If the answer is yes, than you probably have a clutch cable issue in my opinion. Is your clutch pull hard? Try re-routing it, eliminate sharp bends, straighten out the fitting arm where the cable enters the crankcase cover, and if it's an old cable, replace it.
Next, be aware that the engine expands when hot, and you may be able to regain shiftability by lengthening the cable jacket using the adjuster on the perch when the engine is hot.
These are the basics. You will probably get a lot of other opinions and responses, but try these first.

 

[madass140]

I assure you its not a cable issue. "center the star wheel between the two pawls of the ratchet arm while in neutral"
manual says to do this in 3rd gear. However it changes gear perfectly when cold. When hot , wont change.

 

[DogBunny]

I was going by memory, if the manual says to adjust the wheel in third, I believe it.
If you try lengthening the cable sheath with the perch adjuster and get nothing, then your problem needs the help of those smarter than me.

 

[TwoManyXS1Bs]

A few things to consider.
- Cotter pin of middle shift fork. If backwards, will interfere with 3rd entry/exit.
- Excessively worn shiftfork guidebar.
- Shiftfork guidebar inserted too deeply, not retained by the "C" stopper.
- Inner edges of "C" stopper excessively worn.
- Binding neutral plunger.
- Poor tranny lubrication.

Some more ideas in here.

http://www.xs650.com/threads/finding-neutral-while-stopped-and-in-gear.47568/

 

[madass140]

Cotter pin of middle shift fork. If backwards, will interfere with 3rd entry/exit. ( it selects good when cold)
- Excessively worn shiftfork guidebar. ( I would of noticed and replaced this on assembly if needed)
- Shiftfork guidebar inserted too deeply, not retained by the "C" stopper. (I've checked that)
)- Inner edges of "C" stopper excessively worn. ( I replaced the "C" stopper}
- Binding neutral plunger. ( I wondered about that . I need to try and remove it with a small magnet hopefully)
thanks for the tips

 

[TwoManyXS1Bs]

A forum search on "fork cotter" will get you more tranny pics for comparison...

 

[madass140]

the fact that the shifting problem only arises when the engine is hot leaves me to believe that something
is binding due to heat expansion.

 

[TwoManyXS1Bs]

The tranny's mainshaft, countershaft, shiftdrum, and guide bar are all locked to the case at one side, the other side full floating. Allows for case expansion and contraction.

Except for the shift shaft. It's retained by a circlip and large washer, just under the sprocket. If it has insufficient end spacing, it *could* jam. Too much clearance and the shift claw *could* jump out of the starwheel.

I like to shim mine to about 0.016" - 0.020" (0.4mm - 0.5mm) lateral play.

http://www.xs650.com/threads/gear-selector-trouble.51071/

 

[madass140]

Ok. I just removed the bottom case half and inspected the middle fork cotter pin.
It was in the correct way BUT I had replaced the cotter pin and not flattened the
tail end of the cotter pin all the way flat against the shift fork. It was protruding
probably about 1/16" or so out from where it should be which is hammered flat against
the shift fork . Everything else is in order. The end float of the shiftshaft is fine but will
recheck that on assembly. If this cures the problem then I'll be left wondering how the
heat could of affected this. stay tuned

 

[TwoManyXS1Bs]

Just for reference, this thread delves into gear spacing and shims.
Many pics and service bulletins.

http://www.xs650.com/threads/first-gear-issue.49825/

 

[madass140]

update, well before I reassembled the engine I rotated the shift drum after "fixing" the cotter
pin and the issue still remained. It seemed 3rd gear wouldnt engage for some reason,
so I installed another gear cluster and the shift drum seemed to select all gears like it should.
I reassembled the engine and installed it and have had it idling for 15 minutes to heat up as before
Now its moving thru all the gears like it should. Off for a test ride.
8 hours from start to finish (engine running to splitting the cases and engine running again), not as bad as I thought

 

[gggGary]

The Cebu Transcentral Hwy looks like some great riding!

 

[madass140]

The Cebu Transcentral Hwy looks like some great riding!

yes its a sunday haunt for many

 

[madass140]

update, well before I reassembled the engine I rotated the shift drum after "fixing" the cotter
pin and the issue still remained. It seemed 3rd gear wouldnt engage for some reason,
so I installed another gear cluster and the shift drum seemed to select all gears like it should.
I reassembled the engine and installed it and have had it idling for 15 minutes to heat up as before
Now its moving thru all the gears like it should. Off for a test ride.
8 hours from start to finish (engine running to splitting the cases and engine running again), not as bad as I thought

Oh well. that didnt work. 20 min ride , engine heats up, cant change gear. Replaced the following
Complete Clutch
Clutch lever, cable, clutch mechanism in the Left engine cover
Shift shaft
EVERYTHING that can be seen once the clutch is removed,
Complete gear cluster and bearings.
The only thing I havent replaced is the shift fork assembly ( shift drum and forks)

 

[gggGary]

Ouch!

 

[TwoManyXS1Bs]

... cant change gear...

Maybe you could expand on that a little.

Is the shiftshaft frozen?
Does the shiftshaft move a little, only to be stopped by a frozen shiftdrum?
Can it shift with the engine off? Clutch engaged and non-engaged?
Rocking the bike fore/aft have any affect?
More?

 

[madass140]

the shift shaft is not frozen. It turns the shift drum but not all the way for it to engage gear.
I have the bike on blocks rocking the wheel backwards and forwards when attempting to shift.
Its mainly changing down from 3rd to 2nd. But only when its hot.
Clutch in or out makes no difference, when cold it changes fine.

 

[TwoManyXS1Bs]

Very bizarre.
Thoughts, grasping.

Shiftdrum roller bearing.
Shiftfork pins in shiftdrum grooves.
Shiftfork guide bar.
Slider gears jamming on shaft splines (mismatched pre/post '77 parts).
Loss of lubrication due to heat.
Shiftfork bent just enuff to cock a slider, cause it to jam.
Shiftfork bent just enuff to cock it on the guide bar.

The only thing I can think of at the moment is heat-related lubrication.

Thinking...