Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Unable to engage any gear.

Unable to engage any gear.

Post Wed Jun 07, 2017 11:47 pm

Posts: 1729
Just trying the flathead, and for no reason I can understand, I'm unable to engage any gear or move the lever full range. This wasn't a problem before.

The only thing I can think of as a change, is that I've filled the transmission (which didn't have any lube in it before). I used 90W transmission oil, because that's what I use for all my racing bikes. Could that be the problem, causing a hydraulic lock in the selector mechanism or preventing the gears sliding?
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Thu Jun 08, 2017 2:37 pm
Pa Site Admin

Posts: 6034
Location: Ohio USA

90w is way to heavy. 50w is what you should be using. However, that is not the reason for your shifting problems. There are dozens of reasons whay you may not be able to get a gear. My first thought is something came loose, such as a shifter fork. You may need to remove the gearbox from the bike and open it up for a good look see through, starting from mainshaft endplay and all the way out through the standard rebuild spec checking.

Post Thu Jun 08, 2017 3:57 pm
GuS

Posts: 408
Location: Bergen, Norway
Agree with Pa.
Nothing should be able to block the drum action unless something came loose inside.
All outside the trans case, you should be able to eliminate by visual inspection.
Did you remember the lock pin for the drum shaft?
The shifter fork shaft shall be locked in place by the little pin in the sprocket cover. Assume you got that one under control?

Can you get the top lid off for a first inspection?
GuS

Post Thu Jun 08, 2017 5:43 pm

Posts: 319
Location: Ohio
Can you get it into gear without the engine running? If so, it may be a clutch problem.

Post Thu Jun 08, 2017 5:56 pm

Posts: 1687
Location: Interlaken, NY USA

Don't forget that the viscosity of SAE 50w engine oil is approximately the same as SAE 90w gear oil. See chart in
link:
http://www.doolittleoil.com/faq/viscosi ... so-or-agma
DD

Post Thu Jun 08, 2017 10:19 pm

Posts: 1189
Location: Ojo Caliente,NM,USA
Frankenstein wrote:
Don't forget that the viscosity of SAE 50w engine oil is approximately the same as SAE 90w gear oil. See chart in
link:
http://www.doolittleoil.com/faq/viscosi ... so-or-agma
DD

I sprung a monumental oil leak on my old sporty stroker in northern New Mexico in the late sixtys. Nobody had any 50 or 60 wt oil up there so I ran 90wt from there to Albuquerque where i could get parts and oil. other than making it stink real bad didn't seem to hurt anything.
Dusty

Post Thu Jun 08, 2017 11:32 pm

Posts: 1729
I didn't assemble this gearbox, so I can't answer questions about what's inside it. It won't engage any gear, running or not, even with the clutch dismantled.

I also suspect some kind of mechanical failure of the selector mechanism.

The next few weeks are a very busy period for me, so it looks as though this bike has missed the racing season. I have other projects I want to finish and I simply can't spare the time for an investigation like this, just now.

I already have plans for the next version of this bike, involving new barrels (ported and relieved), and a 2-bolt gearbox and narrow clutch, so I'll move on to that when time allows
Shoot, a man could have a good weekend in Dallas with all that stuff...


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