Gear Shifting Issues, Case cleaning Question, Non Running 75

[Colinmc21]

So to be brief, I bought a non running 75' with 8k miles. When I bought it I knew it was going to be a project because the bike was stuck in gear and the clutch was non functioning.

I have disassembled a lot of the bike, including the clutch assembly but I have not removed the engine or opened the case in any way. The clutch issue was pretty straightforward, the screws had been over tightened and the plates came out of the basket frozen together. I should mention I drained the oil from the case, there appears to be a lot of sludge at the base of the case. After the clutch was out I attempted to thoroughly check the gear shift assembly.

All the exterior mechanics are fine, everything is working as it should outside of the case. Where it didn't shift much of at all before it now shifts pretty good in certain situations. However, it probably shifts into gear about half the time from neutral to first and neutral to second right now when manipulating the shifter and the clutch and drive axles. Half the time it will go fine, the other half it will not go into gear. From second through fourth is smooth up and down. No issues there, and then fourth to fifth is a bit tricky. Oddly enough first to second bypassing neutral seems fine too.

Based on what the previous owner told me, it seems somewhat likely there could have been very very old oil in there before I drained it. Everything does work, just with a bit of effort. I'm wondering if this is likely an engine sludge issue based on the old oil gumming up the gears? Could I check anything else?

I'm trying not to open the case or disassemble the engine any further if at all possible. What would everyone recommend? Some type of solvent or cleaner through the case? I've seen a lot of people recommend kerosene. Should I consider any other likely problems here?

 

[Jim]

I'm trying not to open the case or disassemble the engine any further if at all possible. What would everyone recommend? Some type of solvent or cleaner through the case? I've seen a lot of people recommend kerosene.

My opinion..... if it's gonna be pretty easy to make it run, put it back together and do exactly that. Run it and see if it'll shift OK.

As far as flushing, again just my opinion. Get the cheapest 20W-50 oil you can find. Put 20-50 miles on it and drain it while it's nice and hot. If everything's working good, fresh oil and run it again. Keep looking at the oil. I have a long skinny turkey baster around here somewhere just for that. Go again for 250-500 miles or 'till the oil looks nasty... whichever comes first. Don't forget the filters now and at every oil change.

 

[5twins]

Yes, it should shift better once running and all the shafts are spinning. They don't shift all that well "at rest".

 

[Muckroot]

Yes, it should shift better once running and all the shafts are spinning. They don't shift all that well "at rest".

Agreed. not sure what the case is with newer bikes but on these older bikes the transmission gears have to cycle a couple rotations before they can shift into a new gear. The gears in the transmission don't all have the same tooth counts, and because of this they don't line up most of the time. As the teeth of the gears rotate they line up sporadically with the adjacent gears, allowing an opportunity to shift. the best way to simulate this is to grab the clutch basket and spin it either way as quick as you can by hand and attempt to shift either up or down one gear with the shift lever. if the bike shifts correctly most tries, I'd say... 3/5, then you're best bet is to do as Jim says and really give it a good break in and keep a close eye on your oil. If you still have trouble or if you can't get the gearbox to shift properly at least half the time by hand then you should consider opening the case up and cleaning everything out with cleaner and having a real good eyeball at the tranny gears, bearings, and shift forks.

P.S.
make sure the spacing washer is present beneath the Cir-clip on the shift lever side of the engine. it spaces the Cir-clip away from the shift rod seal. if it is missing, your shift rod won't fall out, but it will tend to push too far into the case and can lead to the spring claws that actuate the star mechanism under the clutch basket to move out of alignment and not work properly. symptoms of this are the shift lever seizing mid shift, or moving too freely when attempting to shift without actually changing gears. best of luck to you.

 

[David Toll]

You can flush it with Kerosene which won't affect your seals. Put the side cover back on, pour in a couple of litres and work the kick starter for 10 mins. You can do this by hand with the plugs out. Drain it and go again 'til it comes out clear (ish). I also rock mine back to front on the centre stand, but, don't let it get away from you. Check the filters and oil it up. I have no doubt Jim is right about running it in but, if you flush it properly, at least you can strike that off the list in your attempt to avoid disassembly. Mailman and 5T recommend the Walmart 20/50.