Suddenly lost shifting

[m in sc]

yup. you 'may' have found it. I hope so.

[92stroker]

We shall see.  I noticed that the shift shaft had what seemed an inordinate amount of thrust play, to the tune of about 2mm.  That's when I decided to review the assembly procedure, and already knew I had installed the washer on the inside.  When I re-assembled it in the correct order, the thrust play was reduced to around .5mm.

It's funny, these bikes are dead-ass simple, but as such, very unforgiving of any mistakes.

[92stroker]

Sooooooo....  Here we are three years later haha wow.

I had to step away from this project for several reasons.  Two new babies!  One being a little boy who is now almost 3, and the other being a HD Shovelhead that's about 45 😜 Anyways, I think in my intro I probably explained the origin of this bike having belonged to the father of a close friend who inherited it when his dad passed.  I was charged with it's repair and care.  Recently, my very good friend (who lives out of state) decided that the best option for this bike was to release it to my ownership.  Naturally that inspired me to dig back in, so here are some updates

If you care to review this thread please do, but I'll give you the readers digest condensed version:

74 rd350 won't shift when hot, approximately 20 minutes of ride time.  Lucas 10-40 semi.  Shifts cold.  Been through the clutch case one million times and everything checks out.

So yeah.  Threw a new battery in, cleaned the tank.  I had run the carbs dry when I parked it.  Started right up, and ended up, as expected, right where I left off, but with a new sense of hope and some new ideas.

I wanted to verify that the issue was driven my heat, and sure enough, after about 20 minutes I lost my shifting, parked it in the shade, and about 20 minutes later was able top back on and enjoy my renewed ability to shift smoothly through all gears.  That got me thinking, why haven't I looked into a potential clutch release issue?  Well the short answer is because it has been working before it stopped, but that's not really adequate method. 

This bike has been converted to a hydraulic clutch.

Red Flag!

Cool, but had already been a PITA anytime I worked on the bike.  The install is pretty cool.  The cover was left fully intact, with an unknown slave cylinder modified to take screws through the factory holes for the release cover.  At some point in my mania I cracked the system, and the bleed valve does not have a nipple on it, so I have not been able to confirm an honest bleed.  I am highly suspicious that the hydraulic clutch is the culprit.  Even when cold I found that with the engine off, the bike in gear, and the clutch released, that there was noticable drag.  In neutral in rolled smooth and free, but in gear I could feel the drag and also hear the clutch load up the flywheels before encountering piston resistance, at which point it would turn through the drag but with quite a bit of friction.  Not enough to move this piston in the bore, but just shy.  So  I pulled the clutch out and noticed that it was short a disc!  The stack finished in a friction rather than a steel.  I'm guessing this was done to give some extra release room for what is most likely a hydraulic system that doesn't have adequate throw.  I also found that the outermost friction that make direct contact with the pressure plate was cracked, and all the friction discs measured fat on one side (probably from the many years of sitting in oil before I ever saw it).  So I replaced the clutch with one of the HD sets from Economy (fzr plates, new steels, new springs), installed it annnddd... Still won't shift hot 🤣. It did improve the bikes power delivery noticeably.  The FZR frictions have metal core which makes them much heavier than the all cork discs that came out, and I think I had been slipping under power based on the condition of the discs and the missing one.  But yeah still won't shift while hot.

So my last hurrah before pulling and splitting the engine is going to be to convert to a traditional cable pull clutch release, and also to look close at clutch basket for burrs on the lugs.

Wish me luck.  I really need some wind therapy right now.

[Striker1423]

The hydraulic clutch is most likely air locked. Bleed it. When it gets hot, it's losing it's pressure because the fluid is most likely boiling.

[m in sc]

you can get a bleed nipple in a banjo bolt fitting. had to do that on mine, been good for over a decade. (13 yrs maybe?)

also, i made an adjustable rod for mine so i would get full throw. is it a necessary mod? absolutely not. but its fun when it works well.

this is an OLD picture, when i first did it.

[92stroker]

The hydraulic clutch is most likely air locked. Bleed it. When it gets hot, it's losing it's pressure because the fluid is most likely boiling.

Totally agree!  I went to a couple parts stores and couldn't find a bleed nipple.  Only thing stopping me from ordering one is general frustration, but cooler heads prevail I suppose.  Was gonna just bin the whole system for the simplicity of cable, but if I can get the hydro work right I'd rather not throw more money at it.

you can get a bleed nipple in a banjo bolt fitting. had to do that on mine, been good for over a decade. (13 yrs maybe?)

also, i made an adjustable rod for mine so i would get full throw. is it a necessary mod? absolutely not. but its fun when it works well.

this is an OLD picture, when i first did it.

Super clean install!  The guy who installed the hydro on mine must have been an amateur Machinist.  There is a secondary pushrod that has a cup to house a ball bearing where it contacts the primary pushrod, and there is a third ball bearing where the secondary pushrod contacts the piston.  The secondary pushrod is stepped so that the piston end fits through the OEM cover and is cupped to hold the second ball at the secondary/primary interface.  It's really a pretty smart design that someone put some effort into.

It does have a bleed fitting, but it just has a pinhole in the top, almost like the nipple was cut off).  I tried bleeding it by pumping it up with the valve closed, holding the lever down, and cracking the system to allow the pressure to release, then closing the valve before releasing the lever (all done with the master open and level, keeping a close eye on the fluid level.  In a perfect world that should work, but it the technique offers no visual confirmation (bubbles in the line) to verify a complete bleed.  I could "bench bleed" the system by just dropping the whole slave into a tub of hydro fluid and bleeding it down like that.  Maybe I'll give it a go.

This afternoon I pulled the plates out and did find some pretty distinct grooves in the leading edge of the clutch basket lugs.  So I'll pull the basket out and true it up.  Maybe that and the bench bleed will get me in shape.

[m in sc]

thanks.

that is -basically- how I did the 'rod extension' on mine, but only 2 ball bearings, one in the cup, the other in the 'stock' location.  I actually used a head bolt, cut it, used the threads on one side to thread an m8 stud into with a locknut to the slave cyl, the other end was opened enough to slip over the stock rod with a small bearing in it, and it worked.

as far as bleeding, i would suggest taking the slave off, putting a small c-clamp on it to hold the piston IN, and holding it above the master if possible. if not, bleed it down low but with the piston held IN w the clamp. this will not allow any compassion of trapped air.

fwiw, i recently had to rebuild my master cyl for this, as it was leaking internally and not getting full throw. so, depending on the age of the unit, might be worth looking into the seals.