QuestionBike/engine: 1974 'mighty green' Honda Trial 70,
Work performed: new kick starter shaft installed, 52mm piston (big bore kit), new clutch disks.
Engine runs great - fires on 1st or 2nd kick
Observed Problems:
1)the bike will not idle in gear - seems like the clutch never disengages. The bike should idle in 1st and actually engage/grab when the throttle increases - correct?
2)when installing the clutch, the engine manual (clymer) lists the torque range (for the clutch nut) between 27-to-32 footpounds. I noticed the kick starter will not engage at that range but seems to want about 34 footpounds. In other words, the kick starter will not 'grab' until 31,32,33 - 34 is what I last tighten it to. (perhaps this is a clue?). And when it 'fails' the kick starter totally disenages and will not re-engage until the clutch nut is re-torqued.
I am about to tear into the case (again!) and install new thrust washers & splined washers- I'm thinking there is some wear in the tranny somewhere that is forcing me to over tighten the cluch nut - which why the clutch never relaxes.....what do you think?
I have measured the clutch spring height and they seem to be fine (hard to find specs - clymer doesn't list any), but maybe I should just install new ones? Especially since Im going to 'tear into it' again.
I have also measured the clutch disk thickness and they seem fine too.... they are new! but I suppose there is a possibility I ordered the wrong onse? It appears all models from 1970 to 1994 used the same disks for auto-trannys?
I also am wondering if maybe the kick starter thrust washer might need to be replaced as well - it seems to be implicated in the problems described above. I'm thinking a little wear on all these washers equals an inoperable condition.....
I have riden the bike. I can start in neutral, manually roll the bike forward to get it moving then shift to 1st and accelerate. It can shift to 2nd, 3rd - up down (1,2,3,2,1,etc). But it eventually reaches a point where once turned off (or it dies), the kick starter will not 'grab' and the clutch nut has to be re-torqued. At that point tear-down is a must and I'm starting all over again, which is a bummer!
I have a small engine mechanic helping me who is really driving the tear-down/re-build operation - I'd be lost with out him! but he has mentioned that on machines he has rebuilt, when problem like this are encountered, usually a washer or shim is worn (or missing! or installed incorrectly) or that seems to be the problem in his experience. This is why I'm about to replace all the tranny thrust washers.
Any suggestions would be greatly appreciated! THANKS!!!
AnswerScott, the clutch function's centrifugal engagement function is controlled by the rollers which are pushed up the ramps on the drive plate #10 on http://www.cmsnl.com/honda-ct70-trail-70-k3-usa_model614/partslist/E++06.html
If there is no appreciable wear on the drive plate and the rollers are in good condition, then go ahead and replace the clutch springs and friction disks.
Torquing the center clutch hub not down to the shaft just keeps it connected to the trans shaft, it doesn't change anything to do with how tightly the clutch will contact the plates.
Be sure to center the clutch lever arm #4 on http://www.cmsnl.com/honda-ct70-trail-70-k3-usa_model614/partslist/E++05.html the shaft so it fits in the middle of the clutch cam plate. You really have to do this with the motor lying on its side, so the parts don't fall off or get off center. Replace the cover and adjust the clutch by turning the adjustment screw as described below:
The clutch is adjusted with the engine off. Remove the cover protector and loosen the adjuster lock nut. Turn the clutch adjuster clockwise one turn; do not turn excessively.
Slowly turn the adjuster counterclockwise until a slight resistance is felt. From this position, turn the adjuster clockwise 1/8 turn, and tighten the lock nut. After adjustment, test ride the motorcycle to be certain the clutch operates properly.
If you put in a high compression piston, the combination of the bore increase and compression increase might be adding to the k/s slipping issues, but in most cases it should be okay.
I can't think of a good reason to tear down the transmission again, as it really isn't related to clutch engagement. There are upgraded parts for the kickstarter spindle/gears, so if you do go back in for a specific reason, check to see if you have old or new parts installed.
http://www.cmsnl.com/honda-ct70-trail-70-k3-usa_model614/partslist/E++11.html
Bill Silver
