4 cylinder woes

[cscott]

i have a 1940 4 cylinder that runs great, starts great,but after about 30 minutes it takes alot more power or rpm to re-engage the clutch without stalling , anyone ever heard of this or know where i should start, thanks once again chris

[charlie frey]

I don't totally understand the problem.
Are you saying that the bike is more prone to stalling when hot, so you have to rev it and slip the clutch more?

[cscott]

yes, after its hot i have to increase the rpm to keep it from stalling as i let the clutch out, when its cold everything works fine?? thanks chris

[charlie frey]

Do you also notice a loss in power once you're moving?
Any missing or popping?
What do your sparkplugs look like?

[cscott]

no loss of power once the foot clutch is released its fine, it only shows the need for extra rpms engaging the clutch, thanks chris

[exeric]

Did you ever solve this problem ? I would be curious to know what you did to resolve this.

[cscott]

4

no, i have the bike apart now for repainting, i will tackle that problem again in the spring.

[exeric]

This problem sounds very similar to a problem I had with my 1917 Henderson last year. I had just finished rebuilding the engine and thought I would drop it in the unrestored frame to see if everything did what it was suppose to do. Like all 4 owners, I treated every component like it was an eggshell and went to ridiculous pains bedding the crank and getting the caps torqued just right so everything would spin like it was in outer space. The great day finally came and it was time to see if it would start. To my joyous relief it started after a few kicks and sounded smooth and mellow. Getting an old motor to run after God knows how many years is one of the great pleasures in life, it's right there after your first . . . . . Well, I better not go there. Anyways, I'm standing there, basking in the glory of my great accomplishment when I thought it would be interesting to see how it would ride. I pushed it off the rear stand, took a seat, and touched my foot to the clutch pedal. The engine made a scream that sounded like a pig with it's balls in a vise. I about s**t myself and immediately killed the mag. After regaining my composure I started it again, which it did with no problem, however the slightest pressure on the cluctch pedal would bring back that scream and more pressure would labor the motor. Boy, did that ruin my day ! After a few days of self pity (and loathing) I got the motor up on the bench and pulled the bottom pan. I fully expected to see some serious galling on the bell housing because I figured I screwed up the the endplay somewhere. Once inside I saw no evidence of anything wrong. Everything looked great ! I'll cut to the chase because this is getting a bit long-winded. I noticed that the clutch release arms didn't have even contact on the throw-out bearing fingers (dogs). In essence, one arm pulled unevenly on the throw-out bearing. I still didn't know if this was the problem beacause it didn't seem that far off. Anyways, I had to pull the crank (watch it ! ) and rotate the throw-out bearing 180 degrees. Contact with the throw-out arms to the fingers looked better so I put it all back together with grave doubts. . . . We're almost at the end now. I gave it a few cranks and the motor fired up. . . . Now for the nail biter. I touched my foot to the clutch pedal and Hallelujah ! The sun shown down on my worthless soul ! Smooth as silk . . . . Except for that wirring noise in the gear chest, but that's another story.

[c.o.]

Eric, feel free to drag on stories like that! It's what makes life interesting!!

[cscott]

tight 4

thanks for your reply eric, that makes sense except the clutch works fine at first and i dont have any problem with it until about a half an hour later when the whole engine comes up to temp,i did not build this engine so i dont know, but i hate to say it but i think there could be a problem with crank end clearance, i hope someone can tell me i am wrong. thanks chris

[exeric]

You could be on to something Chris. The throw-out arm exerts a tremendous pull on the pressure plate to compress the springs. Of coarse that wants to pull the entire crank assembly into thrust faces and the ring gear if there is excessive clearance. Why your motor waits a half hour to do that is a bit of a mystery though. We need some 4 cylinder wizards to jump in that have some first hand knowledge.

[Barry Brown]

what type of clutch plates are you running?

[cscott]

i dont know whats in there i didnt build this one , as i said it runs great, clutch works fine ,just take lots of power to re-engage when hot, thanks chris

[cscott]

problem solved

i repainted this bike took it out the other day and the problem is gone, i did do some work on the front brake( turned the drum) and i believe that was my whole problem, the front brake was binding after running a while causing the rpms to be increased to get started again after stopping.........da................... never really felt like the brake ......just goes to show' always start with the simple things... thanks for all the help,chris

[exeric]

Boy! I've been there. It's unusual problems like yours that make people brilliant diagnosticians. However, years of problems like that will either make you a great mechanic or chuck it all and take up basket weaving.