Topic: Im a dummy...

[Willie501KULT]

Showing off like an ass and doing a burnout on my 78 CB750k and then pop! My #4 cylinder intake valve popped the valve cover right off!! Arghh guess I deserved that.

Hoping for an easy fix, I adjusted the valve and got a new valve cover. The bike starts and idles ok but when I shift into gear I can let the clutch fully out and the bike will not drive… It will rev up and slowly roll forward but something is definitely wrong.

A little about the bike, it is the stock 1978 k model engine with a 4 into 1 header, pod air filters and 120 main jet and 40 pilot jet (I think, its been a while since I did the jetting).

Hoping someone can point me in a direction before I undergo a full engine tear down to find the problem.

Thanks.   

[Jerry Rxman Griffin aka MuthaF'er]

So how are you removing the valve cover??

What actually came loose? Adjuster nut? Bent valve perhaps?

[Willie501KULT]

Both valve cover and adjuster nut came off. I replaced both, visually the valve looks ok but I haven't taken the valve right out.

Thanks.

[ekpent]

Sounds like you broke the little round inspection cover. Did you find the adjuster nut and the threads and all the pieces from the broken cap ? You say the engine though is idling and running OK but the clutch doesn't work. Sounds like a place to start looking.  Does it manually seem to shift through the gears ? Does the clutch seem to function when the engine is off paddling through a couple gears ?

[Willie501KULT]

Yes it was the valve inspection cap! I found the nut, broken cap and threads still in the bike, made sure none of it went down into the engine. Replaced with new parts.

It will shift down into first like normal and I can go through all the gears smoothly with the bike off. With the bike running I shift into first and let the clutch fully out, it all feels normal but maybe the clutch isn't engaging???

[vames]

Sounds like a clutch problem that is unrelated to the valve problem but very related to your burnout problem. Doing burnouts on a bike with a 30-year-old clutch can probably suck any remaining life out of the clutch pretty quickly.
 

[TwoTired]

Burnouts are pretty hard on clutches (and chains and tires).
Expect to replace at least the frictions, and probably the steels as well.

Change your oil and filter, too.  All those clutch worn bits go directly into the oil supply.

The big racers do burn outs, and then overhaul the engine at least weekly.  Hope you have a good bankroll.

[lrutt]

me thinks you better get a better bike for scorching tires. These bikes don't have rev limiters like the new crotch rockets do. When you pin the throttle, they will rev until you blow the valve train, just like you did.

To be honest, you don't deserve that bike. Might be harsh but sorry..I hate to see willfull disregard for a machine like that.

[Willie501KULT]

me thinks you better get a better bike for scorching tires. These bikes don't have rev limiters like the new crotch rockets do. When you pin the throttle, they will rev until you blow the valve train, just like you did.

To be honest, you don't deserve that bike. Might be harsh but sorry..I hate to see willfull disregard for a machine like that.

Thanks for the info,, but I love my bikes just as much as you love yours… 

[scottly]

Hey Willie, the most likely reason the valve adjuster lock-nut came loose was over-revving the motor. How long have you owned the bike? Did you have any transmission/clutch problems before the burn-out?

[Willie501KULT]

I have owned the bike for 5 years. I have done regular maintenance and any required work. As well as changing the exhaust, air filters and jets. Very reliable and strong bike. No problems at all with the clutch/transmission prior to my bonehead burnout….

[Seeker0131]

Clutch...sounds like a clutch issue.  If the engine is running fine after you made your valve train repair, but it won't go, I'm guessing that you burnt up the plate.

It a good reason to upgrade the plates, and springs???