750 commando: left exhaust pushrod lost the rocker ball

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pierodn

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Hi All.
To day i have started my commando again after few days.
The bike started, not easily, only with the right cylinder; the left didnt start and had no smoke that come out from the pipe.
You could listen a great noise from the engine like an hammer against the steel.
I had understood that the left exhaust valve remained closed.
Opened the cover i have seen that the rocker ball end of the exhaust rocker had lost the pushrod!.
I have removed the rocker and i have seen that the pushrod upper cup was in good order, well in place in his lifter, and that it went up and down when i turned the rear wheel with fourth shift engaged.
The question is: what happened?
Can it happens again?
Thank you.
Piero
 
Last edited:
Most likely you lost the stellite foot from the cam follower (tappet).
 
Hi.
I understand, but i dont think so.
If you loose the stellite foot from the cam follower the pushrod remain with rocker ball in place the same because the cam follower doesnt go down more because there is the TAPPET LOCATING PLATE that hold the descent.
Thanks.
Piero
 
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If your valve stuck open then, when the follower dropped down, the pushrod would have been released as it would not be engaged with the rocker arm any more. So you need to check why the valve would not close.
 
kommando said:
If your valve stuck open then, when the follower dropped down, the pushrod would have been released as it would not be engaged with the rocker arm any more. So you need to check why the valve would not close.
Click to expand...
Hi.
I understand what you mean.
But it is not very believable that the valve stucks when it is opened.
Bike has few km and guides and valves are new.
Thanks.
Piero
 
Is it possible that the pushrod was never seated properly in the follower? Then after a few miles it dropped in place, causing a loose adjustment?
 
Hi.
That would be a fortune!.
But, do you really believe that?.
Thanks.
Piero
 
I personally have not seen it happen, but I believe I have read about it on this forum somewhere. Since you are sure that none of the other suggestions are the cause the list of possibilities is getting shorter.
 
kommando said:
If your valve stuck open then, when the follower dropped down, the pushrod would have been released as it would not be engaged with the rocker arm any more. So you need to check why the valve would not close.
Click to expand...

Something jamming the valve --- a broken piston ring entangled at the valve seat maybe. Or there has been insufficient lubrication and the valve has stuck in the valve guide.
Why spend time on guessing causes? Take the head off and have a look.

-Knut
 
pierodn said:
Hi.
I understand what you mean.
But it is not very believable that the valve stucks when it is opened.
Bike has few km and guides and valves are new.
Thanks.
Piero
Click to expand...

It may not be believable but when asking myself why something has failed I first review all the recent work, so its head off and look at the valve stem and guide to see why it jammed open.
 
Hi.
The Pushrod was stright and in good order.
I have seated in place again the rocker ball in the pushrod.
The bike starts first kick, no engine noises, and runs great.
The questionis: can it happen again?.
Thanks
Piero
 
I don’t think that pushrod was seated correctly on the first install. When it dropped into place your valve adjustment was probably way loose or the rod just fell completely out of position. If this is the bike with the different colored exhaust you mentioned in another thread the loosely adjusted/ non-opening valve could be the problem. I had an adjuster back off on my Trident once that caused the the pushrod to fall out of place. Unfortunate I was 70 miles from home and had not tools. Had to limp home on two cylinders.
 
pierodn said:
The question is: can it happen again?.
Click to expand...

Only you can answer the question but unless you know you have the diagnosis 100% correct then the answer must be yes it can happen again.

Why did you say the valve was stuck open, what have you inspected to know that is not going to happen again.
 
kommando said:
Only you can answer the question but unless you know you have the diagnosis 100% correct then the answer must be yes it can happen again.

Why did you say the valve was stuck open, what have you inspected to know that is not going to happen again.
Click to expand...

Hi.
Valve never stucked open.
Piero
 
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