Lifter exhaust - Vincent Comet Serie C

[Michel]

Hello everybody,
Eight months later and a lot of problems (job, family,etc.), I'm back with this one.
This winter, I just check the cable adjustment. Now, as the engine is cold too, sometimes the lift works, sometimes not.
I need to open one more time the timing cover and (I'm afraid) to strip down the timing gear.
If I mark each gear in comparison with the others gears, I suppose it's good enough in anticipation to put it together again ?
I'll make it during my holidays in july.
If you have any piece of avice, you are welcome.
Thank you.

 

[rapcom]

Michel, One of our section members had a similar, and very puzzling, problem on his Rapide, when the valve lifter worked on only one cylinder and not the other. Eventually I found that the problem was that the thread in the crankcase for the rear ET68 was very badly worn, and operation of the mechanism simply tilted the rear ET68 without moving the ET69, but still operated the other lifter. Perhaps your thread is gripping when cold, but expanding and losing the grip when hot?

 

[Michel]

Hello everybody,
Dear Rapcom, you were right. The thread in the crankcase rear ET68 is badly worn. I can take it off with the fingers !
I suppose I could repair with Helicoil. Do you know the size and the thread ?
There is an other solution ?
Have nice sunday.

 

[rapcom]

Michel, The thread in the crankcase for the ET68 is 5/16" BSW, and Eddie Stevens Bible, Know Thy Beast, recommends using Loctite 270 on the thread. However, if you repair with a Helicoil, Loctite is not recommended.
Glad I could help!
Dick

 

[Michel]

Thanks a lot, Dick. I'll order the 5/16" BSW Helicoil.
Kind regard.

 

[John Cone]

The fact that one lifter works and not the other, it has been known that one of the needle rollers in the ET69R or ET69F has become dislodged