Britbike forum Forums Thread Like Summary - A65 thunderbolt new engine build gremlins

so I Had the fresh built motor fired, strobed and run around the block. Felt great to be on her again. few issues that I'm trying to figure..
-Before running, at the exhaust valves/pushrod/rockers, there would be a slight click as the cam would reach it's apex. Wasn't sure if it was full compression on one side or full release on the other as it would happen on both sides.
-There developed a terrible clattery sound when I would run it beyond 3-3.5k. it wasn't there while strobe timing. when I put her up on the stand and pulled the valve cover off I see that one exhaust valve is now SUPER loose at about .035. the adjustment was still tight however. I pulled the pushrods and they don't appear to be bent. I used some extrusion blocks and a height guage to verify as best I could.

I've pulled the head off but haven't pulled the valves/springs out to check those yet.

The other issue is I had the Bob newby clutch set and working well. Ez engage and good solid bite. After getting it back on the stand and going to kick it over to check compression the clutch doesn't bite enough to turn the motor over now. Even after tightening the springs well beyond where they should be.

I will try to upload a pic but I'm curious if this bushing/sleeve shoulder is supposed to extend so far into the clutch basket assembly area and causing issues. Or if the gearbox could float and cause engagement issues. I don't know. Just guessing at this point..

https://photos.app.goo.gl/RKfNJUaUzoeX5PJ86

I don't know how to upload photos apparently but can link to the photo in my Google drive..

Thanks!

Check for coil binding with feeler gauges between the spring coils at full lift, a 3 thou blade should pass through, I dont see how a badly seated spring will change clearances, the valve length and seat wear dictate tappet gaps, not spring pressure. When turning the motor over by hand using the rotor nut to drive it round ,coil binding will be obvious, if the crank gets very stiff at max valve opening that is coil bind,( there will be some resistance as the spring compresses but if you feel a steep hump at max opening thats coil bind, spring pressure rise should be fairly linear.) this is not a good thing, if the motor ran it would indeed be noisy as the forces on the valve train will be immense, to keep running something like Nick describes would seem inevitable. If you have spare rocker arms compare them to whats in the bike now.

Could be. I got some springs from a vendor who shall go unnamed. New springs from MAP solved this issue.

Do the pushrods have pressed on ends? One may not have been pushed completely on and shifted.

Alan, agreeing with Gavin cause he's right. My idea that an improperly seated spring could result in a wider lash if it seats after running was wrong. On a past engine build I had an improperly seated spring which I discovered as I centered one of the valve keepers which was in contact with the other keeper. It slid around loosely with ease and alerted me that something was wrong. Made me think of the OP.'s issues.