4000 rpm knock

[mrbill5491]

Bill he states that it happens in all gears.

Well okay....

[BillGS550LZ]

Hey Tom, mrbill, Zuzu thanks for your input. After further research looks like there is allot of information in the old forums I just did not know what i was searching for.

So to summarize in retrospect I think the knock may in fact be best described as a vibration, my bad. I've other ideas for this old girl and will be looking into that next.

Thanks for your input and happy trails

[tom203]

"....rotated crank 90* from TDC and measured distance from top edge of spark plug hole to top of piston and I get a 1.5 mm difference between the two."
Why not measure when 1 and 4 are at TDC ? measuring gets more iffy the farther down stuff is to measure.And I thought it was the bigger motors that had potential twisted cranks.

[BillGS550LZ]

At TDC the difference is about .6mm which given the margin for error I did not think was worth noting.

Overall I agree, this is a very iffy way of measuring. The top edge of the spark plug hole is not exactly flat and there is no guarantee the thickness of the cyl head around the plug holes is the same across plugs.

It runs great, no hesitation and pulls really nice to 7500+rpm. I can't tell since as you probably know the speedo is limited but I got it to 85mph once and she kept pulling for quite a while after. Didn't appreciate the high pitched buzz/zing but not bad for a 32 year old machine, not that I would know what any other bike feels like at these speeds since this is my first bike

Thanks

[mrbill5491]

At TDC the difference is about .6mm which given the margin for error I did not think was worth noting.

Overall I agree, this is a very iffy way of measuring. The top edge of the spark plug hole is not exactly flat and there is no guarantee the thickness of the cyl head around the plug holes is the same across plugs.

It runs great, no hesitation and pulls really nice to 7500+rpm. I can't tell since as you probably know the speedo is limited but I got it to 85mph once and she kept pulling for quite a while after. Didn't appreciate the high pitched buzz/zing but not bad for a 32 year old machine, not that I would know what any other bike feels like at these speeds since this is my first bike

Thanks

Mine has always buzzed at high rpms and everyone I knew that bought one has said the same thing, just the nature of these bikes. Some are worse some not so bad, some have that sweet spot where the buzzing disappears. Seems like the factory didn't put a lot of effort in balancing these motors.

[BillGS550LZ]

That's good, heck great to know. I've put over 600miles on her since the rebuild and thoughts of having screwed some up still hunt me. Must be love I think

Thanks for sharing.