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Just re-assembled the 250 single engine and when turning over by hand there was a "catch" when either valve was open and the piston was a the top.. I figured it was the valve hitting the top of the piston so took the head off. No noticeable contact on the top of the piston, but I did not turn it over that much. Turning it over with the head off did not have anything noticeable. I have the thick gasket between the cylinder and the case, but did not remember or see a gasket between the head and the cylinder. There were two of the gaskets in the kit like the one between the cylinder and the case. Should I use two there? Just how muck clearance is there between the valves in the open position and the piston? Any other suggestions?

thanks

sjm44 wrote:Just re-assembled the 250 single engine and when turning over by hand there was a "catch" when either valve was open and the piston was a the top.. I figured it was the valve hitting the top of the piston so took the head off. No noticeable contact on the top of the piston, but I did not turn it over that much. Turning it over with the head off did not have anything noticeable. I have the thick gasket between the cylinder and the case, but did not remember or see a gasket between the head and the cylinder. There were two of the gaskets in the kit like the one between the cylinder and the case. Should I use two there? Just how muck clearance is there between the valves in the open position and the piston? Any other suggestions?

thanks

____ There're no head-gaskets.
What piston do you have installed, and in WHICH 250Duke-engine model ?


Hopeful-Cheers,
-Bob

If the valves are hitting the piston,some models used a compression plate with 2 gaskets under the barrel.

I had to go to an oversize piston and the numbers on the top of the piston are 64325/5. I have rechecked the assembly and it appears that nothing is amiss. I am presently looking for the old piston for comparison. The bike is a 1966 250cc Single, I think a Monza. engine # DM250 98018.
thanks

Steve

check the piston does not come up proud of the barrel at TDC. Check the size of the valve pockets in the piston to the size of valves making sure you have the piston the right way round
A thin layer of kids plastercene or blu tak on the piston will show up where a valve is hitting ?

[quote= sjm44 ...
" I had to go to an oversize piston and the numbers on the top of the piston are 64325/5. "

____ How about posting a picture of the crown of that piston ?



" I have rechecked the assembly and it appears that nothing is amiss. "

____ When the piston is at TDC -(beginning of the power-stroke), is your points-cam at the position where it had-JUST opened the points ?


" I am presently looking for the old piston for comparison. "

____ How many ring-slots do each of your two pistons have ?



" The bike is a 1966 250cc Single, I think a Monza. engine # DM250 98018. "

____ How about a picture of your Duke ?
It's motor-number is too new to be a "1966", so I believe it's a 1967-model and should be fairly close to when wide-case models started into production.


Hopeful-Cheers,
-Bob