How To Choose the Correct Base Gasket for Sherco 2-Stroke Motorcycles

[@darkodragic1963]

Great Video and great Help!! Thank you

[@dannyrose5576]

Hey guys have you had any experience with the low compression head are you using the stock squish values with the low comp head?

[@endurisk]

Solide cette épisode! Bravo a vous

[@power2619]

Hi My ktm exc 300 need to have 0.10-0mm x clearence and i just measured it and it is 0.01mm off on one side off the cylinder. is this ok or do i need change thicker gasket?

[@rmatvmc]

It's up to you, and where the next size gasket would put you. I wouldn't change it unless you had something that puts you right in the middle of spec. -Charles

[@power2619]

@@rmatvmc thanks for fast respond this helped a lot.

[@user-sp8eb6iz7f]

That's a cold measurement, what about expansion?

[@sidecarbod1441]

Certain clearances are critical on an engine, an example would be piston to bore clearance, others are not critical, well not when the squish is too large to start with anyway. 1.7mm squish gap is border line too large, it will just about work as a squish band but not all that well, really the max gap would want to be 1.3mm, 1mm being a good figure to aim for on a fairly large engine. I'm not familiar with the Sherco engine so I have no idea whether tightening up the squish band would put the CR to high, if it did then the bowl would need opening up. The other thing is if you just use the base gasket to tighten up the squish you would end up lowering the ports which might not be what you want to do. The solution in this case would be to pick a base gasket and then machine the head to get the squish right, you would then open up the combustion chamber if required. You can even open the chamber up to bring the CR back to stock, with a working squish band you would still get a nice improvement on the engine performance. KTM's are fairly bad with regards to the stock squish gap, I have worked on one GasGas 300, it was REALLY bad, something like 2.5mm. I set the deck height on my KTM 300 to zero and the head has been setup to work with that, when I change the piston or get the crank rebuilt I just have to set the deck to zero and I know that the head will work, I'll have the 1mm squish that I want.