I recently bought a new crank case as the old crank case had almost all the threads stripped and destroyed in it, I'm in Australia so the best brand of parts and engines we have here is really only cdh motors on ebay but im completely unsure as to why i have no compression all gaskets are brand new and i am still using all the old engine components from my old case i have just ordered a new piston along with new rings and i am using a different cylinder that wasn't on the engine originally as my mate is using my original cylinder but don't see how that can be an issue as to why i have no compression any ideas or thoughts as to why i dont have compression????
With clutch out bike has little to no compression
- Thread starter Blizz
- Start date
Over tightening the head bolts will cause the head to warp (& cause a compression leak).
Remove the head, use a piece of sandpaper on some glass & gently sand the head surface flat again.
Then install a new head gasket & torque the head bolts to 12 ft/lbs.
Let us know if that fixed the problem.
Remove the head, use a piece of sandpaper on some glass & gently sand the head surface flat again.
Then install a new head gasket & torque the head bolts to 12 ft/lbs.
Let us know if that fixed the problem.
I have already sanded down the head and tightened the head bolts to the point to where i cannot tighten them no more with a normal socket wrench and it still feels to be the same amount of compression nearly none
When you were assembling it did you check to see if the piston reached the top of the cylinder? There are two different pistons, type A and B, if you know the piston travels to the deck of the cylinder you have a leak as Norm said. Try to true the head and Don't overtighten it, low grade aluminum warps easy, always use a torque wrench. 12 foot pounds is all it needs.
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All cylinders are not the same, the deck may need to be sanded to get the piston travel higher to raise compression. I've sanded several to raise compression.
So, you're saying that you possibly over torqued the head again?
The piston has a good amount of room to travel and isn’t touching the deck of the cylinder so I still don’t understand as to why I have almost no compression
It travels to the top but there seems to be around 5 to 10mm or room between the top and the cylinder
The difference in the two piston’s is a little over 3mm, if you can measure from the deck of the cylinder to the piston at TDC you may find the problem
Unsure how but I managed to get the piston to raise higher up and come to sit around 3mm but still have the same amount of compression
Looks like you have the wrong piston, compare the old piston to the new one. That looks like a type B piston, you need a type A. The only way to know is to compare the two.
How do you know you have little or no compression?
Just curious about what has lead you to believe this is your issue ..??????
When you pull the cyl. look and see what the makings on the side of the connecting rod say, if its marked ZAE50 then you have what is called a "half breed" geometry engine, these engines are 38mm stroke but use the Type A piston with what we call a "low hole" piston.
The piston in these particular engines that I've had myself and seen lack around .060" reaching top of cyl. when at TDC.
When everything is right, good rings, good cyl. with no gouges in wall, etc.... they will still run "OK" not great power, but OK...
Judging from what I see in the pic you posted here, Im guessing you have an engine with a rod marked ZAE50 but I could be wrong... its for sure if I am, its not the first time...LOL
again, how do you know that you have little or no compression?
Just curious about what has lead you to believe this is your issue ..??????
When you pull the cyl. look and see what the makings on the side of the connecting rod say, if its marked ZAE50 then you have what is called a "half breed" geometry engine, these engines are 38mm stroke but use the Type A piston with what we call a "low hole" piston.
The piston in these particular engines that I've had myself and seen lack around .060" reaching top of cyl. when at TDC.
When everything is right, good rings, good cyl. with no gouges in wall, etc.... they will still run "OK" not great power, but OK...
Judging from what I see in the pic you posted here, Im guessing you have an engine with a rod marked ZAE50 but I could be wrong... its for sure if I am, its not the first time...LOL
again, how do you know that you have little or no compression?
I hope its something as simple as a wrong piston and you have it back up to snuff quickly.
I do know that in my experience if you mount a type B piston to a crank that has the short con rod for the older type 40mm stroke engines, the crank will not rotate past the piston skirt making contact with crankshaft counter weights so I know you dont have a type B piston on a ZL marked Rod and If you put a type A piston on a 38mm stroke long rod which I believe is 4mm longer, the piston will come way up above cyl. deck at TDC.
Will be interesting to finally know what you have going on.
I do know that in my experience if you mount a type B piston to a crank that has the short con rod for the older type 40mm stroke engines, the crank will not rotate past the piston skirt making contact with crankshaft counter weights so I know you dont have a type B piston on a ZL marked Rod and If you put a type A piston on a 38mm stroke long rod which I believe is 4mm longer, the piston will come way up above cyl. deck at TDC.
Will be interesting to finally know what you have going on.