MOPED ARMY

air leak on head gasket and base gasket area,

I am sure the 50 cc #22 head is flat and clean, the 70cc dmp where the head and cylinder meet is flat and clean. I am pretty sure the 70cc cylinder is in good condition.

I don't know if the stud is bad... I was tighting the nut and stud broke....two times...i was using torque wrench 10pound....

nuts are new with new lock washer...

I don't know maybe the nuts are not equaly tight? or maybe the compression is too high? I don't know....

what should check? please tell me step by step what to check..

thanks...

what bottom skirt? are you talking about cylinder skirt? or piston skirt? if it's the cylinder skirt(sometime it's hard to push in the cylinder skirt inside the base) this could be the reason of leak?

I did sand it on flat suffice the head and cylinder where head meet.

I couldn't do anything to cylinder wher goes inside the case.

I don't know what I can do... To stop this leak.

If one if that surface is not flat will cause this air leak?

How do I check bottom side of cylinder if it's flat or not?

If my stud is bad, this would happen too?

Puch head nuts are torqued to 10nm, or 7ftlbs. I torqued them to 10ftlbs with a torque wrench for a long time and wondered why I kept stripping studs.

Figure out a way to pressurize the system..

get a squirt bottle with soapy water and apply the soapy water.

If the engine is free .... you can pressurize it and put it in a big tub of water and look for air leaks like one can do for a tire or tube..

http://www.mopedarmy.com/forums/read.php?6,1767503,1768367

one of my friend told me that stud is streched so that is why i broke the stud. when thread strech the nut wont hold tight anymore( the space between the threed should remain same)

I don't know if this is correct but I am waiting for new stud. I might able to find this stud m6x106mm local.

if this solves it I will post again.

thanks to everybody who helped me

So bad stud might cause airleak? Make sense?

I can't find another reason...

Brian Cha Wrote:

-------------------------------------------------------

Doubt it caused the problem, but next time you might want to do 600 then 1200.

The 600 will make it easy to spot any defects and the 1200 will work out the scratches made by the 600.

Best flat surface for sanding is glass. Stop Lowe's or Home Depot and pick up a 12"x12" mirror (they are usually a dollar or two) firmly attach it to a table or work bench and tape the sand paper to it as taught as possible.