saw rebuild

[roundhead]

I put my MS 290 back together and did a vacuum check like paws posted but there is an apparent leak somewhere. the vacuum is not holding. I replaced both crank seals and put dirko on both surfaces and over the seals. I spread it thin by hand and bolted the cylinder head back on after a few minutes. I didnt tighten the bolts as tight as possible until the next day. the impulse line seems to be good. I blocked the ports as best as I could with an old tire tube. is there anything I am overlooking? could I have used too much or too little gasket seal? I guess the only way to figure it out now is to do a pressure check. any ideas on how to put pressure into the cylinder and keep it there?
thanks
SC

 

[ndlawrence]

I put my MS 290 back together and did a vacuum check like paws posted but there is an apparent leak somewhere. the vacuum is not holding. I replaced both crank seals and put dirko on both surfaces and over the seals. I spread it thin by hand and bolted the cylinder head back on after a few minutes. I didnt tighten the bolts as tight as possible until the next day. the impulse line seems to be good. I blocked the ports as best as I could with an old tire tube. is there anything I am overlooking? could I have used too much or too little gasket seal? I guess the only way to figure it out now is to do a pressure check. any ideas on how to put pressure into the cylinder and keep it there?
thanks
SC

Just use the impulse line to pressure test also, you can just hook it up to an air compressor and use some soapy water to check you seals again, make sure that where your blocking of your intake and exhaust that it is sealed good. Here's a vid [video=youtube;VNq07CcWPjs]http://www.youtube.com/watch?v=VNq07CcWPjs[/video]

 

[roundhead]

Just use the impulse line to pressure test also, you can just hook it up to an air compressor and use some soapy water to check you seals again, make sure that where your blocking of your intake and exhaust that it is sealed good. Here's a vid [video=youtube;VNq07CcWPjs]http://www.youtube.com/watch?v=VNq07CcWPjs[/video]

Thanks for the video link. that was very helpful. did you just put some soapy water around the seals? did you need to wait a few minutes to make certain that the vacuum holds? does the piston need to be down all the way when doing the pressure test? should you turn the crank over a few times to make sure that the vacuum holds? I really do not want to start over but I am afraid I might have to.

 

[jbighump]

take it back apart put a good bead of sealer all the way around the pan and a thin layer around the od of the seals(make sure to get some in the corners behind the seals) put it back together AND tighten down the bolts to the full torque rating immediatley never had a leak this way:hmm3grin2orange:

 

[ndlawrence]

Thanks for the video link. that was very helpful. did you just put some soapy water around the seals? did you need to wait a few minutes to make certain that the vacuum holds? does the piston need to be down all the way when doing the pressure test? should you turn the crank over a few times to make sure that the vacuum holds? I really do not want to start over but I am afraid I might have to.

put pressure on it, put soapy water around the seals and look for bubbles and if you don't see any the rotate the crank several times and look again for the leak

 

[jrocket]

be carefull if you use a air compressor to pressurise the crankcase, too much pressure and you could blow the seals right out, set your regulator to about 10lbs, that should be plenty too find a leak.