357xp air leak at throttle screw?

[Sepia]

Now that you have a vacuum tester, you can make an adapter for the spark plug hole for saws without an impulse line. This isn't my idea, but it works well. Take an old spark plug and beat all the porcelain out of it. Mix up some JB Weld and epoxy a nipple fitting into the metal body of the spark plug where the porcelain used to be. I did this mod a while back and have used that adapter a lot - it works great!

 

[Huskitoter]

Does he need to plug the decomp valve hole when doing a vac test? Or is there not enough vac to open the valve?

It's a 50cc saw, block the decomp off. Never had a need for it on my 346 or 359.

I like 'em for cold starts but know they fail. Good to check them every once in a while.

 

[J D]

For the purpose of eliminating the decomp & confirming the rest tests ok you may just need to pull on it while testing, or you can take it out & put a bit of grease in it before replacing it. I've gotten a few to seal properly by putting grinding past in them & rotating them around a bit. A spray bottle of soapy water helps find those pesky air vents

 

[edrrt]

I put gas line thread sealant on the threads, checked with carb cleaner after and no reaction. Can you melt a piston just from a decomp leak? I'm guessing thats why guys always talk about plugging them here?

3 leaks so far. A miss assembled carb, a poorly seated intake boot, and a leaking decomp. All of which can total a top end. Man I had no idea chainsaws were such fickle beasts. I'm kinda nervous about installing the new oem top end until I'm sure I haven't screwed anything else up. I will say I can replace the top end of a ssaw(not correctly prob) in about 20 min now though.

I was pulling the vac through the spark plug hole by taking off the gauge for the compression tester.

It won't do a pressure test though.

I let it run and sprayed soapy water everywhere, carb cleaner... Seemed ok.

I am thinking about pressurizing it with a little hand pump from a blood pressure cuff and submerging it looking for bubbles to be 100% sure I found everything. Saw it on youtube. Unsure if that could ruin the saw.

I guess I could also pay a saw shop to test it for me... prob $150 bucks around here. Or run a chinese top end for a while and see if it melts again.

 

[sean donato]

Gonna have to pressure test it again with the new top end anyway. You seem competent with your skill level, just use your new top end.

yes multiple air leaks will kill a top end in a hurry. That's why we vac and pressure test them.

You need to take the Schrader valve out if the tip of your compression tester to use it for pressure testing as well. Havent ever had a need to submerge an entire power head, soapy water has always worked well for testing purposes. Only so many places they can leak if you will.

 

[edrrt]

Gonna have to pressure test it again with the new top end anyway. You seem competent with your skill level, just use your new top end.

yes multiple air leaks will kill a top end in a hurry. That's why we vac and pressure test them.

You need to take the Schrader valve out if the tip of your compression tester to use it for pressure testing as well. Havent ever had a need to submerge an entire power head, soapy water has always worked well for testing purposes. Only so many places they can leak if you will.

I'm just leary of soapy water finding it. It did not show any bubbles for example at the decomp valve but was leaking. Might just need to buy a pressure tester too.

 

[sean donato]

I'm just leary of soapy water finding it. It did not show any bubbles for example at the decomp valve but was leaking. Might just need to buy a pressure tester too.

If you have the same mity vac I have, just flip the switch under the gauge to pressure and pump. Shell let you know quick.