No impulse on 025

[paddlerdan]

Gents, I'm new to small engines but grasp the basics.
This is long but I gotta get all the details out, You decide...

I bought a beater 025 a while back that was hard starting. I mean it would not start without some external fuel priming. So I put a carb kit in it and it ran a bit better but still is hard to start. VERY hard to start with a prime plus now when it does start it runs for maybe 3-4 mins. and seems to lean and then quit.
I did some checking and pulled the carb to check the impulse port in the rubber flange (thanks Lakeside for the tip) put a bit of grease over the port, plugged the carb port with my thumb and pulled it over--- no impulse vacuum here. I tore it down all the way to the brass impulse hose nipple on the crankcase to check there--- still no impulse. I put a little bit of grease over the nipple plug the carb port turn it over and the grease just stays there. I assume when there is good impulse the grease glob will be sucked into the brass nipple. Right?
Question where to go next. I am sorely tempted to do a pressure test with compressed air. Maybe hold the crankcase under water to see where the crack/hole is. Can this be done? what is the procedure? Does Piston position matter like TDC? How much air pressure?
Help! This is my "new" firewood saw and I gotta get it up and running as I am getting behind here.
Thanks for all, Dan

 

[Fish]

Remove the muffler and look at the piston before going any further.

 

[paddlerdan]

piston seems OK. one line of visible scoring but not deep enough to catch a fingernail in or even feel it for that matter. The saw does have compression.
What am I looking for Fish if these observations don't tell you enough?

 

[Lakeside53]

You need to seal the carb inlet and the exhaust before applying pressure or vacuum. Yes, you can hold it underwater when applying PRESSURE (8psi..), not vac (0.4bar).. but you may as well just use a spray of soapy water. If it doesn't leak under pressure, then you appy vac - it's almost aways a crank seal, and use a drop or two of oil to see which one sucks it in.


The are only two places an undamaged engine can leak - the crankcase pan(check your 4 bolts, or the crank seals.

 

[Fish]

If you have decent compression, and the piston damage is slight, I think
you would be better served on focusing on the fuel system, carb, fuel line,
filter, etc, I think your problem is there. But that is just me............

Go back into the carb and remove the needle/lever/spring, and visually
inspect the hole underneath, blow everything out good. Check the fuel line
closely fror cracks, especially between the tank and carb, and also
check the lower end for mushiness....

 

[paddlerdan]

Thanks all for the tips, I'm on it.
The spraying soapy water thing is great - alot less mess for me and my saw.
I'll get back to you all after I try these angles out.
Dan.