Too Much Compression?

[redtractor]

I was given a burnt up 028AV. When installing the new cylinder, the squish w/o the base gasket was .016. Yeah, tight but the big number with it didn't sound exciting. The compression is now 215. Plenty exciting enough but I'd like the crank to stick around so the gasket will go back in.

My question. While at idle and top end it runs fine, it falls flat in the transition and the carb and fuel system have been gone through. Is that ridiculous compression the reason for the bog?

 

[huskihl]

Are you sure your gauge is reading correctly? 215 seems awfully high for just a base gasket delete, but I have no idea what a 028 normally is. 215 won’t hurt you saw

 

[Duce]

Are you sure your gauge is reading correctly? 215 seems awfully high for just a base gasket delete, but I have no idea what a 028 normally is. 215 won’t hurt you saw

Would you try opening H needle or closing H needle to clean up that bog?

 

[huskihl]

Would you try opening H needle or closing H needle to clean up that bog?

Hard to say without hearing it. Could be lean or it could be rich

 

[ammoaddict]

I had a Husqvarna 55 with an aftermarket closed port top end, the piston was bad so I put a 028 super piston in it. I have to grind a spot off the dome so the plug wouldn't hit it. The compression was 255psi. It cut like mad, but it got really hot. I took it off and bought a used oem top end for it.

Sent from my moto g(7) power using Tapatalk

 

[redtractor]

This gauge is reliable but, just in case, I just tested a known saw and everything is normal.

First step was carb tuning. At no load full throttle, it 4 strokes and at idle it doesn't load up and various needle fiddling wasn't helping.

Being an aftermarket cyl kit I was kinda leaning towards less than optimal port timing made worse by the compression.

 

[Maintenance Chief]

Is the bog in transition closer to the low side or high? The reason I ask is Because the lower side of transition can be a blocked hole or the meter lever height, but the higher side of the transition could be a check valve or fuel line split?
Compression has nothing to do with the bog.

 

[Czed]

Are you sure your gauge is reading correctly? 215 seems awfully high for just a base gasket delete, but I have no idea what a 028 normally is. 215 won’t hurt you saw

The two stock one's I had were in the 190s

 

[jetsam]

Would you try opening H needle or closing H needle to clean up that bog?

L is the jet it's using at low speed. If it won't accelerate but runs good at WOT, I'd adjust idle, adjust L for max RPM and then give it a nudge towards rich, then repeat until the adjustments needed are small. (Then adjust H again.)

If there is no carb adjustment that makes it accelerate right, the carb might need cleaning or rebuilding. The L jet itself might have crud in it.

Normally you'd also look at the fuel tank vent and fuel lines and such, but it sounds like this saw runs well at WOT, so those are probably fine.

 

[Wood Doctor]

Owner of the latest Stihl MS660 I got into the shop said the saw ran OK. I fixed and checked several other things as requested but not much related to the engine. The decomp valve was broken, so I replaced that. Compression measured 75 psi with the new decomp valve pressed down.

Next, I lifted up the decomp valve to test compression and believe it or not, I could not pull it over to get a reading. I seldom run into this. Maybe I need more testosterone.