Stihl 029 Super troubleshooting.........

[mountainlake]

I'll agree 120# should make it run as my brand new snowmobile has 125". Just so you know I just went out and ckecked my old CS6700 Echo with a gauge with the valve by the gauge. 127# with the choke shut and throttle closed, 145# with the throttle and choke open. The down stroke of the piston forces air into the piston when it has air. Steve

 

[Lakeside53]

???

That is is "forcing" fuel air mix... the air you are measuring is uncompressed until the piston has closed off the exhaust port.

 

[Lakeside53]

???

That is is "forcing" fuel air mix... the air you are measuring is uncompressed until the piston has closed off the exhaust port.

The "compressed air" is (piston travel up) from the top of the exhaust port until, TDC.

 

[mountainlake]

On the upstroke fuel and air are sucked into the crankcase through the carb on the downstroke the piston skirt closes the carb port and pushes the mixture through the tranfer ports into the combustion chamber. If you have the choke and throttle closed it won't get as much air in the combustion camber causing less compression. Steve

 

[charlesfarm]

Mountainlake,

Hmmm. Now I am perplexed with the two readings you got when holding the throttle open and keeping it closed. I just did a compression test on my Echo cs-3000. No difference at all in the readings when I had a closed throttle vs. WOT w/ open choke!?!? I did however discover that my compression is quite low (76lb) which would explain the difficulty starting it. The good news is that I need to buy a new saw That sure does hurt my feelings.

I'd be interested to find out if you still get different compression readings when the saw is warmed up to operating temperature?

God bless,
Chris Charles

 

[mountainlake]

Chris Tried out my 044. 1st cold throttle open 157#
2nd throttle closed choke open 152#
3rd choke on (holds throttle open a little) 148#
4th throttle open again 152#
5th choke on again 143# maybe gas washing down cylinder or I'm getting tired causing lower reading
6th let it warm up 147# throttle open
7th choke on 136#
Stayed about the same after that around 9# differance.
Tried the Echo CS670 again, still running around 15# difference. I think with the choke on air is still going out of the cylinder the same time as it's trying to fill it. On your Echo 3000 everything must be so sloppy it doesn't pump air good either way. Still runs with 75# that's has to be about the bottom limit. Steve

 

[STIHL-KID]

Ok, went out to the garage today and tried compression testing again. This time I tried doing compression with WOT. No difference! I also tried choked and non-choked......still right around 120-125psi. I also bought a new "bend-light" and used it to look into the cylinder. The piston top has a little bit of black carbon and the cylinder walls have small random horizontal scratches. The scratches are not deep, but are viewable with the naked eye. I also took apart the carburetor and discovered that eveything looked very clean. The little mesh screen was completely clear and clean. I also noticed that the actual pumping diaphram was still soft and easily moved back and forth. The only thing that made me wonder was that the pumping diaphram had many permenant wrinkles/blisters on it. I imagine this might affect it's performance? I did some carb kit research and learned that you can buy a "gasket/diaphram kit" or a "repair kit". The repair kit includes everything a guy/gal would need to overhaul it. In my case, would a simple diaphram/gasket kit be all I need? The metal screen, needle, and spring look clean and undamaged. Where should I go from here?

 

[Lakeside53]

Even though you probably only need the diaphragms, I'd replace the needle valve also. Don't lose the spring - walbro kits DO NOT include a spring...

The galley covers are needed IF you punch out the old covers to clean out the low jet bores beneath.


I'd just get the K10-HD kit - not the the D10-HD kit (diaphragms/gaskets only).

BTW, the diaphragm with wrinkles is likely the METERING side, not the pump side. The pump side is under the big single screw.

 

[drmiller100]

On the upstroke fuel and air are sucked into the crankcase through the carb on the downstroke the piston skirt closes the carb port and pushes the mixture through the tranfer ports into the combustion chamber. If you have the choke and throttle closed it won't get as much air in the combustion camber causing less compression. Steve

so how do you train all them little air molecules to only go OUT the exhaust port, and never IN the exhaust port when the piston is down???????

porting suuuuuuuuure would be a lot simpler if i knew the magic for air training.

 

[Lakeside53]

Mountainlake has neglected to figure in combustion. but then there isn't a lot of that going on with a compression gauge...

 

[mountainlake]

Just said less air would get in when it's not flowing in the right direction. Steve

 

[STIHL-KID]

BTW, the diaphragm with wrinkles is likely the METERING side, not the pump side. The pump side is under the big single screw.

Lake, I got mixed up on what I was talking about. Took a look at my HD-18B IPL and found that it was the "metering diaphram" that had the wrinkles/blisters in it. Would this condition affect performance?

 

[PES+]

Yes.......very much so replace .......the metering diaphram