Why won't it run!!!!!

[stihltech]

Strange coming from me, but it can happen to the best of us.
Back story. Stihl 036. Customer got it in a trade. Won't run. Fuel and spark OK. Flywheel key OK. Vac and pressure test OK. Carb not leaking, holds pressure to 10 PSI. Fuel system checks OK.
New aftermarket piston and cylinder. HMMM.
Disassembled piston and cylinder. All of bottom end looks good. No bearing play anywhere. OEM crank in good shape, no cracks.
Tried a good used ignition to verify not timing. Same.
I then broke my own rule and took a compression reading with a known good gauge. 85 psi.
Took a chance and broke glaze. Same. Installed new OEM rings. 125 PSI. still no start. 1 pop and that's it.
Checked squish. .060. Kinda large.
Going to delete cylinder gasket and see if it gets closer to .030. Not trying to make extra HP, just run.
To be continued.

 

[The Stig]

Dash of fuel in the plug hole . If it fire’s, obviously it’s not pulling fuel in. Not sure on these Stihl’s, but I had that problem with an old bone, the reeds were varnish tight.

 

[cookies]

125psi is too low, needs to be above 135 to atomize the fuel enough during induction to start and idle

 

[a. palmer jr.]

125 should get it started. I agree that you should put about 1/2 tsp. fuel in sparkplug hole and see if that gets it going. If it runs a bit that tells you it's in the fuel system. I guess you checked the impulse hose? Muffler not stopped up?

 

[stihltech]

One pop only even with the fuel through the plug hole.

 

[Vintage Engine Repairs]

Compression at 125 is the most likely cause as to why it’s not running.

 

[spuldup]

Is the AM P/C a name brand? Not sure how a new P/C would only be 125psi. Is there a decomp valve on it? AM ones also known to leak.

I sanded (advantage to Stihls - no lathe needed) the base of my 360 successfully to get the squish to .18. That really woke it up.

 

[ZeroJunk]

Look at the bright side, at least it is a nice saw. Not a MS170 or something wasting your time.

 

[alexcagle]

Crank seal bad, intake boot leak, check end gap on rings.
Once I got a 46mm piston, with 45mm rings.
I have seen rare flywheel magnet issues causing no start.

 

[lone wolf]

Strange coming from me, but it can happen to the best of us.
Back story. Stihl 036. Customer got it in a trade. Won't run. Fuel and spark OK. Flywheel key OK. Vac and pressure test OK. Carb not leaking, holds pressure to 10 PSI. Fuel system checks OK.
New aftermarket piston and cylinder. HMMM.
Disassembled piston and cylinder. All of bottom end looks good. No bearing play anywhere. OEM crank in good shape, no cracks.
Tried a good used ignition to verify not timing. Same.
I then broke my own rule and took a compression reading with a known good gauge. 85 psi.
Took a chance and broke glaze. Same. Installed new OEM rings. 125 PSI. still no start. 1 pop and that's it.
Checked squish. .060. Kinda large.
Going to delete cylinder gasket and see if it gets closer to .030. Not trying to make extra HP, just run.
To be continued.

Needs new cylinder or is the choke not closing? Did you pull the saw over till the gauge stopped rising?
Edit new OEM cylinder.

 

[old guy]

Some people just don't read what is written.

 

[lone wolf]

Some people just don't read what is written.

What do you mean exactly?

 

[ZeroJunk]

Well, it has fire and at the right time. Doesn't have an air leak.
If you squirt some fuel down the barrel it should run a few seconds anyway, and doesn't.

Doesn't leave much but compression. Or, something really wrong with the construction of the cylinder and piston.

 

[cookies]

Is the AM P/C a name brand? Not sure how a new P/C would only be 125psi. Is there a decomp valve on it? AM ones also known to leak.

I sanded (advantage to Stihls - no lathe needed) the base of my 360 successfully to get the squish to .18. That really woke it up.

What I see is most aftermarket cylinders have a deeper/taller dome combustion chamber and the deck/base is not machined enough. Often the squish over .045 and with the larger dome lt lowers compression badly, I believe it is done to lengthen the lifespan of the inferior parts. I have seen several cases of this that required machining the base just to get compression up enough to run. once running it is very likely the port timing is so far off that it revs but has little to no power. The other likely cause is the cylinder is out of round, I would start by using a bore gauge before going any further. I would only dink around with this if it were a friend/family member, otherwise I would get a different cylinder kit. If they are broke i'd wrap the powerhead in plastic for storage and suggest meteor as the only cheap option plus explain it likely will not be as powerful as a oem then explain the oem kit will be 2x as expensive and a full teardown to install new seals, gaskets, bearings and case cleaning to inspect integrity should be heavily considered to protect their investment for longest life.
I know hyway sells a 48mm pop up piston for this model if you want to pour gas on your trash pile fire lol

 

[stihltech]

Little update.
Found a piston I used in my 034 super. Removed it for more port work and replaced. Still AM.
Piston slightly taller than what was in this saw. Still no difference. 125 PSI. Squish it later. Trying to keep customers caught up before I go in for suspension work.
Took another look at the carb. Stihl cover on metering side. Says C3M on side and NOTHING else on side or pump cover. Chinese carb! Double whammy! But it does hold pressure and lever is correct.
Scrounge around for a used carb (lots of used parts).
Updates when available.
Have a good weekend!

 

[lone wolf]

Little update.
Found a piston I used in my 034 super. Removed it for more port work and replaced. Still AM.
Piston slightly taller than what was in this saw. Still no difference. 125 PSI. Squish it later. Trying to keep customers caught up before I go in for suspension work.
Took another look at the carb. Stihl cover on metering side. Says C3M on side and NOTHING else on side or pump cover. Chinese carb! Double whammy! But it does hold pressure and lever is correct.
Scrounge around for a used carb (lots of used parts).
Updates when available.
Have a good weekend!

China Cyl is crap!

 

[cscltd]

Even without a carb on and you squirted fuel in bore , it should fire and run/rev on the fuel that was squirted?
those cheap cyl kits just don’t like to run sometimes it seems.

 

[The Stig]

So. Check this out. I got this turd which probably hasn’t run in 40yrs. Do what I normally do, wash them, clean fuel system, clean and set points etc. it fired right up as they usually do




View attachment IMG_1820.MOV

I take them Down ( cosmetics ) paint and reassemble. They are still a running unit



So tonight I filled with gas the beotch wont run ??? Spark, fuel, compression, etc good.
What in the actual fk!!!

 

[ZeroJunk]

Really doesn't matter. If it has compression, fuel, and fire at the right time it will run.

Just cause you think it does doesn't count.

 

[The Stig]

Really doesn't matter. If it has compression, fuel, and fire at the right time it will run.

You would think. This ran fine 2days ago. Nothing was disassembled to cause it not to run. I think I got the Whammy