Stihl 046 won't run after rebuild.....please help?

[Mitch Hall]

Picked up an old 046. I checked the compression and it was at 90lbs so I recently replac d the piston/rings, coil and rebuilt the carb. It started up with some starting fluid and idled but kept bogging and dying when I tried to throttle up a bit. After about 6-7 times it stopped running all together and wouldn't fire even with either. It finally flooded so badly that I had to pull the jug and empty the full crankcase. I replaced the jug and checked the ignition for spark then changed the plug but no luck at all. Also, the decamp valve looks leaky. After the rebuild I noticed no change in compression. Thoughts?

 

[Cease232]

Sounds like multiple issue at play here. Definitely don't run it if the decomp is leaking. You need to do a pressure/vac test and find your leaks. BTW starter fluid is never recommended on a saw. Just squirt a little mix in the carb throat.


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[Mitch Hall]

Right. I'm really confused at how it ran at first and then just quit. I just ordered a new decomp valve. What is the best way to run a leak check?

 

[dugide]

where are you located? there might be a member near by that can give you some help.

 

[Boleclimber]

I would re-check the compression, pressure test the carbs pop off pressure and re-check the high/low needle settings.

 

[blsnelling]

If compression was only 90 PSI, what did the cylinder look like?

 

[Mitch Hall]

Spokane

 

[Mitch Hall]

If compression was only 90 PSI, what did the cylinder look like?

It looked good. The top ring was stuck in the groove but I saw no material in the bore.

 

[rupedoggy]

I think it fired because there was some assembly lube in the cylinder and that helped compression at first. Either washed it all away. You say the compression is the same after rebuild? A saw will not usually run at 90# compression.

 

[Jacob J.]

Right. I'm really confused at how it ran at first and then just quit. I just ordered a new decomp valve. What is the best way to run a leak check?

Spraying soapy water around suspected leaks works pretty good. You'll see bubbling as you're pulling the saw over. This would work to check your compression release.

 

[Mitch Hall]

Ok, I'll change out the decomp valve and run another compression check. If it's still low I'll start looking for other leaks. Are there common areas on this particular saw that tend to leak?

 

[Mitch Hall]

I

Spraying soapy water around suspected leaks works pretty good. You'll see bubbling as you're pulling the saw over. This would work to check your compression release.

definitely see oily spray around undo the decomp.

 

[a. palmer jr.]

Have you checked your compression gauge?

 

[Mitch Hall]

Have you checked your compression gauge?

I used it on two other saws I own. One shows 140 and the other 150 or so.

 

[a. palmer jr.]

The reason I brought it up is that I have a compression gauge that works great as long as you don't use the extension piece, it seems to leak and show low compression..

 

[a. palmer jr.]

The problem could well be the comp. release. You can always plug the hole, they make plugs for that. Might be easier to spot the leak. I don't think a leak anywhere else on the saw would cause low compression except the spark plug and compression release. I assume you have the cylinder bolted down good on the case and sealed with a gasket or sealer.

 

[Mitch Hall]

Yep. New piston, rings and base gasket snugged down good. No change in compression. I'm beginning to think its the decomp too. It really flooded worse than I've seen before. Crazy thing is, it ran for a few minutes on and off them just gave up.

 

[Cease232]

Ive seen saws run for a while with the decomp stuck completely open. Did you recheck the piston after running it like that?


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[Mitch Hall]

Ive seen saws run for a while with the decomp stuck completely open. Did you recheck the piston after running it like that?


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I did. No issues noted but it will not crank at all now.

 

[Mitch Hall]

Just installed a new decomp valve and rechecked the compression. It's showing 125 or so now