Lean or rich high end bog?

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Lean or rich high end bog?

  • Total voters
    8
It still sounds very lean. Is it possible that it is partial seizing at WOT when it is getting too hot and then when it cools down it starts to run again? THis is not unheard of with 2-strokes. Hard starting may be another clue that the compression is not to standard.

A non-adjustable carb on a AM engine is a BAD idea. These carbs are tuned to run (and borderline VERY lean) on a specific Stihl motor configuration. It is unlikely that your AM engine is even CLOSE to the same spec. It may require more fuel than that particular carb puts out. At this point your option is to try a Walbro WT-215 fully adjustable carb. This should at least allow you to run the saw (if it is ever going to run) without burning it up.
 
pioneerguy600 said:
Ok Tom, where is the impulse line on this saw?
Click to expand...
Hey mate, impulse is inside the manifold. I did check it carefully when installing, however that doesn’t mean it’s not the fault! I’ll check that next. I’ll pressure test that separately to the manifold and report back later. Thanks again.
 
[QUOTE="Spoon Carving With Tom, post: 7121782, . Cleaned it up and put back together to check. Ran with low compression and tricky to start, but it did and rev’d fine. Put new top end and cylinder from China in knowing I was taking a risk but the saw was so cheap anyway and this is the result. Not sure if it’s too lean or too rich or if it’s a transfer port timing issue[/QUOTE]

You ruled out the vent, gas line and filter. Is those or the impulse pinched or unknown blockage inside?

Would be great to have a known working adjustable carb to try. You could still have ports and passageways blocked.

If you still have the old sparkplug, try it.

Sounds like the motor is starving for the proper gas delivery at higher rpm.

Could it be the case is defective and not working with the impulse. Like the comment that piston seizing when generating heat/friction?

Way out of the box here. At higher rpm, could you have a air leak maybe at the seals caused by a wobble, bad bearings? Totally out there.
 
PV Hiker said:
[QUOTE="Spoon Carving With Tom, post: 7121782, . Cleaned it up and put back together to check. Ran with low compression and tricky to start, but it did and rev’d fine. Put new top end and cylinder from China in knowing I was taking a risk but the saw was so cheap anyway and this is the result. Not sure if it’s too lean or too rich or if it’s a transfer port timing issue
Click to expand...

You ruled out the vent, gas line and filter. Is those or the impulse pinched or unknown blockage inside?

Would be great to have a known working adjustable carb to try. You could still have ports and passageways blocked.

If you still have the old sparkplug, try it.

Sounds like the motor is starving for the proper gas delivery at higher rpm.

Could it be the case is defective and not working with the impulse. Like the comment that piston seizing when generating heat/friction?

Way out of the box here. At higher rpm, could you have a air leak maybe at the seals caused by a wobble, bad bearings? Totally out there.[/QUOTE]
Some great advice and things to consider and check!!! Will check impulse hose and check it for pressure too :) excited to get to the bottom of this :)
 
I am jumping in this thread late and you are already doing more detailed work on saws than I have done. That being said, my 025 purchased at a yard sale started acting up doing somewhat similar to what yours is doing. Cannot remember the exact details as it was several years back, but my simple cure was ordering a new carb with H and L adjustment jets, think it was Walbro brand. Once installed and adjusted it turned into a much better running saw than it was before and runs just as well as my 026.
 
Bob Hedgecutter said:
Tommy lad- you haven't got something assembled slightly skewiff and something like the plastic choke lever rod isn't pinching the fuel line- thus restricting fuel flow at peak RPM?
Click to expand...
It’s funny, I dread what you’ll write here sometimes haha pleasantly surprised with this advice and lack of piss taking:laughing:
 
Spoon Carving With Tom said:
It’s funny, I dread what you’ll write here sometimes haha pleasantly surprised with this advice and lack of piss taking:laughing:
Click to expand...
Bloody heck- does it all have to be kissy cuddly and wrapped in cotton wool?
Are we that PC now?
I am just trying to think of a simple solution- but the truth of the matter is, SteveSr probably sums it up well- if there is no restriction- OEM carb is set for OEM combustion chamber.
Guessing the old cylinder and piston were straight gassed beyond saving and you cannot swap out the rings to see if the original ran any better?
 
good morning tom hows that saw coming? sometimes these saw can really get us stumped I no for me at least but I enjoy it enough I keep trying and learning. don't forget learning cost money nothings free in this world. If you 180 stihl came out of a junk yard and its worth right at around 100 running good you got to ask yourself how much do I invest in this saw? Even buying cheap china parts the money you have into a saw will increase. It sounds like you are into these saws.

from what ive read you have been working on saws a couple months don't be so hard on yourself just be paceint and try to learn threw reading listening and watching videos but another good way to learn is spend money. do what you will with your coin but I highly sugest not to buy china parts with your hard earned money buy something of quality. the answers are out there you got to seek to find.

good luck on the saw I have been reading up on this thread a lot of folks made a lot of good points. your saw is running lean. might be time to wipe you hands clean on that saw put it on a shelf and find another parts saw with oem parts to make 1 good saw.

best of luck to you tom.
 
i,m surprised at the chinese negativity on here ! considering that half of what the world consumes comes from there
and the air filter has a marked effect on the top-end mixture tom (on carburettor engines)
 
Lean in the top end. Get a cheap adjustable carb for it and tune it for the new setup.
I don't even like using non adjustable carbs on weed wackers if I can avoid it, I won't use them on chainsaws. In fact you can't around here, we have such wide temperature swings between summer and winter that you absolutely need a fully adjustable carb to be able to run them all the time, unless you have an auto tune setup, which still might not be able to fully compensate.
With practice you will develop the "tuning ear", a definite asset when running a chainsaw. That's actually a big part of running a saw, the sound of one in perfect tune cutting wood and the satisfaction of knowing that you are the one who set it up that way.
 
Spoon Carving With Tom said:
Cleaned it up and put back together to check. Ran with low compression and tricky to start, but it did and rev’d fine.
Click to expand...

Now becomes the investigation part. "before repair it rev'd fine". It does point to fuel delivery system starving at high rpm. Also since you touched everything you can not rule out everything you touched. Yes start from fuel tank to rubber boot at cylinder. Your biggest unknown at the moment is the carburetor. If you had a new one with adjustments this could settle that unknown, might even fix it and deliver proper fuel at high rpm. Try it without the air cleaner. Try adding choke at high rpm.

You could expand your investigation to other parts, but may not find anything. But you did touch all of this.
  • New Spark plugs have been known to be bad
  • Air gap at coil changed or timing has slipped
  • You might have not tightened coil wires that have become loose or defective.
  • clutch is seizing on the drum. Take bar and sprocket off and run it to confirm. Chain and bar could be seizing.
  • double check the exhaust
  • do another pressure and vacuum test and stress the crank and all associated parts to see if leaks happen, not just at a static position.
The new cylinder and piston. If after new adjustable carburetor does not fix high rpm fuel delivery, and all other attached parts check out, Then yes there could be a problem with the C/P not pulling fuel to the chamber. You do get a short burst at high rpm then starves out. Points to something not working... carb or vacuum pull.

Let the motor warm up at idle for a few minutes to allow the P/C to heat soak and expand before full throttle
 
frank_ said:
i,m surprised at the chinese negativity on here ! considering that half of what the world consumes comes from there
and the air filter has a marked effect on the top-end mixture tom (on carburettor engines)
Click to expand...
I am from the USA and the chinesse own alot of our national parks due to we owe them so much coin. I strive not to buy stuff from China I rather spend more to support our great country and the hard workers in it than to go more in debt to China. Plus China is so fake they copies other people's hard work to make a profit I personally can't honor that. They put there name they didn't design stuff on and sell there junk. They won't even buy back there scrap due to there metal sucks that bad. I see a problem with this. I think the world is a much better place when people shair. Some feel difrently.
 

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