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Help! Chainsaw running rough.

Started by jesterr6216, July 22, 2014, 10:44:44 AM

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jesterr6216

Hi guys. Brand new to this site and looking for some help and guidance.
I have a Einhell BG PC 3735. We have a wood burner in the house so got the chainsaw to go out hunting and gathering logs for firewood. Very satisfying burning logs you have cut, chucked in back of Landrover, chopped and stacked.
Anyways. Was happlily cutting away the other day, chainsaw working great, when it started to run rough, revving high, then low. I stopped it to check the fuel level when I noticed the primer bulb had split (it was looking old yellow and brittle). With my basic knowledge of engines I thought that it must be letting air into the system, hence the revving, so order a new part and that should be it.
Ordered and fitted said new primer bulb, but still got problems.
From cold, turn it on, full choke, ten pumps of primer, pull cord and it starts fine, revs high (on full choke), drop it down to half choke, again runs fine, but then when I pull the throttle to drop it to normal revs it pretty much straight away starts labouring, low revs, then konks out. And that's it. Can't start it again till it's sat for a bit.
One thing I have noticed, is the primer bulb seems to be staying full of fuel even when it's been sat not used for days. I'm sure in the past this would be empty after the initial priming.

I'm handyish with stuff so will to try stripping down to fix things rather than just paying to have a man do it. Wondering if it might be the carbs/jets? Took the plastic air filter off, gave it a good clean and dried it off so it's not that.

Any help would be greatly appreciated.

Cheers

LeeB

Welcome jester. I can't help you, just wanted to welcome you on board. Where are you from? Tell us a little more about yourself. I've never heard of that brand of saw.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, JD 3032 tractor, JD 5410 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

old guy

Sounds to me like it is already siezed, pull the muffler and look at the piston, if it is streaked  and smeared it is done for.
  I've not heard of that saw either.

John

thecfarm

Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

jesterr6216

Cheers for the warm welcome guys. I'm from sunny South Shields which is at the mouth of the river Tyne just south of Newcastle, England. Get's cold in the winters here so our wood burner in the living room gets well used and I spend the summer stocking up the log store, hence the chainsaw. Didn't realise Einhell was a euro only brand.

Will have a look at the piston, as I say though, it does turn over and run initially on the choke, but dies out when I release the choke.

Cheers again.

mad murdock

Any new-ish saw (say last 30 years or so) that is worth anything, if compression is anywhere near respectable you should be able to almost pick the saw up by the starter handle and have the cord either come out a little and stop or drop real slow with the weight of the saw on it. Now this is assuming the piston or cylinder is not scored bad from an extreme lean condition, which could have been what did you in when the primer bulb broke. Best bet would be to pull the muffler and have a peek at the piston/cylinder like has been said, if they seems ok, try and get a compression tester on it, if it is any good at all it should be able to come up to at least 100 psi(which is still on the weak side, but should run and do something at that). Welcome to the Forestry Forum!
Turbosawmill M6 (now M8) Warrior Ultra liteweight, Granberg Alaskan III, lots of saws-gas powered and human powered :D

joe_indi

If it runs fine on choke but dies without choke, the engine might be starved off fuel. Chances are the pickup body (Fuel filter) in the fuel tank is nearly blocked.
Also check whether you have connected the primer correctly. The primer  sucks fuel through the carburetor. The primer does not pump fuel into the carburetor. So, suction of the primer on the carburetor and outlet back to the tank

old guy

Any follow up on this saw, did you get a look inside it?
I hope all it needed was some tuneing.

    John

jesterr6216

Afternoon gents. Short update. Spent the last 2 days stripping my saw right down. Took it all to bits. Couldn't see anything obvious. Put it all back together, and guess what, I think I may have kinda fixed it (accidentally!!!).

On full choke it didn't really want to start, but it kinda got there, got it on mid choke and left it running fast there, then the acid test, clicking the trigger and dropping it off mid choke to normal running, and it kept going!!! This is a plus. BUT. When I go to take my finger off the throttle, it dies.

So, thinking maybe the fuel filter in the fuel resevoir may have been blocked/stuck in a corner and not drawing and maybe me mucking about has resolved it. But now I have the issue of it not idling. I'm guessing I need to play about with the carb screws, need to find where they are!

Ehhhhh it's a joy!

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