Chainsaw lacking power

[Grappler]

My trusty chainsaw has suddenly become gutless under load
So far Ive changed sparkplug, checked for strong spark, replaced air filter, serviced carb, pulled and cleaned the spark arrestor/muffler, checked pickup and pulse tubes for leaks. The choke is operating correctly. Fuel is fresh and the fuel filter is clear

The motor seems to be running lean as it starts and idles fine, but fails under load. No amount of tuning will get it running sweet. What am I missing?
A crank case leak perhaps?

May be time to get a new one!

[isuzurover]

Brand and Model?

Lean would be MORE power, not less. My husky had heaps more power right before it seized from an air leak...

Is it bogging down or is the clutch or bearing on the way out?

[87County]

Sounds like it's possibly the fast run jet blocking ?

Look at cleaning the carburettor renewing the diaphragm(s)

[omnibus]

air leak between carb and block, maybe?

[BathurstTom]

Sounds like it's possibly the fast run jet blocking ?

Look at cleaning the carburettor renewing the diaphragm(s)

+1

Tom.

[Rohan]

Possibly a silly question, but are you running it with the bar removed? Often a damaged bar/chain or the kick-back brake could be the cause..... (I like to try the simple stuff first).

[rijidij]

If you remove the carb and exhaust, check through the ports to see if there are any score marks visible on the piston. If it's had a small nip it might still run, but could loose compression.

Cheers, Murray

[Davehoos]

after checking fuel supply and exhaust,good idea to keep a carby or a kit available--as you never need it if you have one..the current fuel eats the system.

then look at bolts in the casing.
lot of the chainsaw have bolts coming under into the barrel that fall out.

lot of the saw at work have pressurised fuel tank like little mowers do.
they have a pressure check valve to hold a set pressure.

[Bess]

G day, try checking the fuel line for a very small break. Fairly common causing fuel starve issues on some makes. Can be hard to spot if you don't remove the line. Good luck.

[DeeJay]

Most possibilities have been covered, but if it has good compression - if you don't have a compression gauge, try pulling the starter rope until the engine compresses & it should take 2-3 seconds of resistance- then remove the exhaust & check for blocked ( carbonned up) port or exhaust. This happens with a too rich mixture.

[sdt463]

Just a thought but the rakers havn't been taken down to far have they.

[Saitch]

You don't say how old your fuel is but I have to replace the fuel in both my saws & the 2 stroke line trimmer regularly as they lose power under throttle with the old fuel as the octane in ULP breaks down over a short period of time. I've found 4 weeks to be the cut off for 2 strokes although the 4 stroke Honda brush cutter runs OK on it. 8 weeks & I get rid of the fuel.
I bought some fuel extender additive the other week & am interested on how it will go.
Steve

[Grappler]

[Is it bogging down or is the clutch or bearing on the way out?[/QUOTE]

Thanks for all the useful replies
I think IsuzuaRover and Rohan are on the right track

I had a play earlier today and noticed it runs fine when undercutting (using top of bar)

Took the bar off and the clutch drum bearing is allowing the drum to wobble.

Ill order some parts, which are still available, and let you know if it solved the problem

The saw is a Homelite 330, which ive used for 40 years. Before Homelite soldout and became a budget brand. Homelite used to be one of the best saws money could buy.

After 40 years, I will look at a replacement, probably a Stihl. If I can fix the 330 it will be good as a spare.

[Davehoos]

work is changing over from stihl to husky.

[snowbound]

I was at the Murrumbateman field days yesterday and came across a stand selling "Farm Boss" branded saws. I commented that one was a dead ringer for a Stihl and he told me that it was a Stihl, just imported without the decals and logo's. but get this, they sell for half the cost! You can get a kick arse Magnum 660 for around $1100 I paid $2000 for mine a while back being a branded Stihl :eek: They are based in the Gong and happy to ship. Sorry don't know any more details.

Jez

[Grappler]

Ive been barking up the wrong tree.

All the syptoms indicated something other than electrical fault. Especially the strong spark.

I decided to strip the saw down, a bit more, as I need to order the clutch drum and wanted to see what else was worn.

Found the wire from the coil to the kill switch frayed and had been rubbing on the body. The thing is it was only shorting when there was some downward force on the drive. Like when trying to make a cut. The body is vibration damped and the body and power head can move independently This explains why it idles fine but looses power while cutting. It also explains why it worked OK on an undercut.

Put it back together, and it ran fine even with the worn sprocket/clutch drum
Ill give it a bithday with some new parts and she will good for another 30 years.:D

[DeeJay]

Yair, I thought it would be that,,,:eek:

[bushrover]

I was at the Murrumbateman field days yesterday and came across a stand selling "Farm Boss" branded saws. I commented that one was a dead ringer for a Stihl and he told me that it was a Stihl, just imported without the decals and logo's. but get this, they sell for half the cost! You can get a kick arse Magnum 660 for around $1100 I paid $2000 for mine a while back being a branded Stihl :eek: They are based in the Gong and happy to ship. Sorry don't know any more details.

Jez

BBC1 Fake Britain discovers counterfeit chain saws - YouTube

[460cixy]

I was at the Murrumbateman field days yesterday and came across a stand selling "Farm Boss" branded saws. I commented that one was a dead ringer for a Stihl and he told me that it was a Stihl, just imported without the decals and logo's. but get this, they sell for half the cost! You can get a kick arse Magnum 660 for around $1100 I paid $2000 for mine a while back being a branded Stihl :eek: They are based in the Gong and happy to ship. Sorry don't know any more details.

Jez


They will be Chinese clones steer clear. If I had of seen the bloke selling them he would of been told to put em where the sun don't shine. There not fit for purpose

[Lotz-A-Landies]

I had a problem where a mud-dauber wasp nest had blocked up the exhaust (Stihl), the engine would run but nil power. Cleaned out the nest and the saw ran fine.