Please help me locate a fault-McCulloch

[medusa]

Please bear with me as I am rather new to attempting repairs on a chainsaw.

I have a McCulloch Mac 335 (it may be a european only model, but it is 34cc engine and 14inch chain, uses Walbro WT391 carb).

It started to smoke badly and lacked power, I knew it was burning a lot of oil, then it started to race (high idle speed, chain runs when idling). So I stopped promptly.

Discovered that chain oil rather than 2stroke oil was mixed with the gasoline, in error !!!, (petrol as we call it here in the UK).

I emptied the tank and washed it best I can with gasoline, and cleaned air filter, mixed fresh fuel and oil...etc.

I can start it with difficulty, but when it starts it is still idling way too fast and the idling adjustment (T) is ineffective, I can litrally take it counter clockwise almost till the screw is out without slowing the engine.

The L and H adjustments, I left with the limiters in place for now, but they seem to have some effect (all be it so slight, as I can only turn them 1/4 of a turn within the limiters).

I would appreciate your help here.

Is it likely that this is an air leak? (Or just blocked jets ?)

What is the best way to go about repairing it?. I can get a carb diaphragm and gasket kit. But I do not seem to be able to locate a source where I can get a crankcase gasket.

Your input and ideas will be greatly appreciated...Thanks in advance

 

[Dan Forsh]

You should probably start by taking the carb apart and cleaning it. I've never heard what effect using bar oil can have, others will doubtless tell you in detail, but it may well have gunged up the carbs internal passageways. start by stripping it down and a thorough cleaning. You don't say how long you ran the saw on this wrong mix for but you probably haven't damaged the diaphragm.

Check that there isn't a more obvious problem for the high idle, is the arm sticking even when the idle screw isn't contacting it, could be down to gunk in the carb.

If you are lucky you might not have done any damage to the piston and cylinder, I'd suppose wrong oil is better than no oil.

Why do you want a crank gasket?

 

[ozflea]

Sounds to me as if the saw has an air leak, your first course of action should be to pressure test the engine and see if it's a seal or gasket leaking.

I dont believe the chain oil would be causing the saw to race more likely its an airleak or maybe a cracked or old fuel line or pulse line that could be needing replacemen

Mc Bob.

 

[medusa]

@Dan Forsh

Thanks for your suggestions.
The arm is not sticking.
It ran no more than 15 minutes with this wrong oil.
I thought I may need the crankcase gasket if there is an air leak, you obviously think this is not likely (thank heavens !, as I cannot get it ).

@Ozflea

Thanks for your help. I will check the lines, thanks for that.

Pressure testing may be a problem, as I do not have any equipment, but I found a link to a site offering advice on how to make the blanking plates. Seems easy enough, now I need to think of a way to obtain a pressure guage !

So you think the wrong oil was a co-incidence ?
I rather thought as it is much more viscous, it may have blocked the jets as Dan Forsh suggested.

Do you think it is worth cleaning the Carb. first ?

Thanks

 

[Lawn Masters]

try the simple stuff first, then the more risky stuff later. if it doesnt idle right after cleaning the carb, then get it pressure tested, and determine where its leaking at.

 

[medusa]

First Thank you to those who advised.

However no joy I am afraid. Took Carb. out, cleaned, put new diaphragm and gaskets. Managed to start the saw with some difficulty, still racing away!.

What I did discover while dismantling, is that around the clutch area there is evidence of overheating .

I think this is going to be either a job for the service centre if I can find where the hell is it in the UK, and the price is right, or else ebay for somebody to use for spares.

Thanks again everyone

 

[whatsnext]

@Dan Forsh

Thanks for your suggestions.
The arm is not sticking.
It ran no more than 15 minutes with this wrong oil.
I thought I may need the crankcase gasket if there is an air leak, you obviously think this is not likely (thank heavens !, as I cannot get it ).

@Ozflea

Thanks for your help. I will check the lines, thanks for that.

Pressure testing may be a problem, as I do not have any equipment, but I found a link to a site offering advice on how to make the blanking plates. Seems easy enough, now I need to think of a way to obtain a pressure guage !

So you think the wrong oil was a co-incidence ?
I rather thought as it is much more viscous, it may have blocked the jets as Dan Forsh suggested.

Do you think it is worth cleaning the Carb. first ?

Thanks

1. The oil is no more viscous when mixed at a normal ratio like 40-1. Think about it.
2. If it's racing away with the throttle shut it's got to be getting that air from somewhere. Look for the air.

Since it shows signs of overheating near the clutch I'd guess that's where your problem is. It's also unlikely low grade oil would degrade your base gasket so why look there. I would not bother to clean the carb yet because then you may get more fuel when what you really want is less air.
John...

 

[ozflea]

Pressure testing is a very important step as you say there's been overheating around the clutch just maybe the seal just behind the clutch is letting air in.

Thats why a proper testing procedure should be used as it will save time and effort and the customer money.

Alot of old saws i have bought off Ebay have suffered something simple like a crank seal leaking or gasket missing or torn and most times cost little to get running.

You cannot tune a saw with an air leak either.

Mc Bob.

 

[medusa]

Thanks for the valuable comments.

I am sure you are right, there is an air leak, and not clogged carb jets as I originally thought.

I will also need the clutch cover/ chain break-release assembly as it is a bit damaged by heat, still functions though !!

My problem is not so much of finding a way of pressure testing, there are a lot of very good suggestions both here in old threads of this forum and elsewhere on the web, the problem is in sourcing the appropriate gasket kits in particular for this chainsaw, at all , let alone at a reasonable price !. Not to speak of other parts too.

So please if anyone knows where to get those kits and other parts for this chainsaw, I would be most grateful for guidance.

McCulloch seems to have disappeared even from parent company's (Electrolux), website !!.

 

[whatsnext]

Let's speculate that you need crank seals. You'll probably have to disassemble the saw almost completely. Even for someone who knows what they are doing it will probably take at least an hour. One more hour to reassemble plus parts like a base gasket. For you figure three times that. What is this saw worth to you? If it were a 066 or my dad's first saw it would be worth the effort. If it were a 34cc Mac I would not spend more that 1/2 hour on it because I see used saws for $40 all the time and half of them would be better than your Mac and would require no effort at all. If, for whatever reason, you like the saw buy another and use yours for a parts saw.
John...


/logic bores me but it is what it is