bmp01

My wasp lesson was taught to me as a youngster at a french campsite. Drinking from a nearly empty fruit juice carton that had been left out...... Live and let live but killing the odd one or two that become troublesome is alright in my book. Electronic bat zapper ('moderately tuned') doesn't seem to encourage others to attack.

This spark tester goes in series with the plug then ? Does it work if the plug has a short inside it ? I've posted before. ... only ever seen a failed plug once and it was with one of these little plugs. See picture, this is a plug with an internal short, you can see the lines where the arcing has occurred. Get a new plug (or 2) and careful how the wrench interacts with the plug. ....

Coil to flywheel alignment across the face of the flywheel (not the 10 thou gap) ? Have you got the plastic spacer between coil and engine? Try another new plug too?

Accelerator circuit is for response during. ... wait for it. .... acceleration (ie increasing engine speed). In the steady state of wide open throttle it does nothing. You can understand this when you've seen the bits in front of you - the piston doesn't move any further once the throttle shaft has reached wide open throttle. ... So all you are trying to over come once the accelerator circuit is disabled is that initial stumble when you quickly open the throttle. I set the saw up a little rich on the low speed circuit. So at idle, find the fastest engine speed with the low speed screw, then back it out until idle speed drops slightly. Blip throttle , check for response... Worth noting, at operating speeds the low speed circuit is responsible for 25% ish of total fuel to the engine. So there might be a requirement for a small tweak to the high speed circuit. (That 25% number came from Zama website, sounds very approximate to me, but the principle holds). But let's not get too far ahead. Check the condition of the accel piston first.

Nope, my normal approach is to chuck the accel piston, make an ally plug to stuff in the hole and retune the carb. ... so far so good - I've not needed replacement carb. Yes it's a Zama carb as std eqpt. If you have an after market carb that probably doesn't have an accelerator circuit at all. The whole concept was necessary so the manufacturers could run a leaner mixture (for emissions purposes) with good throttle response. Aftermarket carb manufacturers are not subject to the same emissions legislation so they don't bother. Quality and life span of aftermarket is questionable by all accounts.

Yeah, it's not obvious is it. .. The throttle shaft (the one with the butterfly valve) .... where it goes through the carb housing isnt round it has a flat machined into it. That operates on the accelerator piston, which is buried in the carb body. Wish I had a picture. ... but anyway, if you look at the face of the carb, engine side, there is a hole parallel to the inlet port, 5 or 6 mm diameter. Sometimes they have a blanking plug. You should be able to see the throttle shaft running across the hole, you might be able to see its not round. So boringly you've got to disconnect levers, springs, butterfly plate etc and slide out the throttle shaft and the accel piston will pop out. It has a small spring behind it. Usual precaution, take some pictures, lay out the bits in the correct order etc so you can get it back together. You also need to be able to align the butterfly on its shaft and re-peen the end of the butterfly securing screw when you reassemble... If the accel piston is tired the plating is usually worn through see piccy. Worn o rings are often visibly small. Trouble is once the piston is worn there is a good chance the housing is too. The next alternative is to disable the mechanism, seal up the hole and retune the carb a bit richer. All in all - not one of the easiest jobs and time consuming. That's why they would just lob a new carb on at a dealers. HTH, if i can clarify anything just ask.

A proper scammer would have disappeared over the horizon as soon as they had your money, surely ? I can't see any reason they'd hang around ....

Low compression doesn't usually cause random behaviour. If this random behaviour happens even when the engine is warm then my guess would be the carb. You say you've put new gaskets in but did you check the accelerator piston o ring. It's boringly frequent that this little carb feature causes random behaviour. If you can swap in a known good carb that will set you off on the correct path of fault diagnosis. Presume you've tried a new plug, unlikely to fix it but as its easy ....

That's an extract from the Oregon Products pdf file I had in mind. I have it located but at 75 mb I can't post it here,.... Not sure it's needed now anyway.

I have seen an Oregon products guide which had all the different versions of bar mounts, dimensions and all. Just had a look on line, can't find it. I might have a copy on a computer somewhere ....

I reckon thats the answer , give it plenty of welly. If it's not too late take the plug out at the same time as the exhaust is off, lower the piston and you'll get a chance to see the combustion chamber, piston crown . The extra daylight helps a lot.

Picture of the plug with the carbon stuck in it would have been good, one for the library that. ...

This "hard carbon" you mention, are you saying its a lump of carbon that's maybe come off the combustion chamber and has wedged itself between the plug electrodes ? And its done it twice ? On the other hand fouling a plug to the point where its completely carboned up within the space of one tank of fuel is pretty much unheard of too (with modern oils).... Maybe it's just cleaning itself out after previous misuse, it might also be spitting carbon out of the exhaust too, just thinking about the spark arrestors on saws in USA.

Let us know where and when, we'll sort out some backup ! Maybe we could do a nationwide test day or something, that ought to be popular. ..

2 stroke oil is probably the thing that has developed more than the 'bits of metal'. So use decent oil at 50 : 1 (and carp oil at a higher oil ratio if you must). And if the saw starts screaming (high revs) get it retuned / checked out. If you don't expect too much from them and use a narrow kerf chain they are fun saws. Older ones are better than later 170's, so they say.

Bought 2 of those Lidl folding saws for the children to stop them from playing with my Silky Zubat - and to teach them how to be careful with folding saw . So I bought those ones over a year ago and i can see some differences to the one in this post but i have to say they work perfectly fine, they certainly don't jamb in the cut. And for the price, fantastic. Worth cherry picking the best looking blades.... In contrast the Lidl full length pruning saw (from a year or so ago), had teeth 'set' to cut a wider kerf than the blade thickness and looked cheap and nasty.

......don't they have some decompression mechanism thingee on the valve train, for easy starting. ....? That's from memory, I could have imagined it , but if true how would you know if the compression was low? Can't see why they would wear out the cylinder or rings unless mega mileage, no ports to worry about. The one i looked at (a non starter) - one of the push rods had popped out of the tappet due to clearance issue. Put it back together correctly, started like there was never anything wrong with it. Don't give in yet

The oil pump on a saw is a fairly simple device but also a fairly pathetic vacuum device. You've seen you can suck oil through the lines with a proper vacuum pump but don't expect the pump to achieve anything like that sort of vacuum. The reason the pump falls over as soon as it is asked to pull a vacuum is because it will find it easier to suck in air past the seal....and often there is no seal, it relys on a good fit between the oil pump shaft and the housing. With time and wear this clearance increases such that the pump can't pump anything before it sucks air in preference - ie. worn out. Another possibility - the pump shaft is not travelling its full stroke. Maybe gummed up or the return spring might be weak, maybe damaged or even rusted away if it's been in contact with water. I'd pull the pump apart and have a look for wear and / or scoring. See what you can learn. It's unlikely to get any better with time .... BMP01

Length of bar might be an issue but only if your using the full length of bar. If it's a 10" diameter log, I can't see the bar length makes any difference. Assuming the engine speed is not being dragged down near to stalling, then I'd guess the clutch needs a good clean out. Some of these saws can get a bit oily or maybe the clutch bearing has had a dob too much grease in the past. The 181 uses the same clutch as the bigger 211 - assuming genuine parts. BMP01

This. Beat me to it.

It's on the floor, pict 3, just to the right of the gob. But the gob doesn't look like a big enough angle so what you say might still have happened. ...

Dunno if this helps. .. I've never tried this starter cord compression test. My 028 has 155psi after 10 pulls, using an old fashioned "pencil" compression tester (looks like the extending tyre pressure testers but it has a one way valve in there and is rated for cylinder pressures). Anyway, no long tube prior to the one way valve which should avoid low readings. Drop test - the 028 weighs 7 kg with bar and chain and takes appox 20 seconds to get to the end of the starter cord, 3 or 4 revoulutions (each compression event is very obvious). In hind I might have done this wrong? I held the saw in the air and dropped it while holding the cord. It slowed down more and more with each subsequent revolution so by the final compression event it nearly stopped. Didnt attempt to build up any pressure at start... 20 seconds feels like forever by the way, definitely need to do the "1 Mississippi, 2 Mississippi,.....etc" thing And a bit disappointed with only 155 psi, this saw has had new Caber rings and has been squished to 20 thou. But then again it is an old saw design and the combustion chamber is probably a bit big compared to modern saws... runs fine, good torque.

On a sample of one.... bag of excrement. Golf piston for a Husky 136 (so a low value engine), the inside forging was 1 mm offset to the machined detail, so one wide boss and one narrow boss for the gudgeon pin to run in, off setting the rod to one side. The piston was also 8 grams heavier than the original (thats 48 grams instead of 40, 20% heavier). The gudgeon pin, the hole was visually eccentric and not parallel to the outside diameter. Don't know about durability, this particular one was not fitted. Avoid fitting to anything you remotely value. All IMHO based on a single piston, purchased through that auction site from a dealer, came in manufacturers packaging.

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Have a look at my post in your other thread ..... I suspect you are going to find the same thing in due course. Or you could bite the bullet and overhaul the carb and fuel lines now. The trouble is you can chase your tail backwards and forwards ad-infinitum - if bits of the system are misbehaving.