spudulike

Sounds like lack of high speed fuel when you open the throttle. The metering arm suggestion would suggest this may solve the issue as should richening the H screw. Worth checking the fuel line, fuel filter, gauze strainer etc

Funny that, mine came from my fishing kit, used as disgorgers.

OK, sounds like the piston has survived which is good. An idle that unexpectedly increases is a warning sign to stop and get it checked out by someone that knows what they are doing. The manifold is the rubber bellows affair that joins the carb to the cylinder. On older saws they can split, often around the clamp that joins it on to the cylinder. You really need to remove the carb, muffler and cylinder to get to it for changing. I would check or change the impulse line first - they often get pulled off the connector just under the cylinder base especially if the bar gets compressed in a cut needing a bit of pulling to get it out. I did three 026s in three days like that! Forceps make a good tool for refitting them.

Here is a tip for anyone running chainsaws and want to minimise downtime......Take off the fuel cap when the tank is near empty and inspect for small bits of chip and shyte of any type. I used to do a lot of courier based work........on sending saws back, I drained any fuel from saws and always used a modified funnel with a very fine gauze in it and most saws left a lot of shyte in it so repeated the fill and empty process until the tank was clean. This fine sawdust tends to break up, pass the fuel filter and end up in the gauze strainer so...if you want to have an easy life.....clean the dust off your fuel cap, keep your tank clean and make sure your fuel container is also clean. I used a piece of stainless gauze stuffed in to the funnel with a ring of copper pipe....it works for me. Easy enough to do a check and hopefully save you a few £££....had two today like this!

OK, the fast idle is most likely to be an air leak. I have seen fast idles been caused by bits of twig and bark but on your saw, with its age, most likely air leak. Most likely causes, split impulse line (rubber line between the bottom of the cylinder and carb) or the inlet manifold. The impulse is relatively cheap and easy to fit, the manifold less so. The carb settings - set the H & L screw to 1 1/4 turns out from fully in. The saw may have seized, air leaks do that hence why I tend to pressure and vac check all old saws I get in. It will be worth pulling the muffler off and checking the piston unless the saw has loads of compression on pulling it over. You can also get site of the cylinder bore through the spark plug hole, something that makes a quick check much easier. Good luck, ask if you need any further assistance.

Very good Mr A, he did indeed say that he has fitted a new top end. He may have fitted the piston back to front, seen that before! If not, that blokes compression gauge is a bit iffy....unless it was 120 on one pull

Small strips of old larch lap fencing are good!

Should be "too short"....not "to short"......I hate bad English....must be my age!

BTW....where are you based? And I am not looking for work!!!

120psi is very low. If the saw had come to me, I would have popped the plug out and shone a light down the hole to look at the exhaust side of the bore. You can remove the exhaust and look at the piston surface through the exhaust port. My reckoning is that you will find some damage on it....scoring and black carbon. If you lift the saw with the starter handle, does the saw fall relatively freely to earth or does it fall and stop for a few seconds on each compression stroke? Old saws need a pressure and vacuum test, this ensures the LOWER crankcase is sealed by the rubber components and gaskets. The COMPRESSION test shows you secondary compression and gives you an indication on the state of the cylinder, piston and ring. You firstly need to know you have good secondary compression which means the top end is good, the pressure and vac test is to ensure the machine runs correctly and won't seize with use. I have seen saws with seals missing still fire and run......badly!

It was on my list but hey ho......

You sound like Donald Rumsfeld with his known and unknowns speech.....do you fancy a career in politics? You seem to have a good grasp of the facts!

Or leave a bike in the same place with a few razor blades hidden on it!!! A lacerated nether region doesn't sound good and may stop them procreating....best way!!

You can usually work the old ring in and out, scrape a little of the bruised metal out until the ring slides in and out freely.

It is usually a case to see if you can pick up a cheap Chinese one with the same drive shaft end type - splined (number of splines), square (Across Flats), inner shaft diameter and the same outer shaft diameter although the later can be shimmed up with thin plastic sheet, paper etc.

Unusual for NGK to break. The tight ring groove - use the broken ring to make sure the new ring fit isn't tight otherwise the ring will wear badly and not seal well. It is tight as the broken electrode will have impacted the edge of the piston crown - there should be a visible impression of the electrode on the piston crown edge and probably the squish band on the combustion chamber.

Lucky that didn't take out the bore. I have seen some real crap plugs from Chinese Manufacturers. Stick with NGK and Bosch IMO.

In my day we used to get old wrecker MOT failure bikes, get them running and then "bazz" about on them and then...sell them on! You learn a bit and make a bit that way! You just hope these dicks reap what they sow but reckon they will be unemployed most of there lives and go out of this world owning what they came in to it with...cock all!

No way of testing the coil as it contains a lot of electronics rather than just a conventional electronic coil. The usual method is to test the HT lead from the cap to the laminate earth and you should get some sort of reading this way. The next thing is to set the gap much smaller than normal by using printer paper, disconnect the kill wire and see if you get a spark - I open the end electrode up to a 45 degree angle so you really get a good spark as it is easy to think the coil or plug has failed because you aren't generating a big fat spark. Also - give the engine a BIG pull when testing, some need to be spun over fast to generate a nice spark. If you still don't get a spark, it is very likely that the coil is shot - I did have a flywheel lose its magnetism once but it is rare and rarer still on a modern machine - it is usually heavy impact or age that messes them up!

This whole episode sounds a bit like the late 1970s history of the Honda NR500. In short, Honda always favoured four strokes as that is what they predominantly sold so set about trying to win the Motorcycle 500 GP with a four stroke competing with the dominant two strokes of other manufacturers. Honda are pretty clever on engines and got round the "Four Combustion Chambers" rule by using oval pistons with two con rods to stabilize them with eight spark plugs and 32 valves. The pistons were going to be manufactured out of ceramics and have nitrogen cooling - later abandoned. They raced the bikes for the first time - Mick Grant hit the deck on the first lap due to an oil leak and their Japanese rider retired with ignition issues after 7 laps. Honda, not to be deterred, carried on for two years before giving up..........do you see the similarities? You can do much if you are clever, have the money and time but whether it makes good sense is another thing!!

Well done, that has probably scared him off

Old timer torque...the closest I have now is the 181SE but that is 80cc and ported - 24" no issue. 55cc and 24" sounds like no fun to me. The McCullochs were moved on BTW!

From my side, I reckon it is bonkers. 24" bars need a 70cc+ saw. Taking what is a homeowner/semi pro saw and putting a bar this size when a 15" would be about right is madness. If he did get it working, he would be forever lifting it out of the cut to get back in to the power-band to keep the cut going. The oiler won't be up to it, the clutch will slip, the machine will be forever bogging down, AV would suffer.....these size bars are 395 territory........bonkers!

Do a vid once the longer bar is fitted......prove that innovation overcomes experience and common sense

Most issues are carb/fuel system related. A holed fuel line, old fuel filter, blocked tank breather or blocked carb gauze strainer may be the issue. Other than that, a really bad air leak can cause starting issues. I am assuming that with the saw seizing, it is unlikely that the coil or plug somehow failed in the rebuild process. Probably worth changing the plug as it gets a lot of vapourised aluminium on it when a saw seizes and can make the spark fail under compression. Is the plug getting damp with the attempted starting?