bmp01

That piston was running in that cylinder you say. ... But my money says that piston wasn't running in that cylinder when it got damaged, how can the piston have got repetitive impact damage and the cylinder get away no damage? So what's this other cylinder, where did it come from ? Reuse the cylinder with a bit of glaze busting and go for a new piston for peace of mind.

One of these guess the saw games, first one to get it right pays the postage on the double bagger and gets a heap to sort out?

That would be very much appreciated, hopefully it'll confirm where I'm at. ... Clean machine eh, someone's spoiling you ! Thank you mister.

Thanks for that eye opener, had blindly believed chain speed was function of engine speed and no. of teeth on sprocket. But now you come to mention it ....

Time for a bit of an update after running the saw today. This is first run since crank seal replacement and frigging with ignition timing after shearing the flywheel key (weather and access to field). Things I've learnt: Coil is unlimited as far as I can tell, I saw 13250pm on the tacho once while settting the high speed. Coil has no spark advance curve, constant tIming above idle speed. Piston stop method of finding TDC gave me exactly the same result as using a piece of wire in the exhaust port - but it is simpler, less juggling. Sadly I didn't get to check ignition timing before stripping the key out the flywheel. My best estimate of standard ignition timing is 19 degs BTDC. I've advanced timing to 25 degs BTDC, engine seems quite happy, no nasty noises or signs of impending doom. It has had 4 tanks through it today whilst milling oak, 28" bar with 22.5" max cut, (need longer bar...). Engine runs pretty strong, I'd like to think a little stronger than before but no hard evidence to support this. Starting is more precarious, starter rope was ripped from my hands half a dozen times; it doesnt seem quite as willing to start. And that's about it, I'll stick with the 25 degs of advance for now, the starting issues being the limiting factor for me.

Err yeah, its hot because there are twice as many bangs going on inside the cylinder when its 2 stroking rather than 4 stroking. And as you're reving the engine a good deal faster than before thats probably another 50 %. So maybe 3 times the heat input. Smoke will be the acumulation of oils (from rebuild and chain oil) burning off, probably less smoke next time. Proper chain sharpening = faster cutting. As Stubby says, get a sharpening guide, you will thank him once you've tried a sharp chain. It can't be emphasised enough the benefit of a sharp chain with correct cutting angles. The saw will stop bouncing about, you won't need to push on the bar to get it to cut, there will be less wear and tear on you and the saw. The key to it is the 'Top plate angle'. To get that angle right you need to have the round file at exactly the right height relative to the top of the tooth, (which the guide does for you). 4.0 or 4.5 files will make a small or no difference if the heights wrong. Have a look at 'chainsawbars' sharpening here: https://www.chainsawbars.co.uk/chain-sharpening/

Maybe. Have you got a walk through for changing the oil pump just in case? Hopefully just chain tension - couldn't see any blueing on the bar. But slightly intrigued by the tops of some of the teeth which did have a bit of colour. That saw's not going to know what's hit it when it runs right, probably grenade itself in panic (well, lets hope not).

Picture paints a thousand words, video even better. In addiion to whats been said it looks like by the end of your demo the saw wouldnt reach 'high' revs out of the cut... it started out reving piss poorly but by the end the engine is labouring so badly it hardly has enough power to turn the chain even when its not cutting. I could be wrong, cant tell what you are doing with the throttle but the sound says its trying but can't do it - like the chain brake is part locked on, or the chain in is exceptionally tight. Just look how quick the chain comes to a halt, it's almost locked up... If you repeat that exercise and turn the engine off, can you turn the chain by hand? Hot is it? I totally agree with Spuds view but I'd say you've got some sort of chain or chain brake issue too. Oh and the choke mechanism on these is on a par with the thottle linkage.... With age they jam and/or break.

Its a weird setup on these... the link is made to twist when you pull the trigger, the link is bent into a shape so that it acts as a cam which pushes on the carb lever. Twisting the link can take out play.... The wire link wears, the nylon block on the carburettor arm wears and the throttle rod can become dislodged from its location in the handle, then you only get half throttle movement. My favourite hate is the cover for the throttle trigger with its protruding piece of plastic that keeps the linkage located in the handle - it's often broken off during reassembled. Result is notchy, half throttle movement. There have been several threads on here about this, new cover fixes the problem until the next time its taken apart and subsequently broken.....

Chain will start to run dependant on engine speed (so not directly related to throttle position). Presumably you are comparing with the newer saw ? Are you saying there is more movement in throttle trigger before the saw responds (wear in the throttle linkage)? Or you need more engine speed before the chain moves (possible clutch issue) ? Either get agreement or wait until your brother is not watching then borrow the complete carb off his saw and try it on yours ! Taking known good parts and swapping them onto your saw is a sound way to diagnose issues. Complete clutch assy ought to be right up there to try as well. Hope that video makes an appearance soon, Feburary is looming...

I can't see any pictures, just minture no entry symbols ??? If all the parts look ok, could it be the inside of the drum is oil or grease coated ? Too much grease on the clutch bearing ? Oil pump leaking? How long have you been sharpening chains, have you got the raker depth correct (not too deep)? Picture of the saw chips ? (But this type of problem would cause the drum to over heat. ... and drum isn't blue (hot) so...)

Those 2 grooves are in the OD of each tooth. The chain is driven on the face of the tooth, you will see a singIe wear mark on each tooth face - or with extreme wear a slot cut through each tooth (cuts the tooth more or less in half).... One in the attached picture is worn but would still drive the chain.

Bog std Walbro or Zama carb I'd expect. Assuming you start the saw from cold there is unlikely to be much pressure in the fuel tank, you reply on the pump in the carb to deliver fuel to the metered side of the carb. This is controlled by the metering diaphragm in conjunction with the Needle Valve, ok call it a metering valve if you like. That's all pretty low pressure. With running (think vibration) and heat you often get a build up of pressure in the tank (depending on breather type). If the needle valve were a bit suspect it mght not seal adequately. Breather types - modern breathers are one way valves, allow air in, don't allow fuel vapour out and cause pressure build up in tank. Old breathers like 023 were a hose at the top of the tank with a grub screw (or pair of) in the pipe with a tiny drilling through - allow air flow in either direction. Not sure what version the 230 is. But anyway, fuel starvation is most likely, breather or otherwise.

As you say - an engine spluttering to a stop is likely to be fuel issue, after 5 mins tank vent strong possibility. When it stops, have you removed the tank filler cap and tried to restart it? You might even loosen the filter cap before then as it starts to cough and splutter, does it recover? The 5 minute time would vary dependent on amount of fuel in the tank. Does the 230 still have that vent pipe with 2 grub screws in it ? Easy fix if so. But it could also be the other way around, building up pressure in the tank, flooding the carb/engine if the needle valve in the carb isn't closing at pressure, less likely but possible. Let us know how you get on.

I'd be interested in the bar/chain and winch? Might take the lot if you don't want to split. Whats on offer? Have to got pictures or details ? New thread time? Thanks.

John - regarding compression test, in your previous thread you confirmed - the crude hang it from the starter cord test ....the saw dropped and nearly stopped at each compression stroke. Ok, its not precise but it confirmed compression isn't too bad. I think Spud was offering multiple choice type questions, but nevertheless you're one step further on. Got any pictures of the clutch drum?

Sounds like it or the sprocket is so completely trashed the chain is slipping over (or through) the teeth. Either way it doesnt sound like an engine problem.

Open fires win on appearance. Stoves win as a means of heating a room because they only need to draw the right amount of air for the fire to burn. Compare that to the open fire that has a chimney that is also open to the room. The point here - once the chimney is hot it can move (draw) huge amounts of air from the room and that air has to be replaced from somewhere, usually from outside. By opening the fire door (or not having the glass in the door) you are converting your stove to something like an open fire because you've allowed as much air up the chimney as it can suck through the big opening. Ceramic glass is used in stove doors. It's a special high temperature glass, available as cut to shape glass for common stoves but can also be cut to a template shape if need be. Quite expensive unfortunately. Edit - I used the term 'Mica glass' which was wrong, Mica sheets are a different thing. Looks very thin and weak compared to the stove glass.

It would be different for an engine that has 20 thou squish compared to a saw that has 40 thou of squish. Squish being the distance from top of piston to underside of chamber at TDC. You'd have to know what the squish was in ech case and then move the piston down a further equal amount on both set ups. Halfway down the stroke the squish gets less signifcant but its still there in the detail.

Ok, I want that to be the case (just wires, no electroncs). I like simples. I was looking for an explanation for why the strobe timing and the tacho went beserk when the saw started misfiring. ... which I now think was fueling induced not coil induced. Understanding the tacho is easy - its looking at the time between sparks to determine engine speed, if engine speed is changing dramaticlly due to musfire then the tacho can't follow it sensibly. But the strobe, if it flashes in response to a spark and the coil isn't limited type, then the spark and strobe should keep happening at the ssme point in the engine cycle. Maybe the strobe can't operate at high 2 stoke engine speeds, it's a plain and pretty old strobe I'm using. I'll pull the covers off it and hope to find just wires.

Nope, I'm screwed as soon as the flywheel is off as well. All my numbers will be wrong by the amount I move the flywheel on the crank. It wasn't very clever really, I wasn't thinking more than the one step when I did it, just wanted to know the existing timing. Piston stop, yep, much better than my approach, doesn't move about. Just so long as you're a decent distance away from TDC. Making a bespoke one is on my todo list for tomorrow. What do you kniw about strobes ? Must be some timing circuit inside them? Can't believe they flash as soon as the sensor detects the spark. ... nothing can be that quick, surely?

Thanks. Did you get to see part number as well ? No worries if not.

I should make it quite clear - the chain is OFF the saw for all this messing..... Bar and clutch cover on for stability and to shield the other moving parts. My 11 year old son was in charge of camera, that was scary enough for me.

Less good picture, engine being cranked with battery drill. You have to use the geometry of the flywheel to establish timing. Second picture is with the engine stationary as I interpretted it...

Idle speed, strobe above camera to minimise refection. You can see the 10 and 30 marks quite clearly 20 is right where the fin is.