bmp01

Spuds description of how carb works is great explanation of why the saw runs out of fuel off choke. I'd consider the pump side of the carb might be dubious too. So even if the metering side of the carb works and the needle valve opens, could be no fuel arrives. In that case it maybe the pump itself is knackered or the impulse line driving the pump is leaking. The 2 saws at once is either a coincidence or the rubber parts in the carbs have both been affected by bad fuel at some stage and its coming to light now further down line (so it's not down to the current good fuel). Treat them as individal carb problems and see if there is a common fault afterwards.

You are saying the saws flood by them selves and before you even pull the start cord ? I 'd wager you are at the stage the dealer didn't know what to look for. As above the metering valve and the metering arm must be the culprit, t'is the only control on fuel delivery to the engine. Spuds comment about leaving in a hot car relates to the pressure rise in the fuel tank - what is important here is that the metering valve can be over powered if inlet pressure is high enough, somewhere in the region of 2 bar (30ish Psi) will do it. If you have the pressure test kit, apply pressure to the carb fuel inlet and look for a leak at low pressures 7 psi and secondly increase pressure to see when the metering valve is lifted off its seat. Treat it with care though if you get to 2 bar / 30 psi that's good enough. Worth noting: just increasing the spring rate or lowering the metering arm could fix your problem but it might result in poor engine response from low speed. And that might give a clue about how Makita set up their saws. ..

You've read the entire Internet ? Respect..... 😀😀

It's an professional arborist website / forum, have your say, but no point getting embroiled with it, you can't win. This type of subject will always end up in the same place - for a reason, there is no right or wrong answer. But as non-pro's you and I are guests here, best to roll with it. BTW unusual user name, ABBS mod?

Out of 100 ****************wits how many of them identify themselves as a ****************wit do you reckon ? About zero would be my guess....

Yes, almost certainly quicker and more effective than the near useless devices fitted to DIY market saws. Professional saws already a step up from DIY saws but again I'd expect electronic device would be quicker to react compared to mechanical system. Worth noting a correction to your understanding : The existing chain brake (if operating correctly) should automatically operate under various conditions, ie. the "kickback" senario. The user does not manually apply the brake in this case. It is the inertia of the chain brake lever that resists movement while the nose of the guidebar (and chain) accelerates quickly past the object it has "snagged" on. You need to find a youtube video or animation to understand fully. I'd suggest the main cause of injury will be down to lack of experience, no training, no appreciation of danger, stupidity etc. People who find chainsaws a "more welcoming tool" are already in a more dangerous place than those who don't !

You've tried a new plug already ? The ignition system needs to produce a spark that can jump the plug gap in the cylinder under compression (obvs!). In fresh air that means it needs to jump a bigger gap, say 3 - 4 mm. With out appropriate kit, Spud's advice seen on here many a time - is to take a plug and bend the outer electrode to increase the plug gap to a couple of mm. Cobble together a setup that holds the plug against the cylinder and pull it over on the starter cord and look for spark. Worth checking the coil to flywheel gap and plug lead condition too.

Yes it's worth it if the rest of the saw is pristine. No its not worth it if the saw looks like it's had a hard life and is likely to be a dog, no matter what you're told. My point is we know nothing about its condition, how do we judge it ? You've got to gauge the saws condition from scratch, the seller's capabity to mend it (maybe they are hopeless) and their honesty with what they've told you so far. If you're not handy with spanners and not prepared to spend a chunk of money on it, the deal is a punt at best.

Quite possibly. Hard to tell from here but it sorta sounds like you might have flooded the thing. A short run, overly rich (too much fuel) might make restarting difficult, especially if you used choke thinking it had cooled a bit. Regarding tuning - assuming the Chinese carb has 3 adjustment screws (low speed mixture, high speed mixture and idle speed) and assuming you can get it started again (ref Peatff's post) then try adjusting the low speed mixture screw and remember you can always get back to where you began by screwing it back in and then out to the 1 1/4 turns. So what you are looking for initially is the highest idle speed. Once you've found that check for good pick up from idle speed with out the saw stumbling / bogging down. Couple of notes: - small changes (1/8th turn) and pause for a few seconds to let the speed stabilise -winding screws in (clockwise) reduces fuel flow, out increases fuel flow. - engine sould run smooth when the fuel mixture is right. -if you are a long way out (eg close to engine stalling) it will respond immediately to improved fuelling. You've done the hard part, no harm in having a play.

You've adjusted the new carb at low speed and high speed ? Chinese carb ?

You can get adapters to go from 14 to 12mm bar mounts, so if you were to machine it out the slot you could go backwards at a later date - see chainsawbars.co.uk https://www.chainsawbars.co.uk/product-category/bar-adapters/ BUT LoPro bar and chain on the g888...😨 Easier 'n safer to get another bar chain that's suited to the g888, that 7ft bar must have cost a penny or two - 2 ft bar would small fry in comparison.

I'd be keen for any new saw to have a few tanks of fuel through it before milling, to get it bedded in and find any new saw niggles. Plus you get to know a bit about the saws behaviour, set the fueling etc. Idling the saw isn't what you want to do, especially for a whole tank, that won't do it any good at all. I can see your predicament with that bar though. If you've no choice but to mill from the off what about milling something small (say 18 inches with that saw), start with 10 seconds cutting 5 idling, repeat. Increase the duty cycle after a minute or two and progress like that through a tank or 2 of fuel. That's only going to be minutes of running. Run it a little rich for first couple of tanks too which will keep temps down, lubricate bottom end well. I can see issues with enough suitable wood and balancing the mill on 'small' wood with that plan but it might give you some ideas,

Although I had one where the ignition lead was pinched in the casing at the factory. Made a pin hole in the ignition lead where it had arc'd through.

That's definitely true, valve is up near gauge. If the same comp tester was used on a running 2 stroke engine we'd have the low compression numbers confirmed.

Presume new piston/cylinder was assembled with oil on rings, when you did the part 2 compression test ? Did the original piston/cylinder get tested under the same conditions? That could well be the increase in compression you're seeing. Yes the increased compression will make it harder to pull over, along with the higher tension on the rings on the 'rough' cylinder bore. It will take a little running for the rings to polish the cylinder bore and I guess the rings will get heat treated and loose some tension with running. Any oil from the engine build will get burnt off early doors , expect a drop in compression. Maybe a slight increase with time as rings bed in.

If it's heat from the brake band rubbing then the brake band will also be hot and melt the plastic surround, I'm guessing that hasn't happened as it's not mentioned. Heat generated between clutch drum and the clutch shoes is more likely - I wonder if there was excessive grease on the clutch bearing which has now migrated to the inside of clutch drum / outside of clutch shoes. Clean and refit. Worth noting - use the saw at high revs and not in middle of its speed range, clutch should be engaged before you start the cut.

To me the cylinder looks pretty good....I don't like the second to last picture of crankcase where the painted finish shows clean and dirty patches though. With reference to ADW's comment about picture 5 - picture is too dark to tell much but the light patch is just some reflection....I think. ... Look at picture no 3 its the same area and looks fine allbeit slightly blurry. Mike, do you have any other 2 stroke eqpt you could pressure test with that guage, just for comparison, or borrow a mate's spanking new saw to test. Here's a question, if you run a finger nail down the piston skirt (from the ring groove to the bottom of the piston) is it polished smooth or can you just feel the ridges from the machining ?

Worth seeing if the cylinder can be cleaned up (often possible). Finding a piston on its own will be easier or there might be pistons from other saws that can be made to fit.

This one is out of stock sadly https://www.dlastore.com/e_store/cylinder-kit-for-dolmar-123-309-47mm-123130000-by-tecomec.html But it might be worth contacting supplier, see if there are any plans for more.

I've seen drive links damaged from new. Also worth noting the drive sprocket on the chainsaw is applying drive to the chain on the back of each drive link, not the front (front drive link damage is often chain and bar misalignment). Set saw up on the bench without the side cover, turn the drive sprocket and watch ... You are 100 % sure you have the right 'chain pitch', examples 3/8" LP or 0.325 or 3/8" Std ... ? Chain pitch must match the drive sprocket, guide bar must match drive sprocket (and chain ).

Yep thats the sort of thing. Adjustable boring bar directly into the head stock makes life a little easier. I'd need a bigger right angled plate (compared to the adjustable thing I have now) and then getting the bearing running true to the lathe centreline would be a PITA but it's doable.

Sorry I'm a bit confused too. ... but I get that the chain is binding in the guide bar. Two things spring to mind (but there are going to be many others). 1) have you got a chain that is compatible with the guide bar ie correct thickness of chain drive link for the bar groove width? 2) are the chain drive links damaged on their leading edge causing a burr over sides of the drive links. HTH, sorry if I've got the wrong end of the stick.

Production machine shop verses Prototype machine shop..... it used to be the natural progression, the top machinists ended up in the prototype shop. Bridgeport milling machine would have been perfect for this. Mind you, at a pinch I'd give it a go on the lathe - horizontal milling.

Now that's a proper repair, one you can have confidence in 👍 A bit of a surprise to me no one on here offers that type of machining service, just no money to be made I suppose.

I just looked at video on computer, couldn't see it previously. "Oh bugger" is about right, you must have 1/4 mm play there. Something is more worn than the vernier numbers you've shown. Which bit is buggered ? Re shimming, if housing is ovalised to any extent I cant see how you'd shim it without distorting bearing outer race. What saw is it ? Value?