bmp01

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?

The other thing to take into account is that the bearing gets 'looser' in the housing as the engine warms up (different rate of expansion for steel vs ally, mag). This is part of the reason the bearing is a tight interference fit at room temperature so at running temp you still have some interference. And why heating the case allows easier removal of bearing. Using a bearing fit loctite (because it is typically installed at room temperature), faces a 'loose fit' challenge at running temperature. It's one of those 'you might get away with it' games. The difference in expansion is tiny, by the way, 0.015mm for 30mm O.D bearing with a 50deg C temp rise. But then the desired interference fit is also a very small amount, circa 0.025 mm (room temp). Machining tolerances mean that bearings fit is often higher interference than that, 0.05mm. Forget vernier calliper measurements for this level of precision. If the bearing is loose in housing see if you can slide a feeler blade in the gap, that will give you a better idea of where you're at. Sleeving bearing housing is the right fix but it'll cost for a decent job. You can buy shaft sleeves to repair damaged shafts but I've not seen the equivalent for a housing repair. Wonder if you can do a home brew sleeve repair with shim steel ? Fun and games 😆

Thanks for that. I got a sniff of the coil swap after a bit of goggling - seems like the 112 was upgraded to 'coil only' later in its production run. I think deleting the points is the obvious thing to do with it so any experience would be a great help. Saw is in very good condition - I think it has had its problems, so probably stored for most of its life. It does now run, but behaves like it has an air leak so I'm being a bit cautious with it. Also signs of previous tinkering, gets the alarm bells going.... Thanks again.

Aw crap, thought I'd seen the last of those when I converted my old A series to Lumenition 3 - 4 decades ago... Be sad to let it rot though, so we'll persevere.

That's good. Regarding qty of 200t's, blimey. So how many 200t's sold in UK do you think ? Just wondering what your 500 is as a fraction of the total .....

Keep looking.... 😕

New genuine wouId have accel pump too... If you want to keep the original carb, take it to Spud, best person to get it back to original spec and test it. Plenty of advice on here but you might end up chasing your tail if you're not familiar with it or dont have vauuum / pressure test eqpt.

oh good, someone's been in there already, messed with it....not in a good way. That will need a thorough going through (or new carb). A bit of luck with location 👍

The 391 is a plastic case saw ? I'll wager the case flexes a bit more with chain tension. Can't see heat conduction being important (heat from bar into engine case on first run), if anything the metal cases will send heat to the bar one the saw is properly hot...

Billhook, your latest report, says "it cut through it straight" so that's one tick in the box then ? I like that you are eliminating the variables one by one. So doesn't matter which bar/ chain combo, the problem saw is oiling but bar is still getting hot (but we think the chain is ok and its throwing big chips). So what about chain tension? If it gets hot through the cut tension will increase - that in itself will produce more friction, heat and reduce useful power to drive the chain. Whats the starting tension ? Have you considered bar oil type? Is it the same between saws? Sorry if thats been covered already. Watching with interest, pretty sure you'll get to bottom of it .

A bit random given the direction indicated by Spud but have you fed the saw a dribble of fuel, (down the plug hole) when it doesn't want to go? A cough or quick rev and die = carb problem, no sign of it running suggests compression or spark problem. Oh, and take a look at the plug as you take it out, looking to see if its dry or wet with fuel. If the latter then dribbling in extra fuel not likely to help... 130psi after one pull - weetabix for breakfast? Or gauge is measuring small psi's .... its a standard ms210 ? Much carbon in the exhaust or exhaust port? Regarding engine temp after running - although it might feel warm to touch after its stopped for 15 mins the cylinder is relatively cool compared to running temps. Surrounding fuel, ignition components will have a bit of heat soak though.