bmp01

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.

I understand England are playing at the weekend, Covid is available most places if you look. Let us know when you're done comparing....😨

If chain sharpness / condition is in doubt just get a new chain ... Its a small outlay before admitting defeat. Just coz someone else can push harder on a bar and get it to cut that doesn't mean it's the right way to go about it. Are you getting nice 'chips' of wood or saw 'dust' out the back ?

Collection only from Ryde, Isle of Wight. 80 pounds. Just incase that saves 2 mins of internet time. Ah-ha "Wightbay", I should be awake after lunch... maybe....

I agree, the heat pattern says the crank bearing was the hot bit. Gets cooler as you travel away from big end bearing ie up the connecting rod (and along the crank). Ouch ! Edit - Maybe some of the previously mentioned crap got in the bearing at the first rebuild....

Nice one, thanks for posting your result. Did you repeat compression test, number?

Youtube channel afleetcommand has been playing with a g888 recently. Cant say its much of a review or the saws caoability and there's a lot of talk but the guy has run a few saws and he's pretty happy with it. Sounds pretty rough though, bag of nails rough.

Wouldn't have thought of that one, counter intuitive to me .... 👍 I suppose you're releasing any positive pressure (due to heat build up) and getting rid of most of the air (the springy bit). Maybe cooler, more viscous, oil plays a part as well.

Re. chinese clips- yep, its a true story, only safe place for them is in the bin. But its still accurate to say that any extra material (ears) attached to the useful bit of circlip effectively derates the useful bit - cant be any other way. The full circlip is more effort to fit, yes, but in all other respects its a better solution.

Circlips with tails are a personal hate of mine. No good can come from a bit of unsupported wire exposed to the accelerations of the piston. Sure, easier to fit but thats no concillation right now is it. The 357xp I stripped recently had an after market piston in it, same story, every thing is still assembled but tail missing from circlip, cylinder and piston written off. Remaining 'good' circlip was cracked from root of tail.

Well, in amoungst grass cutting and shower dodging here's a piccy or 2. It is a 170 2 mix cylinder, think the brg and seal arrangement is the same... Conclusion, seal will pass though the housing but will not pass the oil pump (another thing to remove then ).

I agree with you, once engine is out of saw just pull the pan off. I've got a 170 2-Mix in bits in the garage, I'm going to mock it up to a look at removing the seal behind the clutch. Picture in due course...

Ha, that's useful info. I wondered if that was the difference between the 2 types of seal listed. And why do they have the lip in the housing anyway ? Its not a feature that exists in many other split bearing designs. Think I'd be tempted to dremel the lip away 😈 😨 What about access behind the clutch though ? If you have to take the engine out that's still 90% of the effort / time / money...

Err, yeah sorry, we're talking different things ..... I think. I was on about the inner race - the hardened steel 'tube' bit, like this....

Needs to be a chuffing hard layer for it to last more than 2 minutes, the sort of thing that you're obliged to grind.... Edit: I've come across shaft repairs where the shaft is machined to accept a needle roller inner race of an appropriate size. Suspect there's not enough meat on a chainsaw crank though.

That's sounding hopeful ! Re carb - I've done the same thing with the metering diaphragm before now, round and round in circles trying to sort that one. The pictures all suggest piston, rings and cylinder are happy. If it now runs properly I'd be looking for an excuse to dismiss the low compression number. Might be the compression tester isn't really the right one for a small 2 stroke engine. ... Might be the decomp valve, blanking it off with a bolt and sealing washer is the cheap solution, common practice. Leave the rest of it assembled, less cleaning and less chance of getting crap inside the engine. Thanks for update btw.