bmp01

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.

52 minutes ago, Conner said:

Also trying to find someone with the skills to do the job. We have a dedicated machine shop with CNC machines. They could not do a repair like this as it is done by eye. We need to skill up on old fashioned manual machines.

 

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 😆

10 hours ago, Fatboy2017 said:

Very simple thing to do on those if you didn't already know is disconnect the lead to points form stop switch, remove coil and fit a coil from say a 6800, this is the stand alone type, no need for trigger, it's in the coil! connect the cut of wire from the switch and away to go, straight swap does away with points and runs better. I have used many cheap Chinese coils for this swap, only because of cost and as yet no problems with any. Points are ok, but prefer hassle free coil set up. Let me know if you need a link. Nice looking 112 by the way😉

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. 

1 hour ago, spudulike said:

I think he is taking it to me and am happy to sort it out. I think, like most 200ts, it has had a life and will probably benefit from a strip, clean inspect and rebuild but will reserve judgement until he passes it over.

I wonder how many of these I have done over the years, must be 500 or so, perhaps more.

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.... 😕

4 hours ago, Lumberjackmike767 said:

I know the thing is its still the original carb with the accelrator pump 

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.

10 hours ago, Lumberjackmike767 said:

.... when I disassembled my carb, the gauze wasn't there

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. 

1 hour ago, spudulike said:

Not sure what is worse, a dose of the Covid or watching England play!!

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....

9 hours ago, Indian_cola said:

All running good now.

decomp valve at fault.
 

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.

45 minutes ago, Paddy1000111 said:

My saws seem to leak a lot less since I got in the habbit of filling them up when I'm finished with them. 

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.

1 hour ago, adw said:

That’s what you get with those crappy Chinese clips, never seen it on Mahle clips

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...