MS193C Fuel and oil tanks separation

[Rein]

I've got a 193C in for a smoking issue. Customer complaint - smokes all the time. Customer got this saw from one of his own customers. It appears to be in little-used condition.

I did a test fire just to check compression, spark, fuel system, etc., and it fired right up for about 30 seconds (smoking, then not smoking), idled, throttled up and down well and ran at full speed very well. Restarted easily 3-4 times. Bar is oiling. Fuel looked and smelled fresh, bar oil present, chain tension correct and extremely sharp.

Before I dig into it I wanted to determine whether the motor housing is all one piece, meaning there isn't a gasketed joint between the fuel and oil tanks that could potentially develop a leak. From the IPL I can't really see any kind joint so I'm guessing it's all cast as one piece. Is that correct?

Just so you know, I'm aware that the fuel and oil caps are in such proximity that it's easy for an operator to pour the wrong liquid in each tank and that could cause smoking. The owner has already run two-plus tanks of 50:1 premix through it and it was still smoking in the wood, so I don't think a failed gasket between the two tanks is the issue. Just wanted to rule that out before I go any further. If the original owner put oil in the fuel tank I don't think it would still be present after two full tanks of fuel have been run through it.

I'll be removing the spark plug and exhaust to have a good look at the cylinder and piston before I put this saw to the wood and give it my own test to rule out scoring, stuck ring, etc. The arborist I'm doing this for is good about cleaning the intake, not letting any debris fall into the fuel tank, etc. and the air filter does look clean right now so I'm expecting to see a healthy cylinder.

While I have the muffler off I'll be looking at the spark arrestor and torching both to see how much residual oil needs to be burned off. That could also be the problem, I suppose. I'll also, of course, be having a good look at the spark plug to see if this saw has been running rich or lean (rich!).

Anything else I haven't thought of yet?

 

[Rein]

It's been a month with no replies. I've been sidetracked (with life, what else?) but recently did a bunch of research and came up with what I hope is a comprehensive list of reasons why a chainsaw can smoke. FWIW, here it is, in no particular order (no particular level of expertise implied).

-bent or warped bar
-bar not dressed properly
-carb adjusted too rich
-bar oil and fuel in wrong tanks (fire danger from fuel on overheated bar/chain/clutch, exhaust)
-idle speed too fast (overheats while sitting idling)
-lack of airflow (blocked air filter, air passages, dirty flywheel/recoil compartment)
-bar oil not flowing well enough (several causes including worn or broken oil pump, blocked passages, filter) or no oil in tank
-depth gauges not filed low enough
-chain not sharp (causing chain and clutch to smoke and melt plastic)
-chain on backwards - smoking wood, chain and bar
-brake left on - wearing/burning clutch and clutch surround
-adjusted too lean (runs hot and will smoke at least slightly)
-uneven chain sharpening (one side sharper than the other, causing one side to burn while the other cuts)
-fuel mix too rich (too much oil in mix)
-chain too tight (causing bar nose sprocket to wear and recede back into bar, bar edges to wear excessively, etc.)
-trying to cut too fast, especially when chain is dull (i.e. applying pressure while cutting)
-bar oil getting onto exhaust (from leaking tank)
-oil/fuel tank gasket leaking
-worn piston rings
-scored piston
-scored cylinder
-leaking seals causing oil to seep onto hot surfaces?

Anything I've missed?

 

[Wood Doctor]

Operator has a lit cigar or cigarette hanging out of his mouth.

Huge, exhaustive list, no question about it. Two thumbs up.

 

[Lightning Performance]

Operator has a lit cigar or cigarette hanging out of his mouth.

Blu**
Pipe

 

[Rein]

Operator has a lit cigar or cigarette hanging out of his mouth.

Huge, exhaustive list, no question about it. Two thumbs up.

Thanks!

 

[Rein]

I finally got around to messing with this saw and tried adjusting the H mixture screw towards the lean side and the smoking stopped. Job done! Glad I did all that research because I was able to guess what the issue was with little hesitation.