Bad crankcase seals?

[Rusty-880]

Saw in question is a ms880 mag.
For awhile now has been odd to tune- 1/2-3/4 turn on low to get it to idle(1/4 turn normally) and then with high screwed in will still four stroke. Bogs/stalls chain in cut quite easy, lot less power than it should/had.
A mate of my brother has had many dirtbikes, if he dosnt have a crankcase tester ill make one.
Carb had been fully rebuilt a few times with no difference.

 

[splitpost]

sounds like its getting way too much fuel ,check the needle and lever height

 

[Rusty-880]

I set that up last time carb was apart, didnt make much if any difference.
Have to set idle very rich to run, same setting on low screw would flood an 880 normally. Any leaner it wont run.

 

[wigglesworth]

Is this the same "ported" 880 u can't get right?

IIRC, the general consensus was that the jug was ruined and that's why it wouldn't tune right...

 

[Rusty-880]

Same saw different cyl.
Other cyl was not ruined making it hard to tune. Ran well with very broad torque range. But everyone decided it was stuffed and wouldnt believe or read the whole question.
This problem had been there for some time before and now a decent time after.
Cant be cyl......

 

[mopar1rules]

Does the idle seem to jump around or hold rpms pretty good? When my buddies 026 wouldn't idle well and it wouldn't tune for squat, i checked for airleaks and found that the flywheel side crankseal was leaking. I found the leak by spraying starting fluid at it, and took note that it would kill the saw everytime i sprayed there.

 

[Rusty-880]

It will idle ok, only if mixture screw is turn out close to three times factory specs. At this it will still four stroke at wot with H screw just cracked off seat

 

[mopar1rules]

I would spray starting fluid to find air leaks. Seems like you have one somewhere.

 

[Whiskers]

Agreed, if it will idle only when you're delivering way more fuel than should be required it's always an air leak somewhere. Checking fuel line, don't recall if the saw has and impulse line, intake boot, and proceeding to pressure test the carb, and the case would be the route I'd go. If the carb and case won't hold pressure, soapy water will find the air leak.

 

[half_full]

soapy water will find the air leak.

Like this one (husky 272)

 

[splitpost]

It will idle ok, only if mixture screw is turn out close to three times factory specs. At this it will still four stroke at wot with H screw just cracked off seat

i agree with the other fellas that you may have a vac leak that is affecting your low side but to have the high needle just cracked of the seat and still 4banging at wot,there is another issue at play

 

[blsnelling]

Is anything on the saw currently modified? If it's running that poorly, I wouldn't be cutting with it at all!

 

[Rusty-880]

Would do it stock, muffler modded either way.
Wasnt happy with it, low on power too, but ran it on mill for a few months like that. Had no choice
Cyl looks great, just wont tune normally and bogs way to easy.
Try and make up a tester and do something with it oneday, dnt need it for work currently

 

[splitpost]

Would do it stock, muffler modded either way.
Wasnt happy with it, low on power too, but ran it on mill for a few months like that. Had no choice
Cyl looks great, just wont tune normally and bogs way to easy.
Try and make up a tester and do something with it oneday, dnt need it for work currently

Maaaaaaaate you gonna leave us hanging?