'80 340 enticer compression test? - Snowmobile Forum: Your #1 Snowmobile Forum

drmax · 02-27-2008, 10:32 AM

Feel like a slug for asking this, but have never performed this.

What is the procedure for checking compression?
(eng not running)

Where do I buy/rent a compression tester.

What should the compression be on this model sled.

Thx, Greg
(I did search here for my questions, didn't find anything)

**RJ Gleason** · 02-27-2008, 01:06 PM

Buy a good one, the screw in kind.

With both plugs out and the switch off, hold the throttle wide open and pull it over as fast as possible at least 5 times.
Both should read 120 psi or better and within 10% of the other.

drmax · 02-27-2008, 03:03 PM

Quote:

Originally Posted by RJ Gleason

Buy a good one, the screw in kind.

With both plugs out and the switch off, hold the throttle wide open and pull it over as fast as possible at least 5 times.
Both should read 120 psi or better and within 10% of the other.

autozone has one to borrow, screw in type.
i will report back tonight.
RJ, i'm the same guy with the fuel pump rebuild. (doing this tonight. just getting my "chit" straight, as what to look at next.

ck'ing the compression will not show a bad crank seal, will it?

yes, i'm picking up a can of ether on the way home.thx, Greg

also thinking of picking up an in-line spark ck'r to see if I'm getting enough juice. any advice on this? i read where this could be somewhat of an issue. my plugs are not white, rather wet. (not oily)

**smallengineguy** · 02-27-2008, 06:41 PM

No, a compression check will not tell you if a crank seal is bad.
Get a Windex bottle with some 2 stroke fuel mix in it instead of ether! Ether is NOT good for them.

NAPA has the inline checkers for $6.95. Good stuff!

drmax · 02-27-2008, 09:58 PM

Quote:

Originally Posted by smallengineguy

No, a compression check will not tell you if a crank seal is bad.
Get a Windex bottle with some 2 stroke fuel mix in it instead of ether! Ether is NOT good for them.

NAPA has the inline checkers for $6.95. Good stuff!

rented a compression tester. both cyl's at 120 psi. rebuilt fuel pump. basically same
problem. had to put gas in cyl's, got it started, ran with full choke. had only ether
and ck'd sheave side, carb area and what little i could on the right side. no rev
noticed. then sputter out and quit, maybe 1 minute of idling time.
wondering now if something is messed up with the carb, adjustment wise or internally.
if i had any snow, i could have run the hell out of her and i bet she'd stay running,
but i don't have any. what next?
guy at a local yamy dealer said they had a crank pressure tester, but not cost wise
for a bloke like me to keep one laying around. i have a gut feeling it is not a crank seal
issue. love to be able to mount a different carb on in and see what happens.

**RJ Gleason** · 02-27-2008, 10:10 PM

Disassembly and Cleaning of a Mikuni Round slide Carburetor

drmax · 02-28-2008, 08:24 AM

Quote:

Originally Posted by RJ Gleason

Disassembly and Cleaning of a Mikuni Round slide Carburetor

I read your attachement and I see nothing different with what I had already done, twice. With the amount of smoke when it was running and the smell on my clothes this morning, it's definetely running rich. Pull plugs and they're wet after it quit. Got the spark tool and it jumped over 20. (passed)
With everything I have tried, what could still be the problem.
I need to try to figure out if it is looking like an internal engine problem, as this is where I'll donate this for a marine habitat. I would really like to be able to slat another carb in there and try...that would be ideal.

**the left head gasket has the ominous sign of a leak, but not enough to fail the compression ck**

**$100 dollar question, can old gas do this?**

**RJ Gleason** · 02-28-2008, 08:49 AM

Definitely running rich.
Check where the E clip is on the slide needles, should be on the middle (of 5) positions.
What is the air screw set at? (this is the small screw that is closest to the intake end of the carb)
It should be at least 1 full turn out from gently bottomed.

drmax · 02-28-2008, 09:12 AM

Quote:

Originally Posted by RJ Gleason

Definitely running rich.
Check where the E clip is on the slide needles, should be on the middle (of 5) positions.
What is the air screw set at? (this is the small screw that is closest to the intake end of the carb)
It should be at least 1 full turn out from gently bottomed.

I need to ck what you are asking. I have no idea.
Could old gas cause this type of big problem? I sort of doubt it.

Check this out. The other night when I was blowing air though my gas line back into the tank, (filter removed) I observed the tank slightly expanding from the pressure. When I removed air form the fuel pump line, it rush right back out of that line.
In the cap of the tank, there are 2 other lines, which appear to be vent lines. If they were clogged, it would seem the tank would pressurize and overcome the pump? what ya think about this?

The other night when I took it out and ran the hell out of it, I didn't mention that I pulled the plugs and they were golden brown. (good thing)

How is the choke set, or adjusted?

drmax · 02-28-2008, 10:06 AM

Quote:

Originally Posted by RJ Gleason

Definitely running rich.
Check where the E clip is on the slide needles, should be on the middle (of 5) positions.
What is the air screw set at? (this is the small screw that is closest to the intake end of the carb)
It should be at least 1 full turn out from gently bottomed.

This carb is a butterfly style, no slide.

**RJ Gleason** · 02-28-2008, 12:25 PM

OK. part #7 is the mixture screw, turn it out 1/8 turn at a time and make runs each time to check it for performance changes.

drmax · 02-28-2008, 02:13 PM

Quote:

Originally Posted by RJ Gleason

OK. part #7 is the mixture screw, turn it out 1/8 turn at a time and make runs each time to check it for performance changes.

before i do this, i'm going to get a 1/4" hose a fill clean beer bottle up with fresh gas...put in some new plugs and try it this way. it won't run long enough for me to adjust...anything

drmax · 02-28-2008, 08:01 PM

I lined in a fresh source of gas before the pump. Put in new set of plugs. After several pulls, she fired off. So it would appear the crank vacuum is good.
My local repairman said that if the air jet screw is needle-like, that this could be adjusted out to almost 2 turns. I did this and it appeared normal.

Ok, I removed the phucking gas tank and dumped it...may 2 quarts or so...it was an awful looking dark dark brown. No wonder it wouldn't run good. My dad had someone put on a second hand tank and didn't tell me. I thought the gas was fresh, it was not.

Now a new problem...The line that goes from the bottom of the tank up along the left side, to show quantity...well the damn nipple that goes into the tank has a crack, which is leaking.

It appears JB weld will not make this repair. Not sure what type of product would repair plastic, yet hold up to gasoline.

Thx gents...I'm almost there.
Greg

**RJ Gleason** · 02-28-2008, 08:54 PM

I have had good luck with a flat tip soldering iron and welding into the gap.

kccats · 02-28-2008, 09:01 PM

There are a few products out there to make the repair! There is a plastic bond, a plastic weld and a complete plastic repair kit! Good luck!

drmax · 02-29-2008, 09:01 AM

I thought of the iron, but this is a tough area to get at with that. I bought some of that poxy paste last night and applied.
Put the tank back in and this morning put a little gas in it.
If it's leaking when I get home, I'll have to figure out something else.
It is really a useless nipple and would consider just yanking it out and plugging.
May have to find another used tank.

drmax · 02-29-2008, 09:04 AM

Quote:

Originally Posted by RJ Gleason

OK. part #7 is the mixture screw, turn it out 1/8 turn at a time and make runs each time to check it for performance changes.

what bad would happen if the screw is out too far, or out of adjustment? at idle, i can run this screw in and out it doesn't seem to make a huge different. right now it's turned out almost 2full turns. thank you.

drmax · 02-29-2008, 10:36 PM

Chalk it up to mostly...bad gas...Sorry for dragging 'yall into to this, over something like this...
however, I did learn much more about this machine and small engines. VERY valuable
lesson. I also learned about spark testing, compression testing and getting to know
the carb. Thx to all!
Oh yeah, the poxy tank repair so far, really does work.