LOTS of BLUE SMOKE at high RPM only

[indydave]

1980 Erude 9.9hp 2-stroke (fresh 50:1) Low and mid speed seems to run wonderful not a miss and normal level of 2-c smoke... But at near-max throtle or high revs she sounds like it's drownding... Like the sound you make when gargeling with mouthwash and smokes... I MEAN SMOKES REALLY BAD!!!! My neighbor thought my garage was on fire....

I have recently installed new main ig-coil and CD2 module new plugs which produces good spark now.... idles fine and I have cleaned the carb 3x the float looks and level (in the upside-down position). The float needle and seat appears clean look smooth and fairly new under magnafyinglass.

I want to think it may be a carb High-speed jet issue because someone has a .040 and the manual indiacated a .038 or is it a float adj issue.

What am I missing?

Newbe posting... but please be nice I feel I have done my penance and spent the neccessary hours reading all the archives and can not find an answer to my issue. Thanks in advance, All help is truly appreciated, Dave

 

[tashasdaddy]

Re: LOTS of BLUE SMOKE at high RPM only

are you the original owner or is it new to you. some one could have put the wrong jet in it, and it could be overfueling. also try a decarb, could be carboned up and burning off carbon, increasing the smoke.

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

 

[Rick.]

Re: LOTS of BLUE SMOKE at high RPM only

My first thought is your motor is overheating. Can you hold your hand on top of the head cover for a couple of seconds while it is fully warmed up? You have made some important improvements but I notice you say nothing about changing the impeller. You need to do that if you don't know when it was last done. I would also recommend doing a compression check prior to the decarb but the decarb is a great idea. Rick.

 

[dlngr]

Re: LOTS of BLUE SMOKE at high RPM only

Near max throttle in your garage? Are you running it in a barrel of water?

 

[coolguy147]

Re: LOTS of BLUE SMOKE at high RPM only

lol i hope he is

 

[indydave]

Re: LOTS of BLUE SMOKE at high RPM only

Thank You for all the advice. I'm going to try adjusting the carb float down a little and see what it does? if this doesn't change anything, I will then try the decarb procedure. Last resort I may have to solder and re-drill the main jet to .038 to see if that's it.... but what a pain. In the back of my mind I'm wondering if it could be a weak reed valve or timing issue?

I am running in a tank, one of those plastic city trash cans with 2 wheels ~100 gal. I?ve tested several motors in this tank and tellin-ya works GREAT!!! You can?t beat the price and even has a lid when you?re not using it.

This motor is new-to-me and don't know what had been done prior... But can tell someone has messed w/ the carb.....

The compression is ~110psig on both (I'm think?n good).

Don?t think it?s overheating, it?s peeing well and I can put my fingers on the fins and not get burned? also checked w/ an inferred thermometer ~80-100degF.

Enjoy Your Thanksgiving and God Bless America

 

[ezeke]

Re: LOTS of BLUE SMOKE at high RPM only

First, you are at great risk of blowing up the motor if you run it over 1500 RPM in a tank without a test prop and without it being in gear.

It sounds as though you are loading up with oil from running with no load, then burning off the excess oil somewhat at the high RPM.

You need to run the motor under load for a while unless you do a total decarb; and you can't do a thorough de-carbon treatment without a run under load between treatments.

 

[indydave]

Re: LOTS of BLUE SMOKE at high RPM only

I adjusted the float to further lower the fuel level in the bowl, currently the float is set MUCH LOWER than typical. This may have helped a little but not much.

I also preformed part of the decarb process with no noticeable improvements (barrel testing).

I will bundle-up and take it out this weekend for a full-out run to complete the decarb procedure. I will take an extra can of fuel to run a "True Load Test" after, as recommended.

Thanks, Dave

 

[Harker]

Re: LOTS of BLUE SMOKE at high RPM only

A lot of smoke that wouldn't be seen on the lake will bubble out of the tank. Almost sounds like it needs a Linc and Sinc. Put it in gear, not running, twist it to full throttle and see if the plate in the carb is LEVEL. I'm betting it is going past level and flooding a bit causing the sound you are hearing. The plate has to be almost perfectly horizontal or some choking will happen. If this is the case, I would reset your float to spec so you don't run too lean and fry your motor.