50 hp high speed misfire

[cdavy000]

Blue smoke is uh oh? This is a two stroke so shouldnt blue smoke be expected? Before the seafoam there was very little smoke. The fuel I was using did have some seafoam that I added just as a light cleaner and fuel stabilizer. The motor ran as if all it needed was some very slight adjustments. Since then, it sat for two weeks, then this last weekend I was running it in a barrel to do these adjustments as per the clymer manual. It didn't smoke right away, I warmed up the motor to so I could start tuning. Eventually, on high revs it started smoking as if I was doing a shock treatment. Only at high rpms though. The smoke would stop at idle speeds. At first I thought it was due to the sea foam basically having been hot soaked for two weeks and then burning off, but it wouldn't clear up as one would expect.

The little bit of smoke before the sea foam is normal. How long have you ran the engine for after adding the sea foam?

 

[kalebsheridan]

Oh one time when I ran it after the trigger swap. Normal amount of smoke then. When I took out the next time I added the seafoam to help degunk the inside. Maybe a teeny bit more smoke then, probably the seafoam. This was two weeks ago. I didn't have any serious smoke like this until this weekend.

 

[topgun3690]

would the clymer manual suffice?

Clymer and Seloc are better than nothing.....they try to cover too many different motors, models, and years and don't have the detail of the factory manual.
You using 50:1 mix with a quality oil? Extended periods of idling will cause a lot of smoke.....a good Italian Tune Up on the water usually clears it up......

 

[Chris1956]

Clymer and Seloc service manuals often have grossly inaccurate info in them. I would not use them, unless you are real familiar with the motor.

BTW - whenever using ether, have a fire extinguisher nearby, as that stuff is real flammable. An engine may not have enough spark to run, but often has enough spark to set the ether alight.

ABTW- if you spray ether into a cranking engine, and she doesn't run for a few seconds, you do not have any spark.

 

[kalebsheridan]

Okay I see, yeah the clymer manual definitely leaves a lot to be desired. Okay I see what you mean about the extended idling, but how long is too much? I maybe had it idling for 15 minutes at a time. Isn't the fuel recirculation system supposed to alleviate this?

 

[kalebsheridan]

Yup copy that Chris 1956. However lack of spark does not appear to be the issue.

 

[Chris1956]

Those statements were of a general nature about ether. The fire extinguisher statement was for you though.

The common dry chemical fire extinguishers are real corrosive, so if you need to discharge one, clean up the chemical promptly or it will corrode the carb, the throttle plates and most anything else it contacts.

 

[kalebsheridan]

Those statements were of a general nature about ether. The fire extinguisher statement was for you though.

The common dry chemical fire extinguishers are real corrosive, so if you need to discharge one, clean up the chemical promptly or it will corrode the carb, the throttle plates and most anything else it contacts.

Ooh okay I see what you mean. Yup I'll be sure to be extra careful spraying that stuff in the future.

 

[kalebsheridan]

So here's what I found in my clymer manual. I think this hits the nail on the head and I'm curious what you all think. So the manual references the fuel recirculation system, which feeds unburnt crankcase fuel back into the cylinders. Fuel pools during idling and gets fed back in to be burned. At high rpms, recirculation isn't needed since the fuel burns more completely. When this system gets clogged (uses fine mesh at the inlets crankcase outlets so how would it not), you get a lean condition at idle due to pooled crank fuel not being burned, and when you punch the gas, excess crank gas gets dumped into the cylinders resulting in an overly rich condition. Symptoms includes:
Sputtering and stalling at idle
Poor low speed performance
Poor exceleration
Fouled plugs
Excessive smoke
I was experiencing all of these symptoms, especially the longer I went on with the motor running while I tried to diagnose the problem. Especially the smoke, which only occurred at higher rpms, like pooled fuel was getting dumped into the cylinders, and last time I ran it, it started sputtering hard and dying without some throttle. I also had wet fouled plugs like when you have flooded the motor, but after it running for 10 minutes. Also, I was suspicious of this and I pulled the hose going to the fuel pump from the recirc cover, and the hose was completely dry on the inside. Could my recirc be clogged? Did running seafoam dislodge a lot of crap that clogged my recirc? Am I making a stretch of could this be a part of my problem?

 

[topgun3690]

Am I making a stretch of could this be a part of my problem?

A plugged up recirc will cause some problems.....won't cost anything to check it (maybe a gasket). Take off the cover part#17 and check the 2 small screens (#10) and the hose (#20) for blockage. Pretty simple system.....

 

[Chris1956]

I doubt that is your issue, however, as was said, it is easy to check/clean. But, hey let's be optimistic.

 

[kalebsheridan]

A plugged up recirc will cause some problems.....won't cost anything to check it (maybe a gasket). Take off the cover part#17 and check the 2 small screens (#10) and the hose (#20) for blockage. Pretty simple system.....View attachment 389776

I will definitely be checking that. I need to pull the powerhead off to replace some exhaust gaskets anyways so I'll do those at the same time. I read a thread on this site with guy with an 85 hp force with the same exact issue. Seafoam dislodged carbon chunks which plugged up his recirc. Plus this motor sat a while, could fuel varnish and glog those screens?

 

[kalebsheridan]

I doubt that is your issue, however, as was said, it is easy to check/clean. But, hey let's be optimistic.

I understand, but I'm running out of options I think. So far, spark is good, no vacuum leaks, carb is clean, rebuilt and tuned, fuel pump appears to be working well, compression seems good, water is flowing well (blew a gasket so maybe too well haha), fuel tank is good. All I can think to check now is the recirc and my timing. Before those two things can be checked though, I have to replace that leaking exhaust gasket so my cowl stops filling with water.

 

[topgun3690]

could fuel varnish and glog those screens?

That and carbon deposits can plug it up......just check it and clean it up to be sure.....

 

[kalebsheridan]

Okay I copy. I will do that.

 

[kalebsheridan]

Okay so just got the motor fired up after the exhaust gasket replacement. Attempted my tuneup as per the Haines manual. Runs very nice at higher rpm but bucks on its way back down to idle. Idle seems rough to me as well, but it seemed to be the best I could get it. I'll attach a video of it idling.

 

[kalebsheridan]

Here's the motor idling

 

[kalebsheridan]

Also, I did check the recirc. Had some junk in it but symptoms appear to be the same

 

[kalebsheridan]

Just checked the timing as well. I think it's good. The 28 mark lands right on the dash on the timing sticker while cranking at WOT

 

[The Force power]

Just checked the timing as well. I think it's good. The 28 mark lands right on the dash on the timing sticker while cranking at WOT

Have you tried to see if it misfires with the rectifier disconnected?