unburned fuel

[DudeAbides]

so my1989 85hp motor is all back together again.

compression is good
carbs are all clean and synced

I did the timing and it seems to run better at 30 not 28.

When I first did the timing I found it at 30 changed it to 28 and the engine ran noticeably worse.

So here I am the motor runs but it is not burning all the fuel.

Here are pics through the exhaust chest

Plugs look the same Gas/Oil


I got a cheap spark tester . All cylinders are firing for sure. But I am skeptical about the accuracy and the quality of the spark.

 

[Jiggz]

Not all fuel fed through the intake will be burned and this is especially true during idling speeds. In fact, this is the very reason there is a fuel recirc system and it is designed to recoup unburned fuel from the low spots in the crankcase and feed it back to the intake system. This is as long as the fuel recirc system is properly working. Otherwise, it will result in poor acceleration, poor low speed performance, spark plug fouling, excessive smoke at acceleration and stalling or spitting at idle. Of course, at high speed most of the fuel fed through the intakes is also transferred to the cylinders for proper combustion.To avoid accumulating unburned fuel, you should minimize idling as much as possible. Idling is never good for any 2 cycle engines.

 

[DudeAbides]

Thanks Jiggz

I do agree with everything you wrote.

But I believe that the amount of unburned fuel that I am leaving on my plugs and through my exhaust is just too much.

Do you have any thoughts on the timing working better at 30?

The thing is that it still does not really idle right no matter what.

Yesterday I ran it on muffs in my driveway. It was the best it has run yet. It started right up idled pretty good sounded good when I revved it a bit. But it would still leave a puddle of fuel on my plugs.

It was very reliable to start and run. I felt great so I brought it down to the lake and suddenly it won't stay running and is harder to start.

Couldn't even get it to go into gear without stalling.

 

[DudeAbides]

I also meant to say that my entire fuel recirc system is spotless. Cleaned out new gaskets and all new fuel lines

 

[Jiggz]

The timing at 30 is acceptable and is actually the original setting from the manufacturer. Actually based from my tune up specs from my manual the max timing settings for your motor at Dynamic is 32 BTDC. As for the unburned fuel puddling, make sure your carbs air-fuel mixture are set properly. I understand that is a little vague but personally, I'd set them now at 1 turn out first and see how it performs and if the puddling is reduced. Although I recommend going to 1 1/8 turn out for everyday use. Another thing is to inspect the air-fuel mixture screw to make sure the pointed end is not blunt or worn out. If it is you need to replace it. And finally, make sure you have the right size of jets on each carbs.

 

[DudeAbides]

No Title

Thanks Jiggz.

I have only set timing with cranking speed.

the air fuel mixture screw looks good. as does all the other carb components. I beleive they all original.

Whether the screw is in some or out some from 1 1/8 turn out. problems persist

I pulled off my blue boxes and found this on one of the ignition coils primary wire.

 

[Nordin]

As for the coilwire ,wrap electrical tape at the damage. Looks like melting from a hot engine part.
When reassemble the ignition mountingplate try to route the wire away from hot parts or squeezing.

About the unburned fuel follow jiggz adwise. Remember that after a rebuilding of an engine you have to run in the new pistons and bore with ritcher mixture and not to run the engine at WOT for to long times.

 

[Jiggz]

Wow that is really a biggie. Same with that yellow wire in the background which seems to have a pinch on it. You can use liquid electrical tape, let it dry, wrap with two layers of electrical tape and if possible shrink wrapped and it should be good. If you do not have liquid electrical tape use 4 layers of electrical tape and shrink wrapped.

So basically the source of unburned fuel puddling is due to misfiring.

 

[DudeAbides]

Yes. I thought it was a biggie also.

I will be sure to wrap her up real nice like.

It looks like the motor got hot and melted the insulation off the wire.

There are a couple that look similar just not as bad. It is just this one primary coil wire that melted all the way through to the wire.

It had to be virtually pressed against the engine block. So I am sure there was some arcing to say the least.

Just a little bummed that I won't be able to work on it for the next few days. I will be sure to post how it runs when it's all tightened up.

Thanks again