So my 2002 883 has been giving me trouble with dieseling for a while now. It started off as intermittent and has been getting much, much worse. I am here to ask some of the veterans if you have any other tricks (short of taking off the heads and cleaning it out, which I may do this winter) to help cure this.

Symptoms
Diesels upon shut-off. Sometimes a short period, sometimes a long time. It occasionally will run backwards, and I know because if I let the clutch out to stop it the bike jumps back.

Doesn't matter if it is 40*F and oil is 150* or it's 100+ air/200+ oil temps. It diesels either way.

My plugs and mixture are ok, I know other bikes that are leaner/hotter range and don't diesel and it didn't do it the first 100000miles of the bikes life.

My Fixes So Far
1) Run premium fuel. No joy. It doesn't matter if I run 87 or 93 it still occurs equally.
2)Seafoam gas tank. 2oz/gal and it doesn't make a difference.
3)Adjust idle. In spec at 1000rpm and still diesels.
4)Adjust timing. Timing is spot on, and it diesels without a spark so it is not timing.
5)Water/seafoam directly in the carb throat. Lots of smoke, but no fix.

Essentially, I am pretty sure it is carbon build-up/casting defect that is making a hot spot allowing it to spark without ignition. I just don't want to tear down the cylinders on an otherwise flawless bike. I'm cheap and in college, that money can be much better spent if I can fix it as is.

I appreciate any input you all have to offer.

 

Your observations sound spot on to me. Can you see heavy carbon build up through the spark plug hole. Might need to run some fuel cleaner to loosen up the carbon. Or you might have an intake leak causing a lean condition.

 

Looks like water is cost effective and less chance at damage

 

yamaha makes an upper engine cleaner. i've used it in the past and it does wonders. another is marvins mystery oil. on my '77 wing i'd run a couple of ounce per tank, every fill up. a lot less harsh, but may take a little longer.

 

Maintain about 2000rpms and squirt some water from a spray bottle directly in the carb. If you have your bike a few feet from a wall, you'll hear the carbon shoot out.

 

+1 - Water in a spray bottle works as good as anything. Remove the air filter and spray it into the carb throat.

 

My grandpa would pour water into his old 383 bb Chrysler. Are you saying the water method actually works. No chemicals,no combustion bi-products. DAMN. disregard my above post.

 

Marvel mystery oil. Ya it works but it's meant to dissolve gum and varnish slowly,with repeated use.

 

We use to have an old wheel dyno outside and we would run a car about 3/4 throttle and squirt water in the carb and watch the carbon shoot out the exoust.

 

Thanks guys. I have actually tried this before. Maybe I'm doing it wrong?

I took a spray bottle (like you get 409 in or something like that) and set it to jet (narrow stream). Then I spray it straight into the carb underneath the slide so it'll go into the cylinders. I do all this while keeping the RPMs up. Should I spray a lot of quick shots? Or just a few here and there?

I know too much water/steam will hydrolock the engine. But a little, in theory will "steam clean" the cylinders. I just haven't had much luck with it. Any advice on technique?