Rigid_EVO Run on(Dieseling), fast idle when hot & black cylinders

[sportymike02]

Here's my problem.
It's been really hot here in the Northeast & since then I have had this issue;
when the bike is hotter than "normal" the idle tends to kick up some, I have searched other threads & found that this is not uncommon. It also runs on(dieseling) when I shut it off hot. When I pulled the plugs to check them I looked in the plug hole & saw only blackness, which I was able to scrape away with a chopstick.
The motor is a stock 2002 1200C except for stage 1 thunderslide & cycleshack slip ons done 7 or 8 years ago & nothing has been touched since.
I have also notice some carb farts running a stready 60 mph or so that never happened before.
Here's the front plug

and the back

and inside the front jug, you can see the scrape mark.


I run regular gas & have run 3 tanks with a 1 oz/gal seafoam mixture & this is what I have. Please don't tell me to use higher octane gas, I think that's fixing a symptom not the problem?

[Bruce]

I noticed when I was on the PA. run a couple weeks ago, I had a little dieseling, some preingnition on starting. I blamed it on the north east gas. Got back home and everything is fine. Have they started running more ethanol in the gas lately.

[einheit 13]

A change to a higher octane may well fix your issue. I had almost the same thing happen this week since the heat index was any where from 101-114 in SE Va. I usually run mid grade, and once it started acting up I went to hi test and it stopped. the motor is hot and your symptoms are showing the typical reaction. All that black crap is carbon, you see more of it when more corn juice is added to the gasoline. This has gone on for decades.

And i have an aftermarket ignition, 48/180 jets, Forcewinder and thunder header. It runs rich, it covers the pulley with soot, but its happy and so am I.

[sportymike02]

Originally Posted by Bruce

I noticed when I was on the PA. run a couple weeks ago, I had a little dieseling, some preingnition on starting. I blamed it on the north east gas. Got back home and everything is fine. Have they started running more ethanol in the gas lately.

10% is the max I think
starts right up in the morning, some times a backfire when starting hot, like after gassing up

[MacSporty02]

I run 91 OR 92 octane ONLY, had to use 87 once and that was terrible, same problems as
Sportymike02

[sportymike02]

Originally Posted by MacSporty02

I run 91 OR 92 octane ONLY, had to use 87 once and that was terrible, same problems as
Sportymike02

it's run great on 87 for 10 years, that's what I don't get. What happened?

[Kunze]

My 99 dieseled for first time last weekend. I just chaulked it up to extreme heat.

[ironhead1313]

I run 87 most of the year. As it gets closer to being in the 90's I'll run 89. The past few days of 100 + temps I've been running 93 (especially this past weekend getting up as high as 107).

This was just to avoid run on, and pinging under HEAVY load.

your idle will change with engine temps... I welded an extention to the idle screw on mine to have complete control over idle speed on the fly.


Other things that could cause your issue, since you say it has never done this..... I'd look for intake leaks, vacuum leaks, maybe ignition or timing ......

[khaskins]

Just putting SeaFoam in the tank will not solve the carbon build-up problem. You have to buy the spray can version of Sea Foam and follow the directions.

FYI point your pipes in a direction where the crap that is spit out will not cause a major cleanup later.

[Cherrylady2]

Yep! Every time I run less than 91 octane (I prefer 93+) I get the same damn thing. AND it's especially bad when the temps are above 80 & the engine is warm. I carry octane boost with me when I know I'm going to be in areas where hi-octane is going to be a problem finding....like the rural areas of Iowa.

When I bought the bike...I was told by several of the techs...."make sure you run hi-octane, 91+". I follow that advice whenever I can.