Dieseling

[NCB]

What would be the cause of dieseling when I shut the bike off?

[davej]

possible idle to high

[Bikerron]

A member on RSC FB page thought the same thing.

“Well, I just fried my starter and possibly more. I was trying to adjust the pms. I thought I had it dialed in. But when I tried to shut her down, she started deiseling. I pulled plug wires, pinched fuel lines, killed electrical...nothing. Finally, I put my covered hands over the exhaust. She finally gasped her last breath, (and boy, was she gasping) she reluctantly died. When she finally died, my starter hissed and smoked. What the hell just happened? The exhaust was sucking, not blowing. I hope I didn't fry the rings or worse.”


Keeps chuffing over after you turn the key off? Turn the key back on and it starts running again?

I’m betting the starter relay was hung and still spinning the crank.

[Jclevesque]

Looking at the wiring diagram and possible chance starter relay welded contacts or key switch failed on. Whatever happened, had to of had full power to all keep working.

**edit** read the facebook post again maybe detonation happened and started engine going backwards. Hmmm......

[Bikerron]

He confirmed that his starter eventually smoked. When relays weld the contacts, and the bike starts anyway, the starter motor will continue to spin without the rider even knowing it. It is when the key is turned off the engine tries to stop, but the sprag clutch on the starter drive train grabs and continues cranking the motor. He just thought the engine was dieseling.

BTW. Four cycle engines of this caliber can’t run backwards.

Here’s a link to the whole thread.

https://www.facebook.com/groups/4579...7515632346730/

[Jclevesque]

Thank you Ron good info you posted.

*edit* I am not on facebook.

[NCB]

Any suggestions on how to verify the starter relay is stuck? It's only happened a couple of times. It's diesels for a sec or two then it shuts off?
Should I replace the relay or starter. This is something I have no knowledge of! Thanks

[davej]

if the relay was stuck it the starter would be trying turn over the engine all the time with or without the key being turned on. That is not your problem.

[NCB]

Well that is good! Any ideas of what it might be. Nothing has changed since it started.

[davej]

how high is the idle?

[davej]

is it possible to post a video of it doing this?

[NCB]

900-950

[davej]

Kinda hard to guess anything more without hearing what it is doing. If you are just hearing an occasional starter whining on shut down that is normal. If it is truly dieseling I would like to see/hear that

[NCB]

Checked the idle again it was 950-1025. Lowered it to 850-900 and it shut off this time. What it was doing every now and then sounded like the piston was making one rotation after I turned the key off.

[Bikerron]

“sounded like the piston was making one rotation after I turned the key off.”

Engines don’t stop rotating immediately. And a 45 pound crank will have enough kinetic energy in it to pull it through one more compression stroke from time to time.


Man, I was under the impression that you were experiencing ‘run-on’ that was very common with early pollution equipped cars that would practically re-ingest its exhaust to help burn off pollutants and it carboned up the combustion chamber so bad it was like having hot glow plugs in there. A high idle would allow it to keep sputtering, knocking and gasping after you turned off the key.

Yea. I’d like to hear what you’re trying to convey here, myself. An extra chuff here and there ain’t nothing.

[NCB]

Kind of hard to get a recording when it only has done it a couple times. But a "extra chuff hear and there" is a good description of what it does. Thanks for the input, gonna keep putting the miles on her!

[davej]

if your idle was 950 to over 1000 my guess is that by turning it down to where you did will correct the issue.

[Bikerron]

Yea, when you got two big, ol pistons thumping around in there, it’s not unimaginable for an occasional kick back on a compression stroke or a spit up through the carb, etc. You’ll even hear a ‘zing’ from the starter getting spun backwards for a second when it does that.

Ride it.

[Doc_V]

I'm with BIkerRon, 1000 rpm idle should be fine, unless you've got a lot of carbon build up, then the fuel is re-igniting due to hot pieces of carbon acting like glow plugs, even when the key is off. i.e. dieseling. I'd run through a few tanks, with several ounces of SeaFoam, and ride the snot out of it regularly hitting the rev limiter as you go through the gears. If you really want to clean it, get a can of SeaFoam DeepCreep, remove a plug from each cylinder, and spray a ton of DeepCreep in there. Then let it sit at least over night. If you do, before you try starting the motor, turn it over several times with the plugs OUT, to clear the excess DeepCreep. Place a rag over the plug holes so you don't spray the stuff all over.

FYI This was the before and after of my pistons and that's not unusual:

[D-Fresh]

Doc,
Are you saying using deepcreep as you described cleaned up the piston that good? Those are before and after pics from just using the deepcreep? If so, WOW!

[Doc_V]

Ha. I wish. I probably I could have worded that better, but no, I had to scrape that by hand. The after photo is to illustrate how significant the before is. And that amount of carbon isn't unusual.

[NCB]

Yea, ran some seafoam in it yesterday for a 60 mile ride and rode it hard! Got back and set the idle to 850-900 and it shut down nice and quite! I used to use seafoam on every other fill up, but stopped for whatever reason. Going to go back to that schedule and see how she does. Thanks again to everyone for the input!

[Pauli466]

if your idle was 950 to over 1000 my guess is that by turning it down to where you did will correct the issue.

i've found mine does that if i don't let it idle a few seconds before shut down.

[davej]

with the exception of my car I do the same on all my gas powered equipment. in fact riding lawn mower carbs have a anti backfire solenoid on the carb that instantly shuts off fuel to the main jet when the key is shut off to keep fuel from being sucked into the carb and entering the engine causing a backfire after shutdown.

[Pauli466]

What would be the cause of dieseling when I shut the bike off?

not letting the engine cool down before shutting it off, if you have been running it hard let it idle a bit before shutting down