Dieseling?
Yeah...refueled today and I'm pretty sure it was just shitty gas...Wife's Sporty was running like **** as well before the fill-up, then we were both running good.
Never-the-less I think I'm gonna have the local shop do a dyno tune on it... I'm not sure if they have a kit, but that shop has extra jets....or something...
Never-the-less I think I'm gonna have the local shop do a dyno tune on it... I'm not sure if they have a kit, but that shop has extra jets....or something...
Last edited by Mars47; May 6, 2016 at 10:21 PM.
Club Member
Joined: Aug 2008
Posts: 22,864
Likes: 17,922
From: Lafayette, Louisiana
Three main causes of dieseling are running too lean, ignition timing too far advanced, using gas with too low of an octane rating.
Other factors may cause or exacerbate the problem are spark plug gap too wide, spark plug heat range too high, and compression too high.
Most people talk about compression in terms of compression ratio, but in all honesty is relatively meaningless. What is more important is cranking pressure. Cranking pressure is affected by cam shaft. Most low rpm high torque cams will increase cranking pressure as a function of their profile while high rpm high horsepower cams decrease cranking pressure. It is part of why these high rpm high horsepower engines usually run higher compression pistons or have heads with lower combustion chamber volume to increase the pressure thus compensating for pressure reduction caused by the cam.
Engine running too hot for whatever reason could also cause it.
A lean condition could be caused by several things. Carburetors needs adjusting or cleaning. Carburetor is improperly jetted. Air cleaner and exhaust system was modified to flow more and carb was not adjusted or rejetted to compensate. Same thing with changing the cam.
Frankly, if your bike was dieseling, I am surprised that you did not hear knocking/pinging/valve clatter while you were riding.
I don't wear ear plugs because I want to be able hear crap like that going wrong on my bike before disaster strikes.
Other factors may cause or exacerbate the problem are spark plug gap too wide, spark plug heat range too high, and compression too high.
Most people talk about compression in terms of compression ratio, but in all honesty is relatively meaningless. What is more important is cranking pressure. Cranking pressure is affected by cam shaft. Most low rpm high torque cams will increase cranking pressure as a function of their profile while high rpm high horsepower cams decrease cranking pressure. It is part of why these high rpm high horsepower engines usually run higher compression pistons or have heads with lower combustion chamber volume to increase the pressure thus compensating for pressure reduction caused by the cam.
Engine running too hot for whatever reason could also cause it.
A lean condition could be caused by several things. Carburetors needs adjusting or cleaning. Carburetor is improperly jetted. Air cleaner and exhaust system was modified to flow more and carb was not adjusted or rejetted to compensate. Same thing with changing the cam.
Frankly, if your bike was dieseling, I am surprised that you did not hear knocking/pinging/valve clatter while you were riding.
I don't wear ear plugs because I want to be able hear crap like that going wrong on my bike before disaster strikes.
Seasoned HDF Member
Joined: Aug 2009
Posts: 9,243
Likes: 3,267
From: west Michigan
Dieseling or "running on" will hammer the bottom end of an engine. If your bike's engine is going to "diesel" when you shut it off, pull the choke as soon as you shut it off. If you get some bad gas, and the engine is knocking badly, running with it partially choked will help a bit until you can get some good gas. Gasoline quality was more of an issue with carbureted engines than it is with EFI engines.
Seasoned HDF Member
Joined: Aug 2009
Posts: 9,243
Likes: 3,267
From: west Michigan
It's been the same thing in my experience. I always kept my carb'd bikes in good tune and always bought premium, at major brand stations if possible.
If my bike's engine knocked after a fill up, it was because of crap gas, and that included gas with less than advertised octane.
If my bike's engine knocked after a fill up, it was because of crap gas, and that included gas with less than advertised octane.
Road Master
Joined: Nov 2009
Posts: 1,228
Likes: 417
From: Outer Banks, NC
"your ignition timing is off and thats why its running backwards."
I heard no pinging or any valve train noises prior to the incident.
I did, however, notice it wasn't idling correctly. It didn't have the usual "potato" sound, but rather a "bup bup bup bup". Ran it yesterday for ~150miles and had no issues. I always opt for the highest of octanes; 93 if I can get it, but 92 has sufficed.
Regardless, I will be getting a dyno tune this week or next depending on time and weekly finances.
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