Technical effects of lugging an engine..... : V-Twin Forum: Harley Davidson Forums

Deejay · 10-27-2006, 03:43 PM

I have heard in several threads that "lugging an engine" is bad. I tend to like to keep my EVO in the 2000 to 3500 rpm range, but have occasionally misshifted and heard the "lug". I have also heard that keeping the revs high cause more wear and tear. I like to go by "sound", cause I think the bike "tells" you when to shift.

I would like to hear the details of what happens to an engine / tranny when long-term lugging occurs..... like buying a 6 speed and shifting into 6th before 70 mph....... regularly starting out in 2nd gear..... pulling hills at 1600 rpm..... etc.

Deejay · 10-27-2006, 04:25 PM

Hmmmmm.... maybe nobody knows the effects of long-term lugging because nobody is dumb enough to do it.....

newultraclassic · 10-27-2006, 05:33 PM

Reasons not tolug your engine:

1. Loosening up of the entire drive train from the compensator sprocket to the transmission hub to the rear wheel pulley.
2. Premature wear on chains and belts, transmisison.
3. Damage to the connecting rods.
4. Overheating and subsequent damage to the pistons and valves in conjunction with pinging, detonation or pre-ignition (pick your favorite term)
5. Potential for shifting the flywheels at the crankpin.
6. Damage to the main bearings.

etc.

Deejay · 10-27-2006, 05:46 PM

Thanks for the info!!! I suppose as you increase compression, HP and TQ <like a lot of us do>,
those parts are more susceptable to damage from lugging as well....

I wonder if "quality" HD techs can identify if damage is caused by lugging and void warranty repair....

geoffreyt · 10-27-2006, 06:37 PM

If you RIDE your bike you probably dont lug it enough to damage anything. I find it agrivating to have it lug, but I ride a Sportster and almost never is it under 2K rpms. But rarely am I above 5K.

road_king · 10-27-2006, 06:38 PM

According to S&S here is what they have to say about the affects of lugging your engine.

"Lugging an engine means putting the engine under an extremely stressful load. A common way to lug an engine is to operate it at an extremely low rpm while the transmission is in a higher gear (for instance, leaving the transmission in fourth gear when it should be in second or third where engine speed is better matched to transmission speed). Lugging causes extreme stress between the rear thrust faces of each piston and the cylinder walls. Small bits of piston skirt can break away causing the rear surface to scuff. The best prevention for lugging an engine (either old or new) is to downshift to a lower gear where the engine runs more freely, and the transmission assists the engine in delivering peak power to the rear wheel."

newultraclassic · 10-27-2006, 11:08 PM

Quote:

Originally Posted by road_king

According to S&S here is what they have to say about the affects of lugging your engine.

"Lugging an engine means putting the engine under an extremely stressful load. A common way to lug an engine is to operate it at an extremely low rpm while the transmission is in a higher gear (for instance, leaving the transmission in fourth gear when it should be in second or third where engine speed is better matched to transmission speed). Lugging causes extreme stress between the rear thrust faces of each piston and the cylinder walls. Small bits of piston skirt can break away causing the rear surface to scuff. The best prevention for lugging an engine (either old or new) is to downshift to a lower gear where the engine runs more freely, and the transmission assists the engine in delivering peak power to the rear wheel."

That's good information, too. Basically, if you keep the engine turninig nicely and don't go much below 2000 in the proper gear, you shouldn't have much trouble.

godzilla22 · 10-28-2006, 03:45 AM

I cruise at 3500 to 4000 RPM on the highway. That is where I have found that the engine is happiest. That also means that with the 6 speed tranny I don't shift into 6th below 80 mph. Anything below 3000 rpm is lugging in my opinion. I have heard varying opinions in this regard but that's what works best for me.