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Author Topic: Lean Burn Engines  (Read 4682 times)

dan_h

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Lean Burn Engines
« on: July 11, 2007, 05:06:38 PM »
I've noticed that other brands of air cooled motorcycles have overheating problems, partly related to running too lean.  Presumably the Lean Burn engine was designed to prevent this problem, but some more detail about the features of Lean Burn engines would be helpful.  Commuting everyday on surface streets and freeways, sometimes in hot weather, requires a motorcycle that is not prone to overheating.

Kevin Mahoney

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Re: Lean Burn Engines
« Reply #1 on: July 11, 2007, 06:43:44 PM »
On average the Lean-Burn engine is not prone to overheating. You are correct when you say that it was designed to run on a lean mixture. I would caution you however about extended freeway riding. The Lean-burn engine is more freeway capable than the Classic Bullet, but I wouldn't recommend driving all day on the freeway especially when it is hot outside.
« Last Edit: July 11, 2007, 07:20:25 PM by CMW-Rhett »

Thumper

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Re: Lean Burn Engines
« Reply #2 on: July 13, 2007, 03:13:53 PM »
Dan,

I have accumulated some information on the AVL LB engine, with an emphasis on how it differs from the Classic engine. I'm at work, but will post it asap when I get home.

The "Lean Burn" tag is enough to make anyone nervous.

However, in this case the design is equal to the name. Despite it's extremely lean (and 'corked up') condition, my stock engine broke in flawlessly. It idled smoothly, ran smoothly and started easily. Never so much as a misfire. This gave me a lot of confidence in the design.

The real beauty of this engine, though, is it's potential. When you pull off the restrictive intake and restricitve exhaust, and plop in a carb to match freer-flowing replacements - this engine ROARS! Mine is a bit loud with a Goldy-style muffler and Amal MK1 carb (with a K&N-like cone AF). But it cruises happily at an honest 60mph. I don't normally cruise that fast (usually I'm on 50-55mph roads) - but it's real nice to be able to do it when you want or need to. Even more, I can cruise a good 10-15 miles on the interstate at 65 mph and my Electra X handles it competently. In addition to the extra horses, you also get the benefit of the engine running cooler.

When in stock form my Electra X felt and sounded like a Honda 250 (almost electric-like). This is baaaaad for a thumper fan! (It didn't help that the overall size and weight were comparable to a Honda 250 as well!). The performance upgrades change all that. It now sounds and feels like a thumper and I couldn't be happier.


<INSERTED>
Well of course Murphy's law dictates that I cannot find my text file listing the differences between the Electra X and the classics...
Here's what I recall from memory:

Front disc brake

Electronic (CDI) ignition
   - programmed to provide a longer spark for easy starting and to improve battery charging

AVL Lean Burn Engine
   - Aluminum Head
   - Increase in 1 HP
   - new gear driven pump supplies more oil to the big end
   - The big end itself has changed from a plain floating bearing to a much stronger full roller bearing
   

Different frame at rear fender
Different side panels

Gas shock absorbers

Higher gearing

<END INSERT>

Matt
RE Notes:
http://members.verizon.net/allofusmorrows/RE_Notes.htm
« Last Edit: July 13, 2007, 09:26:56 PM by Thumper »

luoma

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Re: Lean Burn Engines
« Reply #3 on: July 20, 2007, 06:12:16 PM »
What I like about the new AVL engine is thta they didn't try to copy anyone else with their changes. Instead, they did all the things that RE owners have been doing to their own bikes for years. As for the 1 hp gain, you also have to factor in that there is about a 4 lb torque gain and an overall gain in the width of the power band. With the performance kit, the power band gets even broader.

justin_o_guy

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Re: Lean Burn Engines
« Reply #4 on: July 21, 2007, 08:15:49 PM »
What happened to the MPG when the air was allowed to flow & you richened the mix a bit? What is it delivering on the road?

Thumper

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Re: Lean Burn Engines
« Reply #5 on: July 21, 2007, 08:46:13 PM »
What happened to the MPG when the air was allowed to flow & you richened the mix a bit? What is it delivering on the road?

jog,

During my break-in period (600 miles) I got mid 70's MPG. I put on the performance kit at 700 miles and still get 75 MPG. My guess is that my engine was not getting its best gas mileage during break-in (which is often true with other vehicles) and would likely have gotten upper 70's to even 80 after full engine break-in and in stock trim. 80 mpg is not unheard of for stock Electra X's.

My current 75mpg with the perf kit is not surprising either. Even with the perf kit I am still running on the lean side of things. It has the typical lean POPping in the muffler when I roll off throttle; and that sharp raucus bark you associate with a lean mixture. Given the fact that the engine is designed to run lean, I feel comfortable running it like this. Besides, it runs like a startled cat.

I just received a second throttle valve (1 cutaway richer) to put in my Amal for just-off-idle throttle; and will likely raise my needle 1/2 position. These aren't really necessary but will allow, respectively,  slightly better cold starts out of my neighborhood, and also cooler engine temps during most of my commuting.

I'd expect my mileage to drop to low 70's and even upper 60's with these mods.

Matt

justin_o_guy

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Re: Lean Burn Engines
« Reply #6 on: July 22, 2007, 05:06:44 AM »
Saving $$ at the pump is nice, but if it costs a guy a holed piston, it may not translate to savings at all. But, I do like a growling, snarling single on decel. Thanks for the response. Is that MPG avg. highway, town, mixture? You ride kind of agressive & still get that kind of MPG? I have a Suzuki 650 thumper & it has LOW pegs & a long set of forks, Its a Savage, I get mid 40's out of it & the Guzzi gave me 50MPG the other day, but I was riding it like I was in a coma. Next day I got 47 cuz I goosed it a couple of times. If I can play & have fun & still get 70 MPG I think I have found the bike I want. 

luoma

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Re: Lean Burn Engines
« Reply #7 on: August 10, 2007, 11:18:50 PM »
I didn't notice too much of a change in mpg with the performance kit. It takes less throttle to get moving because of the additional power, and a larger front sprocket kind of offsets it too I guess.