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General Category >> Rubber Side Down! >> Carb and Exahust Mods and MPG?
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Message started by Balderdash on 09/11/06 at 09:15:53

Title: Carb and Exahust Mods and MPG?
Post by Balderdash on 09/11/06 at 09:15:53

I've just started using a 1996 LS650 (I've only put on about over a hundred miles so far), beautiful shape, low miles (less than 2600 miles) and my purpose is pure daily commuting and gas mileage is the objective. I've been reading about the re-jetting and exhaust clip on’s and the air filters etc., and the performance increase and reducing the backfire when idling off and what not, but I haven't seen anyone talking about how this affects gas mileage.

The bike I got came with a stock exhaust AND a Jordine clip on, the stock is on it the Jordine (old man said the other pipe was too loud) and I deciding if I want it on the bike or not. By the bluing of the pipe and the backfiring at speed etc., my guess is that the carb., has NOT been re-jetted.

If I put on a cone filter, re-jet and the exhaust clip on- will my gas mileage get worse? I'm thinking that horsepower isn't free and my performance will increase at the cost of gas mileage. HOWEVER, I'm also thinking a better breathing system will be better efficient and get better gas mileage if I don't 'jump' on the throttle all the time...

So, which theory is right? Remember now, I’m trying to max gas mileage, not get better speed or horsepower for the sake of fun alone. Thanks in advance for any answers.

Title: Re: Carb and Exahust Mods and MPG?
Post by SavageDude on 09/11/06 at 09:43:07

Even after all the rejetting and muffler mod, you only loose about 5 mpg. But in return you have extra passing power when needed. I think it worths loosing the mpg for the on-the-road-defense. Just my humble opinion .

Title: Re: Carb and Exahust Mods and MPG?
Post by medel on 09/11/06 at 13:35:36

I certainly do believe that with any mods you will have a decrease in mpg. the bike is probbably most fuel efficient when stock. Even though an air filter would deliver a more efficient air flow; more air, you would then need to add more gas to keep the air-gas mixture properly balanced. But if you could put those extra horses to good use, mod it and you will only lose a little bit of mpg.

Title: Re: Carb and Exahust Mods and MPG?
Post by Reelthing on 09/11/06 at 13:36:19

Well as a reference bike the '95 has a Jardine, 152.5 main, ~1/2 white spacer ~2 turns out from a light seat on the mixture, stock aircleaner, ir plug. It is well tuned with 0 backfires from the mixture or exhaust leaks - this takes many hours on the bike of 1/8 turn or less adjustments to get it right on - turned in a very steady 52-54mpg for 10k+ miles last year.

Title: Re: Carb and Exahust Mods and MPG?
Post by Balderdash on 09/11/06 at 13:49:46

Thank you all for the responses.

Reelthing wrote:

Thank you for the 'target.' I'll drive it for a couple of weeks and see what I get for regular mileage and compare it to this and see what the risk/benefits might be for me.

Thanks a lot. ;D

Title: Re: Carb and Exahust Mods and MPG?
Post by Brewbrother on 09/11/06 at 15:57:16

You should also consider that a lean backfiring condition will reduce engine life. If you live in the deep south like me the lean engine runs hotter again reducing engine life. I'm also concerned with how the backfire effects the valves. My mods resulted in around 52-57 mpg that is mostly city riding. Hopefully I will be back in the saddle in around 5 weeks.

Title: Re: Carb and Exahust Mods and MPG?
Post by Balderdash on 09/11/06 at 17:59:20

Brewbrother wrote:

I take it the mods you are talking about are the ones in your signature.

55, 155 and NO spacer at all. I'm surprised by the no spacer at all part, how does this bike idle at street lights etc.,? Does it bog down a lot, like a racer would, or is it alright even for non-attentative daily users (you know those morning when you just aren't all there yet and you can’t be expected to know what the heck you are doing :P )?

Do you think that slide in K&N breathes as easy as a cone would?

Title: Re: Carb and Exahust Mods and MPG?
Post by Brewbrother on 09/11/06 at 18:37:59

Balderdash wrote:

The mods in my sig are accurate. Like many on this forum, when I do my air screw adjustment, I turn my idle down till the engine is almost dying then adjust the screw out till I find my sweet spot. Then adjust to a nice gentle idle. My bike never stalls at read lights. It will idle with ease as long as I want. I idle it for at least 10 minutes prior to leaving. As Kropatchek says, Never ask your bike to scream before her throat is warm. As for the K&N drop in, mine works fine. I saw no real reason for a pod as IMHO, that would add more air and further lean the fuel mixture. I would guess with one of Lancers carbs a pod filter would be fine. I sure some even have velocity stacks.