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General Category >> Rubber Side Down! >> Smaller Carb and Cam for MPG?
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Message started by Drifter on 07/27/10 at 14:45:52

Title: Smaller Carb and Cam for MPG?
Post by Drifter on 07/27/10 at 14:45:52

Has anyone changed there carb or cam to get better mileage? I have done the gearing change on several bikes and it helps but i was thinking of how to get 75-80 mpg out of this engine. Royal enfields get in that range and have a little less HP than the Savage.

So running a smaller carb with a longer intake manifold, milder cam removing some weight from the bike along with taller gearing chain drive should increase the MPGs alot?

Title: Re: Smaller Carb and Cam for MPG?
Post by Stimpy on 07/27/10 at 15:03:27

1. replace main jet for a smaller one ($2)

2. replace carb with vm36 or similar ($200)

3. replace whole bike for a different one, 250cc? ($2000)

* 75-80mpg?? dude, my 125cc gets 72mpg and
you want that from a 650cc?! okdokey, good luck

Title: Re: Smaller Carb and Cam for MPG?
Post by bill67 on 07/27/10 at 15:28:15

You can put an insert in your intake chamber it would give your better low end torque and may help the gas mileage but you might have to put smaller jets in for it to work best,the insert would be giving you less air.

Title: Re: Smaller Carb and Cam for MPG?
Post by james may on 07/27/10 at 21:04:48

you don't want to run too lean and get detonation and blow up your engine will cost you more than a few cents of gas per mile... if you put a restricter in the intake that might work, but kill power and since it would be like running with the choke on all the time it may not use less gas as it increases vacuum and gas suction. get a 50-150cc scooter and there ya go, 75-100mpg and then just use the savage for highways when you need to if milage is your real concern.. or get a prius :) more storage and better milage than a savage.

Title: Re: Smaller Carb and Cam for MPG?
Post by LANCER on 07/28/10 at 01:58:29

if you want to max out your milage then tune the stock carb on a dyno

the ideal air/fuel ration is 14.5:1, tune for 13.5:1 in all throttle ranges on the dyno and that should max it out for you SAFELY

Title: Re: Smaller Carb and Cam for MPG?
Post by Drifter on 07/28/10 at 04:44:00

I have 9 motorcycles right now including a 125 and a few 250s they get in the upper 70s low 80s My 250 Virago has gotten 96 MPG My 500 bagger Vulcan has seen 66 MPG. Ninja 500 has hit 65 MPG and it will run 132 MPH. My 800 Bonneville has hit 50 MPG So 75 out of a slow turning single is not unreasonable, Royal Enfield 500s get 75+mpg.

Removing 40 or 50 pounds tall gearing a smaller carb and milder cam and 75 is possible with this bike!

Title: Re: Smaller Carb and Cam for MPG?
Post by onelunger on 07/28/10 at 05:03:38

Personally, I wouldn't bother w/ cam/carb changes for mpg. It's a lot of money for very little gain.
My suggestion would be:
Change out the muffler for a better/less restrictive one. The stock muffler is VERY reastrictive. Restriction does not help effeciency and that's what you're really after.

Next, tune that carb within an inch of it's life. Leaner doesn't always make for better MPG so don't just go putting in tiny jets. You'll do more harm than good. Also, for steady cruising you will mostly be using the pilot jet so that would be the place to look for mpg as well as the needle setting. The main jet doesn't come fully into play until you crack her open and changing it will only have a very small affect on small throttle opening riding and MPG.

After that, re-gear. The Savage is hopelessly short geared. It may take some experimenting to find the best gearing for mpg. Gearing too tall will make the motor struggle too much and hurt MPG, too short will cause unnecessaryly high rpm's. A chain conversion is pretty much the only way to accomplish the gear change. Sprokets are fairly cheap too so buy a few different sizes to experiment. The front sproket will make bigger changes and their VERY cheap (last one I bought was like $10) so I'd start by messing w/ it first. You can "fine tune" your ratio w/ the rear sproket which will make smaller ratio hanges and cost more.

Lastly, adjust your riding style. Use small throttle openings to accelerate. Keep your speed down to the speed limit or whatever you can get away w/ without getting ran over. Pull in the clutch and coast as far as possible to stops. Just letting off of the throttle w/ the clutch out isn't going to net you good MPG. The RPMs are still up and the engine is sucking in fuel. Letting it drop to idle and coasting uses VERY little fuel and because you're still moving MPG will be VERY high during this point. This will help boost your average MPG.

I don't think 70+ MPG is out of the question w/ the Savage. I have an 883 Sportster and on a recent day trip I averaged 60mpg w/ that thing (over the course of 3 tanks). My Buell XB9S would consistantly get me 55+ MPG when I had it (so long as I could stay out of the throttle 8-) ) A small motor isn't necessary for good mpg so there's no need to go to a 250. A well tuned machine can get great MPG if you ride it right and make the right changes.

Title: Re: Smaller Carb and Cam for MPG?
Post by Drifter on 07/28/10 at 05:06:47

See above post.

Title: Re: Smaller Carb and Cam for MPG?
Post by jjn on 08/01/10 at 19:17:27

I have a 2007 Royal Enfield 500 Bullet that has got in the 70s and 60s mpg. I can also verify that a Kawasaki EX500 (mine was pre-"Ninja") can average 65-66 mpg.My 1985 HD XLX 1000 Sportster iron head averaged 65 mpg. My current 2006 XL883 doesn't do near as well.It is getting 45-49 on my short commute, while it can get 59.5 on longer rides.

I would have expected a Savage/S40 to get maybe mid 50s. That Bullet gets great gas mileage, but it's far from a powerhouse.

jon

Title: Re: Smaller Carb and Cam for MPG?
Post by bill67 on 08/01/10 at 19:25:52

A lot of S40 here get in the 60+ mpg range