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Message started by cmbmw on 02/07/07 at 15:39:44

Title: Carb tune advice needed
Post by cmbmw on 02/07/07 at 15:39:44

I am trying to cure the sluggishness/flat/poor throttle response condition on my wife's Savage. It pulls strong as long as the RPM's are up, and idles fine. I am also not chasing any popping on decel or shutdown. Just looking to improve power and driveability.

I am familiar with re-jetting, and members here have told me how to deal with the white spacer, so my questions are;

Is there a formula that's generally accepted as a good starting point? Say main jet X, pilot Y spacer Z?

Has anyone ever dyno'd their bike with an exhaust gas analyzer and gotten good results? Say a nice flat F/A ratio in the 12.3 range? If so, would you be willing to share the specifics of your set up? (jettting, spacer etc.)

I ride an EFI Harley that you tune with a computer. I might see if the custom shop down the street from me will give a 2fer deal on the dyno. If I do, and end up with a good tune, I'll post the results and specifics here.

Thanks to you all. This is a great forum.

Title: Re: Carb tune expert advice needed
Post by Reelthing on 02/07/07 at 18:19:34

don't know that word expert may have run um all off!

We can give it try - first is the bike completely stock ? and was it made in '95 or later (older bikes had a different carb)
Are you near sea level or up in the hills?

Title: Re: Carb tune expert advice needed
Post by sparkett on 02/07/07 at 18:20:05

look in the teck section for Lancers carb tuning thread. He is the best at carbs. I even got good at it from these guys ;D take off battery cover and air connection, twist , tilt and bing! its out.

Title: Re: Carb tune expert advice needed
Post by cmbmw on 02/07/07 at 18:44:38

Reelthing wrote:

Thank you for responding. I took your advice and changed the subject line.

Bike is stock, it's a '96, and I'm 30 miles from the Atlantic Ocean so sea level is close enough. I see some ideas in your sig line.

Thanks.

Title: Re: Carb tune expert advice needed
Post by cmbmw on 02/07/07 at 18:54:24

sparkett wrote:

look in the teck section for Lancers carb tuning thread. He is the best at carbs. I even got good at it from these guys ;D take off battery cover and air connection, twist , tilt and bing! its out.

Thanks for the suggestion. I have read pretty much all I could find already. Just looking for recommendations from people who have done it on where to start in terms of jet / spacer sizing.

Title: Re: Carb tune expert advice needed
Post by Brewbrother on 02/07/07 at 19:04:03

cmbmw wrote:

Thanks for the suggestion. I have read pretty much all I could find already. Just looking for recommendations from people who have done it on where to start in terms of jet / spacer sizing.

my sig line says it all. I can generally see the gulf from my house.

Title: Re: Carb tune expert advice needed
Post by cmbmw on 02/07/07 at 19:13:38

Brewbrother wrote:

my sig line says it all. I can generally see the gulf from my house.

Do you think I'd be running rich if I used your set up with the stock muffler? I see you're running a Sporty muffler.

Thanks

Title: Re: Carb tune advice needed
Post by Reelthing on 02/07/07 at 21:48:57

likely the 155 would be a bit much for stock - should have a 145 in it if no has changed it - going up to around a 147.5 or 150 might be where to start - but the main really feeds 3/4<>WOT - the height of the needle effects the midrange that we are adjusting by hacking the spacer in half because we no longer have multi groves in the needle to move the c-clip - unless you do the dynajet kit - and the mixture screw controls the low end - where a general starting place is 1.5 to 1.75 turns out from a light seat.

where is the flat spot?

Title: Re: Carb tune advice needed
Post by cmbmw on 02/08/07 at 05:14:35

It's pretty flat all the way through the low end and midrange. If you go through the gears easily it feels sluggish the whole way. If you keep the revs up and delay shifts a bit it pulls pretty good. Based on what you've told me I think it makes sense to start with the mixture screw and spacer and see what effect that has. What are your thoughts on the pilot jet? Best left alone?

Thanks for the advice.

Title: Re: Carb tune advice needed
Post by Dynobob on 02/08/07 at 06:20:04

cmbmw wrote:

What are your thoughts on the pilot jet? Best left alone?

Since you're in there, I'd go up one size on the main jet (147.5), go with 1/2 spacer, and skip the pilot jet. The 1/2 spacer will take care of most of your performance issues.

What muffler and what intake mods you've done determine your starting point. Since you're near sea level, altitude isn't relevant.

Title: Re: Carb tune advice needed
Post by Savage_Rob on 02/08/07 at 07:10:35

Reelthing wrote:

My thoughts exactly.

Title: Re: Carb tune advice needed
Post by cmbmw on 02/08/07 at 18:48:43

I'm at sea level, intake and exhaust are stock. My plan going in, based on your collective wisdom, is as follows;

Main jet 147.5
Spacer 1/2
Pilot untouched
Mixture 1.5 to 1.75 turns out

Everybody concur?

Thank you all very much for taking the time to help me out. I'll let you know how this formula works out.

Title: Re: Carb tune advice needed
Post by Reelthing on 02/08/07 at 19:52:52

Sounds like a good place to start - you'll have to adjust on the mixture screw maybe 1/8 a turn or less at time after it gets warmed up until you find the sweet spot

if your going to do the work your self - read very careful about it - those are very soft screws - they should be replaced with s/s allen head - and the little ones at the bottom of the slide are #1 phillips - use a new/good tip
and have the slide clean when it goes back in - also inspect the diapharm for any pin holes or rips,etc....

Title: Re: Carb tune advice needed
Post by Greg_650 on 02/08/07 at 20:25:02

Actually the generally accepted Fuel/Air ratio is 14.7 to 1.

I learned that as a jet engine mechanic in the Navy (way back when). Always stuck with me...

More info? Go here...

Fuel Air (http://en.wikipedia.org/wiki/Air-fuel_ratio)

Title: Re: Carb tune advice needed
Post by barry68v10 on 02/09/07 at 03:38:30

A fuel/air ratio of 14.7:1 is the ideal stoiciometric ratio as Greg stated for pure gasoline air mixture. However, max power is usually achieved between 13.1:1 and 14.1:1. Ratios above 14.7, up to about 16:1 will decrease power but increase mpg, but watchout...the leaner the mixture, the hotter the burn, and 16:1 can burn valves and cylinder heads. Again, richer is better, especially in an air cooled engine. If I can get an exhaust/gas analyzer, I'll try to tune to 13.5:1.

Title: Re: Carb tune advice needed
Post by barry68v10 on 02/09/07 at 03:41:16

Quote:

fuel/air ratio of 14.7:1 is the ideal stoiciometric

In case this created confusion, this should be 14.7 parts air to 1 part fuel...air/fuel ratio.

Title: Re: Carb tune advice needed
Post by Greg_650 on 02/09/07 at 05:21:58

barry68v10 wrote:

In case this created confusion, this should be 14.7 parts air to 1 part fuel...air/fuel ratio.

Yeah, I just read that. Ooopth :P

Title: Re: Carb tune advice needed
Post by Kropatchek on 02/09/07 at 05:59:55

Basics, my dear Watson, basics.

Greetz
Kropatchek ;D