SuzukiSavage.com - Print Page

SuzukiSavage.com
/cgi-bin/YaBB.pl
General Category >> Rubber Side Down! >> Carburetor tuning help
/cgi-bin/YaBB.pl?num=1344431067

Message started by DangRider on 08/08/12 at 06:04:27

Title: Carburetor tuning help
Post by DangRider on 08/08/12 at 06:04:27

I tried tuning my carburetor last night and it didn't seem to make a difference, so I'm asking for some input.

Relevant info: bike is '97, stock carb, white spacer mod (replaced with 3 washers - original spacer on hand), pilot screw plug removed, Old Feller's inexpensive air filter (polyester batting soaked with 90/140 oil), four 3/8" holes drilled in stock muffler, 4,800' elevation, Lancer's jet kit on hand but not installed.

I first read through Lancer's and Serowbot's tuning posts in the tech section. After warming up the bike and turning up the idle screw to get a fast idle, I adjusted the pilot air screw out 1/8 turn at a time, blipped the throttle and waited 5-10 seconds to listen for any difference. To me, the bike seemed to run the same no matter what the position of the pilot air screw, from all the way in to all the way out.

I'm open to suggestions on what adjustments to make next.

On a related note, it seems I need to pull the battery box to get enough clearance to pull out the carburetor. I'll do that if needed but wondered if there was a simpler way.

Thanks in advance.

Title: Re: Carburetor tuning help
Post by Dave on 08/08/12 at 06:47:55

The fast idle you have may have opened the butterfly enough that the idle mixture screw is no longer applicable. The mixture screw has the most affect at low rpms. I also don't believe the blipping the throttle is the way to adjust it. I would warm up the bike by riding around the block, then let the bike settle down to an idle. Then turn the mixture screw in and listen for the engine to slow down as a result of the mixture becoming too lean......and the engine will probably stall if you turn it in too much. When you find the point at which the idle speed drops....then turn the screw out until the engine speed increases and gets smooth......then keep turning it out until you hear the engine start to lose the smoothness becuase it is getting too rich. If you turn the screw out more than 3 turns from fully seated and it still doesn't burble as a result of being too rich - you probably need a larger pilot jet. When you do turn the screw in and find the lean point - then back it out and find the rich point - try to put the mixture screw between the two. Then do for a ride and see how it runs. If you get too much backfire when closing the throttle - try backing the mixture screw out an additonal 1/8th turn and see if that helps. You may never get rid of the backfire......and as some have noted hot humid weather causes the backfires to increase. Ultimately you idle speed should not be too low, as it causes low oil pressure.

Title: Re: Carburetor tuning help
Post by CalisOsin on 08/08/12 at 07:46:52

What made you think it needed tuning to begin with?

Title: Re: Carburetor tuning help
Post by Serowbot on 08/08/12 at 08:06:39

+1... at 4800ft,.. you might not need any bigger jets...

Title: Re: Carburetor tuning help
Post by EJID on 08/08/12 at 08:18:53

Dang,

I'm south of you about 50 miles, so basically the same elevation & climate :)

I've got mine setup with a cone filter and a Fishtail exhaust that doesn't have much baffle.

Stock is Main Jet 145, Pilot Jet 52.5

I also had trouble hearing much for differences but felt I needed to feed it a little more, so I upped my Main to a 147.5 and the Pilot to a 55. I haven't taken the top of the carb off to fiddle with the white spacer, but I feel mine runs strong and pulls hard everywhere I want it too, so I don't see much reason to tear into that yet.

I think that my backfire pops are mostly related to possible exhaust leaks that I need to better address. When I shut mine down, I usually only get a small poof, so I believe it is jetted about right ;D

Best of luck getting it setup, maybe our paths will cross, or we will be able to ride together sometime. 8-)

Title: Re: Carburetor tuning help
Post by DangRider on 08/08/12 at 09:21:12

The bike was stock when I got it. I changed the air filter and drilled out the exhaust for more air flow so I'm tinkering with the fuel to see if it needs adjusted to match.

Dave: thanks for the tips. I'll try that tonight

EJID: I'm tempted to copy your recipe for success. Hopefully we'll cross paths! :)

Title: Re: Carburetor tuning help
Post by Serowbot on 08/08/12 at 09:46:32

7D607B7D7C707D677C76120 wrote:

The bike was stock when I got it. I changed the air filter and drilled out the exhaust for more air flow so I'm tinkering with the fuel to see if it needs adjusted to match.

Great!... It don't hurt to try... I was just asking, to point out,... that bigger jets don't always make more power...
Some folks believe the more the better, but it don't work that way...
Best luck... ;)...

Title: Re: Carburetor tuning help
Post by Halvor on 08/08/12 at 13:38:40

I tried the "simple method" for tuning. But it did not work. After 1/4 the engine did not slow down before 1,5 turns. But the middle was to rich.

What worked was to turn in unthil it slowed down, and turn out again app 1/8, resulting in 1/4 setting. Maybee it is becauce of a relatively large (55) pilot jet. Setting it to 1/2 (carb jetting a progressive guide) gave the same idle but it was like driving with the choke on. The engine never got warm. I gues a lot happens with little change on the mix screw with the 55 pilot?

Title: Re: Carburetor tuning help
Post by Halvor on 08/09/12 at 13:54:07

I tried the simple method again, and found out that the engine run a bit faster on 1/8 TURN, so no it is 1/8.