SuzukiSavage.com - Advice from VM owners needed-tuning-UFO

BurnPgh

Serious Thumper

Offline

SuzukiSavage.com
Rocks!

Posts: 1732

Advice from VM owners needed-tuning-UFO
05/17/10 at 10:50:39

I just got my head and cylinder back from valve work and a rebore and slapped on my VM and Im getting nowhere with tuning. I have the UFO from Lancer with the pilot jet soldered shut. Im having a whole lot of trouble with the idle and mid-range so closely tied together. No matter what setting I have the needle at when I come off idle I get a hesitation. No matter what needle setting Im at idle speed is not affected by the air screw. Raising the slide at all makes for an extremely high idle. I was able to minimize the hesitation but not eliminate it with the needle at the middle setting and the air screw 1 turn out. I took it out for a couple mile ride which wouldve been longer but it died on me suddenly and I had to push it home. Im about to just take it somewhere and pay to have it tuned. I waited a month to get my head and cylinder back and I just want F&^%king ride.

Back to top

IP Logged

MMRanch

Serious Thumper

Offline

Evil flourishes if
Good Men do Nothing.

Posts: 5835
LYNCHBURG TN
Gender: male

Re: Advice from VM owners needed-tuning-UFO
Reply #1 - 05/17/10 at 19:28:56

Been there !

The first thing that came to mind is the float level ? I've found more fuel in the bowl makes for rich running and vice versa. There is more that just "Right or Wrong" in adjusting the fuel level in the carb. Its like a high fuel level with a small jet do the same thing as incressing a jet size.

Good luck with it

Back to top

I see and feel the Holy Spirit in the world , as does anybody who has eyes to see.

IP Logged

BurnPgh Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 1732	Re: Advice from VM owners needed-tuning-UFO Reply #2 - 05/17/10 at 19:40:48 with the main jet too or just in the midrange(or in this case idle/midrange)? Do you have a UFO installed? Was your float height the underlying issue? If so did what did you end up setting it at? edit - My first question was dumb after thinking it over.
Back to top	« Last Edit: 05/17/10 at 22:01:09 by BurnPgh » IP Logged

BurnPgh

Serious Thumper

Offline

SuzukiSavage.com
Rocks!

Posts: 1732

Re: Advice from VM owners needed-tuning-UFO
Reply #3 - 05/18/10 at 10:29:15

Update - Raised float level. Still idles well. Still, if I increase throttle very slowly it will rev up. Still hesitates/stutters right off of idle if im anything but very slow and steady with the throttle. Does not hesitate/stutter with the choke on. Im upping the main jet to see what happens.
Any advice or ideas welcome.

Back to top

IP Logged

klx650sm2002 Serious Thumper Offline The more I learn the less I know. Posts: 2041 Cumbria,England Gender:	Re: Advice from VM owners needed-tuning-UFO Reply #4 - 05/18/10 at 10:39:43 The way I saw it the pilot jet with the UFO should be in the area of 15 to 20. That will richen idle and off idle,without choke. Clive W
Back to top	IP Logged

BurnPgh

Serious Thumper

Offline

SuzukiSavage.com
Rocks!

Posts: 1732

Re: Advice from VM owners needed-tuning-UFO
Reply #5 - 05/18/10 at 19:03:23

Lancer told me it was unnecessary and that the UFO increased air velocity to the point that fuel would be drawn up through the needle valve even at idle. To that end he soldered the pilot jet shut.

After some more screwing around - At 0 turns out on the air screw with the slide raised slightly, the needle on the lowest clip, and a 195 main jet I was able to reduce the hesitation/stutter to almost nothing...almost. Any messing from that point with the air screw, slide height or needle height bring the hesitation back with a vengence.

Back to top

IP Logged

onelunger YaBB Newbies Offline SuzukiSavage.com Rocks! Posts: 38	Re: Advice from VM owners needed-tuning-UFO Reply #6 - 05/19/10 at 04:39:15 0 turns and a big main are definately not the "correct" settings. You should never have to change the main to fix a low speed setting. Here's the best tuning advice I've been able to find: http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm... Good luck.
Back to top	IP Logged

BurnPgh Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 1732	Re: Advice from VM owners needed-tuning-UFO Reply #7 - 05/19/10 at 10:44:15 you shouldnt except that the pilot jet has been soldered shut and idle fuel is drawn up from the bowl through the needle jet and the fuel has to go through the main jet which is right under the needle jet before it goes anywhere else.
Back to top	IP Logged

BurnPgh Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 1732	Re: Advice from VM owners needed-tuning-UFO Reply #8 - 05/19/10 at 11:32:22 took a ride. Died on me. Now I have no spark. I get the feeling Im not going to get this to work before the end of summer. Where is Lancer? He's usually all over this kind of thing.
Back to top	IP Logged

onelunger

YaBB Newbies

Offline

SuzukiSavage.com
Rocks!

Posts: 38

Re: Advice from VM owners needed-tuning-UFO
Reply #9 - 05/19/10 at 12:25:05

BurnPgh wrote on 05/19/10 at 10:44:15:

you shouldnt except that the pilot jet has been soldered shut and idle fuel is drawn up from the bowl through the needle jet and the fuel has to go through the main jet which is right under the needle jet before it goes anywhere else.

The pilot fuel jet is soldered shut not the pilot air jet??? If that is indeed the case I can't see how you're ever going to get it running good. There is no way the main fuel circuit is going to be able to accurately provide a low speed mix. That's the whole point of the pilot circuit. If it's just the air jet that closed that's a different story and there's just some tweeking that needs done.

Back to top

IP Logged

BurnPgh

Serious Thumper

Offline

SuzukiSavage.com
Rocks!

Posts: 1732

Re: Advice from VM owners needed-tuning-UFO
Reply #10 - 05/19/10 at 13:00:50

It ran "well" except for the stumble right off idle. If I yanked back on the throttle hard it would stumble for second and then continue revving as normal. At this point its irrelevent because my ignition coil seems to have died on me mid ride. Im getting power in the two line up to the coil but no spark. Which might have been the cause of the stumble in the first place.

Back to top

IP Logged

Charon

Serious Thumper

Offline

Posts: 1811
Harvard, NE
Gender: male

Re: Advice from VM owners needed-tuning-UFO
Reply #11 - 05/19/10 at 14:23:25

That "stumble" right off idle when the throttle is yanked suddenly open is precisely the reason accelerator pumps were invented. The sudden throttle opening reduces air velocity because of the suddenly larger air opening. The reduced velocity reduces the suction that pulls fuel up through the jet, so the mix goes very lean until air velocity increases. CV carbs pretty much eliminate the difficulty, because they control the air velocity. Accelerator pumps squirt an extra shot of fuel into the air stream to overcome the momentary leanness. Lacking either of those, you will have to learn not to yank open the throttle at low engine speeds.

Back to top

Eschew obfuscation.

IP Logged

BurnPgh Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 1732	Re: Advice from VM owners needed-tuning-UFO Reply #12 - 05/19/10 at 18:29:52 I understand now why its happening. Theres just no way to tune it out totally? I was able to minimize it to almost nothing but theres no way to be totally rid of it? Just a feature of the type of carb then?
Back to top	IP Logged

Charon

Serious Thumper

Offline

Posts: 1811
Harvard, NE
Gender: male

Re: Advice from VM owners needed-tuning-UFO
Reply #13 - 05/20/10 at 12:19:21

I'm not sure I'd call it a "feature." More of a "characteristic." To add to the sport, the problem is more pronounced when a larger bore carburetor is used. So, when one installs a big-bore carburetor to get that wonderful top-end power, and a mechanically operated slide for that wonderful responsiveness, one also installs an off-idle stumble.

Back to top

Eschew obfuscation.

IP Logged

bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Advice from VM owners needed-tuning-UFO Reply #14 - 05/20/10 at 12:30:41 I had a 1973 Suzuki 550 with the VM carbs and a 1975 750 Suzuki with the CV carbs,To me the CV carb was a big improvement to throttle response at all speeds.
Back to top	william h krumpen IP Logged