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PMS (air/fuel) screw setting 2007 vstar 1100   Tuning&Exhaust:04cal/06 up

Started Jul-28 by Rod580sl; 502 views.

From: Rod580sl


Looking for help on setting the above. Some YT sites say back out 2 to 3 turns; one said 5; and a mechanic said 1 to 2 turns. 

Machine idles fine but backfires on acceleration and deceleration. 

Don't have a vacuum pump so wondering if anyone has same machine and can advise?

Thanks for any help 


From: 4Strokes


I'm at three turns out and still have a little popping on decel but nothing bad.

That's with pod filters, stock pilot jets and stock exhaust.

Donn (99Orton)

From: Donn (99Orton)


You need to do a lean drop to get it right.   V-Star 1100 Wiki Knowledge Base - Pilot Mixture Screws (google.com)


From: PnutsC


Just did mine. I’m a 68 yr old mechanic and have adjusted 100s of cabs in my day on everything from farm equipment to daily drivers to full on race cars.  I’ve used vacuum gauges, gas analyzers and everything else. 90% I adjust by ear which is basically lean drop method. I just did mine (yesterday) I took them off and drilled out tamper plugs. So they were still at the factory setting. They were at 2 rounds. I opened them to 3. On startup there was a very noticeable difference. Set the idle down as low as it will idle and not die. Run them in until you here a difference. If it’s like mine it’ll be pretty quickly. (From the 3 turns out method). Back off until it smooths back out. Back in until you here it drop again and find that sweet spot where moving it back and forth 1/4 turn or so make no difference but another 1/4 turn in does. I usually go another 1/4 to 1/2 from there to allow for differing conditions. I feel sure I’m still around the 3 turns mark, they’re so hard to get to I can’t say for sure because of the screwdriver slipping and you’re not always moving the screw when you’re turning the driver. Set your idle back and then do the above one more time tho usually your idle is about right using this method. This works on all carbs/engines. Mine is bone stock, hadn’t been ridden in 8 yrs, new plugs and oil change. I only drove it a couple of miles (not licensed, transferred or insured yet) and I haven’t synced (doing that today).  This was my first ride and first ride in nearly 50 yrs but it ran flawlessly,  accelerated well but did have light popping on long decels. I’ll assume popping would have been louder with more open exhaust. All carbs since the 70s are leaner than that perfect sweet spot from the factory. If you set them with a gas analyzer you’ll end up back close to the factory setting but not the optimal smooth idle. Any time you hear on any carb on any vehicle set it at x turns from seated understand that is a starting point. Fine tune from there

In reply toRe: msg 4
Sick Mick* (quick_mick)

The lean drop will get you very close, but if you are still getting backfire through the exhaust after tuning, it's still a little lean on the idle circuit. Try opening them up 1/8th turn increments until the backfire goes away. 

That's why Tim's thumbscrews are worth every penny. One ride after the lean drop and you can be 100% dialed in.

Even if you get no backfire after the lean drop, you can turn them in the same amounts until you do get a backfire, then back out until it goes away. That way you know you're as close to perfect as you can be.


From: PnutsC


Yea, I see that. I’ll get this thing licensed today. If I decide to keep it I’m sure I’ll get rid of this ridiculous air filter set up and do pods and exhaust. I’ll have to rejet then anyway. This set up worked, don’t recommend it as this is all stuff I already had. Still couldn’t say for sure if I was turning the screw all the time so yea, the thumb screws will be a must have. I have several old cars, one a Corvair which has multiple carbs and I occasionally have to retweek.