Two BS34 Questions

I have a stock airbox and stock exhaust except that I have a foam air cleaner, no cover to the airbox and short aftermarket mufflers with less baffling than the stock mufflers. I have been running 125 main and 42.5 pilot jets just to make sure it isn't too lean, and it has run well - no stumbles or hesitation from idle to redline - for the last couple of thousand miles.

I just put on a different set of BS34s with stock jets (120/37.5) and it is noticeably faster. Could this just have to do with the jets? Is there any danger of it being too lean with the stock jetting and my setup?

When installing the second set of carbs, I used a ColorTune to set the fuel mixture screws. One cylinder (#4) wasn't firing at all with the screw 1.5 turns out and didn't start firing well until 5 turns and didn't get really smooth until 6.5 turns. The carbs were just cleaned and I'm sure the pilot jets are clear (using the K&L carb wire to check). What could be going on with that one carb?

Thanks for any suggestions.

Was the bike lever when you adjusted the second set of carbs?

I run 40/140 jets in my 34's with posd and open header.

OK - your origional setup was way too rich on the pilot. Most who add pods can still use the stock pilot jet, and just adjust the mixture screws. + throw in slightly larger pilot.

The origional jetting should be close. 37.5 Pilots, needle on 3rd clip postion. The Main will probly have to be 122.5 - 125, depending on a few factors like altitude, avg temp, and such.

The problem your having with that number 4 carb is that the pilot fuel passages/circuit in the carb is partially blocked, OR your syncronization is off by too much.

I like to hook up my carbtune pro vacuum guages, while I am using the colortune to set the mixture screws, then set the vacuum balance, then colortune again, then vacuum balance again. Makes for very finely tuned idle/pilot mixtures.

With your setup, 1 1/2 - 2 turns out should be where you'll find the sweet spot on your screws.

The more power, the better! It requires a slighty rich mixture to make power, so the harder it pulls, the better.

Good luck!

roy-b-boy-b wrote:

Was the bike lever when you adjusted the second set of carbs?

Yes, it was level when I adjusted them.

TeK9iNe wrote:

With your setup, 1 1/2 - 2 turns out should be where you'll find the sweet spot on your screws.

The more power, the better! It requires a slighty rich mixture to make power, so the harder it pulls, the better.

Thanks, I thought 1 1/2 - 2 turns should be about right. I'll take them off and go through #4 again.

I'm guessing it's not the jetting in the new carbs that is making it faster since both jets are smaller than in my original carbs. Is there something else that could account for it being faster with these new carbs?

Lynn

Maybe the needle was moved. I have it on good authority that the needle has more effect until about 90% open.

T_Dub wrote:

Maybe the needle was moved. I have it on good authority that the needle has more effect until about 90% open.

These are the US carbs so there's only one needle position. I don't think there were spacers added or any modification to the needles.