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Sat Mar 06, 2004 3:10 pm

Late last summer I installed dual 34mm carbs from cb performance on in my split bus. I am running a 1600 dp with 009 dist. The jetting the carbs came with are 50 idle jets, 100 a/c jets, and 130 main jets. I have not driven the bus much this winter, but have been concerned that it is running a bit rich with this set up. The plugs are pretty black and gas mileage is a bit lower than when I was running a single Solex 34 pict-3 on it. Suggestions? Do I have to worry about shortening the life of the engine or is it not too rich? It sure runs well, but with gas prices going up, economy is also a concern (and I thought these were supposed to be fairly economical).

Sat Mar 06, 2004 3:35 pm

With my experience with dual carbs better 2 b rich than lean. I run dual 40 webbers on my bug. The money you spend at the pump is better than having to build a new motor or replace the heads from being too lean! But if you want to try alittle experimenting. try smaller idle jet take it for a spin and recheck your plugs. :D

Sat Mar 06, 2004 10:13 pm

Are you sure you are running more rich then before? With those size jets, you should be just about right for a 1600. You can't get much smaller on those jet sizes. Even a stock 34 pict has a 130 main and a 55 idle.

The idle jets will affect the mileage more then the mains unless it's really a change in size. If you can find some 45 idles, give them a try.

The mileage going down could just be the fact that you are running dual carbs instead of a single. Duals do really well on the freeway but not too good in town. They really suck if you like to punch the gas a lot.

Sun Mar 07, 2004 11:24 am

Perhaps the mix is fine. True, I can't really go down in size much (50 idle is the smallest CB Performance sells). I was just going by the look of the plugs which seem more blackened than before or those in my Ghia where I am running a Bocar H30/31 on a 1600 sp. Compression check shows that my rings are okay (about 125 psi all around), so I was just assuming that the plugs were blackened from too rich a mixture--but wrongly. Thanks.

Sun Mar 07, 2004 10:52 pm

What type of exhaust do you have on your bus? If it's still the pea shooter, you might want to think about changing to a merged header. The extra flow will lean out the mixture a little.

Mon Mar 08, 2004 6:58 am

Great idea. I had not realized that the header could effect the mixture. Right now it has some old empi design where the heads flow into the muffler from the opposite sides. I have not seen anything like it, but it needs replacing this summer in any case. Thanks again.