Pilot jet sizes

[MPittma100]

Anyone know what difference, such as performance or MPG, you would see between these two carburetor setups:


1) 42.5 pilot jet and 180 pilot air jet.

2) 45 pilot jet and 210 pilot air jet.

Same main jet for both setups.

MP

[DGXSER]

Personally, I think it matters which carbs your dealing with. I know the early style, in 78, came stock with the 45- 210 jetting. In 79 and in all the 80 and up carbs the 42.5 and 180 jetting was stock.

I would think in the 78-79 style the 45-210 jetting might give you a little more low end power, but hurt millage maybe 5 MPG?

I would think upping the jetting in the 80 and up style carbs might be less hospitable and may cause more problems than increase performance.

Another consideration is that IIRC, the cams in 78 were an imrpoved / performance grind over the 79 and up cams. The valves were also changed in the 80 and up models. All of this would contribute to how effectively the engine could use the increased fuel of the larger jets.

[natemoen]

I would think in the 78-79 style the 45-210 jetting might give you a little more low end power, but hurt millage maybe 5 MPG?

Well, I get 35-38mpg....

[DGXSER]

Well Nate, just think, with the 42.5 pilots and 180 air jets, you could have 41-43 MPG.

Besides, I was suggesting on his bike, which is not the 78 model that was designed to run the 45-210 setup. And yes, it was a complete SWAG. But typically you do not gain power without losing some milage.

[MPittma100]

Pilot Jetting Differences

I just installed the 45 and 210 jets (from 42.5 and 180) in a 79 Special. I have not ridden yet with them installed, but I do see a noticable difference in throttle response off idle - much more crisp and quicker to RPM. The warm up time is shorter and it is not as "cold natured". There is no noticeable smoke out of the pipes suggesting that it may be too rich.

Adjustment wise, the carbs synced properly. The air/fuel mixture screws wanted about a 1/2 to 3/4 lean as compared to the OEM jets. Will determine MPG change after I ride with them for a while.

Thanks for your input.

MP

[DGXSER]

Very cool, look forward to hearing how it goes!

[MPittma100]

Results

I will post results as I obtain them. Going on a few hundred mile ride next weekend and the on to the rally the following weekend.

MP