34 pict-3 to Bocar 30/31

I don't know much about carbs. What exactly do the 34 and 30/31 refer to? Some kind of volume size that limits the power perhaps?

Throttle bore size.

How did he bolt a 30/31 on a 34 intake?? He must have used an adaptor since the stud spacing is larger on a 34....

30/31 are normally on single ports. 34's are normally on dual ports.

I have heard but never seen, a dual port center section with the smaller

30/31 bolt pattern.

Europe got tons of 1300 dual ports with the smaller carb. 1600's were a rare luxury, only found in Supers and not even all of them :)

Jan

Karl wrote:

The US did not get the 1300 DP's. I wonder where he lives?

I was just wondering how he this: "Finally changed from my banged up original 34 pict-3 carburator to the brazilian equivalent, a Bocar 30/31" without an adaptor.....

He says he has a '70 1300 bug..... that should mean he has the smaller spaced intake.... more than likely a SP.

>

I believe Macsoft's mail ends in .pt so does that mean he is in Portugal?

That would explain the '70 1300 bug.....

>

Yap, I'm from Portugal. its a DP and the Bocar came with and adaptor for it bolted on. that way SPs can unbolt the adaptor and use it too.

But my question remains: does the 30/31 gives me better millage? or did Ijust lost power with no benefits?

Thanks! :)

The 30/31 carb has a 30mm throttle body, the 34 had 34 mm body. So the

34PICT can breathe more air. Assuming both carbs were well tuned, and ignition timing identical in both cases, the 34PICT would give a bit stronger wide open throttle performance than the 30PICT (or equivalent), at mid to higher revs. In this case, more performance means more fuel consumption, if you use the extra power. For example, if previously you could travel to 125km/h and now to 115km/h, you have less fuel consumption now. But for the same speed, or same acceleration, you will have the same fuel consumption, since the engine is the same.

You should not feel a big difference anyway. Maybe the mixture on the 30/31 carb is a bit lean. This is not a very good thing, as lean mixture can burn the exhaust valves. Check the main fuel jet size. The main jet is the one accesible when you remove the hex nut in the left side of the carb. The jet is located inside the fuel bowl. Find the number stamped on it. Look also at the main jet of the old carb. If the new one has a smaller jet size (e.g

120, 117, 115, 112) and the old one a larger size (probably 125 or 127 or 130), then try the old one and see if it drives any better. If you don't notice much of an improvement, then use the original jet, as the larger jet will consume more fuel without any benefit.

Bill Spiliotopoulos. '67 bug.

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