Hi guys, new member here. Been doing some reading around here and have come up with a few questions. I just yesterday hauled home a bobcat plane from a fellow up the road. Apparently the owner previous to him built it, had it flying and decided to start on another plane building project so took out the engine and controls and sold it. Sat in this gentlemans yard for the last year and incurred some damage here and there but nothing i don't see as fixable. Going to obtain a set of plans to fabricate the landing gear as well as effect repairs. After much research i think i have decided on a 1/2 VW conversion for eventual power. I am a little puzzled as to why it seems that anyone with a twin cly engine feels the need for 2 carbs. I would think keeping 1 carb in tune is easier than keeping 2 running optimally and synchronized as well. Plan on installing a ballistic chute in this plane as an added safety precaution. I have about 35 hours in the air working on my private lic so i should be able to get the hang of this with relatively little instruction hopefully. Happy to be a member around, here seems like a great place. I'll get a pic of the new toy up ASAP. Hmm, site seems to dislike letting me upload pics, will not work no matter what i try :-(

"scooter01922"

> I am a little puzzled as to why it seems that anyone with a twin
> cly engine feels the need for 2 carbs. I would think keeping 1 carb in
> tune is easier than keeping 2 running optimally and synchronized as
> well.

In the case of opposed two cycle two cylinders, the use of one carb would
necessitate long intakes where the mixture would tend to condense out on the
walls of the pipes. They both usually are drawing at the same time, so it
would have to be twice as big of a carb.

If this is a multi cylinder with separated crankcases so the charge goes
into the cases, they are not connected internally, so separate feeds would
be necessary or use separate carbs.

Another advantage of individual carbs is that you can tune each cylinder for
equal head and exhaust temperatures, to make it run as smooth as is
possible. You need to have two carbs for that, as one would have to be a
compromise for each of the cylinders.

It isn't all that difficult to sync carbs, anyway. A simple set of manifold
vacuum gages is all that is necessary, for minimal needs. I once tuned a 4
carb MG by sticking a tube down the throat of each carb and listening to the
volume of the sucking of each carb. Guess what. That is how the book for
that car told you to do it! <g>
--
Jim in NC

I suppose from a tuning point the twin carbs do make sense and the long intake tube argument as well. Suppose i need to settle on what i'm going to use for an engine before i go thinking too much about carbs anyway.