Weber Carb Conversion

[Glyn Pickering]

Hi All

Some have you will have been bored in the past with my ravings about fitting an IDF Weber twin throat downdraft carb onto my Vision. Well it's finally finished. I was ready to eat truckloads of humble pie and well expected the motor not even to catch. Well it didn't for about 10 mins. Drrrr, got the fuel lies crossed on the re-mounted fuel pump. This is needed since the Weber inlet is a fair bit higher than the Mikuni.
Re fitted and she started on the button. No choke on this carb, but does have squirters, so initially for the first 100 meters of so it was cough splutter. Should have warmed it up on the stand first.
After that it cleared it's throat it went like a scolded cat.
Really smooth even from quick roll on in high gear. Even with a relatively cold motor I just couldn't get it to stumble and I tried hard.
My engineering skills are "backyard" to say the most so I'm sure such a conversion would be easily within the scope of most out there.
My carb came off an RX7 car and the IDF Weber seems really the only model suitable, well at least the easiest to fit.
I junked the rubber engine mounted inlet stubs and made up
mild steel items which bolt to the motor. They were a real prob and by far the most complex thing about the whole job. The rest was just time. If any one wants any pictures or further info on how I went about it I can do a bit of a proceedure list. I'm on pickteam@xtra.co.nz.  
Would be good to post a picture on the site - but not sure of how to do this? If I could mail a couple to someone who could load them that would be cool.
Main venturi's are only 28mm since 30mm were not available. Still have to give it a decent road test (read long term thrash)
to see if the initial impressions are not a flash in the pan.
The carb and top hat air filter look great with the tank off and seem almost as if was made for the bike. Only a small mod to the rear top engine plate was needed to allow the throttle
linkage to rotate cleanly. If a small batch of alloy/stainless manifolds could be made up it would literally be a bolt of conversion. Anyone with an alloy smelter out there...

Will report on longer term performance / jetting changes etc as time goes on. I have no YICS fittted and the whole afair is now easy to get at and tune.

 Regards

Glyn ;)

[Lucky]

Send me pics, i'll post a page on my site about the conversion.
--Lucky
luckyvision@hotmail.com

[Superfly]

Wow, I would love to see pic's, being a "driveway mechanic" myself (in North Carolina some driveways were gravel....), it seems like a very interesting project.  Please keep us posted on the long-term effects of the weber.

[Walt_M.]

I have always thought that would work but I don't have the patience or skill to fabricate the manifolds. The 28mm venturi should give it better low rpm performance but it'll lose some on top end. Nice job though and congratulations.

[Riche]

Great job Glyn.

[Koaps]

I was curious as to what year RX-7 you got the carbs from and what years you think that would work with?

I might be interested in trying this mod.  ;D

[wolfman]

The Fiat 124 Sport Spider uses the Weber IDF. ?Specifically the 40IDF-13/40 IDF15 (1608  )

This version HAS 32mm venturis, larger main jets AND a starting enrichment circuit.

[crazyjimmy]

Koaps, the weber carburator that was used is not a stock mazda rx7 carb. All stock rx7,s use a 4 barrel carb up until 1985 i believe. After that it was fuel injection.
Jim

[ArrrGeee]

Wow, thats very cool that you got it working.
I could see where a setup like this could get rid of the
stumble, because lets face it, the vision is overcarbed stock.

While I'm familiar with the Fiat carb which is I believe a
progressive 2-barrel, is the RX7 also ?  I thought they
ran 4-barrels...   must be a european/uk thing.

some pictures of the setup would be excellent.
I can host pictures here also if you need them posted.

thanks for the update!

-Ron

[silicon_toad2000]

good work glyn, There's a saying I heard about you kiwi's, you can build a battleship with a roll of fencing wire and a welder. You have certainly held that legend true (how much fencing wire did it take to make that manifold j/k)

have you made many more jetting changes since we spoke last?

ron, as far as I know japanese sports cars don't come from the factory with italian carbs fitted, I think glyns was aftermarket. The IDF has two primary throats. its not progressive.