bike carbs on lampredi sohc?

[ghostdancing]

any knowledge or experience on fitting motorbike carburetors on this motors? as far as now i didnt found any example on the web..

 

[JimD]

From the Xweb archives, which look different now that TapaTalk has taken them over. Kelvin in Texas had bike carbs on his X many years ago. I believe he sold the car. Some of the old picture links are still active.

 

[ghostdancing]

saw the pics, neat job; so looks like is not a popular conversion..

 

[Rupunzell]

Done this about a decade ago for the LeMons racer.
https://jalopnik.com/5429364/lemons-legends-some-of-our-favorite-24-hours-of-lemons-cars-from-2009/

Works fine.

Bernice

 

[Dr.Jeff]

This was something I was working on. But a turbo package came my way so I stopped the project. Here are some references. I haven't reviewed them in awhile so not certain if all the links are still good:

https://xwebforums.com/forum/index.php?threads/has-anybody-run-a-single-weber-idf-on-x-or.22672/

https://xwebforums.com/forum/index.php?threads/motorcylce-header.12556/#post-95997

https://www.tapatalk.com/groups/xwe...rb-conversion-dial-up-warn-t12122.html#p80690

https://xwebforums.com/forum/index.php?threads/kawasaki-carbs-on-the-x.3392/#post-15051

https://xwebforums.com/forum/index.php?threads/kehins-on-the-x.1778/#post-9831

http://www.redpepperracing.com/forums/index.php?showtopic=38290

https://clubgti.com/forums/index.php?threads/bike-carb-conversion-dummies-guide.266303/

http://japanesenostalgiccar.com/for...6-fitting-cv-carbs-from-a-motorcycle-to-a-car

http://www.v-performance.com/articles/mikuni_carb_installation_and_tuning_instructions_.html

https://forums.vwvortex.com/showthread.php?4647341-Switching-to-Bike-Carbs-Heres-a-write-up!

 

[motoTrooper]

Seems like it was carbs for a 600cc motorcycle that were in the ballpark for the sohc Fiat engine, from my understanding.

 

[Pete Whitstone]

Seems like it was carbs for a 600cc motorcycle that were in the ballpark for the sohc Fiat engine, from my understanding.

I assume we are talking about quad carbs here. I would think 600cc would be too small to deliver the required fuel. They would have to flow enough fuel to feed an engine 2.5 times that size. Yes, bikes rev higher, so they have some extra capacity, but they would have to rev to 7k x 2.5 = 17,500 rpm. I don't think most 600cc bikes will get there.

When I looked into it, the carbs of choice were Kawasaki KZ1000, as I recall. Still have a couple sets around here somewhere...

Pete

 

[ghostdancing]

of course larger carbs will make the motor running best @ higher rpm, but for road use, on a 1300cc i would try with 34\ 36 CV carburetors..it's definitely an interesting field to explore

 

[PaulD]

I assume we are talking about quad carbs here. I would think 600cc would be too small to deliver the required fuel. They would have to flow enough fuel to feed an engine 2.5 times that size. Yes, bikes rev higher, so they have some extra capacity, but they would have to rev to 7k x 2.5 = 17,500 rpm. I don't think most 600cc bikes will get there.

When I looked into it, the carbs of choice were Kawasaki KZ1000, as I recall. Still have a couple sets around here somewhere...

Pete

I think that the volume of air that the throats can move to the engine is the critical factor, versus engine size comparisons. I am using 4 individual throttle bodies from a Honda CB600 fi on my 1610 cc fuel injected engine. The throats are 36mm. Four 36mm throats is the same as dual 36mm DCNF carbs. The engine is built for torque with a 6500 rpm red line (ok, 7000 in a pinch). The honda CB600 engine revs to 14,000. These throttle bodies do an extremely good job of delivering the goods for my engine.

Paul Davock

 

[Dr.Jeff]

When I was looking into this, I found exactly what people are saying here. Bike engines move a LOT more air than the old design of the Fiat SOHC ever could. Plus they are tuned for top end performance (larger venturis). Furthermore these are open slide type carbs that have much higher ratings than a standard carb of the same size. So even a much smaller bike engine will have rather large carbs with sufficient flow for our SOHC. And yes we are referring to four of them. Think about 4 times of anywhere between 32 to 38 mm bike carbs, with the equivalent flow rating of say 36 to 42 mm standard carbs. That's a lot of induction potential. The "CV" (constant velocity) bike carbs are interesting in that they are somewhat self-compensating for the conditions. So tuning is actually much simpler than say a Weber or equivalent. Bike carb conversions are fairly common in the VW water-cooled world (hince some of my references above). Those engines have greater capacity and higher flow levels than the Fiat SOHC, and many of them run carbs from a 600 sport bike. Plus most 1000cc bikes went to FI long before the 600's did, so there are more 600 options available. They actually work better than I would have expected, given it is a bit of a "hack" set-up. Cheap and easy compared to most of our options (e.g. Webers). I also have a Nitrous Oxide kit designed for sport bikes that would be a great complement to a set of bike carbs. Maybe if the turbo project fails I'll go back to that idea.

 

[Dr.Jeff]

I found my file with a few sample pictures of X1/9's with bike carbs. No particular significance or other details, just something to look at:

 

[kmead]

I prefer the way the first three photos dealt with the offset of the carbs, the last three the inner carb manifolds have such a distinct kink to them. The first two seem ideal with the carbs offset evenly to each side to deal with the size of the carbs. The third one must be using a much smaller carb to have the pairs separated by that amount.

On the third picture, the manifolds are quite long, one would think this would have benefits for torque and allow fitting a proper air cleaner possibly.

Some nice work on all of them.

 

[carl]

Because Dr. needs slapping around sometimes, I'll point out the second pic is a 128, not an X.

 

[Dr.Jeff]

The third one must be using a much smaller carb to have the pairs separated by that amount.

Actually on that one the carbs were separated in the middle and spaced out between the two pairs. Fairly easy to do with some bike carb set ups, but not with others. And with that one he was using the runners from a FI manifold. Agree about others having rather compromised designs. Another design consideration, some bike carbs are intended to be positioned flat (parallel to the ground) while others are intended to be tilted at an angle. Preferably they are kept as intended to work properly.

I'll point out the second pic is a 128, not an X.

Good eye. I did realize that, but wanted to offer as many SOHC application pictures as possible. I am surprised there aren't more attempts at doing this with any Fiat SOHC vehicle. It has been worked out and shown very effective on other applications and the few that have done it with the SOHC seemed to be successful. Cheap alternative to dual Webers.

 

[carl]

The problem is the manifold. 99% of us are not in a position to have custom intake manifolds made. Also, 97% of us have no experience with bikes and would have no clue on their carbs. It would have to take someone who sold complete kits, or at least the manifold and recommendation for what model bike carbs to use to get this as a viable consideration.

 

[Dr.Jeff]

Good points Carl. Although making manifolds for bike carbs is MUCH easier than making manifolds for regular carbs, because the manifolds for bike carbs are extremely simple. But I realize not everyone has the equipment to make any manifolds, regardless how simple. The carbs themselves are also extremely simple compared to normal carbs. But once again, only after you have played with them and find out what they are about. I suppose a kit could be made, however the better choice of bike carbs to use are ones from about 15-20 years ago. So they need to be sourced and cleaned up, and used carbs don't make for a good kit.

Even with all of that in mind though, there are enough guys here making much more involved projects that could do this. I think mostly it's something that just hasn't been done enough (yet) to provide the comfort level most desire.
Perhaps that is also the reason the Weber DFV carb conversion hasn't been done much on X's...another great option.

One thing that would help with either of these options is the availability of flanges or adapters. That will help to make the build process much easier. In the case of the Weber DFV, the manifold adapter is being produced as we speak, and will be listed on eBay soon. For something like a bike carb conversion, manifold flanges to fit the head would be great to have. This also applies to making custom exhaust manifolds; for a turbo installation or tube headers, etc. We started developing the needed file to make flanges but it never quite happened.

 

[carl]

….add to the "I wish they would make" list is someone to market a reasonably priced fiberglass front spoiler to replace the metal ones on pre-79 Xs.