Looking for six large bore side draft carburetors. Used is fine as long as rebuild kits are available.
Originally planned on using SU’s but choked on the cost. Even used they caused my wallet to flutter. Plus every set I’ve looked at lately is showing so much throttle bore wear I question if even the over sized throttle shafts will completely correct it. I suspect I’ll need to put bushings in.
Source motorcycle carbs? 6 used ones from big singles...
How big? Any concern about no accelerator pump?
Some on road motorcycle carbs will be CV carbs, but I don’t know If that will be good or bad. I think the off-road are more traditional butterfly or slide style carbs
Snowmobile carbs may get big enough and are really simple, but may not provide the tuning that you want. They only have main and pilot jets, along with an idle mixture screw, and needle (taper and position) on the slide for tuning.
NermalSnert said:Source motorcycle carbs? 6 usually ed ones from big singles...
HD’s can run on the Big 2” SU’s so the stock carb should be big enough.
No Time said:How big? Any concern about no accelerator pump?
Some on road motorcycle carbs will be CV carbs, but I don’t know If that will be good or bad. I think the off-road are more traditional butterfly or slide style carbs
Snowmobile carbs may get big enough and are really simple, but may not provide the tuning that you want. They only have main and pilot jets, along with an idle mixture screw, and needle (taper and position) on the slide for tuning.
SU’s have no accelerator pump ( as such) they would work fine.
I’m looking for something that will flow about 200 CFM each. That’s what a 2 inch SU flows.
Simple works for me. This is going racing so I’ll jet it rich enough to idle and rich enough at peak RPM. Anything below 3000-3500 isn’t going to be used.
I think I could even use twelve 100 CFM. Carbs if they are cheap enough. ( and not too bulky. I’d have to put 6 on a side.).
Details please :) Sounds interesting!
Dell'orto motorcycle carbs have accelerator pumps, the PHM series go up to 41mm.
I don't think they're the answer you're looking for though, big boy motorcycle parts are spendy.
NermalSnert said:Details please :) Sounds interesting!
I race Jaguars. Most of the V12’s use fuel injection that really isn’t adjustable. Oh you could use something like a mega squirt but in reaching out to that community they seem to have little to no experience with racing Jaguar V12’s. Those That have been successful converting the Jaguar system to Mega Squirt for the street don’t seem eager to share their knowledge and experience.
Early V12’s ran just fine on carbs. But fuel mileage was bad. Group 44 got a relatively mild V12 to 450 hp using 4 SU’s ( Huffaker was at 470 hp)
the FI flows 1200CFM and if you cut the face of the fuel injection manifold off there is room for 3 SU carbs per side.
I had a set of Weber’s but they are sooooooooo expensive not to mention the cost of jets etc to be able to tune it. Plus no real power gain. Not going back down that path.
Ignition is simple, one wire into the coil. Yep it still uses a distributor.
No Time said:How big? Any concern about no accelerator pump?
Some on road motorcycle carbs will be CV carbs, but I don’t know If that will be good or bad. I think the off-road are more traditional butterfly or slide style carbs
Snowmobile carbs may get big enough and are really simple, but may not provide the tuning that you want. They only have main and pilot jets, along with an idle mixture screw, and needle (taper and position) on the slide for tuning.
How expensive are used/ big snowmobile carbs?
Cool! I bet it will make glorious noises.
Weber's are available up to 48mm , and parts are available ,
The larger side drafts are 52mm 55mm and 58mm I think , it is not the same casting as the smaller ones.
Sounds like a neat project
In reply to californiamilleghia :
I did 40 IDA’s but the short intake kills power. That and the fact the hood is about 3/4 of an inch away means air is curling around a lot. DCOE’s might offer the potential for more power but I’d have to start all over again buying Jets, Air correction meters, chokes, etc etc etc I used to go to the track with $1800-$2200 worth and change as air density changed. Plus how many hours on the dyno until I’ve got my bases all covered?
NermalSnert said:Cool! I bet it will make glorious noises.
The bizarre part is at idle. It will sit at 600rpm Idle no matter how wild the cam is. But when you go back and listen to the exhaust you’ll swear it’s turning 15-1600 rpm. That’s because you clearly hear all 12 cylinders fire. A V8 all you hear is 6 and a stumble.
Depending on what you thing "affordable" is, the Lectron carbs seem to go for about $350 ea new are are actually a very good side draft. I had one on my 80" shovelhead. The shop that did it once put 4 of them on a race 4 cylinder.
frenchyd said:No Time said:How big? Any concern about no accelerator pump?
Some on road motorcycle carbs will be CV carbs, but I don’t know If that will be good or bad. I think the off-road are more traditional butterfly or slide style carbs
Snowmobile carbs may get big enough and are really simple, but may not provide the tuning that you want. They only have main and pilot jets, along with an idle mixture screw, and needle (taper and position) on the slide for tuning.
How expensive are used/ big snowmobile carbs?
Mikuni VM44 carbs are a bit over $115 new on amazon or summit racing.
I’m not sure about used, but this is offseason so prices may be low since demand will be down right now.
Depending on target budget, RS series carbs may be better. Here’s a link to a chart that may help figure out what bikes may be potential donors:
900cc carbs too small? These are $33 each..
In reply to nimblemotorsports :
Wow!! Very very close! Each carb feeds 300 cc but I need to feed 441 cc’s. But!!!!! I’m feeding a plenum chamber rather than a individual cylinder. Against that I’ll be using E85 so I’ll need to increase the jet volume by about 60%. On the other hand the Kawasaki probably makes a lot more power per cylinder.
I think they might work wonderfully. Need to do a few minutes of research before I pull the trigger but the price is right down my cheapskate’s alley.
I think we have a winner!!!
In reply to frenchyd :
Keep in mind those Kawasaki carbs are potential feeding those 300cc cylinders at a much higher rpm, so the CFM may not be that far off from what you need.
In reply to No Time :
I got lost in the calculations and need to start over. Horsepower vs size. RPM & CFM. Plus fuel capacity calculations.
My gut tells me they will work, now I’m trying to do the math to prove it.
The stock Fuel injection flows up to 1200 CFM total or 600 CFM per side. That allows up to 450 hp, my target.
A 2 inch bore carb wide open flows slightly over 200CFM. TOTAL of 600 CFM
50.8 mm = 2 inch. 50.8mm x 3 = 152.4
40 x 4 = 160 close enough
now 6,500 RPM vs Kawasaki’s 8500rpm approx. .75
5300cc Jag 948 Kawasaki approx 5.6 times size
Jag 300 hp vs Kawasaki 100 hp
Jag 25 hp/cyl vs Kaw 33.hp/ cyl
Jag 441 cc/ cyl vs Kaw 316 / cyl
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