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Bike Carbs


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13 replies to this topic

#1 cubastreet

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Posted 13 December 2008 - 01:49 PM

Has anyone tried firring bike carbs to a subie engine.
Not really planning on this, but it seems a logical next step from a single weber - would avoid the crappy intake manifold too.

#2 opus

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Posted 13 December 2008 - 04:36 PM

You mean like a Mikuni carb? I've seen a 300-6 Ford with 3-34mm Mikuni carbs on it. No accelerator pump though, so you might have a flat spot.

#3 moosens

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Posted 13 December 2008 - 07:09 PM

Haven't done it yet but but I've brought the same subject up before.

Older Mikunis would be really cool.

But my cut off would be the EA71 cars,personally. I can't see the EA81's with that old English/European sports car look under the hood.

#4 GeneralDisorder

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Posted 13 December 2008 - 10:24 PM

You would need multiple carbs for almost anything to work. A co-worker has a harley carb on his Samuri but that's about the largest engine (1.3 liter) that it would support. Plus it's a variable venturi carb and has no provision for vacuum advance.

Large Mikuni's could work but you would need like 4 of the 40mm style.

Bike engines are a LOT smaller than even an EA81 so it difficult to fit and tune off the shelf bike carbs for automotive applications. Besides - SPFI is much better.

GD

#5 4x4_Welder

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Posted 14 December 2008 - 12:06 AM

Maybe if you used split port turbo heads, so you could run four carbs, but then you'd have to set up a linkage, and airbox-

#6 Phizinza

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Posted 14 December 2008 - 05:47 PM

I was talking to a guy the other day who sad people used to put a Harley carb on each of the subaru motors.
I would imagine you would need some off of a very large V twin.
Mounting would still need little custom manifolds because of the water jacket. So my thoughts are you may as well run two small Weber's on each head

#7 cubastreet

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Posted 15 December 2008 - 12:16 AM

By water jacket I guess you mean the water channel that runs through the manifold?

I figured you'd just make up a flange on each side with a small hose for the water channel and a pipe the size of the inlet port going up to a carb mount.

My original thought was weber IDFs but the siamese ports mean they wouldn't work as designed.

twin DGVs might be pretty sweet, or even two hitachi carbs. It would take two right angle bends out of the inlet, which can't be a bad thing.

#8 The Beast I Drive

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Posted 15 December 2008 - 12:48 AM

I went over the idea of dual Webers with the guys at an old school import autoparts store near me, for anything less than a bored and stroked and boosted beyond belief 2.2 a pair of DGV carbs would be way too much carb. I plan on running twin IDF carbs on my 2.5 hybrid, they can be choked down to 34 from the 40 they come with. For a 1.8 or so I think a pair of the old Holly 1bbl glass float bowl carbs would be sweet under the hood, or a pair of Rochesters or Strombergs.
-Bill

#9 simple monkey

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Posted 15 December 2008 - 01:45 AM

the only answer you're going to get here is "spfi is better than carbs, blah blah blah." a friend of mine recently had gsx600 throttle bodies on his 2.0 rabbit, so the carbs off of a 600 or bigger should be fine on an ea81. there are many sets of these on eBay motors, normally at a very decent price. i would look other places for inspiration such as volkswagen and porsche forums. Posted Image
these carbs are for some sort of vw boxer engine. the linkage is the only real difficult part as the manifolds in the picture seem very simple. hope this helps a little, best of luck on your project.

#10 cubastreet

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Posted 16 December 2008 - 03:12 PM

You would need multiple carbs for almost anything to work. A co-worker has a harley carb on his Samuri but that's about the largest engine (1.3 liter) that it would support. Plus it's a variable venturi carb and has no provision for vacuum advance.

Large Mikuni's could work but you would need like 4 of the 40mm style.

Bike engines are a LOT smaller than even an EA81 so it difficult to fit and tune off the shelf bike carbs for automotive applications. Besides - SPFI is much better.

GD


Here's a twin mikuni setup on SUB4 heads from RAM, borrowed from backinbrat on the EA81 turbo conversion thread.

Posted Image

SPFI isn't optimal because the manifold has to go through two tight turns. Twin cabs or MPFI is better.

#11 opus

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Posted 16 December 2008 - 06:18 PM

Interesting, how does it run?? What [size] carbs are they?

#12 backinbrat

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Posted 16 December 2008 - 07:29 PM

hmm, interesting, is it that pic which shows seperate manifolds? it just shows a red cross at me 2day for that pic


yeah, would be mine that one hahahahaha!!!!!!!!!

well, if your handy with carbs, i reakon it would be pretty easy, but ive started with a whole new setup, and its being a bit of a *************** to be honest! if your gonna keep with standard ignition and stuff (in other words, dont touch any of it) your basically need one 90 deg bend on each side, and a small tube for balancing the 2 which would need to be hard lined, because its a vaccum, and then a sealed, solid nipple for a vaccum for you brakes and advance on the dizzie, not too hard, and a twin throttle cable setup, again not too bad, ive made one out of homemade parts, it works nice, shall put some pics up of it, and then you need to remember that the carbs are gravity fed, well mine are, so a small adjustable pressure regulator is also nessercary, all in all, if you got the carbs, would cost me about £80 max i would say, and thats overdoing it, its worth a go in other words, and if its not going well, you can just put the standard setup back on, oh, and you need to get a thermostat housing as well, with a subie thermo in there, or somin that does the same job and run a water pipe with T piece for the heater in it and fuel T piece.

my carbs are 36mm 'round slide' carbs, they have a plunger in them instead of a butterfly, i can take out the jets and have a look sometime to see what they are, but i need to get mine goin properly first

its possible alright, somin i would give ago if i had them laying around or were cheap, and most of the stuff you could make without 2 much trouble if you've got a creative mind and your a bit handy.

all in all

-inlet manifolds with balancer tube and vaccum holes (two 90 deg bends basically)
-twin throttle cables
-fuel T piece
-fuel pressure regulator
-sepertate water passage with thermostat and reader, with inline T piece
-and 'thats it'

i can put some pics up of mine when it was halfway and stuff, but its late for me now, shall put up 2moz

#13 opus

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Posted 16 December 2008 - 07:39 PM

I'd love to see more pics when you can. Mikinui's are great, and simple to deal with. Sure would like to hear how they performed.

#14 backinbrat

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Posted 17 December 2008 - 02:59 PM

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i dont actually have a pic of the finished article, all the parts on, the last one is about the closest (ive had to experiment with various things)

The only thing i can think of being a bit difficult is the water passage, as mine is completely different, and seperate, instead of right next to the inlet, using the same gasket surface, you would need to knock up a flange plate which you can then weld what you like on for your water passage, again, not too much of a challenge, and if you can get access to the right equipment, would be quite easy

the alternator location shouldnt be a trouble for you, so a balancer tube will be easier to fit, ive had to cut up some old oil filler tube off my other trucks to make it go over the alternator, works a treat!

Edited by backinbrat, 17 December 2008 - 03:04 PM.





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