mikuni carb conversion?

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Re: mikuni carb conversion?

Post by higgy »

all that effort and in the end you still will have a CV carb
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Re: mikuni carb conversion?

Post by koko64 »

But a more effectkve CV carb.

It will do until I get some FCRs. If the bike I find has a Weber carb, I will first test it, then take it off and study it. I will give it an overhaul in consultation with my car tuning mates and the local Weber specialist.

The Weber is an interesting performance carb and I will enjoy understanding it. They were fashionable in V8 cars when I was young.
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Re: mikuni carb conversion?

Post by paso750 »

is there any written info about CV carb modifications ? Just being curious.
all that effort and in the end you still will have a CV carb
true, but while you can find a CV for less than $50 a FCR is hard to be found under 500.
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Re: mikuni carb conversion?

Post by koko64 »

Doug Lofgren Motorcycle Performance Service website has tests for modified CV38s. He trims the throttle shafts and taper bores the body,and did internal mods to carb, but he doesnt give details. He used to do a carb overhaul for his customers.
Check out his site and the dyno tests.

A few things stand out to me.
Porting the bellmouth
Setting the float level (usually out from spec of 14mm and from each other)
Using stiff oem springs
Fitting hard needle jets from Factory Pro
Porting the long inlet manifolds but leaving a machined finish inside
They are a compromise carb because they have no accelerator pump. Dont be fooled into jetting too rich for cruise speed in order to compensate for no accelerator pump. You dont snap them open, you wind them on and they perform ok.
The manifold rubbers can crush and work like a restrictor, so its ok to trim them.
Many including myself, tried softer springs for more response, but that made us need an accelerator pump

I dont know of anyone besides DL who has modified the carb itself.
Last edited by koko64 on Sun Apr 07, 2013 5:55 pm, edited 1 time in total.
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Re: mikuni carb conversion?

Post by fasterdammit »

Do we know which inlet manifolds will/won't work with a pair of Mikunis? I've seen one Mikuni conversion for Pasos where the two carbs are split, and there is a special manifold for the horizontal cylinder which 1) allows air to reach the vertical cylinder's carb, and 2) keeps the carb float level tipped properly - a company called AutoTrim Design - even though it doesn't appear on their website, they still offer it (I emailed them; $140 +s/h) - details on this piece can be found on YouTube here.

However, instead of splitting up my pair, I figured it'd be simpler to keep them as-is, and install them the way they're normally installed, between the V. Since the Mikunis don't have the same outlet trumpets that the Weber does, it appears longer inlet manifolds are in order. I found a pair on ebay for a '95 SS ... can anyone confirm or deny whether these will work appropriately?

Considering they'll be $100 cheaper than the split-carb design mentioned above, I should just give it a shot ... but figured I'd ask anyway.
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Re: mikuni carb conversion?

Post by koko64 »

They'll work. :thumbup:
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Re: mikuni carb conversion?

Post by Skins »

:cool:


DelOrtos forever!

My 750 starts on the first turn, purrs like a pussy, and bolts like a scared cat with a pair of 36mm.
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Re: mikuni carb conversion?

Post by fasterdammit »

Thanks koko64. :) Ordered!

Skins, if I can find somebody to swap me straight up a pair of Dell'Ortos for my Mikunis, I'd do it ...
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Re: mikuni carb conversion?

Post by Skins »

:cool:


I think you can get new ones online for about $200 each.
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Re: mikuni carb conversion?

Post by paso750 »

faster, are the carb manifolds you got from a 600/750 or 900 ? (they are not identical).
You can use either or, the only thing is that the carb will stand slightly shifted when using 900 manifolds on a 750. Not a problem unless you intend to make an airbox.

G.
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Re: mikuni carb conversion?

Post by koko64 »

My apologies. You are right Paso 750. The 900 heads are taller and the manifolds would be a little different.

Besides the airbox option, is the oem electric fuel pump going to be used? If the vacuum option was considere, say if someone had a crook oem fuel pump and wanted to go vacuum they would need the Monster manifolds or modify the SS manifold(drill and tap an extra hole), or put a fitting for the vacuum line on one of the synch fittings.
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Re: mikuni carb conversion?

Post by randtcastell »

Skins wrote::cool:


DelOrtos forever!

My 750 starts on the first turn, purrs like a pussy, and bolts like a scared cat with a pair of 36mm.

I must concur! The 40mm De'llortos w/accel pumps and Malossi intake manifolds and Malossi flame resistant pod filters perform flawlessly. (My paso's head has been ported and flowed by BCM, thus the use of 40's) I've never had a bike start, idle and rev so cleanly through the range.

:thumbup:
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Re: mikuni carb conversion?

Post by fasterdammit »

paso750 wrote:faster, are the carb manifolds you got from a 600/750 or 900 ? (they are not identical).
You can use either or, the only thing is that the carb will stand slightly shifted when using 900 manifolds on a 750. Not a problem unless you intend to make an airbox.

G.
ah, they're off a 900. hrm. Well, I wasn't planning to fab a new airbox - I figured I'd go with a pair of pods (K&N, UNI?) But, would it be possible to grind them down a bit too, or would this make the manifold openings too far away from the carb exit?

We'll have to see how they fit, I suppose ... they should be here this week.
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Re: mikuni carb conversion?

Post by paso750 »

it`s hard to tell the exact difference(s). It may be only the length but it also may be the angle, or the angle or length of the bend.
I have 750 and had 900 manifolds but it`s about impossible to say just from the looks.
Try them. Also be aware that the manifold for the front is not the same as the one of the rear cylinder.
If they are swapped you`ll see that the top angle of both manifolds doesn`t match.

swapped
Image
correct
Image

G.
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Re: mikuni carb conversion?

Post by Andrew2 »

randtcastell wrote:
Skins wrote::cool:


DelOrtos forever!

My 750 starts on the first turn, purrs like a pussy, and bolts like a scared cat with a pair of 36mm.

I must concur! The 40mm De'llortos w/accel pumps and Malossi intake manifolds and Malossi flame resistant pod filters perform flawlessly. (My paso's head has been ported and flowed by BCM, thus the use of 40's) I've never had a bike start, idle and rev so cleanly through the range.

:thumbup:
I had 40's on my paso also and it ran great.I just used what ever manifolds I had lying around at the time.In fact I think they are still connected to the carbies in a box after I removed them when I sold the bike.

Cheers
Andrew
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