Author Topic: FL250 Mikuni Carb  (Read 18419 times)

jeffwesst5599

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FL250 Mikuni Carb
« on: September 10, 2012, 06:58:07 AM »
I have an 83 Fl250.  Looking to replace the carb.  Can I just get a Mikuni 30mm vm series carb and bolt it up to work.  What is the best option and if I uses this carb do I need to replace the fuel pump or need the check valve in the tee.  Any advice is appreciated.

LiveWire

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Re: FL250 Mikuni Carb
« Reply #1 on: September 10, 2012, 07:13:47 AM »
I looked the info on this up for someone else. I can't remember specifics, but I believe the OD of the spigot on the Mikuni 30 is larger than the stock carb. A 32 VM is larger than a Keihin PE32 which is why I machine them down for the FL350.

LiveWire

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Re: FL250 Mikuni Carb
« Reply #2 on: September 10, 2012, 07:14:10 AM »
The tee and pump would stay the same.

cd

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Re: FL250 Mikuni Carb
« Reply #3 on: September 10, 2012, 07:29:07 AM »
Livewire,

This is copied from "odysseysalvage":
"Mikuni Carb.   32 mm REPLACES STOCK 29mm KEIHIN CARB  BEST STOCK CARB REPLACEMENT, would be a MIKUNI 32mm CARB (includes 2  extra main jets)   ( STOCK THROUGH SUPER STOCK,  A SUPER STOCK IS A ENGINE WITH ALL BOLTED ON ACCESSORIES, A 32MM IS GREAT BUT CAN GO AS BIG AS A 36MM  ON A MODIFIED ENGINE THAT HAS ALL BOLT ON ACCESSORIES AND PLEASURE  PORT WORK OR HIGHER, A 38 MM WILL WORK...   
Remember with MIKUNI carbs, if you have not replaced your fuel pump, replacing the fuel pump is important. Either modify the Honda pressure T/ that was made into a check valve with metering jet when ever using a Keihin carb. With Mikuni carbs run the fuel line DIRECTLY from fuel pump directly to Mikuni Carbs   ON OVER HEAD TANKS, NEVER GRAVITY FEED!"

Is what he is stating correct when using Mikuni carbs?

LiveWire

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Re: FL250 Mikuni Carb
« Reply #4 on: September 10, 2012, 08:13:23 AM »
The FL250 stock pump is the same as the FL350 stock pump. One in good condition can supply a 39 PWK on a highly modified FL350. It can certainly supply enough fuel for a 32 on a 250. The only reason to replace the pump is if it is not in good condition. It is possible that it is in such a condition that it could supply the stock carb, but not a larger one. Rebuilding the stock pump is an option besides replacing it.

I have never agreed with Randy's approach to putting a main jet in the return line. You want to meter the fuel going to the carb, not meter the fuel going back to the tank. If your pump supplies more fuel than what is needed by the carb and what can flow through the return line, it will overflow the carb. If your pump cannot flow enough to still feed the carb after the amount the return allows back to the tank, you will go lean.

If the float pressure/inlet valve on the Mikuni carbs is sufficient to prevent overflowing with full pump pressure on it, I have not personally tried it and have no reason to doubt it.

That info does not address the spigot size issue. It may have been reasonable at the time it was written to expect the stock boot to stretch over the spigot of the 32. Personally, I would not feel safe stretching an old hardened stock boot. Just because it does not tear when you install does not mean it will not tear later.

jeffwesst5599

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Re: FL250 Mikuni Carb
« Reply #5 on: September 10, 2012, 08:26:02 AM »
Is it safe to say then if I go mwith a 28mm or 30 mm universal carb whether Mikuni or not it would work fine.  I know stokc is a 28mm.  Just looking for a quick changeout.


odypilots

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Re: FL250 Mikuni Carb
« Reply #6 on: September 10, 2012, 08:39:57 PM »
I've heard about Mikunis being hard to jet, and had trouble jetting the one I owned, although I got it used. Plenty of people like them, but I would stick with a Kehin(sp) carb.

But, yes, a Mikuni VM carb should operate about the same, 28mm compared to Kehin(sp)28 mm.  Mikuni jet numbers will be way different, much higher numbers than the Kehin(sp), could be into the 300s with the jet sizes, as well as being much easier to spell.
« Last Edit: September 10, 2012, 08:44:55 PM by odypilots »
The usual 'my two cents' disclaimer applies. :)


odypilots

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Re: FL250 Mikuni Carb
« Reply #8 on: September 13, 2012, 03:20:34 PM »
For that kinda price difference, I'd be looking at Mikuni, too! :)
The usual 'my two cents' disclaimer applies. :)

cd

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Re: FL250 Mikuni Carb
« Reply #9 on: October 01, 2012, 02:18:29 PM »

LiveWire

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Re: FL250 Mikuni Carb
« Reply #10 on: October 01, 2012, 02:48:01 PM »
VM30-164

cd

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Re: FL250 Mikuni Carb
« Reply #11 on: October 01, 2012, 02:51:15 PM »
VM30-164

Do you sell on eBay, or do I need to order off your site?

TEXASBAGMAN

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Re: FL250 Mikuni Carb
« Reply #12 on: October 01, 2012, 05:29:13 PM »
i saw some fact carb on ebay for sale

LiveWire

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Re: FL250 Mikuni Carb
« Reply #13 on: October 03, 2012, 09:57:03 AM »
VM30-164

Do you sell on eBay, or do I need to order off your site?

I have not sold on eBay in probably a year and many years since in volume. eBay made more money than me off my sales.

cd

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Re: FL250 Mikuni Carb
« Reply #14 on: October 12, 2012, 12:02:02 PM »
Not meaning to be an idiot about this, but if I go with an VM30 Mikuni my OEM stock boot will not fit? What do you get to as far as hose goes for making it work? And why not go 32mm?