carb swap?

Has anyone successfully swaped their Hitatchi's for something else on a 650? I was curious if there was something that would bolt right on.

 

Though I don't know of anyone who has done it, Mikuni's are used on the Maxim X. Should fit right in but would need rejetting. Of course jets are available for Mikuni's but the carb rebuild kits have been hard to locate.

Why do you want to change from Hitachis?

 

I was curious because parts are cheaper and more readily available for mikuni's.

 

Not cheaper, if you figure in the cost of time spent (lots!) to adjust the carb jetting to match the engines' demands. That'll take you a weekend, minimum, if you're a jetting wizard and you have access to all the carb metering parts you'll go through, chasing perfection.

-If you're unwilling to get more intimate with your new carbs than you are with your wife, you don't want to do this.

You'll also probably need to fabricate a new throttle cable or modify your old one, so you create a new parts-availability problem of your own.

The Hitachi parts are available if you know where to look.

 

I was hoping that some one already did the hard work and could put me in the ball park. The only used Hitatchi's that I see on ebay look worse than what I already have.

 

Is the problem with your stock carbs simply an appearance issue?.

 

No, The bike will start right up, no choke, and idle fine for a few mins. then when it warms up it will die. If I readjust the idle to keep it running at this point it is ok until I run the rpms up above 2500+ and then it will stay at 2500 rpm. I've had them apart a few times and I don't see anything obviously wrong with them. The idle air screws have been messed with and don't really have too much effect if I turn them. Any ideas?

 

Check the shaft seals. You can look at the two most outer ones without taking the carbs off the bike.

 

If the idle fuel screws have little or no influence on the engine, do what's described in this thread-
http://www.xjbikes.com/Forums/viewtopic/t=1961.html

Here's a link to one of our forum members' throttle shaft seal repair- http://www.xjbikes.com/coppermine/cat=10176.html

 

They "Look" bad ... Good for you! That ought to keep the price down!

They're still made out of Aluminum and Brass. You ought to be able to clean-off the outsides ... and then, spray-on some "AlumaBrite"

The stuff that the Airstream Mobile Living Capsule people use to keep those Classic "Trailers" -- (They hate it when you call it a trailer) -- all nice and shiny and clean.

Spray it on ... it foams-up ... you rinse it off ... Presto -- New Carbs.

Don't let it dry before rinsing ... and you'll be just fine!

 

I am a carb wizard and I have done it before on a 100 bikes (OK OK 50 of those ... OK 99 of those were GS500's ... but you get the idea) ... and ... I have seen the carbs off both 700 air and water cooled maxims ...
The carbs off a Max X will almost be jetted right for the air cooled and vice versa ... why ...
Carbs care much more about intake and exhaust than they do about the motor itself. Also carbs that are capable of filling 700CC at 10,000 rpm with 5 valves will more than likely fill them with about the same mix of air and gas with 2 valves - get this, the air to fuel ratio is the same ... the amount of mix that has to be pumped in is different ... you will not have trouble with lean or rich mix ... but you go from a 10K rpm redline motor, to a 12K rpm motor, you'd suddenly discover you're missing a couple a K ... as in ... jetted right is jetted right no matter what motor ... you will lose rpm. The water and air max both have about the same redlines, and so I'd really doubt you'd actually feel anything with the swap.
I did a lot worse and came out smelling like a roast ... yea like a pot roast ...
I put in carbs off a concourse 1000 on a 900 eliminator. I jetted it with a kit made for the concourse. It was a 91 cc decrease in displacement - 998 CC to 907. The bike didn't even skip a beat.
I'd almost say, you can put in a set of carbs off anything (literally anything regardless of displacement) say a Katana 600 carbs on a Katana 1100 ... you will not ever affect the leanness or richness of the thing. OK 1100 GSXR's from 86 actually fare great with Kat600 carbs ... OK its why they slap in 33mm carbs on 1100's and 36 on 750's and 34 on the less revvy 600.
I cannot seem to put it in words. Revvy motor = larger carbs, larger displacement = smaller. In our case ... they are way too close to actually do much of anything.
Cool.
Srinath.

 

You figure Mikuni parts are cheaper than others?

I've got Mikuni's in my '85 XJ750 Maxim-X and I've been getting horrendous quotes on carb parts. I've been told that the $12 carb kits on OldBikeBarn won't work on Mikunis.

As far as I can tell, cheap carb kits are not available... of course I'd be extremely happy for someone to prove me wrong... I'm going to do a complete rebuild this year and not looking forward to the parts bill.

Corey