Carburetor Interchangeability

I just picked up my first xj, an 85 xj700 MAXIM. It has no carburetors, and I am playing hell trying to find a set of carburetors locally. My question is this, Can I use the Carbs from another xj bike, and re-jet accordingly?

 

The 700 airhead Max had 33mm Hitachi CV carbs. The carb mounting boots that bolt to the head for the 33mm carbs are no longer available. Most people use the boots and CV 32mm carbs (Hitachi or Mikuni) from a 83 750 Max and re-jet.
You could do a EFI conversion that runs great and gets good mpg's, but can be costly.
Kehein makes some CR race style carbs that will work well for around 800 bucks.
Mikuni round slide carbs are cheaper and easier to deal with, but will require some work to adapt to your bike. I did a 2 carb conversion with custom 2 into 1 intakes, but I have seen a 4 carb setup recently on Thechopperunderground.com forum.
Conversion's often lead to other conversions like petcocks, fuel lines, throttle and choke cables. Some conversions are hard but offer better results, some are expensive and some are easy but are a pain to maintain.
Whatever choice you make, it will require some work, patience and knowledge of carbs. Whatever help you need, someone on site can help.

 

Yes and no, so kind of "sorta"...........but, best advice is to find a set of XJ700 carbs (and be aware that the air-cooled engines and the water-cooled engines use completely different carbs).

If you have a water-cooled XJ700 engine, then you MUST use a set of carbs off of another XJ700 water-cooled model, these are Mikuni carbs.

The air-cooled XJ700 models used Hitachi carbs, series HSC33 (33mm diameter throat). Almost all other XJ bikes of this era with Hitachi carbs use the smaller HSC32 series carbs, with a smaller throat and less spacing between the carb throats (i.e. the rack is physically narrower on the HSC32's than on the HSC33's).

Again, the best advice is to find a set of Hitachi HSC33's from another XJ700 air-cooled model.

However, you can use the smaller HSC32's as long as you change to the XJ650/750 air-cooled engine intake manifolds (otherwise, if you try to use the HSC32's with the stock XJ700 intake manifolds, they won't fit properly and you'll end up with vac leaks). BUT......the HSC32's will have to be completely re-jetted and re-needled (and re-just about everything else internally) to get them to perform properly, which is going to add to the cost and your frustration level immensely.

These engines become rather cantakerous to tune and make perform well when changes are made to their carbs or air intake systems........

 

If you have an air-head I have a set of 750 carbs that is missing a few pieces that I would be willing to part with. The missing bits are jets and an emulsion tube, so it wouldn't be a problem for you.

 

I have Parts Carbs, too.
PM me with what's missing.

 

KrashKadillac,

Welcome to the Club. I don't know anything about the 700's, but I believe I just saw a set of air-head 700 carbs on e-bay for $189 w/no bids. Seems pricey to me but based on what Chacal is saying about having to re-jet everything you might want to get in touch with them and see if you can talk them down. Plus with what JP and Rick is offering and the fact that those carbs are hard to find it might be worth it if you have the 700 manifold and airbox boots. I just try to help out in the way it has and continues to be given to me. Hope this helps.

Gary

 

I do have the boots, so I suppose I will keep looking for the 33mm carbs for now. Unless I can pick up the 750 setup on the cheap.

 

Well looks like the boots are shot. Off to bob's to find a set of carbs and intakes!

 

If your looking for the original 700 33mm boots, good luck. If your going to use the 750 carbs and boots, make sure the boots are from a 83 or later because they have the same bolt and mounting pattern as the 700. Earlier 750 models are slightly different.