Swap out for bigger carbs?

I just got an 83 xj550 maxim, hasn't run in 10 years, and has been sitting outside. In trying to remove the rusted screws from the diaphragm cover of one of the carbs, I broke a corner off of the top of the carburetor body where the black seal of the diaphragm assembly sits. It seems I will not be able to get a proper seal, and will always be running lean from that carb if I kept it as is.

1. Is it possible to repair the piece by bonding it back to the carb body?
2. What is the problem with swapping all 4 carbs out for a set from an 81 xj650? The 650 would have 4x32 instead of 4x28. I found the 81 xj650 carbs on eBay.

 

The spacing is different and since one bank is Hitachi and the other is Mikuni you can't space the Hitachi's with Mikuni rack. If you want to experiment with larger carbs try FZ600 Radian or FJ600.

 

Why not just look for a replacement body for the broken one. Make sure it is the right position as they are different. Get it running correctly before drastic experimentations

 

550 carbs (Mikuni BS28) should be plentiful so keep looking ebay etc.. as Simmy says some 600 carbs will fit easily (BS30s are physically the same size) BUT BS32s are bigger and will not fit easily without all the correct rubbers and even then it's a right PITA..

 

And read "the Church of Clean" on this forum.

 

the 28mm carbs are what you need
if you want to do anything you could swap (rejet) for Seca carbs and Seca cams.
not realy much differance in the speed specs for maxim and seca so it is not worth the cost
the Maxim/Seca XJ550 is quite a mover, but if you want quicker/faster buy a 650

Kroil for stuck bolts works wonders. treat all the screws before you remove them heat as well.
which carb body is broken? left to right as you sit on bike. I may have one.

you will want a JIS screw driver as well I find dry wall bits work well as compared to regular screw drivers

check your in box

 

Sorry to say that carb body is toast..even I would not try to JB weld that, you won't be able to get a real good seal ... Look for a carb body , you can use parts from broken body.

 

I see it is the #4 carb

you should remove the carbs from the bike before trying to work on them.

 

I've had no luck finding BS28 carbs on Ebay, but its good to know they are in circulation, so I will keep looking.

Thanks everyone.

 

there are 2 sets but no individual carbs or bodys


you should ohm out your ignition system and measure your valve clearances before you go much further if motor is free and you can a compression test would be good to do pre and post valve check. oil up the cylinders or a mixture of 2 parts atf and 1 part acetone before trying to turn it over let it sit over night or a few days

 

Which carb are you looking for? I may have one and I'm not to far.

 

I have only seen the whole system of 4 being sold, can you buy a set of two?

That's a good idea. I hooked up a new battery and all the lights, signals, cluster display, and horn works, so electrical seems to be in pretty good shape. I was able to hand crank and the shaft rotated fairly easily which was encouraging. I was trying to get away with attempting to start it up without cracking open the engine, do you think that's reasonable?

 

Hi Xjrider92117, I need the Mikuni BS28, I believe it was used on the 1981-1983 XJ550s. Do you have that one?

 

I just looked at your pic. I'm pretty sure l've got a spear one. Do you want just the one that's broken or are you looking for all four?

 

The 55o carbs a finicky enough as they are....I wouldn't try to use anything other than what should be there to begin with----

 

yes there is no reason to crack open the motor if it is moving free

by 2 sets i mean 2 complete sets of 4

 

Hi I am looking for a number 3 Mikuni for xj 550 Seca 1982. Pic attached.

 

I have no clue what those are--- sure doesnt look like any xj550 rack I've ever seen.

Here's an xj550 rack


Dave F

 

Sparky,
I hope that someone here can name those for you. Many different carb sets out there but as Dave above has noted, they don't look correct for your bike. I would go through those with a fine tooth comb as they look very suspect. Even the bowl on #3 looks different. Good luck and work on many of the other things that will need attention while you are looking for a replacement.

 

Hi Dave, Bike is pretty much done aprt from carbs. They are mikuni as marked with a bore of Airbox side, outside 50mm inside 45mm, engine side, outside 35mm inside 26mm. I cant find specs for what they should be but bike did run on them. The bike had been laid up for about 10 years and the owners never rode it, just started and pushed it! The inlet and outlet rubbers where pretty hard and I reckoned the carbs where glazed/stained, hence the strip out and re-build and rubber replacements. Any advice gratefully accepted.

 

Well:

-the casting around the butterflies is too thick
-the little nipple with the black cap is odd
-the throttle shafts are nothing I recognize
-there's no idle adjustment screw

I wonder if they're from some other bike.

Look on the sides of all the bowls and see if you can find any numbers stamped on them. May be very faint, but let us know what you can find.
------
Here's the back of an xj550 rack (yes I know parts are missing..... it's a parts rack)


Dave

 

Should have kept all this in your other forum--- didn't see that til now---

http://xjbikes.com/forums/threads/xj-550-carbs-1982-seca.109976/

 

Hi everyone. First time post and new to the forum. I was gifted my dad's '81 550 Seca and have been disassembling it to restore it. Got the carb rebuild kits and was taking apart the carb but was struggling with some rusty bolts. I busted off the corner of one of the carb bodies. I'm not sure if this is carb #1 or #4 though (see picture). I've found a couple of used ones on ebay but they are in worse condition than mine and are super pricey regardless. It's a long shot but I'm wondering if anyone here has an extra carb body that I could buy.

Any help would be greatly appreciated. Thanks!!

 

STOP right there. It appears you've already broken the rack, which probably means you're not following the book.

While possibly/probably necessary at some point in the future, those carbs look pretty decent on the inside and may well benefit from the basic service ritual outlined in the manual. DO NOT submerge them in anything until you are ready to remove the butterflies and replace the throttle shaft seals which is not covered in the manual, and not to be undertaken lightly. There is a whole lot that can be done with the rack still together.

If you don't have a factory service manual, you're going to need one. The Clymer 550 book is woefully inadequate for all the stuff you're going to need to do.

How long was the bike out of service? And how many miles on it?

 

Yeah I was using an impact driver to remove a stripped/rusted screw on that corner that is broken now. The bike has been out of service for at least 2 years with fuel in the carbs so I'm assuming it's in need of cleaning. I will order a service manual before I do anything else. For now, I need to find a replacement carb body.

 

Also, the reason they look offset is because I already removed a couple of other parts in an attempt to separate the carbs. They were lined up correctly before that.

 

Let me see what I got

 

Please start a thread for your bike if you haven't already.

Also, do not assume anything. Inspect. Diagnose. Never assume.

 

K-Moe is right you need your own thread for this.

He's also right about making assumptions and jumping to conclusions. Two years parked is nowhere near as bad as thirty years which most of us are dealing with or have dealt with. Even ten years is no big deal, comparatively.

We'll find you a #1 carb body, stay tuned. Don't tear the rack down just yet. Get a factory manual, turn to Section 2, "maintenance" and begin. By the time you get to the carbs, you'll have the part situation solved. Carbs are not the first step in a proper recommissioning.

And start a new thread of your own, please.

 

Hmmm, I was told this when I went to put xj/fj600 mikunis on my non yics 650 - it wasn't. Maybe the 600 spacing is different to 550, but the 600s lined right up. The manifold diameters on the 600 mikunis were slightly bigger than the Hitachis, but maybe the 550s are smaller, and fit straight on. The 600 mikuni air inlet that goes onto the boots were bigger than the hitachis and no way would fit. Lastly the jetting on the 600's was close enough to feel right, but I haven't done any plug cuts or anything else to verify.
All in all a right faff about, so I would avoid if possible.

 

I just took a pic for you @Minimutly
FZ600 30mm Mikuni's and an XJ650RJC (YICS) motor.
This combination is never going to work. 650 YICS or non-YICS are same spacing.

 

Hmmm, so what goes on here then - I assure you the carbs I have (2 sets) were xj600, and both lined right up?
I never respaced them or anything...
Is the xj 600 different to the fj/fz?

 

You guys are trying to compare North American market models to UK models hence the confusion.

 

You're right @bigfitz52 , but what's the difference? Is it the 600 head, or the manifold rubbers?

 

Intake port spacing from the looks of it, so the head. And the fact that they are completely different motors...

 

Here we have my xj600 carbs - Actually BS32's

Xj600 carbs on a 650...

Poo, I tried to post my bs32's next to hogfiddles 550 carbs, and my 650 next to simmy's....

 

Which ones are completely different? Us and uk spec 600's - really?
550 and 600 could be different, but way up earlier in the post someone mentioned fz and fj600's, I would expect the fj and xj600sbto have been the same engine.

 

Similar, but not the same. Yamaha had seperate design groups for each project during that era. Also consider the legal requirement at the time that a certain percentage of parts used on a machine be supplied by other Japanese manufacturers. That's a large part (but not the only part) of why thre are so many models and sub-models of each Yamaha line during the 80's and 90's.

 

So what have we learned? Xj 600 (at least uk ones) carbs spacing is the same as xj650's, xj600s use BS32 Mikunis.
Some of this may be simply down to the carb size - bigger catbs need more room, unless the body sizes were made bigger, and metal left in on the smaller ones.

 

OK @Minimutly I've figured this out.
The carbs you're holding are not from an FJ600 FZ600 XJ600 or YX600, US, CDN, UK or Somalian.

You'll notice your enrichener plungers stick in from the side, just like the Mikuni's on the 650 Turbo or Maxim-X.

All the XJ550's and 600's screw into the body 90 degrees from this.

The carb spacing on the XJ550's and 600's are all the same, regardless of UK, US or elsewhere.
Yamaha are the parts bin specialists, there's no valid reason why they would change this for any particular market.
There's a practical reason (economics) why they are all the same.

 

They, and the ones on my 650, are these - xj600, chain drive yamaha, circa 1983.
https://www.ebay.co.uk/itm/Four-35m...520780?hash=item289eb78b8c:g:Qs8AAOSwrmRfd1dg

 

Oops!
I'm eating some crow.
The FJ600 and XJ600 has the plungers from the side.

I never understood the explanation of using BS30 carbs on the FZ600 for space considerations.
I suspect the FJ/XJ600 are wider spaced and use different rubber manifolds to fit the same head which they all use.

 

Whatever. Actually the ebay add is incorrect -those are 35's, but they do look identical to the xj600 carbs.

 

When they bored and stroked the 550 into the FJ/XJ600 I read they took the bore as big as they dared with the existing bore centres.
This meant a 58.5 mm bore x 55.7 mm stroke, not as over-square as the current designs were heading then.
They sized a Mikuni BS32 but they have the enrichener coming out the side of the body, requiring a wider spacing than the 550 BS28's which have the enrichener coming out from the top of the body.
They spread them out for the enricheners to fit, conveniently settling on the same spacing as the XJ650 as you have discovered.

When I read the FZ600 was a mongrel combination of the Japanese market FZ400R and the FJ600 motor, they mentioned the BS32's from the FJ600 could not fit the 400's frame.
I never understood this until now.
By using the BS30's with the enrichener coming out the top they could fit the rack tighter together and they would fit between the 400 frame spars.

 

Thank you, I'll tell my 5 yr old grandson - (the one holding the 600 rack), I'm sure he'll be impressed that they weren't indeed from Somalia.