Will 85 XJ700 Function with Mikuni BSR-36 Carburators?

Hello Everyone. So the usual story. I picked up a 85 XJ700 14k miles that was someone's unfinished project for cheap. The bike was sitting out in the elements for 1+yrs. It cleaned up nice, has good compression and spark. The carbs were full of rust, water and some kind of solid mass.
Instead of spending time and money attempting to rebuild the stock carbs. I have a freshly rebuilt 4 carb bank set of Mikuni BSR-36. They are off a 02 Suzuki GSX-F Katana 600 or 750 which are oil and air cooled in line 4's. If I get proper boots to correct the slight spacing difference will the Mikuni BSR-36 carbs work on a 85 XJ700 with pod filters? Let me know your thoughts on this. In the mean time I am going to look for some intake boots that are a bit more off set on one side to match up to Mikuni carbs.

 

Any carb will work if jetted right, most likely you would need to make some changes to what is currently in them but you may get lucky

 

Thanks for the reply. I made up my mind. I am going to install the Mikuni carbs on the XJ. What I need help with is the spacing. I need to find carb intake boots that go from the XJ spacing of 77-85-77 to the new Mikuni spacing off a Suzuki Katana of 77-93--77 all while keeping the other boot circular and bolt pattern the same. This sounds like easy math, right? I must be going about searching for these the wrong way. Plus I have to take into consideration the clearance over the starter and possibly petcock if there is too much upset. Not to mention whatever I have not considered yet. I know I saw a Mikuni RS flat side pumper carb set up kit being advertised and sold as new for XJ700's maybe I will try to contact that company and see if the boots they use will solve my problem. I know their boots will be out of my price range but maybe they will be a good sport and point me in the right direction. If anyone out there knows of a boot set up from another manufacturer or model that would allow me to bolt up and clamp down to mount these Mikuni BSR-36 carbs spaced 77-92-77 to a 85 XJ700, your knowledge would be much appreciated.

 

Almost forgot. I am going to need a push -pull throttle cable set up for the new Mikuni carbs. What length am I looking for? Is there anything else to consider when going from a single cable to a push-pull set up?

 

I have a one to four cable pull, works fine. A little strong to pull but good return even without
pull open, pull closed dual cables. I often wonder why they are called PUSH/pull?
Cheers, 50gary

 

Alternatively you could collect the carb rails from an XJ that came with Mikuni carbs.
Then change the spacing to stock dimensions by changing the rails.
I'm not sure if the fuel pipes and o-rings will allow enough adjustment so they may be needed also.
The enrichener shaft will be needed also.

Mikuni carbs with the correct spacing are XJ650Turbo, XJ700X, XJ900 and FJ600.

But seriously, rebuilding the XJ700 Hitachi bank and keeping the airbox is by far the easiest approach.
Sell/trade the Suzuki bank for what is needed.
Something you already mentioned, the carb hats on the BSR-36 are taller and may present some interference.

 

The fj 600 mikuni carbs will fit a non yics head. They are slightly bigger in the carb/boot dimension, but easy enough to turn down to fit. I found they worked well as original jetting on a 650 with pods. In the end I fitted an fj airbox because I was too mean to buy four k&n's. The spacing is about right too. This is on a 650 maxim non yics.
I never bothered with the cable enrichner, just pull the rack.

 

Missed out that you had listed the fx600 @Simmy.

 

I won’t forget the discussion we had with your carbs. I learned from you the XJ/FJ600 carbs are spaced the same as the 650.
I could never figure out why Yamaha said they couldn’t fit BS32’s on the FZ600 so they went with BS30’s. The 32’s draw the enrichener from the side and the 30’s pivot from the top. This allows closer spacing on the 30’s, same as the BS28’s on the 550. The carbs fit between the frame rails on the FZ600.

 

Thanks for all your insight. The xj700 has a YICS head. Were Mikuni BS carb banks spaced the same across all Motorcycle makes and models? If so the boots for a Yamaha with port spacing equal to 85 xj700 w/ YICS and stock Mikuni BS carbs will work. Alternatively if I had the port spacing for a 98-06 Suzuki GSX600F. I may be able to figure it out that way.

 

I figure there are 2 ways to easily figure this out. If Suzuki GSX600F and Yamaha XJ700 w/YICS intake port spacing is the same then I go with Suzuki boots. Bolt hole spacing for individual boots is the same for Suzuki and Yamaha boots,6.6cm i believe and both have 30mm round intake port holes. If Mikuni BS carb spacing is the same across all makes and models then I go with Yamaha boots off, say, a XJ900f. As Simmy stated above.

 

nope

 

some Kawasaki (KZ750 KZ1000) are same spacing as the Suzuki bank you have.

Welcome to Mikuni Power - RS Series Carburetors

 

If yics heads and non have the same spacing then fj600 Mikunis will fit.

 

Ok. I read all of the suggestions. Thanks again for taking the time to answer. I exhausted googles algorithm researching on my own. I am itching to take this bike out for at least 1 ride before the snow flies in Central New York. Aftermarket boots are inexpensive so I am going to pick and order one set of Yamaha boots and one set of Suzuki and one set of Kawasaki boots. If a matching set works I will send back the other 2 sets. If it takes a combination of the three sets plus I have the originals then so be it.

Plan B: I repair broken post and rebuild the stock Hitachi bank. The only thing preventing me from doing that in the first place is the fact that the carbs were full of water for long enough to completely break down all but the spring steel in the bowls. I know All those parts are replaceable. However The reaction of water and what fuel was in there over x amount of time did a number on the finish of all the bowls and the bottom/left side throat of carbs #1 and #2. I have them disassembled, cleaned and sitting in kerosene because if I leave them exposed to air they flake off in chunks. I am afraid that fine aluminum sediment, or whatever they are made of, will continue separating get sucked into some small orifice, build up and leave me stranded. Could I coat the inside of the bowls with por15 gas tank sealer? I have a quart of that around somewhere. First I will plug that hole that goes up to that pipe on the edge and pull the drain plug so I don't seal them shut.

 

@AnimalMother have you considered having your Hitachi carb bodies vapor blasted? @hogfiddles had a set done that way and they came back looking as new. This is the worst rack I've seen YET!!! | XJBikes - Yamaha XJ Motorcycle Forum. This set of carbs came off what I am sure was a flood bike. If you see the whole thread you will see what he was able to make of them. As you in Utica he is nearby to you and maybe can help. I would not do the POR-15 thing to the carbs, that stuff is pretty thick and leaves a thick layer when cured and would do a great job of plugging the finer ports and passages in the carb bodies. Good Luck with either other route.

 

I have a HF soda blaster. I have not used it yet so I don't know much about it. Vaper is dry ice, right? Soda is a special baking soda that is used for blast medium. Would soda blasting compromised aluminium be a good or bad idea? I tried polishing a bowl with the dremmel. It definitely looks better but the pits are still rough. To make smooth I would have to sand gently with high number liquid or paper then polish. The volume of the bowl will increase slightly. Not enough to effect anything, I don't think. I just received a OEM rebuild kit for the Hitachi carbs so I have started the rebuild process while I wait for the new boots to come in.
What Yamaha bikes or other manufacturers have intake port Boot bolt hole orientation / / \ \ like the XJ700 with YICS head? I ordered a set of aftermarket boots for a fzr600.
I have a correction to make on my mikuni carb bank size. They are BSR-33's. The throttle butterfly side opening measures 33mm. 36mm including the rim. The physical measurements of the mikuni spacing is 83mm-88mm-83mm. And the intake port hole spacing on the XJ700 measures 74mm-98mm-74mm. The original Hitachi carb spacing measures 74mm-86mm-74mm.

 

I'm doubtful those will be any use to you, FZR using downdraft carbs I would expect the angle to be way off.

 

I am not sure what the media is in vapor blasting but it is suspended in liquid. Sort of like a combination of dry media blasting and pressure washing. I bet you could use walnut shell media in your blaster as well as soda crystals. Walnut shells are used on delicate materials and I am pretty sure is too soft to damage aluminum. The bowl volume change will be of no issue as the fuel level will need to be set when reassembled anyway. Volume does not matter, level of that volume does.

 

Vapor blasting is baking soda in water. I know other media can be used, but mine were done with the baking soda.

 

What Yamaha models and models from other manufacturers have intake boot bolt hole orientation: / / \ \ ? Same as the XJ 700 YICS.

I am rebuilding the stock Hitachi carbs but I would still like to mount the Mikuni's at some point to see if there is any change in performance. Mikunioz sight talks about a 20-25hp increase with RS carbs on a XJ. That seems a bit optimistic. I would be happy with half that. You would definitely be able to feel a noticeable difference with just a 5-10hp increase on a bike.

 

Dreaming...
Where's this magic power coming from? It can only be from more air in - so are the Hitachis restrictive..
I suspect not that much.