simple carb fix

Ok, I'm seeing alot of threads about carb problems. Recently my son in law needed his carbs cleaned & synced. Went through the whole 9 yards, never could get the bike to idle below 4k. No signs of air leaks. After 10 times of install/removal we took my Mikuni round slide 2 carb conversion off my bike( since I can't ride it anymore) and put it on his bike.
Easy-peasy, just some simple idle adjustments and He's riding and having fun
So my recommendation to all you guys is to ditch those lousy CV carbs and replace them with the round slides. So simple and easy, no aggravation, cussing or pulling hair out. You could do the 2 larger carb conversion or just replace with 4 of the same size.
Cost of the project would be 400 to 600 in all, but look at the final results. Bike runs great, handles exhaust and air intake mods, easy to clean, easy to setup and sync and easy to do final adjustments. May sound expensive at first, but the ease of maintenance and happiness is worth it all.
Materials needed
2 carb conversion: 2-Mikuni round slide carbs at least 1 size bigger than your present carbs, 2-2 into 4 intake manifolds(made of aluminum or some other metal) from a 4 wheeler or self made, 1-2 into 1 throttle with cable, replace the original petcock one that has a 5/16ths diameter nozzle, 5/16ths fuel line and inline filters if needed, pods or adapt the airbox, and permantly block off the YICS if your bike has it.

4 Carb Conversion: 4-Mikuni round slide carbs that are the same size as your present carbs, 1-4 into 1 throttle and cable, replace original petcock with one that has a 5/16ths nozzle, 5/16ths fuel line and inline filter if needed, pods or adapt airbox, leave YICS passage as is.

 

Changing to a different type of carb is hardly a simple fix. You just traded one type of work for another, and I'm not sure that the people who are having difficulty with their carbs now are ready to make an intake manifold. Carb swaps are not a bad thing to do, but it really isn't necessary in order to get a good running, and reliable XJ.

 

30mm mikunis are 35$ on ebay. connecting them to the intakes would be easy.
just tell me how to sync four throttle cables.

 

K-Moe said: Changing to a different type of carb is hardly a simple fix. You just traded one type of work for another, and I'm not sure that the people who are having difficulty with their carbs now are ready to make an intake manifold. Carb swaps are not a bad thing to do, but it really isn't necessary in order to get a good running, and reliable XJ.



Yeah, I changed difficult and aggravating work for easy work. That's why I said a simple carb fix. The intakes aren't that hard to make, you can use copper tubing and solder them together if you can't weld. Or do the 4 carb conversion without having to make intake manifolds. :wink:
It's not a necessary fix, it's a simple fix that alleviates all the BS. That could be a necessity depending on the person. It was in my case. :lol:

 

Polock said: 30mm mikunis are 35$ on ebay. connecting them to the intakes would be easy.
just tell me how to sync four throttle cables.


The throttle I have is a 2 piece unit, the bottom piece(shaped like a V) has 2 ends that attach to the carbs and a third end that attaches/hooks to the top piece going to the throttle. You would use 2 bottom piece cables, 1 attached to #1 and #2 carbs, and the other attached to #3 and #4 carbs. Then attach both bottom cables to the single top. Or you may find a cable already made for this kind of setup by a racing carb supply house.
Each carb has a throttle adjust screw on 1 side and a air mix screw on the other side. Very simple to adjust.
No problems running pods, velocity stacks, breadboxes, straight pipes or aftermarket mufflers.
As Polock mentioned, these carbs aren't expensive. Save yourself the aggravation.
Just remember to get right side and left side carbs.

 

The really simple fix would be an EFI conversion, but it wouldn't be a cheap one.

 

True that. IMHO, anything is an improvement.

 

On the FJ board I just read that Randy of RPM Racing has a prototype FI conversion for the FJ1200. By the looks of it, it will not be particularly adaptable to other inline fours.

Most conversion kits seem to run $2000-ish. However, there is this, and I'm wondering if it can be adapted...

http://www.ecotrons.com/products/small_ ... ction_kit/

 

http://dave_jack.tripod.com/id27.htm

http://www.xjbikes.com/Forums/viewtopic ... t=efi.html

 

Holy cow, Tripod is still around?

That relies on rare and hard to get parts.

That one is neat.




I am kind of interested in the idea of a single-inlet throttle body FI. That oughta simplify setup quite a bit, with the hardest part being figuring out the manifold. It's to FI like what OnB's setup is to carbs.

 

Those EFI's are cool, but a little pricey.
You could get a rack of CR's for 800. My conversion is still the cheapest route.
If I owned a Seca, I would do the 4 round slide carbs.
As far as the 4 into 1 EFI goes, the intake could be similar to mine(but hooking up all 4 cylinders) with the throttle body on 1 end and use a large Harley type throttle body. Think the Harleys are using 38mm to 42mm throttle bodies.

 

Found this on Ebay: http://www.ebay.com/itm/Mikuni-Drag-Rac ... 12&vxp=mtr


Carbs and throttle with cable

 

They're flat slides, but will work just as good.

 

They have individual choke knobs.

How would that work?

 

Mine has those and they're easy to reach between the carb and tank. For a 4 carb setup you would be better of with 2 rights and 2 lefts, and somehow link the handles together. The 2 rights going toward the right side and the 2 lefts going out toward the left side. Or you could rig up your own choke circuit to activate with a cable like the enrichment/choke you currently have.
BTW most of the choke handles on these round slide carbs are really enrichment circuits.

 

Is there a thread for your conversion? I'm contemplating a carb swap on my build since I just busted one of the posts for the float pin to go through.

 

Colehole...

Check this out...

http://www.yamaha-triples.org/workshop/Mikuni_MKII_Post_Repair.pdf

 

http://www.xjbikes.com/forums/index.php?threads/orange-n-blacks-700.26691/ My build thread has all the info on how I converted to 2 carbs. The first version intake were pvc that let me test a intake design. Second intakes were mild steel square tubing.

 

So if I wanted to do this dual carb mod on my 550 with Mikuni BS28 cv carbs, I'd be looking for a set of 30mm round slides? or would 32s work better. The manifolds I can fab from scrap metal at work, so that's not a problem. Man I gotta stop reading these posts. Just when I think I'm done with the brat, y'all give me more ideas.

 

If you go the dual carb setup, 30mm round slides would probably work. Or you could put 4-28mm round slide carbs on it without having to make intakes. Either way will require modding the petcock and fuel lines to a 5/16ths line and a 5/16ths to 38ths petcock.

 

Im intrigued.... Do you have any pics p f the final setup? How does it affect your performance?

 

It ran better with this setup. lost maybe 2mpg, but that may be because I was having a lot of fun with it.
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