Some useful tips when dealing with the carbs - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 3 (permalink) Old 04-04-2011, 02:06 AM Thread Starter
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Some useful tips when dealing with the carbs

After much digging I found out a few things buried in these forums about our carbs. I also did a lot of head scratching around the bike as I couldn't get her to run right (have pulled the carbs four times now) and came up with a few useful bits of information for removal/installation, and cleaning. Not thorough, not very well organized, but hopefully useful knowledge nonetheless.

Air duct removal/installation: Have a hard time taking the upper air ducts out of the air box? While a screwdriver may be used to deform the rubber boot at the air box, the pressure is concentrated and does not deform the boot very well. It also has a chance to tear the rubber. I use the business end of a 3/8" drive T-handle to deform the boot, as it does not flex, has no sharp edges, and a good, broad surface. If you are pulling the boot out of the left side of the bike, push at it on the right and vice versa. When installing, try to get most of your pressure going upward. A couple dabs of penetrating oil may help them along.

Clean the underside of the airbox and the surrounding area before intallation. You don't want dirt to get knocked into your nice clean carbs.

The carb boots connecting to the cylinders can be tricky. While the front boot may stay on the engine and the rear boot on the carb for removal, they seem to get in the way of installation. The carbs are much easier to get in with both boots off. Once in place, lift the carbs up as high as you can and fenagle the boots in. There is a small tab on the boot that should align with a similar mark on the cylinder. If the rubber tab looks like it might fall off, get some paint or something and mark this point. Check this before you remove the boot. If the tab has already fallen off, you can mark it while it is in the correct position. The front and rear boots are labeled, do not mix them up.

Always make sure the boot clamps are screwdriver accessible. They won't spin all the way around the boots with everything in place, as the screw part hits the cylinders, carbs, etc. Ask me how frustrating it is to get the carbs set and then have to jostle them around some more so everything can get socked down.

Usually people stuff a rag or some paper towel in the cylinders with the carbs out. I find that this doesn't always stop dirt from getting in at the edges. Heavy duty tin foil does a good job of covering this hole (do this before cleaning the underside of the airbox) Tin foil also does not absorb moisture or shed fibers, something to consider if the carbs will be out for any length of time.

The cables are usually easier to connect/disconnect with the carbs partially removed. Even raising the carbs 1/2" will make the choke cable much easier to deal with. The accelerator/decelerator cables are also easier to disconnect with the carbs partway out. I like to reconnect them before they are all the way back in place as well.

I spray some good ol' PB Blaster around mating surfaces of the carbs before I separate them. PB restores rubber and loosens the goo that can stick to and rip the seals. I have an '86 with carbs that have been taken apart a few times and I fortunately haven't had to replace any seals. They were pretty scary the first time I separated them, but if I had any parts that stuck I just got some PB underneath and gave it a few minutes.

The jet needles ARE NOT INTERCHANGABLE (at least on my '86). I saw a post here that said they were. This is only the case for the vn700. On the vn750 one carb has an N27V needle, the other has an N27U needle (couldn't MawKaw pick two slightly less similar letters?). I forget which goes where, but make a note when removing the needles.

It easier to install the filters with the carbs out. Leave a little extra line if you can so you don't fall short. If you find it hard to fit a filter and bend the line without kinks, buy two 90 degree brass elbows. You can run carb-line-filter-line-elbow-line-tank, or something like that. This puts the filters next to the carbs, but that is also where they have the most space. Sounds like a lot of stuff, but the sections of line can be short. With this setup there are almost no bends at all if your fuel hookups point "into" the bike. Alternatively you could find filters with a built in 90 degree elbow. I didn't install fuel filters recently, thought I had nice clean gas going into the engine, and after the fourth pull of the carbs realized that my just-cleaned idle jets had clogged up again. I used clear fuel line from my local bike shop, and the gas looked terrific, which brings me to my next point.

When the carbs are installed, before you start the bike, open up the drains and flush the carbs with clean gas. Any debris that may have found its way to the fuel inlets, downstream of your filters, will have a better chance of being washed out and not clogging your idle jet. NEVER blow high pressure air into an assembled carburetor, you could damage the float or diaphragm.

I'm a bit embarrassed to admit that I can pull or install the carbs in less than a half hour now, but hopefully some of this info will save you some time and trouble down the road. Again, some of this info has been posted before but has since been buried, other stuff might just actually be some new ground.

Best of luck,
-Luca
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post #2 of 3 (permalink) Old 04-04-2011, 02:42 AM
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Very good write up Bazooka. I pulled my carbs after I had my engine out, and I left both boots on the heads, and loosened the clamps on the carb side. I give them a slight twisting motion, and they slid right off both boots w/o any major force.
I am going to try to get them both back on w/o removing either boot from the engine, and see how well it goes. I will use either pb blaster or wd-40 to lube the boots.
If I can come up with a trick, I will share it with you.
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post #3 of 3 (permalink) Old 04-04-2011, 11:55 AM Thread Starter
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I'd use PB, it will restore the rubber and wont leave a tacky residue behind. Furthermore, any that does get inside the boots will help clean off your valves.

**edit** just noticed you have the engine out. Don't you like having fun? As long as there are no scratches where the carbs meet the boots, you could probably just slip them in.

Last edited by Bazooka_Luca; 04-04-2011 at 12:06 PM.
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