rejettin carbs - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 15 (permalink) Old 05-25-2009, 04:33 AM Thread Starter
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rejettin carbs

hi all,
ive got a 750 vulcan with straight through pipes,i am going to add k&n filters do i need to rejet the carbs if so where can i purchase the jets??
cheers all
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post #2 of 15 (permalink) Old 05-25-2009, 07:07 AM
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Welcome Larry;
Sorry, I don't know if I am a washin or a hangin out on your question, but have seen many posts on rejetting and am pretty sure you should do it...
A lot of the folks here have rejetted and will let you know what to do & where to get the jets...
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post #3 of 15 (permalink) Old 05-25-2009, 09:59 AM
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You can go the vulcan verses on the forum and find a lot of information on that.
Welcome to the group.

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post #4 of 15 (permalink) Old 05-25-2009, 11:05 AM
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Originally Posted by larrythebiker View Post
hi all, ive got a 750 vulcan with straight through pipes,i am going to add k&n filters do i need to rejet the carbs if so where can i purchase the jets?? cheers all larrythebiker
K&N aftermarket replacements that fit the stock housings, no; K&N pods directly on the carbs (ear shave), yes.


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post #5 of 15 (permalink) Old 05-25-2009, 12:33 PM
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^+2 to what he said.....Where to get the jets, local bike shops have them, that will be your easiest and probly cheapest route. Wont have to pay shipping and they arent that pricey to begin with.


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post #6 of 15 (permalink) Old 05-25-2009, 01:14 PM
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Welcome to the forum from sunny southern Alberta, Larry. Where are you from? Tell us a little about yourself, and how you came to own and ride the vn750.

If you go over to the fuel and carbs forum and look through the first 3 pages of thread titles, you will find several threads regarding re-jetting. You will probably find several that are mis-directed in the General Discussion and Engine tech forums as well.

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post #7 of 15 (permalink) Old 05-25-2009, 02:50 PM
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Here's some valuable information that I have collected regarding the Ear Shave.
This should get you started, but may require some more research.
Please note that I am not a mechanic. This is information only. If you're
unsure, have a pro do it. Feel free to email me or post any q's.

Check out Jason's Ear Shave:

Check out Frank's Ear Shave:

Thanks to Jason Spivy for posting the parts list.

Ron Ayers:
1 x 14-20900 EMGO crank case filters* = $10.63
(this one mounts on the left side and connects to the crankcase
or you can order one more for the right side, connects to the
breather on the carb float bowl assebly)
Shipping = about $8.00 from California
*There has been problems with the adhesive on these filters,
most of us who have them used a stronger silicone or epoxy.

Auto Zone
1 x Spectre 3995 Breather Filter $9.00
(this one is used for the breather on the carb float bowl and
can be placed underneath & behind the seat)

2 x 019-812 40-Idle jet = $8.90
1 x 019-194 140-Main jet = $4.45 (2-140's seems to work for most)
1 x 019-195 142-Main jet = $4.45 (optional)
1 x 009-396 0.126" Shim 12 pack = $4.00
Shipping = about $8.75

Auto Zone (may have to special order)
2 x K&N RC-2340 = $71.82 (not including local tax)
AJ USA ( 1-800-877-1911
2 x K&N RC-2340 = $58.70 (includes "FREE" shipping!!)

1 x 1/4" rubber vacuum cap $1.59 (Autozone comes in pkg of 4)
(Used on right side of carb vacuum fitting)

Small cable tie (for the vacuum cap)

True Value: (optional)
2 x 20mm chrome bolts = $6.38
2 x chrome washers = $1.78
(non-chrome bolts and washers about $ .75)

Total = about $135.00

In case I made a typo, verify parts numbers before ordering.

The chrome bolts and washers were used to mount the crank case filters
(stock bolts were too short). One filter was used for the crank case
and the other for the carb breather hose. There are cheaper filters
than K&N but that is a personal preference.

You'll also need a new breather hose which can be bought at any auto
store. I used some hoses laying around here but it looks like you need
the hose, 45 elbow, and 90 elbow.

To answer several questions in one post:

Q: Why do you add shims?
A: After the ear shave, the needles need to be shorter.
As far as I can tell, no one makes a shorter needle for these carbs.
You may have read some other members posts about Sherm's rebuild
kit that includes replacement needles. I used the stock needles.
The only way to shorten the stock needles are to add shims
(obviously doesn't shorten it but raises it up a little).

Q: How many shims did you use on each needle?
A: I put two under each needle and that seems to work fine.
Two shims seems to be the standard that works for most people.

<This is assuming that you are using the original stock needles.>

The following is part of a discussion regarding the stock
needles -vs- the needles that are supplied with The Factory Pro
Jet Kit from Sherm's:

Just to clarify -- I used 4 shims ON "TOP OF" each
needle, not under. -Pick

The shims go "UNDER" the head of the needle (like the head of a nail).

If someone said that they put a washer under a nail, it would most
likely be understood that the nail went "through" the washer, not that
the point of the nail was on top of the washer.

The needle is tapered, and with more air flow from the ear shave, more
fuel is needed to maintain the correct fuel to air mixture, so raising
the needle opens more area around the needle to flow more fuel.
I removed each needle, slid two spacers on, then put the needles back
in. This puts the spacers on the top end on the needle but not on top
of the needle. ??? I'm confused. What does putting spacers on top of
the needle do?-doowriter123

OK, I don't claim to know the whys and wherefores, but I got the ear shave
kit from Sherm's before they went out of business. I got a selection of
jets, shims, and new needles with the kit. I used 40 pilots and 140 mains,
with the clip in the 3rd position on the new needles. IIRC, that was in the
middle slot. I did not use any shims. The bike ran fine while
accelerating, but when I let off the throttle, it would stumble badly --
sort of like it was running out of gas or something (maybe it was
flooding?). I popped the tops off of the carbs and put 4 shims on top of
each needle, and the stumbling disappeared. The bike ran great all the
time, throughout the rpm range, accelerating or decelerating. I don't know
why this worked for me. It didn't make any sense to me either. I thought
the shims would have to go under the needles. I can only guess that putting
the shims on top causes more pressure to be applied downward, keeping the
needles from "floating" as much, or something like that. -Pick

Sooooo.... You didn't use the original needles. You had needles that
used clips that came with Sherms kit. The clip position limits the maximum
down limit of the needle. This explains the 3rd clip position.

If the clip on the needle is enough smaller than the vacuum slide
spring seat, the needle could possibly be able to wiggle around and
up and down, so putting shims on top could hold the needles down
where they should be.

The needles and clips are a more expensive way to get the result,
but they may have been chosen because of their profile. -doowriter123

That sounds plausible to me. The new needles came with the Factory Pro jet
kit, so I thought I may as well use them. If I had stayed with the stock
needles, I would most likely have used a different configuration to get it
to run right. -Pick

After the ear shave, the needles need to be shorter.
As far as I can tell, no one makes a shorter needle for these carbs.
The only way to shorten the needle is to add shims
(obviously doesn't shorten it but raises it up a little).

Use the stock needle, and two shims "UNDER" each needle. -Frank Braun

Q: My new jets seem shorter than the stock jets, is that okay?
A: The jets that come with the PRO Jet Kit are the same length
as the stock jets. The jets from Sudco seem to be shorter but
have the same effect. So length does not seem to be an issue.

Q: you mention bolts to mount the crank case & breather filters. Where
did you mount these?
A: I mounted them at the top bolt hole from the ears. (Some have
mounted to the bottom bolt hole) The old bolts
were too short so they had to be replaced.

Q: Whats the vacuum cap for?
A: The carbs have two vacuum connectors. One goes to the gas tank
petcock and the other one used to go to the surge tank. I decided to
plug the vacuum on the right side of the bike and secure it with the cable
tie. The engine seemed to idle better. Some people buy a small filter
and connect it under the seat. It's optional.

Q: did you take carbs out or do the needle & jet work with them in place?
A: I installed the shims with the carbs in place. I did everything I
could to install the jets without removing the carbs but couldn't do
it. Removing the carbs was easier than I expected. Plus it gave me a
chance to inspect the diaphrams and the connections.

Q: what is wrong with the ears ? why remove them ?
A: There's nothing wrong with them*. Some want to increase air flow in
order to increase power (and decrease fuel economy*). Others want a
cleaner, less cluttered appearance. I had one ear busted and needed to
replace it. Also, it seems that every time I did work on the bike, I
was hitting the ears with my elbow, head, etc. I don't mind the look of
the ears, but I do enjoy having less stuff in my way.

*Keep in mind that the ear shave may be illegal in some states due to the emmissions.
Save all the old parts just in case the laws change.
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post #8 of 15 (permalink) Old 05-25-2009, 05:59 PM Thread Starter
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Exclamation cheers guys

thanks guys,
im glad to have stumbled across this site by accident ,wow what a find,im on the south coast of the uk so my vulcan is an import over here its standard excep
t for vance & hines straight through pipes.(loud pipes save lives)!cheers for the warm welcome i look forward to many hours chatting to everyone on here cheers &beers larry.
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post #9 of 15 (permalink) Old 05-25-2009, 11:16 PM
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Since you are using a non baffled "open" exhaust you will need to use #42 pilot jets and a minimum #145 main jet, 2 shims under each needle and pilot air/fuel screws turned out 2 1/2- 3 full turns from closed. This is only if you put pod filters on the carbs.

If you tell me your elevation above sea level and what intake system you will be using I can tell you where you need to set the carbs.

I highly reccomend you use an MF AGM Battery and NGK DPR7EIX-9 Spark Plugs.

I also reccomend you purchase a Gunson Colortune Kit, it will allow you to see into the combustion chamber and dial in your air/fuel Spot On.

85 VN700 "Old Yella"


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post #10 of 15 (permalink) Old 05-26-2009, 05:23 AM Thread Starter
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Exclamation thanks

thanks lance ,
that is exactly the sort of advice im looking for im quite a confident diy mechanic but the language barrier even though its small can be confusing . EARSHAVE i take it is the removal of the standard air filter boxes(is this correct).i was thinkin of using k&n filters in the standard air boxes, then someone suggested the earshave was the way to go im still researching this option.I like basic simplisity when it comes to my cycles less is more and all that.
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