Dynojet (or other jet kit) listing for the VN700//VN750 Vulcan needed!

i'm confused :blink:
i thought all zn models came with the bs34 series carbs on them.
that is what i have on mine.
are you keeping the airbox?
on my 650 and 1000, we went up two sizes like you said and they ran pretty good.
but that was with pods along with the open exhaust.
maybe someone with a kz 750 can chime in here.

wiredgeorge wrote:

This is the wrong place to be looking for rejet advice for the baby-BUBF. Go ask at www.vroc.org . There is also a 750-only forum somewhere... maybe yahoo groups?

I would have posted this on VROC, IF, like I previously stated, I could remember my sign-on info to that site. :S

Thanks for the tip on the 750-only forum WG!
I did a brief search via Yahoo and Google with no luck, but I'll do a more thorough search later today to see if I can find it.

wiredgeorge wrote:

Anyway, I doubt the bike needs to be rejetted because you are using Jardine pipes. If you pull off the ugly "ears" and replace them with pod style filters bolted directly to the carbs, you will have to rejet.

Not being as familiar with the V-twins (carb or EFI), I assumed (Uh, oh? :whistle: ) that running a set of straight pipes on a carb'd bike would require rejetting just like an inline-4 engine normally would.

Rose is still running those ghastly looking "ears" on her bike, but it's more for the plasti-chrome "bling" look than for a performance aspect.
I did however swap out the disintegrated crappy OEM foam filters for a set of direct replacement K&N's, so I can rest assured that I won't need to yank and tear down the carbs again (what a pita that was! :pinch:) to fish out miniscule pieces of foam from the passages/jets.



Steve,

Check the thread title bro.
I'm looking for jetting info for Rose's bike which is a VN750 Vulcan (water cooled V-twin), not my ZN700 (air cooled inline-four).
I do appreciate the help though bud.


I guess I'll just bolt these puppies on, swap in a new set of plugs, and see what kind of reading I get after doing the "throttle chop" test.

Thanks for all the replies and suggestions guys, I appreciate it!

Post edited by: RetroRiceRocketRider, at: 2007/12/09 11:34

OK, now I get it. I thought (maybe along with some other members) that there was only one bike.:blink: You have a ZN700 AND a VN750! Only saw the one "N" bike listed in your sig. Cool, got it now. (senior moment :woohoo: )

RetroRiceRocketRider wrote:
[quoteSteve,

Check the thread title bro.
I'm looking for jetting info for Rose's bike which is a VN750 Vulcan (water cooled V-twin), not my ZN700 (air cooled inline-four).
I do appreciate the help though bud.


[/quote]


again i'm guilty of pwai
( posting while Ability impaired)

Rx4 - I asked over on the VROC site and got this rather long answer but it does have the groups where you can pick up tips on that bike:

autos.groups.yahoo.com/group/VN750/
and also
VN750.com/
There should also be a file in the VROC Archives on 750 ear shave that would also include rejetting (usually done at ear shave time, since you don't have to do it if you are just replacing pipes)
And from the yahoo group.. one of the write-ups about an ear shave / rejetting
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: photos.yahoo.com/jaster131/

Check out Frank's Ear Shave: photos.yahoo.com/fcb64

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)

Sudco:
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)
-or-
AJ USA ( www.ajusa.com ) 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).

BOTTOM LINE-
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.

Dianna
Conway, AR
Patriot Guard Rider
2000 VN750 Sere w/Velorex sidecar
1990 GL1500 "Ole blue" and "Babe" (sidecar)
VROC # 11628
TNVROC # 45 (H)
VROC-AR # 12 Coordinator/Crowd Control
WBRA #27183-3
vroc-reunion.com

Wow! :woohoo:

Thanks for posting those links and all of that info WG.

I tried to check out the ear shave pics Jason and Frank did, but it looks like Yahoo has closed the photo hosting portion of their site to concentrate on "Flickr", a newer photo hosting site.

I have to admit though, even after reading all the info you posted and what is listed in those links, I'm still unclear why a V-twin doesn't require rejetting when running straight (open) pipes only, yet an inline-4 with similar open pipes does. :S

R4... Your proposition that a V-twin doesn't need to be rejetted because an inline four does has some faulty reasoning. SOME inline four carb assemblies come relatively LEAN from the factory and some come fairly rich. Let me use the VM26 for example. The 76 KZ900 version of the VM26 has #115 main jets, 5DL31-3/0-6 jet needle/needle jet and #17.5 pilots with a 1.5 slide cut out and smallish air jets (fixed size). This carb has a 1.2mm pilot outlet (keep this in mind) This carburetor can actually be run decently without rejetting even if pods and an open exhaust are used... it does benefit from a somewhat larger main jet but the #115s can take the bike to redline.

In 78, the VM26 used on the KZ1000A2A has #102.5 main jet, 5CN7-4/0-3 jet needle/needle jet, #15 pilot jet and 2.0 slide cut out... the pilot opening is .8mm.

Note the 78 1/2 A2A carb has not only smaller main and pilot jets but a much smaller needle jet. The jet needle used on the 76 VM26 and needle jet are the same combo as used on the 29 Smoothbore. Note that the 78 1/2 slide cut out is 25 percent larger allowing a lot more air flow than the earlier 76 version of the VM26. When you mix 25 percent more air with less gas (#15 pilot versus the #17.5 pilot) the air/fuel mixture of the later VM26 is much leaner.

If you add an unbaffled pipe to the 76 VM26, no problem... if you add an unbaffled pipe to the 78 1/2 VM26 the bike will be very lean.

I have some experience with Vulcans. I wrote how-to articles on how to add pod filters on the larger VN1500A/B models and how to rejet that are still being used today by a lot folks. The 750 folks adapted some of this work and came up with their own jetting recommendations but the VN750 is relatively rich from the factory and can accomodate pipe changes without much fiddling. Making GENERAL statements about whole classes of bikes seldom works well regarding the carbs... it all depends on the carbs and not the bikes. Hope this long and tiresome explanation helps. Or you can do what that fella told me works yesterday... just put in the biggest jets you can find! Get 'er done! Go find that 750 forum that I suggested and ask around. They acutally ride the bike! They will have opinions on rejetting for pipes like yours. I personally would just stick the pipes on and check the plugs after riding a bit... I bet they are fine but if they are white, I was wrong and you need some bigger jets. In that case, I will say sorry... if I am right, let me know and remind me to gloat as I am old and will forget to otherwise hehe.

I totally lost track of this thread, but did want to give a follow-up on how the bike performs after running these pipes for awhile now (about 3K miles) without any rejetting.....WOW!:woohoo:

Absolutely no more popping on decel.
The pipes look really nice and the bike sounds like a larger/more powerful critter now.
It literally dropped about 20 pounds away.
And the biggies are how amazing the throttle response is, as is the overall power increase it gained.


I'm sure the chrome on these pipes isn't as good a quality or as thick as the OEM chroming since the pipes are bluing slightly near the exhaust manifolds, but the engine hasn't seized up (yet?:huh:) so it should be ok.

The 750 Vulcans weren't really designed as a long distance bike, and that shows in the final gearing - at 70mph it's at about 5K rpms, yet sounds like it's screaming along at 10K rpms!:ohmy:

I've been riding it back-and-forth to work the past few weeks (stop-and-go traffic and 70mph cruising), and even rode it last Saturday from Covina up to Santa Barbara (240 mile round-trip at a steady 70~75mph), and I'm averaging around 43 miles per gallon.
Not to shabby!