Any chance what I think is a carb issue isn't?

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onspeed

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Been having a constant issue with my 98 for some time now. Bike has 16k miles, 4-1 Kerker, Stage 7 dynojet kit with the individual K&N pods, air correctors, S7 needles, and drilled slides. I've never been able to get the bike to run smoothly. My main problem is WOT sputtering below 6-7k RPM, and I've tried many different combinations of main jets and needle positions to no avail. Carbs are clean, plugs, oil/air filter are good, has COP mod, and regular VBoost. Currently running DJ 165 mains, 177.5 PAJ2, 90 PAJ1, 40 PFJ, and S7 needles 3.5 from blunt end. Wet floats are 16mm +/- 1mm. Have tried DJ175, 170, 160, and MK150 mains with all different combination of needle positions and haven't found anything that runs very well from 2k-6k WOT or any throttle position above 50% actually. Normal driving around town with throttle positions below 50% is a non-issue and gas mileage seems about on par with what everyone else here gets.

Is it possible it's not carb-related? I've been considering getting my hands on all stock equipment and just run stock carb settings to see how it is, but would like to not spend the money on stock stuff if I can.
 
What springs are you running...stage 7 or stock?

Also you tune a Vmax....from the top down.

This is the Factory Pro method of tuning.

Factory Pro, CV Carb Tuning

Follow steps in order....First, dial in:

1. Top end (full throttle / 7.5k to redline -

Best Main Jet must be selected before starting step 2 (needle height)!

Select Best Main Jet

To get the best, most even top end power (full throttle/after 7500 rpm), select the main jet that produces the highest top speed / pulls hardest at high rpm.

If the bike pulls harder at high rpm when cold and less hard when fully warmed up, the main jet is too large. Install a smaller main jet and retest until you find the main jet that pulls the hardest at high rpm when fully warmed up. This must be done first - before moving on to the other tuning ranges.

If the bike doesn't pull well at high rpm when cold and gets only slightly
better when fully warmed up, the main jet is too small.

In order to properly tune the midrange and low rpm carburetion, THE MAIN JET
MUST FIRST BE PROPERLY SELECTED after 10 to 15 minutes of hard use!

Do not pay too much attention to the low-end richness when you are changing
main jets - you still need to be using the main jets that produce the best
power at high rpm. You will deal with the low-end / cruise later - after step 2.

2. Midrange (full throttle /5k-7k)

Step 1 (Best Main Jet) must be selected before starting step 2!

Select best needle clip position

To get the best power at full throttle / 5k-7k rpm, adjust the needle height,
after you have already selected the best main jet.

If the engine pulls better or is smoother at full throttle/5k-7k in a full
throttle roll-on starting at <3k when cool but soft and/or rough when at full
operating temperature, it is too rich in the midrange and the needle should be lowered.

If the engine pulls better when fully warmed up but still not great between
5k-7k, try raising the needle to richen 5k-7k.

If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set.

Do not pay too much attention to the low-end richness when you are changing
needle clip positions - you still need to be using the clip position that
produces the best full throttle / 5k-7k power in conjunction with the main jets (Step 1) that produce the best power at high rpm. You will deal with the
low-end / cruise next.

3. Low end (full throttle / 2k-3k)

Step 1 (Best Main Jet) and Step 2 (needle height) must be selected before
starting step 3!

Float height (AKA fuel level & how to...)

To get best low-end power, set float height (fuel level) so that the engine
will accept full throttle, without missing or stumbling, in 2nd gear from 2.5k to 3k rpm at minimum.

Float heights, unless otherwise specified in the installation guide, are
measured from the "gasket surface" of the carb body to the highest part of the top of the float - with the float tang touching but not compressing the float valve spring.

If the engine has a "wet" rhythmic, soggy area at full throttle / 3k-4k rpm,
that gets worse as the engine heats up, lower the fuel level by resetting the
float height 1mm greater (if the original was 13mm - go to 14mm). This will
lower the fuel level, making full throttle / 2k-3k rpm leaner.

If the engine is "dry" and flat between 2k to 3k rpm, raise the fuel level.

Example: change float height from 15mm to 14mm to richen up that area.

REMEMBER, since the main jet WILL affect low speed operation, the MAIN JET has to be within 1 or 2 sizes of correct before final float setting.

Warning: If the engine is left with the fuel level too high,, the engine may
foul plugs on the street and will be "soft" and boggy at part throttle
operation. Adjust Floats to raise/ lower the Fuel Level.

Base settings are usually given if a particular application has a history of fuel level criticalness. The Fuel level height in the float bowl affects full
throttle/low rpm and, also, richness or leanness at cruise/low rpm.

Reference: a bike that runs cleanly at small throttle openings when cold, but
starts to show signs of richness as it heats up to full operating temperature, will usually be leaned out enough to be correct if the fuel level is LOWERED 1mm. Check out and RESET all: Suzuki (all), Yamaha (all) and Kawasaki (if low speed problems occur). Needless to say, FUEL LEVEL IS EXTREMELY IMPORTANT!!!

If there are low-end richness problems, even after lowering the fuel level much more than 1.5mm from our initial settings, check for needle wear and needle jet(part of the emulsion tube). See Worn Needle and Worn Needle Jet diagram. It is VERY common for the brass needle jets (in the top of the "emulsion tube") in 36mm, 38mm and 40mm Mikuni CV carbs to wear out in as little as 5,000 miles. Check them for "oblong" wear - the needle jet orifice starts out round! Factory Pro produces stock replacement needle jets / emulsion tubes for 36mm and 38mm Mikuni carbs.

4. Idle and low rpm cruise

Fuel Screw setting (AKA mixture screws)

There is usually a machined brass or aluminum cap over the fuel screws on all
but newer Honda. It's about the diameter of a pencil. Cap removal details.
Newer Honda carbs have no caps, but use a special "D" shaped driver, usually
supplied in the carb recal kit. We do have them available separately, too. 800 869-0497 to order -Set for smoothest idle and 2nd gear, 4k rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear 4000 rpm steady state cruise , and 1/8 throttle high rpm operation. (pj tuning information)

Pilot fuel mixture screw settings, float level (but, you've "fixed" the fuel
level in Step 3 - which you have already done!) AND pilot jet size are the
primary sources of mixture delivery during 4000 rpm steady state cruise
operation.

If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn
increments. Alternative pilot jets are supplied when normally required.

Pilot fuel mixture screw settings, float level and pilot jet size also affect
high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems
when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.

NOTE: A rich problem gets worse as the engine heats up.

If the throttle is lightly "blipped" at idle, and the rpm drops below the set
idle speed, then rises up to the set idle speed, the low speed mixture screws
are probably set too rich: try 1/2 turn in, to lean the idle mixture.

NOTE: A lean problem gets better as the engine heats up.

If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before
dropping to the set idle speed, and there are no intake leaks and the idle
speed is set at less than 1000 rpm, the mixture screws are probably too lean:
try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!

Carb Kit Design is a combination of science, art, intuition and and at times, a fair dose of wizardry. There is no dyno that "tells" one how to assemble or
modify the carb to deliver proper power and response.

Perfect Carb Kit TUNING requires patience and perseverance and "reasonable"
feel to feel the changes - of which - most motorcycle riders have a good
ability to do.
 
I go by a full throttle roll on in 4th or 5th gear at 4k rpm because its right at the threshold of the slides retracting from what I've read. Its worked well for me.
 
Yeah I've tried that. Just can't find a needle setting that runs smoothly like it should.
 
I don't have stock springs, bike was bought with a Dynojet stage 1 kit installed, with stock air box.
 
One thing I've noticed is that from about half throttle to full throttle, I don't feel much of a difference in the bike's power. It gets a bit louder, but doesn't really seem to accelerate any faster.

Any chance the pods are making it harder to get dialed in? I have my stock air box around still... I'm wondering if the pods even offer very much benefit over a stock box..
 
One of the R6 coils I had from the COP conversion was not firing the spark plug consistently. Was fine at idle and small throttle openings, but arching a bit when at WOT. Put an old coil back on for now.

Also fixed my Vboost, was only opening maybe 50%. Had to move the black box all the way down to get it to open fully.

Bike actually feels fast again.
 

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