What can I check? Cleaned carbs- LOW power. Feels like it's on 3?

[supervetteracer]

Just finished cleaning the carbs. I did NOT drill off the caps and re-do the fuel air screw. The bike now idles fine. When I take it to red line and shift it wants to almost studder.

The pull seems linear if not a tiny bit exponecial. In other words it pulls pretty evenly throughout the rpm range. Perhaps the V-Boost is not operating? How can I check this?

I'm pretty bummed out. Bought this bike. It's only got about 3k on it. And not one single good ride yet. Can you guys give me some thing to check?:ummm:

 

[[email protected]]

Need more info on your symptom.
Where in the RPMs is the problem, is it consistant at this rpm or does it come and go. Did you have it before the carb rebuild. What is your setup?

Stock carbs, exhaust, intake, filter, etc...?

I had an issue that I would consider a stutter but it was in the low to mid rpm range. I had to lower the clip position on my needle and it was fine after that.

 

[naughtyG]

the vboost is easy to check - when you first turn the ignition on you should hear it cycling open and closed, sound like a little whirring electric motor going twice long, once short: it opens the butterfly valves, then closes them, then takes up the cable slack.
If you remove the carb cover on one side and use a bright flashlight, you can see it operating, right in the middle just below the carb rack. With the bike on the center stand, if you start it up, let it warm up then rev it quickly to 6000rpm you should also see it operating.

Have you checked you spark plugs, how do they look? Have you checked you are getting a good spark on all four?

 

[bazwell]

+1 on more info.

Is it running on 3?
Test by disconnecting 1 plug lead at a time. If it makes stuff all difference on one plug then that cylinder isn't going bang.

 

[sdt354]

I have a friend

, he didn't seat his carbs fully down. His bike didn't run to bad, at low rpms. And he was a mechanic! Doh award next time he does that
More info, like Mike already mentioned would be good.
Steve

 

[supervetteracer]

I have a friend

, he didn't seat his carbs fully down. His bike didn't run to bad, at low rpms. And he was a mechanic! Doh award next time he does that
More info, like Mike already mentioned would be good.
Steve

This is very possible.

The motor sounds ok. It's 100% stock. I may not have seated the carbs down enough.

I don't hear the VBoost thing. Is it common for the Vboost to stop working?

 

[Redbone]

Yes, check that the...ah...yes..the carbs are...er...umm...seated...and did I mention I like your signature? But, yes make sure they are well seated!:biglaugh:

 

[supervetteracer]

the vboost is easy to check - when you first turn the ignition on you should hear it cycling open and closed, sound like a little whirring electric motor going twice long, once short: it opens the butterfly valves, then closes them, then takes up the cable slack.
If you remove the carb cover on one side and use a bright flashlight, you can see it operating, right in the middle just below the carb rack. With the bike on the center stand, if you start it up, let it warm up then rev it quickly to 6000rpm you should also see it operating.

Have you checked you spark plugs, how do they look? Have you checked you are getting a good spark on all four?

New plugs. When I turn on the ignition I do hear what I believe to be my Vboost system engaging.

I have a friend

, he didn't seat his carbs fully down. His bike didn't run to bad, at low rpms. And he was a mechanic! Doh award next time he does that
More info, like Mike already mentioned would be good.
Steve

Looks like the carbs are not seated down as far as they can go. Will do that tonight. Keeping fingers crossed.

Yes, check that the...ah...yes..the carbs are...er...umm...seated...and did I mention I like your signature? But, yes make sure they are well seated!:biglaugh:

Not bad for a 44 year old dude. :eusa_dance:

 

[supervetteracer]

I'm having one hell of a time getting these carbs to sit down in the holes correctly. GRRRR!

 

[Miles Long]

I'm having one hell of a time getting these carbs to sit down in the holes correctly. GRRRR!

Try using a thin coat of silicone grease, such as "Molycoat Valve Sealant". This will reduce the friction when trying to seat the carbs, and also serve as a sealant against air leaks, which are common as the rubber boots harden with age.
good luck!

 

[supervetteracer]

I have all four carbs seated correctly. New spark plugs. All wiring end everything looks good.

But this bike is NOT FAST! There is something wrong. It's faster than my Harley Dyna with the twin cam 88, but not by much.:ummm:

I'm fustrated. It sucks when you get that feeling like you wished you had not bought a bike.

I really don't know what to do next. Anyone know of a good Vmax mechanic in Louisville?

I hate this because I know it's something simple. Something small that I have over looked...

 

[Boostmax]

I don't hear the VBoost thing. Is it common for the Vboost to stop working?

If you dont hear the Vboost cycling when you initially turn the key to the on position, it most likely isnt working.

If your Vboost is not working, you're bike isnt going to be very fast as you are DRASTICALLY underfueling the cylinders above 6000 rpms.

Correct me if I'm wrong, but when Vboost opens, it allows each cylinder to essentially be pulling it's intake charge through 2 carbs as opposed to only a single carb with the Vboost closed.

This allows up to 2X as much air and fuel at WOT with Vboost open.

If you're Vboost is not opening, you are only pulling through one carb and are limiting yourself to 1/2 the air and fuel that is available when Vboost is open.

In short, with Vboost closed at WOT, you're essentially running at 1/2 throttle!!

Fix it! :biglaugh:


EDIT:
I just noticed that you said you might hear it. You need to verify it is actually moving the butterfly's. If in doubt, find a way of securing the butterfly's open and take her for a spin. Easy way to rule out VBoost problems. Disconnect the actuator if possible first so you're not fighting the Vboost actuator or potentially damaging it.

The VMax is not fast until the VBoost opens......

 

[supervetteracer]

If you dont hear the Vboost cycling when you initially turn the key to the on position, it most likely isnt working.

If your Vboost is not working, you're bike isnt going to be very fast as you are DRASTICALLY underfueling the cylinders above 6000 rpms.

Correct me if I'm wrong, but when Vboost opens, it allows each cylinder to essentially be pulling it's intake charge through 2 carbs as opposed to only a single carb with the Vboost closed.

This allows up to 2X as much air and fuel at WOT with Vboost open.

If you're Vboost is not opening, you are only pulling through one carb and are limiting yourself to 1/2 the air and fuel that is available when Vboost is open.

In short, with Vboost closed at WOT, you're essentially running at 1/2 throttle!!

Fix it! :biglaugh:

Thanks and good thinking. But I have verified that the V-boost is working.

I guess I am going to pull the carbs again. This time I am going to drill off the caps and do the A?F mixture parts as well. At least I know that it's still technically winter time. So if I'm going to have to screw with something like this I guess this is the time to do it.

 

[Boostmax]

Thanks and good thinking. But I have verified that the V-boost is working.

I guess I am going to pull the carbs again. This time I am going to drill off the caps and do the A?F mixture parts as well. At least I know that it's still technically winter time. So if I'm going to have to screw with something like this I guess this is the time to do it.

Agh, have you verified that VBoost is in fact opening at 6000 rpm? Try this.....

After turning the key to the "on" position, when the VBoost solenoid cycles, unplug it when the butterfly is fully open and take her for a spin.

After you do that test, unplug the VBoost servo in the closed position and run it again and note any differences.

Report back when done with this........ right now! I'm impatient! :biglaugh:

A/F mixture screws do nothing during WOT. They only affect idle and just off idle. If both are good as is now, save yourself the time of taking the carbs off and fixing nothing....

If the bike starts and idles and otherwise runs smooth and clean, I wouldnt think that you'd be having a carb problem.....

Air filter is clean?....long shot...... I know.....

Stock ignition?

Can you feel a cylinder dropping? Or is it just nice and smooth and normal sounding, just weak....

 

[Boostmax]

What is the background on the bike? Why did you pull the carbs to clean them in the 1st place? Any history of previous running condition might help.... What year is the bike? Diaphrams all in perfect condition? If a diaphram had a tear or pinhole, I could possibly see where you're not getting WOT. Anyone know how to test the diaphram? Maybe best to just replace if unsure?

I'm no expert on the CV carb. I have a single Holley 4 barrel on mine.....

 

[Boostmax]

oooh, how about a carb sync? Said you pulled em and cleaned em, but are they sync'd?

Not sure of the effects of improperly sync'd carbs.....probably very little at WOT I assume.......

 

[supervetteracer]

Agh, have you verified that VBoost is in fact opening at 6000 rpm? Try this.....

After turning the key to the "on" position, when the VBoost solenoid cycles, unplug it when the butterfly is fully open and take her for a spin.

After you do that test, unplug the VBoost servo in the closed position and run it again and note any differences.

Report back when done with this........ right now! I'm impatient! :biglaugh:

A/F mixture screws do nothing during WOT. They only affect idle and just off idle. If both are good as is now, save yourself the time of taking the carbs off and fixing nothing....

If the bike starts and idles and otherwise runs smooth and clean, I wouldnt think that you'd be having a carb problem.....

Air filter is clean?....long shot...... I know.....

Stock ignition?

Can you feel a cylinder dropping? Or is it just nice and smooth and normal sounding, just weak....

I re-cleaned the carbs---- COMPLETELY... I hear and see the V boost mechanism working when I key the ignition. I can't see down teh tubes to verify if it is actually opening and such. Is there a way?

And how would I disconnect the vboost with it open? Is there a wire to unplug?

The bike runs fine, it's just slow. (For a Vmax) Perhaps my zx10r has my SOTP meter off, but my HD should have it dialed in...

Guys, I'm looking for ideas. Guess I will do a compression test next. But with only 3900 miles on it I doubt that is the problem.

This bike was purchased from the Original Owner. Sat in his garage too long and ran like it had very dirty carbs when I got it. Now it runs and sounds decent, but has about 70-90 HP. (If that)

 

[TurcoLoco]

It might be a polite way of your bike telling you that you need to lose some weight?

On a serious note, my bike wouldn't even run on gear and even after cleaning and rebuilding the carbs which made them new-like. Carb floats were off.
The fuel looked clean coming out of the carb bowls however further investigation revealed that the gas had tiny small jello pieces despite using stabil. I took out the old gas and I will putting in fresh one. The gas in the tank might still be ok but somewhere in between, there is no-too-clean gas lurking. After putting the gas, I am thinking about circulating the gas in the entire fuel system to make sure before reassembling the carbs.

Easy way to check this possibility: put a container under the hose that comes out of the fuel pump and connects to the carbs. Turn the ignition on (without starting the bike of course) and watch the gas, and see how it is coming out it won't be a big stream but it should be strong and steady.
With this, you will also be checking your fuel pump. Also check the fuel hoses including the filter if the fuel is not coming out correctly.

Good Luck.

 

[supervetteracer]

It might be a polite way of your bike telling you that you need to lose some weight?

On a serious note, my bike wouldn't even run on gear and even after cleaning and rebuilding the carbs which made them new-like. Carb floats were off.
The fuel looked clean coming out of the carb bowls however further investigation revealed that the gas had tiny small jello pieces despite using stabil. I took out the old gas and I will putting in fresh one. The gas in the tank might still be ok but somewhere in between, there is no-too-clean gas lurking. After putting the gas, I am thinking about circulating the gas in the entire fuel system to make sure before reassembling the carbs.

Easy way to check this possibility: put a container under the hose that comes out of the fuel pump and connects to the carbs. Turn the ignition on (without starting the bike of course) and watch the gas, and see how it is coming out it won't be a big stream but it should be strong and steady.
With this, you will also be checking your fuel pump. Also check the fuel hoses including the filter if the fuel is not coming out correctly.

Good Luck.

Cool, did this. It seemed to flow pretty well. Not high pressure like in FIN applications. I'd say it had about 8 lbs of pressure. Wonder if my fuel filter may be partly clogged? Perhaps it has enough fuel to run but when I rev it up the supply may be restricted. I'll throw on a cheap lawn mower style filter in place and see if that does anything.

 

[sdt354]

Are you getting full advance? Just a thought. Stick a timing light on there and verify that the Map sensor is advancing the ignition as rpm increases and giving full advance. Is the vac. line off, bad,or sensor bad ?
Also, a bike with low milage that sat a long time could have a stuck ring. There are some good products out there to deal with this. BG comes to mind. The compression test will verify a ring issue.
Find another Vmax or two, and go have at it. That's the best way to see how you're Max is running. 2nd ear roll ons tell a tail.
Steve-o