Stumble Under 2.5k RPM?

[Kuprebel]

When I throttle over 1/4 to 1/3 and the bike is under 2500 rpm it will stumble and almost make a tst tst tst sound while giving zero power beyond the amount it starts to stumble at. I've also noticed that it will do the tst tst sound when i go past about 1/3 choke. Any idea what it could be?

 

[Traumahawk]

Can you tell us your set up? Completely stock....stage 1.....stage 7....etc.

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[Dragmaxster]

Does it sound like air being sucked in? Cracked intake boot?

 

[Kuprebel]

I've been running carb cleaner through it and fixed my electrical system and that seems to have cleared up the lower rpm stumble. But I still get that tst tst sound when choked too far and the bike doesn't give me much power at around 5 grand with under 1/4 throttle. Any ideas?

I have stage 2 kit with K/N air box and supertrapp exhaust system. I've also noticed that I'm missing the y cover on my air box and those 4 tubes that are behind the y (2 on each side) are missing as well. Could that be affecting my performance?

 

[Traumahawk]

What is a stage 2 kit? I'm only familiar with the dyno jet stage 1 and stage 7 kits......and dale walker also sells a stage 1 kit. Also there is a stage 1 kit from factory pro.

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[Traumahawk]

I believe that your talking about the vent tube that attach to the carbs.....and hook to the air box. Yes.....you need those. But....depending on jetting......needles.....that may not be your only problem. Do you know what the jetting is....etc.....of this stage 2 kit?

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[Dragmaxster]

I've been running carb cleaner through it and fixed my electrical system and that seems to have cleared up the lower rpm stumble. But I still get that tst tst sound when choked too far and the bike doesn't give me much power at around 5 grand with under 1/4 throttle. Any ideas?

I have stage 2 kit with K/N air box and supertrapp exhaust system. I've also noticed that I'm missing the y cover on my air box and those 4 tubes that are behind the y (2 on each side) are missing as well. Could that be affecting my performance?

I have a set of the vent tubes that go from the carbs to the airbox 4 sale.

 

[lethal dose]

It's start with the basics. Check for vac leaks. Do you have a hanging idle at all?

 

[DMAN999]

I believe you mean a DynoJet Stage 1 jet kit.
http://www.dynojet.com/jetkits/motorcycle/yamaha.aspx
http://www.dynojet.com/pdf/4116.pdf

There is no such thing as a Stage 2 kit for a Vmax.
But Factory Pro makes a Ti ProKit carb kit kit that some people call a stage 2 kit.
http://www.factorypro.com/Prod_Pages/prody11.html

As stated above you definitely need those carb vent hoses and re-installing the Y should help as well.

 

[sdt354]

When I throttle over 1/4 to 1/3 and the bike is under 2500 rpm it will stumble and almost make a tst tst tst sound while giving zero power beyond the amount it starts to stumble at. I've also noticed that it will do the tst tst sound when i go past about 1/3 choke. Any idea what it could be?

Did this just start happening, or was it running this way since you got it? +1 to
an intake leak. The Y off can sometimes cause problems. With that set up I'd go back to a stock configuration except maybe a main jet change.

 

[Dragmaxster]

Is that Hebron in Palestine? 3000ft altitude?
I think with the supertrapp and at that altitude your will need a smaller main jets-(150 or 147.5). You definately need the "y" and the tubes wouldn't hurt.
In the meantime you can try covering the opening of the "y". Good luck.

 

[Morty76]

I am new to VMAX life and need some assistance. I bought a 2005 max from my brother and it seems to run rough at lower RPM. I have no idea how long the gas has been in the tank, brother is deployed and unable to answer questions. It seems to run like a raped ape at high RPM. I can feel the missing cylinder on the lower left pipe and also hear minor bubbling from the exhaust. I replaced the plugs with factor rec with no change. Also, what octane fuel should I use? Book says 81-91, but under tank cover says 91. I plan to run carb cleaner in gas today, but any suggestions? Thanks

 

[brad bruggeman]

When I throttle over 1/4 to 1/3 and the bike is under 2500 rpm it will stumble and almost make a tst tst tst sound while giving zero power beyond the amount it starts to stumble at. I've also noticed that it will do the tst tst sound when i go past about 1/3 choke. Any idea what it could be?

How long has the suppertrapps been on the bike?How many discs are you running?I am just guessing from my own experience.When i first got my suppertrapps i was experimenting trying to get the number of discs right.I started a 6 ,then when down to 5, then 4.when i got to 4 it did what you are discribing.It fell on it's face at low rpms.So i went back to 6 and left it.It has been running fine since.By the way my 95 it totally stock except the suppertrapps and k&n air filter.

 

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I am new to VMAX life and need some assistance. I bought a 2005 max from my brother and it seems to run rough at lower RPM. I have no idea how long the gas has been in the tank, brother is deployed and unable to answer questions. It seems to run like a raped ape at high RPM. I can feel the missing cylinder on the lower left pipe and also hear minor bubbling from the exhaust. I replaced the plugs with factor rec with no change. Also, what octane fuel should I use? Book says 81-91, but under tank cover says 91. I plan to run carb cleaner in gas today, but any suggestions? Thanks

87 Octane is fine

Sounds like another vmax with plugged idle jets. Very common problem if the bike sits for any length of time.

Running some seafoam or similar fuel treatment might help. Don't overdue it, follow the instructions. Give it some time to work.

If you see no improvement after running a couple tanks thru it you will most likely need to pull the carbs, split the rack, and open the jet blocks in the float bowls and pull out the jets for cleaning.

 

[Traumahawk]

Well if the pilot jets are clogged......here is a simpler way than having to split the carbs.

http://vmax.lvlhead.com/tips/shotgun.htm

Here are the directions.....and its easy to do. Sometimes it helps to take out PAJ#1 and PAJ#2 (you will find out what those are on the shotgun directions.)