engine not revving and sputtering at 6000rpm and above

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Fire-medic

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The Dynojet Stage 1 is not a system people have had luck with installing. Their Stage 7 is what people have had luck with, I have that, and kept my VBoost operational, instead of removing the VBoost butterflies as the Stage 7directions call for. Removing the butterflies makes it harder to synch the carbs.

https://www.dynojet.com/amfile/file/download/file/1032/product/3713/
Stage 1

Stage 7

Sean Morley offers Morley's Muscle jet kit, contact him [email protected] for information. I suggest using the 'search' function here (the forum) to find info on the Morley's Muscle jet kit and the results people have had with it.
 
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3-Max

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Aside from the previous comments I'm wondering if the mods have just altered the scavenging phase to the lower rev bands at the serious expense of the higher ones. In that case there would be no mitigating mechanisms built into the exhaust/intake systems available to the higher rev band.

Going one mod at a time from oem is the best course as you can tell dirrectly if there's a benefit & where it comes from but also bare in mind that one mod on top of another will also be interacting with the previous mod. This may nor may not be beneficial. Each may have some benefit on it's own but they cancel eachother out when together. The only way to tell is do one - take it off try the next etc. then once you know which is doing what try combinations. Laborious & possibly expensive process I know. Just depends on how much you want to do it & how much you're prepared to spend in time & money. Only other way is fit a tried & tested 'kit'. Good luck.
 

g2501

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quck update:
Ok then, I'm going to roll back everything and save the modded parts for when I can purchase a full header exhaust.Following Sean Suggestion I've ordered the mikuni 150 main jet.I've also ordered the air correctors, but I will save them for future use.

This will be the configuration after the roll-back
Standard air-box with the "Y" section shimmed about 4mm
K&N air filter ( original shape )
Standard mikuni needles ( clip installed at 3rd slot from the pointed side ) with standard washer
150 main jet
170 paj#2

other jets will be leaved alone since I didn't touch them.

after all the operations I will re-sync the carbs using a carbtune pro-4

I ask for your suggestion regarding one last things :
Since I had enlarged the hole of the carb slide ( as per dynojet kit instruction ) I wonder if it is possible to still use the lighter springs of I you advise to use the original springs .
Will the lighter springs be useful with the standard carb configuration?
 

MaxMidnight

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If it were me I'd go back to completely standard which you know will work. If you still have issues you will at least know it isn't down to one of the modifications.
If not already done so I would plug and re drill the carb slide hole to the original size...I'm sure someone can chip in as to what that should be.
Once you have it running correctly it is straight forward to swap the springs over to assess what difference it makes.
Going forward you should only do one mod at a time so if it doesn't go to plan you will know where the problem lies.
 

Fire-medic

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other jets will be leaved alone since I didn't touch them.
But the prior owner did, or someone working on it for him, did. See what ya got. My advice.

I suspect shimming the airbox 4mm is too-much. That's > 15% more opening than OEM. I'd suggest having it closed, and then think about opening it a bit at a time, to work-up to whatever seems to work best for you.

"Honey, I have to go 'road-test' my Y-gap!"
 
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