engine not revving and sputtering at 6000rpm and above

[Fire-medic]

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

https://www.dynojet.com/amfile/file/download/file/1170/product/3785/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.

 

[3-Max]

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]

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]

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]

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!"

 

[g2501]

Hello guys, just an update for suggestions and ideas.
( in the end I hope this thread will be helpfull to others that are going to make some mods )

As I wrote I completely rebuild the airbox. Now is all stock...except for the airbox itself that is a K&N and not a paper filter.
after the usual struggle I managed to remove the carbs from the bike , and guess what? Jets are out of specs....

Main jet was 152.5 , ( but I swapped with DJ 170 when I changed the air filter with the open one ).
I will come back with original Mikuni 150 ( thanks Sean ).
Now the fun part
PAJ#2 was DJ 165 , ( dunno why ) and I will change them to original Mikuni 170
PAJ#1 should be 90, but mine is 95 (????)
Now I suspect that even the main jet is different... Is it possible to check the main jet without disassembling the carbs?

The european Vmax have different jet size from the U.S. Model , and I would like to know if these differences are mostly for environmental purpose or for something else.

Can someone tell me what are the relationship from PAJ#1 and PAJ#2 ? is it advisable to change these jets with smaller ( or larger ) one?

One last question : since I have the original Mikuni needle with grooves I would like to know a good starting point for the clip position.
I noticed that the original needles are shorter than DJ , so the clip in 3rd position on DJ needle is way too different from the clip at 3rd position on mikuni original needle.
Does some of you have a suggestion?
Please excuse me for the bother, I know that I have to try and change by myself.....but I have no place to use for dismounting the parts. I have only a parking spot in an underground parking ...without the lights . So everytime I have to change something on my bike it's a royal Pain in the neck.
Thanks again.

 

[MaxMidnight]

In the period specified there were full power and restricted bikes and I don't know if there were differences between the carb set-up.
As yours is a EU spec then I'd go with the EU jetting.
That said Yamaha only appear to list one part # regardless of year or market - 26K1494190-00. I've not checked every year/ market so happy to be corrected.

For the needles, try the middle clip position and determine if it is rich or lean.

Re PAJ1 & 2 this may help - don't have details of the original author so I can't acknowledge it.

"Air enters PAJ1 and PAJ2 and is merged to extract fuel from the pilot fuel jet. The mixture screw controls the resulting mixture. The screw has an affect on carb operation up to 5000 rpm. PAJ2 is part of the coasting enrichment system and is closed at idle and begins to open starting at off-idle throttle positions.

PAJ2 is closed at idle and starts to open at small throttle openings. It's part of the coasting enrichment circuit so I believe it has the greatest affect at off-idle. PAJ2 combines small amounts of air with PAJ1. This combined air is used to mix with fuel from the pilot fuel jet. The pilot fuel jet has an affect up to about 5000 rpm.
I changed mine from 170 to 150 once, and off idle wasn't very good. There just wasn't a very good transition from the idle circuit to the needle (about 2500 rpm).

The needle has a tiny affect, even at idle. A very small amount of fuel can squeak by the needle at idle. If you put a more aggressive needle, you'll notice a change in idle. The jet needle controls how much fuel goes from the emulsion tube to the needle jet.

The idle, mid range and main circuits all bleed together so where one circuit starts and another begins isn't very cut and dry.

Some people do put a slightly smaller PAJ2 in to enrich up their off idle. IMHO, I think it's a waste of time. A slight turning out of the mixture screw will enrich the idle up just fine."

 

[g2501]

thanks a lot MaxMidnight.
ok, I've got all set and ready to go.
Cleaned the carbs with appropriate cleaner, spraying a lot through every jet/orifice.
Main Jet : mikuni 150
Pilot jet : should be 42.5, but I didn't had the chance to check it , because this requires a full dismount of the carb rack , and I don't have the replacement gaskets.
Pilot Air jet #1 : mikuni 95
Pilot Air jet #2 : mikuni 170
Needles : mikuni 5EZ19-3
Needles clip : 3rd notch ( the needles have 5 grooves, I put the clip in the middle one)
Needles spacers : no
Idle screws : 2+1/2 turns out ( I had a strange set-up on these screws... some are 1 turn out, other 3+1/2 or more )
Float Level : not checked...wil do that after

1st step : re-synchro the carbs with the carb-tune
*
2nd step : go for a ride and check the behaviour for hi-rev ( 6000 and beyond ). if the bike delivers then I will go with step 3, if I still have sputtering or idling above 6500 I suppose that I have to take out the carbs again....
*
3rd step : check for middle-rev issue or lack of pull. starting at 2000 RPM give a WOT until 6000 RPM and look for dead spot in power delivery. If everything is good go ahead with step 4 , else take out the carb slides and adjust the needle clip position ( one clip beyond the blunted end ) and test again until I found a sweet spot.
*
4th step : check for low-rev and idle issue. If there are some I will try to solve them adjusting the idle screws below the carb cap cover.

Do I miss something or wrote something wrong?
Have you some suggestions for further checks ?

 

[one2dmax]

That pilot jet is way larger then normal (which is 37.5)

 

[g2501]

Hello Sean ,
42.5 for pilot jet should be the standard size for EU models.
Unfortunately I didn't had the chance to check it with my eyes , because I don't have the replacement gasket for carbs, but I'm pretty confident that the pilot jet was not touched by the previous owner.
I carefully inspected the screws on that side of the carbs and they are original ( cross section screws ) , but most important there is no sign or scratches on the head of the screws. (These screws are pretty tight, and when taken off they easily scratches on the surface.)
Anyway , for my knowledge I will greatly appreciate if you could tell me what the symptoms of a larger pilot jets are , or when a different pilot jet size should be choosen.

 

[MaxMidnight]

Over the years I've collected various articles on setting up carbs.
Not sure if it will help or confuse but it is attached for your dissemination.

 

[g2501]

wow... this is GOLD !!! thank you very much Max !
Update : carb sync is done. I've noticed that the carbs were not so misaligned as excpected. i take this as a good thing.
If it doesn't rain AGAIN ( insert swearing here...) i will go for a ride this evening .

 

[g2501]

ok, first ride made.
everything is back to "normal" .
I've focused my attention to high RPM, and now I have no sign of hesitation . from 5000 to 9000 the bike does not sputter or "cough" anymore.
Maybe the V-Boost is not kicking in as I expected, but the bike goes pretty good even if I stay at high RPM with low throttle opening.
I've tried to check the mid-range RPM , going in 2-3-4th gear from 2000/2500 RPM with WOT to 6000.The bike takes WOT without stubles, but I believe that the pull could ( ....or SHOULD ) be better.
I will work with needle height today or tomorrow.
Will try to rich the mixture using the higher slot of the needle and a washer as a spacer.
Next I tried at idle and low speed wit WOT. I got some random misfire ( a "spit" noise ) occasionally, both in cold and hot engine.
I'm also planning to change the spark plugs and to do a cleaning of the engine chamber using a can of Seafoam.
Mybe these 2 operation will cure the random misfire at low RPM.
Should I do these operation before or after the carb/needles tuning?

 

[3-Max]

If recall correctly (which is always open to question) the 'spit' / 'sneeze' is weak mixture/too much air.
See if a little bit of choke makes it disappear.
If so check your carb joint rubbers (to engine & air box) are in good condition & fully seated clamped tight. If there is no vacuum leak I would next suspect your K&N filter letting in too much air (kind of why they get fitted). Other than fitting a OEM type paper one (to check this is the case) I don't know what needs doing to carb settings.

 

[MaxMidnight]

Should I do these operation before or after the carb/needles tuning?

After.

The trouble shooting diagnosis from Dynojet may also be of use.

 

[Mikepppp]

Hy guys,
first of all I would like to apologize for the bother, but recently I had a series of annoying issues with my Max that are really going to make me desire to sell it.... although I really love this bike from when I was 13 Y. Old

INTRO:
A friend of mine tested my bike ( 1996 EU VMAX 1 gen with the vboost and every limitation removed ) . He told me that even if it has a great low RPM torque it is not as "powerful" as everyone say. In his opinion a standard Honda hornet 600 have the same "pull".
Since then I start to think about what is wrong with my bike, all in all it should have at least 145HP! and to tell you the truth I never felt "my arms to be ripped off for the acceleration".

What I've done is that from that moment I tried to gain some more HP with some mod ( COP, better oil, better sparks ,ecc,ecc ) but still very little ( or nothing ) changes.

BIKE CONFIG:
since the issue regards the motor I will not list the mods that I've made that are not related, such like suspensions , clutch or brakes.

Standard EU motor ( 1198CC )
COP
DynoJet stage 1 kit ( installed from previous owner )
--dynojet stage 1 needles
--lighter springs
--enlarged holes on carburetor slides
--mikuni 152.5 size main jet
Modified air box ( top cover removed and a single large flat filter installed and sealed )
Iridium spark plugs
rapid gas throttle from DOMINO
Dyna 3000 digital ECU ( no change in configuration were made )
Complete V-boost system with new servo cables , vboost unit ECU, and flasher relay mod to be fully operational.
custom modified carbon fiber muffler ( no mainfold tubes ) installed from previous owner with no dbkiller and larger internal tube .

THE TROUBLE:
Some months ago I found a bargain for a flat K&N filter ( paid 30$ new ) so I decided to modify my airbox to be something like the Stage 1 mod from Mr. Morley.
From that moment on the bike starts to run poorly, but I was expecting it, because I know that should also take care of a lot of other parts such like exhaust, jets , needles and so on .
The issue is clearly a lack of power from midrange to top range.

WHAT DONE SO FAR:
with the new air filter the bike stops revving at 4000RPM , so I move the carb needles 1 groove inward from the original position
result: slight better mid-range , but when I hit 5000RPM the bige goes from "VROOOOM" to "WWWOOOOO" and stop pulling.
Take off the carburetors and clean them in every orifice without taking them apart, then swap the original mikuni jet 152,5 with dynojet 170 jets.
mount carbs and filter back and test.
result: slight better, but up to 6000RPM then the bike stops pulling and starts to sputtering.
At that RPM I expected the vboost to come into play, but I feel nothing.... just a sputtering bike .
It doesn't want to go over that.

The mechanic in my city told me that the bike is running lean and suggest me to install larger jets, but I found this very strange since I already have a 170 ! What jets should I put inside the bike ? a 180????? Is this possible?

Is there something I can do without taking out the carbs from the bike ?
I still have original needles , springs and jets , but please remember that European needles are slightly different from US needles. My original needles have 5 grooves and are pretty similar to the dynojet needles, just more stained from age.

I’ve just finished the work that you have done regarding the air filter it allows tons more air and the jetting required for your bike to perform is 200 mine was 165 and wouldn’t run above 4000 easily I went to 180 but still had flat spots on acceleration, 200 and it is flying supertrapp exhaust, heavy duty leads, bigger fuel tank and top tank.
Your jetting is too low!

 

[Mikepppp]

Hy guys,
first of all I would like to apologize for the bother, but recently I had a series of annoying issues with my Max that are really going to make me desire to sell it.... although I really love this bike from when I was 13 Y. Old

INTRO:
A friend of mine tested my bike ( 1996 EU VMAX 1 gen with the vboost and every limitation removed ) . He told me that even if it has a great low RPM torque it is not as "powerful" as everyone say. In his opinion a standard Honda hornet 600 have the same "pull".
Since then I start to think about what is wrong with my bike, all in all it should have at least 145HP! and to tell you the truth I never felt "my arms to be ripped off for the acceleration".

What I've done is that from that moment I tried to gain some more HP with some mod ( COP, better oil, better sparks ,ecc,ecc ) but still very little ( or nothing ) changes.

BIKE CONFIG:
since the issue regards the motor I will not list the mods that I've made that are not related, such like suspensions , clutch or brakes.

Standard EU motor ( 1198CC )
COP
DynoJet stage 1 kit ( installed from previous owner )
--dynojet stage 1 needles
--lighter springs
--enlarged holes on carburetor slides
--mikuni 152.5 size main jet
Modified air box ( top cover removed and a single large flat filter installed and sealed )
Iridium spark plugs
rapid gas throttle from DOMINO
Dyna 3000 digital ECU ( no change in configuration were made )
Complete V-boost system with new servo cables , vboost unit ECU, and flasher relay mod to be fully operational.
custom modified carbon fiber muffler ( no mainfold tubes ) installed from previous owner with no dbkiller and larger internal tube .

THE TROUBLE:
Some months ago I found a bargain for a flat K&N filter ( paid 30$ new ) so I decided to modify my airbox to be something like the Stage 1 mod from Mr. Morley.
From that moment on the bike starts to run poorly, but I was expecting it, because I know that should also take care of a lot of other parts such like exhaust, jets , needles and so on .
The issue is clearly a lack of power from midrange to top range.

WHAT DONE SO FAR:
with the new air filter the bike stops revving at 4000RPM , so I move the carb needles 1 groove inward from the original position
result: slight better mid-range , but when I hit 5000RPM the bige goes from "VROOOOM" to "WWWOOOOO" and stop pulling.
Take off the carburetors and clean them in every orifice without taking them apart, then swap the original mikuni jet 152,5 with dynojet 170 jets.
mount carbs and filter back and test.
result: slight better, but up to 6000RPM then the bike stops pulling and starts to sputtering.
At that RPM I expected the vboost to come into play, but I feel nothing.... just a sputtering bike .
It doesn't want to go over that.

The mechanic in my city told me that the bike is running lean and suggest me to install larger jets, but I found this very strange since I already have a 170 ! What jets should I put inside the bike ? a 180????? Is this possible?

Is there something I can do without taking out the carbs from the bike ?
I still have original needles , springs and jets , but please remember that European needles are slightly different from US needles. My original needles have 5 grooves and are pretty similar to the dynojet needles, just more stained from age.

Btw I build race bikes