Half throttle chopping

[Bigcaddydaddy]

Hello everyone Im new to the forum and Ive only had my vmax about a month now. When I bought it I noticed it didnt quite run right past half throttle but I figured I could work it out. It runs perfect up to about half throttle but if I give it more than that it starts cutting up in any gear at any rpm. I have been reading and trying things but nothing seems to help so here is the deal. Its a 93 with a kerker 4 into 1 exhaust, k&n air filter with the Y removed and a dynojet stage 1 jet kit. So far here is what ive done, started out with new ngk plugs and wires, put in a new fuel filter, ran seafoam for 1000 miles,set the a/f screws to 2 1/2 turns out,synced the carbs, set the needle clip up one then down one,did the peashooter and the shotgun covered the airbox cover like the Y was on there, and removed the airbox cover but nothing really helps. I did notice it seemed to run better the other night when it was cooler outside, so do you think its to rich? I looked at the plugs and they didnt look bad, so I just dont know what to try next, should I try smaller mains? Right now I think it has 170's in it, or take the carbs off and clean them or what? I would really value the opinion of you guys that have ran the bikes for years and have alot of experience with them. Thank you

 

[sdt354]

Rich no doubt. 170's (especially Mikuni's) are very big. 150's should work alright. If the Y is removed it should have air correctors installed. I'd tear the carbs down and check float levels after putting in much smaller main jets. Stage 1 isn't the easiest set-up to tune. If it were mine, I'd put stock needles back in, or stage 7.

 

[Bigcaddydaddy]

Thanks alot, I dont know what air correctors are though, I'll have to look that up. Would it just be better with the Y back in? I dont have it but I could get one somewhere. What about the stock springs? Should I put them back in, I have them. I also have 150,160,165 jets but you think 150 with stock needles will work good?

 

[scuff]

Those are DJ 170's I assume and are you looking at the PAJ2's under the slides on the side of the carbs? You have to take the carbs off and remove the float bowl plugs to see the mains. I had DJ 150's in mine. You will want to get rid if that Stage 1 kit asap. You are probably running way rich as stated before. If your carbs are set up as mine were your float levels are wrong too which will also affect your running rich problem many people have had problems with the Stage 1 kits. The good thing is that you have full exhaust system so going to a Stage 7 or Morley's kit (which is what I did) is just one step away and I think you will be much happier with it.

 

[blaxmax]

Thanks alot, I dont know what air correctors are though, I'll have to look that up. Would it just be better with the Y back in? I dont have it but I could get one somewhere. What about the stock springs? Should I put them back in, I have them. I also have 150,160,165 jets but you think 150 with stock needles will work good?

Do your jets have "dj" stamped on them? Mikuni's have a square with a smaller square in the corner.With the needles having slots I assume they are dynajets. And having the 150's 160's and 165's make me assume even more they are dynajet. You said you move the clips on the needles up and down but did not say which notch they are on.
I would get the "Y" for the airbox and if you have 170 dj mains that are = to 160 mikuni, I would put the 160 dj= to 150 mikunis in the mains and move the needle to the 1st slot from the blunt end. A/F mixture screws 2 1/2 in front and 3 in the rear.

 

[Bigcaddydaddy]

Yeah it is a dynojet kit and the paperwork with it tells the jet sizes it came with and the 170's are not there so I assume thats whats in it. The clips are on the 3rd slot from the top. Thank for your suggestions I'm gonna try them

 

[Nubicon]

If you don't have air correctors in you need the Y back on. These carbs won't rev for shit with any kind of airbox mod without them.

DJ 170's are only Mikuni 157.5 mains, so it well might be a little rich...but it isn't breaking up because it's rich.

Put the airbox back to stock, and if it still doesn't run right check for mechanical issues.

 

[caseyjones955]

I could never get mine right with the stage one either, I did realize quite a bit of improvement once I removed the stage 1 paj behind the diaphragms back to stock size. At this point all of the stage 1 is gone. I had my stage 1 needles on the leanest clip for best results at 3500'. W/stock air box and kerker 4-1 and 147.5 mains.

The air correctors you can get from Sean Morley on the cheap. As stated if the air box is all.stock with the Y installed you shouldnt need those.
Link below to a jet size cross reference chart.

http://vmaxoutlaw.com/tech/dyno-mikuni.htm.

 

[Nubicon]

Have you checked the plugs by any chance?

 

[Bigcaddydaddy]

I looked at the plugs and they are a little dark but not black or anything. What are the stock mains 152.5?

 

[blaxmax]

I looked at the plugs and they are a little dark but not black or anything. What are the stock mains 152.5?

Yes 152.5

 

[sdt354]

I looked at the plugs and they are a little dark but not black or anything. What are the stock mains 152.5?

Yes, and as big as I'd go. I believe the needles are giving you issues at mid range. But, best to know all your settings, starting with float heights,wet. I will look for picsof correctors installed.
Steve-o

 

[caseyjones955]

Stock mains are 152.5

If the installer followed the instructions (bad) tbey may have replaced the air jets to (bad again). Rich to stupid rich is a common result with the stage one installed by the book.

 

[Bigcaddydaddy]

Thank you all for your input. So maybe I should put it back to stock (besides the exhaust) and start over ? Then just do one thing at a time to see what the big problem is. I mean with the the exhaust and k&n filter it should need richend up some right? I just dont see what the real culprit is. I will get the Y in when I can get one but I tried duct taping a piece of cardboard over it so air only went in the side holes but that didn't help either.

 

[adambweird]

The carbs work the opposite of what you would think. With the full exhaust and k&n filter (y piece removed), you have to put in air correctors and lean the mains out in order to get it running right. The increase in air flow through the carbs pulls more fuel than is needed with out the above mentioned changes.

 

[[email protected]]

The carbs work the opposite of what you would think. With the full exhaust and k&n filter (y piece removed), you have to put in air correctors and lean the mains out in order to get it running right. The increase in air flow through the carbs pulls more fuel than is needed with out the above mentioned changes.

Actually, air correctors are not needed with the stock airbox and the K&N drop in filter that replaces OEM. If you had a setup like Sean's lid, stage 7, or other pod filters, then air correctors would be needed.

Lots of opinions about the airbox Y. Most say to either leave it alone or to shim it just a bit. Removing it completely typically leads to problems.

 

[sdt354]

I like the going back to stock idea to get it running well. Make sure there weren't air correctors installed already or you'll have issues. Like Mike mentioned, they aren't needed with the air box in stock condition. I suspect the kit was put in by someone not experienced with the bike or kit. So you'll need to check everything that was done.
Steve-o

 

[Bigcaddydaddy]

Thank you fellas