Need help! Bike is terrible over 4k rpm

[Traumahawk]

Yep.....fourth clip from the blunt end is a bit rich. Usually if you HAVE to run fourth clip from the blunt end....then that means that you have to go up a jet size.....but that's probably not the case here. It sounds like the PO followed the directions. ..and set it up really rich.

Sent from my SCH-R890 using Tapatalk

 

[Rosholm]

Here comes an other update.

Tried the clip on first 3 then second clip from blunt and it got a little bettre. Pulls hard on first and second gear. Then it starts stumble on WOT at around 4k. If I have half throttle it goes pretty smooth all the way. Still pulles hard on WOT over around 7k.
Did the shotgun again when I changed the needle and checked that everything is moving as it should.

 

[Traumahawk]

Well 4k is where the needles first start to kick in. With it getting better going to the 2nd clip.....your making it run leaner right there. Now I wonder if your main jets are too rich.

Sent from my SCH-R890 using Tapatalk

 

[Rosholm]

I was thinking the same but it runs great on high rpm. Should I try the first clip?

 

[Traumahawk]

I was thinking the same but it runs great on high rpm. Should I try the first clip?

You can....and see what happens....if there is still and issue, you will need to drop the main jet 1 size, and put the needle on the 2-3 clip and start working your way back up.

Sent from my SCH-R890 using Tapatalk

 

[Rosholm]

I also need my a/f screws almost 4 turns out to not have leen issues on low rpm.

 

[Traumahawk]

I also need my a/f screws almost 4 turns out to not have leen issues on low rpm.

That's OK. ....I have mine at 3 turns in the front....and 3.5 in the rear. My A/F at idle cold is 13.8 and warm is 13.0. So 4 isn't bad if that's what the bike wants.

Sent from my SCH-R890 using Tapatalk

 

[Rosholm]

Do you think it could be worth to try the 190 DJ apj2 to get more air in midrage? I saw some other who hade success with bigger paj2

 

[Traumahawk]

I've tried it.....and so have other people without success. It's way easier to keep the stock air jets.....and only tune with fuel. With one variable. If you also tune the air......then you are having to tune 2 variables. There are quite a few people that make over 120 hp at the rear wheel still using the stock air jets.

Sent from my SCH-R890 using Tapatalk

 

[Rosholm]

I just tried the 190 PAJ2 mostly to see what happened and it got a lot better. Still a little rich at full WOT but if I just let go a tine bit on the gas it runs like hell all the way to redline.
At least I think it running rich adj t wot couse it´s the same symtoms as before. Feels kinda strange thou with my 175DJ main, 190DJ PAJ2 and clip on second.
Gonna ride it some more, finetune the A/F screws and get new plugs to see were am at.
Big thanks to Traumahawk for your inputs!

 

[Traumahawk]

Wow....no wonder your rich running the DJ 175's. Below is a chart comparing the size of DJ's vs Mikunis. Most people here make the most dyno HP with MK's 150's-155's.

The Vmax likes to run lean uptop.

 

[thor_eyerdhal]

I ran DJ175 many years and thought it was running good.
When i try the wideband for the first time i saw horribly rich results...
AFR was about 10 at 4000 and 11.5 near the redline!

 

[Rosholm]

I will change to the 165DJ mains as soon as I have time.

 

[caseyjones955]

I had the DJ170 and it was drowning and stumbling from 4k rpm. Someone at Dynajet must think we're jetting small block V8s. The MK150 (DJ160) were still a touch rich up here at 3500' and a slight stumble remained, even with the stage one needles on the leanest slot. I cant even imagine a DJ175.

 

[Rosholm]

Now I finally got some clarity in things.
Pulled the carbs to change the mains when I suddenly saw that the PAJ1 read 175???
Suddenly everything became clear. The ****** that installed the stage 7 kit hade changed the PAJ1 to 175dj instead of the mains. I always asumed that the mains were 175 beacuse the 165 were left unopened in the box and the kit came whit those two.

Hade a pair of stock 90 PAJ1 so I changed them and checked what mains I hade. 152,5 mikuni.
Now my setup is stock PAJ1 and 2, stage 7 neddles and springs on second clip from blunt, stock mikuni 152,5 mains. Screws out about 3 turns.
It runned better than ever but still not god at WOT. Second and therd gear it pulles good but not forth or fifht. Hard to say if it is lean or rich. Feels about the same as before and it must have been running leen whit the 175dj PAJ1.
What should I try next?

 

[Dragmaxster]

Now I finally got some clarity in things.
Pulled the carbs to change the mains when I suddenly saw that the PAJ1 read 175???
Suddenly everything became clear. The ****** that installed the stage 7 kit hade changed the PAJ1 to 175dj instead of the mains. I always asumed that the mains were 175 beacuse the 165 were left unopened in the box and the kit came whit those two.

Hade a pair of stock 90 PAJ1 so I changed them and checked what mains I hade. 152,5 mikuni.
Now my setup is stock PAJ1 and 2, stage 7 neddles and springs on second clip from blunt, stock mikuni 152,5 mains. Screws out about 3 turns.
It runned better than ever but still not god at WOT. Second and therd gear it pulles good but not forth or fifht. Hard to say if it is lean or rich. Feels about the same as before and it must have been running leen whit the 175dj PAJ1.
What should I try next?

Pulling the spark plugs- black if rich white if lean.
I would say your running lean if wot is not good. Try your 165's from the kit as they are between 152.5 and 155 and with the taper of the stage 7 needles they will seat better with the kit jets than they will with stock mikuni's.

 

[thor_eyerdhal]

Needles never seat in the main nets...!

Look at the jet block and main jet position.

 

[Dragmaxster]

Needles never seat in the main nets...!

Look at the jet block and main jet position.

Straight down the center of the Diaphram assembly #10 (slide), through the main nozzle #35 (needle jet) through the jet block #33 and right into the main jet #30.

http://www.boats.net/parts/search/Yamaha/Motorcycle/1985/V MAX 1200 - VMX12N/CARBURETOR/parts.html

 

[Dragmaxster]

If you take a stock needle and put it in a mikuni main jet you will see how the end was made to seat in the jet. If you take a needle from a jet kit and put it in a dyno jet you will see the taper was made to seat in that jet. If you take a jet kit needle and put it in a mikuni jet you will feel a lot of play where it does not seat the same way as a stock needle will.
This is one reason that bikes will have a bleeding effect at idle. Once the throttle pulls the needle out of the main jet it is out of the idle circuit and is no longer effecting the main jet.

My apologies as i was just working on rebuilding a set of 1988 gsxr carbs.

 

[asherc]

Part #30 is a washer not a jet. The main jet is at the other end of the jet block and never touches the needle.


Sent from my iPhone using Tapatalk