UFO 4 into 2 with stage 7

Hi Guys, just wondering what jets and needle clip position is being used with stage 7 and UFO exhaust.
Bike runs good except for hesitation at wot.
Tried multiple configurations between needle position and main jets and can't get rid of the problem.
Is there something else i need to check? Thanks,

Dave.

What's your current setup? Where are you located?

needle clip on 3 from the blunt end, 175 main,190 paj.
I know the 175 main is rather large but the problem is worse with a smaller main.
I live in Rhode Island.
Dave.

That tells me you're lean. Since you're near sea level, you'll need it richer than others. For example, my elevation at 900 feet I'd use DJ165's. Anyway, I would leave your DJ175's in there for now. I assume you have air correctors in PAJ1, drilled slides and DJ slide springs? Where at wide open throttle does it stumble? Everywhere? If not, what rpms? Do you have stock vboost or is it open full time?

Dave D said:

needle clip on 3 from the blunt end, 175 main,190 paj.
I know the 175 main is rather large but the problem is worse with a smaller main.
I live in Rhode Island.
Dave.

Click to expand...

Checking the things Mark is talking about are all a good place to start.

also;

Dynojet recommends the 175 for an aftermarket exhaust so you should be good there.

Dynojets recommended starting point for the needle clips is at groove #4 from the blunt end. If your at #3 then the needle is leaner than recommended. If it's stumbling in the mid to upper mid range then this might adress it (Mark, am I right on this? still figuring these damn carbs out! Damn I love fuel injection and laptops!!!)
I would back the needles out to the #4 setting and try that.

Dave, I forgot to ask if you checked/set your float levels? Make sure that all four are the same. They should all either be 16 mm or 17 mm. Rich or lean here affects the fuel mixture everywhere.

Dave, I forgot to ask if you checked/set your float levels? Make sure that all four are the same. They should all either be 16 mm or 17 mm. Rich or lean here affects the fuel mixture everywhere.

maleko89 said:

That tells me you're lean. Since you're near sea level, you'll need it richer than others. For example, my elevation at 900 feet I'd use DJ165's. Anyway, I would leave your DJ175's in there for now. I assume you have air correctors in PAJ1, drilled slides and DJ slide springs? Where at wide open throttle does it stumble? Everywhere? If not, what rpms? Do you have stock vboost or is it open full time?

Click to expand...

I do have the air correctors installed, slides are drilled,using the stock springs.
Bike pulls up to 7000 rpm and then stumbles, V boost is stock.
This has been driving me crazy, could it be something electrical, coils, wires? Thank you for the help.

Dave.

maleko89 said:

Dave, I forgot to ask if you checked/set your float levels? Make sure that all four are the same. They should all either be 16 mm or 17 mm. Rich or lean here affects the fuel mixture everywhere.

Click to expand...

Floats are fine, that was one of the things i checked after this problem started.

7000 rpm is the beginning transition from the needle to the main jets. You need to raise your needles. Paul Czernics makes a him kit. You get 8 shims....4 1/2 shims and 4 3/4 shims. Raise the needles in 1/4 incrememts. Sometimes a full clip is way too much of an adjustment.

In your case, go to 3 1/4 from blunt end, then 3 1/2, etc. In order to know your needle is set correctly, do the following test.

1) 4th gear, 4K RPMS: WOT until 6K RPMS; let off throttle and if it speeds up, running rich and lower the needle.

2) 4th gear, 4K RPMS: WOT thru 6K RPMS; at 6K, give it some choke; If it speeds up, running lean and raise the needle.

If neither condition happens, needle position is fine.

If you unplug your vboost to the open position, I bet it might take care of your lean stumble. Only issue is doing this makes you rich everywhere. You may have to make pilot mixture adjustments.

Thanks for the help Mark.
How do i get in touch with Paul?

His email is [email protected]. Tell him Mark Milne told you about his shims. He may have a set already made up.

No problem on the help!

I would put the 165 mains back in and start on 2 clip from the blunt end.Open the vboost all the time by unplugging it when it opens.I am running the same setup and exhaust as you.I had the same problem as you for awhile till I finally figured out that one of my vboost boots was cracked allowing it to suck air at higher revs and lean pop on me.I was running 152.5 mikuni mains(stock).It showed a touch lean on the dyno.175 dg mains are huge,equal to 160 something in mikuni size.Most of the stage 7 guys are running 155 mikuni mains with good luck.It is also easier to tune with the vboost open all the time.Mario is the only one that I know that uses the vboost still with good luck.

Try running the bike at idle and using an unlit propane torch to search for air leaks on all the rubber boots.It will idle up faster if it sucks any propane in.Be carefull with it.

wfcall said:

Checking the things Mark is talking about are all a good place to start.

also;

Dynojet recommends the 175 for an aftermarket exhaust so you should be good there.

Dynojets recommended starting point for the needle clips is at groove #4 from the blunt end. If your at #3 then the needle is leaner than recommended. If it's stumbling in the mid to upper mid range then this might adress it (Mark, am I right on this? still figuring these damn carbs out! Damn I love fuel injection and laptops!!!)
I would back the needles out to the #4 setting and try that.

Click to expand...

shawn kloker said:

Try running the bike at idle and using an unlit propane torch to search for air leaks on all the rubber boots.It will idle up faster if it sucks any propane in.Be carefull with it.

Click to expand...

What an awesome idea....

I love this place!