2-3k stumble at wot. Need help

[Rusty McNeil]

Alright. I put in an afr gauge. Paj2s are 117.5, needles on 4th from the blunt end. The paj2s were the only thing that helped with the cruising surge I had. The mains are staying between 12.5 and 13 wot 7500-xxxx. I dont even know where the idle screws are. I got #1 to idle at about 14 to 1, and put the others at the same spot. Prolly not exactly perfect, but it works. The stumble from 2-3 k is still there. It's bottoming out my afr gauge at 10 to 1. My floats are at 17mm. Anybody ever had to leaner? I'm gonna pull em and adjust em to 18 tonight. I'll update when I've had a chance to try it. By the way, any suggestions are more than welcome.

Sounds like the mains are spot on at least, although if it was me on a stock motor I might go one Mikuni size leaner, that's a judgement call though.

Moving on...

When you say PAJ2's are 117.5's is that a typo or is that what you really have?

Stock are 170's the smaller the PAJ2 jet the richer its gonna be since its an air jet.

Idle at 14:1 is good/ok too, but you could actually go a lot leaner on idle, its never going to detonate or lean burn at idle with no load on it. Mine idles at about 17:1 or higher. As soon as you crack the throttle it goes down.

Going back up on the PAJ2 might also help your way rich problem at 2-3 but probably not as much as the float level will.

Now, when you say it stumbles at 2-3k is that when slowly rolling through that range?
When whacking it open to WOT at 2-3k?
Or trying to maintain that RPM?
Or a combination of?

What is the a/f at steady state cruise 4000rpm?

If it was me I would keep working the factory pro method, working on needle setting/slide spring selection next.

Then float level and paj2 selection. I've never has to mess with a paj1 jet. Usually they are 90, some are 100,
If you do have 100's is change 'me to 90's tho.

Float level has a lot to do with all circuits of the carb, especially low mid WOT and steady state cruise.

If you do lower the float level I would ignore my comment about lowering the main because lowering the float level may lean out the WOT on main as well.

I have no idea what 17mm wet is compares to my method. I set mine at 1.112" caliper method, and wet check to verify they are all the same. Not saying that's the right way tho.

 

[Sweetwilliebrownjr]

Supposed to be 177.5 paj2s. I'm referring to wot on the stumble. Like I said it bottoms out the wideband. I've already started leaning out the idle mixture, just not terribly concerned with it right now because I'm gonna have to reset it all anyways. I'm gonna stick with the main jet I have for now, as I can't get my data log stuff to work properly. At those speeds, I'm trying to watch the road and the gauge. I figure its alright for the time being. Right now cruising at 4k is in the 14 range or so. I'll lean that out later, though a number to shoot for would be nice instead of trial and error. I'm gonna take a good look at the needle jets when I pull the carbs apart tonight too. They've got 22k on em at this point.

 

[Rusty McNeil]

Then the next thing I would do is set the needles as lean as they will go, or try the stock springs if that's not what you already have.
Easy experiment before pulling the carbs off.

Don't give up, these carbs are frustrating as heck but once you figure 'em out you'll get a lot of satisfaction out of it.

Also, if you don't know it already the choke is a decent diagnostic tool for testing "which way to go" as well. Since its actually an enrichment circuit you can feed it choke at the same time its acting badly and see if it gets better or even worse and get a little data from that.

Congrats on the a/f setup!
What kind did you get?

Mine can log all kinds if stuff but I only use a/f and RPM.

The display on mine is analog so its actually pretty easy to see even when a "lot is going on"

 

[Sweetwilliebrownjr]

I actually pulled the afr gauge from my car since I couldn't afford one. It's a 2-channel one from daytona sensors. Wego iii. I've got it zip tied in front of the speedometer. It's just a little scary to look at it and rpm and the road. I need a longer open road.

I already put the stock springs back in, and it didn't help any at all. I haven't had a chance to swap the needles back leaner. I went from clip 3, to clip 1, then when I put the larger paj2 in, I put it on clip 4 because I figured it would be leaned out by the paj. Same results after every change. It was messing with the 5-7k range, but the 2-3 k was still hitting 10 to 1. That's why I'm thinking maybe needle jet.

 

[Sweetwilliebrownjr]

Well, I pulled the carbs apart, and checked everything I could get to without pulling the jet blocks. Everything looks like new. I set the levels .5 mm leaner. Haven't had a good chance to check it yet, because it's raining. I did take a look at the coils, and everyone of them has massive cracks in them. I'm working on getting a cop setup now. I'm wondering if maybe it was misfiring and causing some of the problems I'm having. It runs so smooth everywhere else, I wouldn't think so, but I guess I'll find out when I swap them jokers out.

 

[m-cman]

Unfortunately the jets that clog the easiest and most often are in the jet block under those rubber plugs. I'm afraid you will have to go in there and clean them before you will fix your problem. Hopefully I am wrong... :confused2:

 

[tugla]

Sorry if I'm repeating what others said here but how are the carb boots/joints.....no cracks right and how is the sync....
id run 16 mm on wet float setting and for sure chg those coils as can be your issue. What's the exhaust system and your elevation there.

 

[Sweetwilliebrownjr]

it seems like I should be lean if the pilot fuel jets were clogged. Let me know if I'm wrong, and please explain so I'll know what's going on. I'm at 17.5mm (have tried everywhere from 17.5 to 15.5 with no change). on the wet float check. Carb and vboost boots are new. I've got dale walker head pipes with supertrapp cans. Elevation's around 250 feet.

 

[tugla]

And needle jet still stock size or you haven't had chance to look at it?

And the sync is good?

For fun I'd put new plugs in it ....even with the coils the way they are

 

[Sweetwilliebrownjr]

sync is spot on. I'm on my third set of new plugs. Everything was stock before I started on this.

 

[tugla]

Mmmm..... Well if not the coils then something clogged in the carbs.....have to think about this.....the a/f screws are all nice no worn tips in them?

 

[Sweetwilliebrownjr]

everything in the carbs looks like new. As mentioned earlier, I did not remove the jetblock, so I've not cleaned pilot fuel jets, but just seems like that would make it lean, not rich. My cop's will be shipped Saturday, so I should know for sure next week if that's what's causing it. I also just started working on all the charging system fixes just in case, although my voltages are good anyhow. Just trying to cross a few things out on the list of possibilities. Shotgun and peashooter have been done as well. Several times to no avail. I'm beginning to wonder if it's the stage 7 needles. Maybe they're too aggressive on this particular bike. Swapping those back out to stock is prolly gonna be my next step. Right now, I've leaned the needle out a bit, because it was rich on my last test run.

 

[marsmax85]

Did you silicone the cracked coils at least the back ones .

 

[Sweetwilliebrownjr]

Did you silicone the cracked coils at least the back ones .

Nope! I just said the hell with it. I've been eyeballing the cop's for a while anyhow.



I did notice something while fooling with the bike earlier. When the key's cut on, the vboost cable opens the v-boost, then back out, then it pulls itself back up just a bit. I would think to take the slack out of the cable, but it actually goes past that a bit, and opens the butterflies a bit. I've unplugged it fully closed but haven't had a chance to test it yet.

 

[Sweetwilliebrownjr]

The vboost made no difference (still 10 to 1) so I hooked it back up. I'm pulling 12.3-12.5 wot 5-7k on the needle, so I'm gonna go 1/2 clip leaner. Past that, I guess I'm gonna have to wait on the coils and see.

 

[D-Max2012]

Dood,
Your problem sounds a lot like what I am dealing with.. 2 - 3K WOT in 2nd and it bogs down like crazy. I tried a little test that determined I might have my main jet size too small for the amount of fuel. To test it, simply take two pieces of duct tape with you. Enough to cover 1/2 of each air intake on the air box. Test ride it.. See if it gets better or worse.. If it gets better, then you're running too much air to fuel mix (lean).. If worse, the opposite applies. I finally got an explanation that the previous owner has smaller jets for the mains.. (I only got the bike last year). I ran the test yesterday and I’ve NEVER had that bike pull like it did. I shot off doing 80 in less than 6 second. I’ve never had my max perform like this. Now I’m looking to replace the 118 main jets with Mukuni's 152.5 and test again without the air restriction.
Run the test and let us know what happens.

 

[Sweetwilliebrownjr]

I have an afr gauge. I know it's rich. When on the main I'm between 12.5 and 13.1, when on needle, its around 12 (a touch rich prolly 1/2 clip on needle). Between 2-3k wot, it's 10 to one. 10 to one is incredibly rich. Even with the larger paj2, which leans everything out, and the float set at 17.5mm, its still hitting 10 to 1. Duct tape won't help. If I hooked a leaf blower to the intake, it might.

 

[D-Max2012]

That sounds like a turbo charger to me.. Like this bike needs one.. LOL

 

[Sweetwilliebrownjr]

That sounds like a turbo charger to me.. Like this bike needs one.. LOL

sounds like fun to me, but I haven't found a good way to carry it yet.

 

[D-Max2012]

Man, it’s raining or looking like it’s about to pour over here today.. I wanted to do more testing with the air box restrictors and the DJ118 mains that’s in the bike now.. I'm calling around to see if anyone has the Mukuni #150 and #152.5 locally, but no dice.. So I have to order them. I'll bet I'll get good gas mileage with those 118's in there but I don’t want to blow my engine from running it too lean. I don’t know why the previous owner put 118 in running F.P. needles and (baffle removed) stock pipes. I read that removing the baffles on the stock pipe does not require a needle / jet mod.
ANYWAY!!.. I have a question for anyone concerned about carbs leaking gas.
I was at the local MC shop yesterday and I overheard a guy talking about his carbs leaking fuel. The shop tech told him what to look for and possibly change, and to tap on the float chamber to loosen of a stuck float valve. Good advice.. BUT.. I've had that happen to me twice, on 2 different carbs. After the 1st time it happened, i cleaned all carbs and added drain tubes.
Here's the kicker. I removed my carbs for the 1st time to give it a good cleaning, all looked fine afterwards. While still trying to diagnose my power problem, I removed the carbs again. This time to give it an Ultra Sonic cleaning (I have never seen so much **** come off using regular carb cleaning methods). When removing the bowl parts, I found some growth happening inside the float chambers. It looked like yellowish rock candy or salt crystals growing on the jet block and under the gasket. I have pics of this.. SO, even after a nice cleaning with the Ultra Sonic cleaner, I had another carb leak gas last week. Now I'm wondering, even if I purchased new float needle valves (softer rubber), and this growth still happens beyond my control, it could cause the valves not to close fully and cause another leak. A total waist of money.
Has anyone else seen stuff like this growing inside your float bowls?