Jetting problem

[TeamRealtreeHD]

Just got a new set of 35mm PWK's off of Jeff at Fast.

 

I was running 33mm PWK's before.

 

My settings from before were 158 main, 48 pilot, air screw 2 turns out, CEL on 3rd/middle clip. With this setup I was right on with jetting. Ran as good as you could ask for.

 

I installed the new carbs with the same jetting, and it has a serious bog when you pin the throttle. Bad bog.

 

I tried moving the clip on the needle, tried different needles, tried different size pilots up and down, etc.

 

Nothing I did changed this issue.

 

Could this be a float problem? As the bike is idling on flat ground, there is a little fuel entering the vent hoses.

 

I didn't check the float height on these carbs, assumed since they were new they were set right.

 

Could float height problems cause this bad bog? It is acting like it is flooded and very rich as you pin the throttle off idle.

 

This is the only thing it could be, as I checked everything else. I just wanted to ask here as maybe someone had this problem before.

Edited July 3, 2010 by TeamRealtreeHD

[locogato11283]

421 cub right? Chances are you're noticing the effects of going to a bigger carb. Does it sit and idle fine? Start up ok? What do the plugs look like? That's about as close of jetting you're gonna get on that motor with those carbs. We always ran 45 pilots and 160 mains in our 4mm cubs.

[TeamRealtreeHD]

Tyler, yes, 421 cub.

 

However, it ran great before with the 33mm. Responsive, no dead spots. From start to finish, right on. My bike was a runner before.

 

This isn't just a small difference. We are talking a bog that almost stalls the bike. This is serious.

 

The bike starts right up and idles fine. Synced carbs, etc. I'm no rookie with this stuff Tyler, as you know.

 

This is a problem. Not the way 35mm PWK's should run on a 421 cub.

Edited July 4, 2010 by TeamRealtreeHD

[TeamRealtreeHD]

Update...

 

checked float heights. They were off. Set them to 16mm. Got them all straight and put bike back together. Nothing. No change.

 

Went down on pilot, nothing.

 

With the smaller pilot in it, I turned air screw all the way in. It took the bog away

 

So this tells me I have a rich condition on the pilot.

 

I was running 48 pilots in my 33mm PWK's on this motor. Now I go to 35mm PWK's and 45 pilots are still too rich. It doesn't make sense.

 

I put 45 pilots in this, still rich as heck.

 

Oil coming out exhaust pipes on rear....

 

Rich, rich, rich.

 

My question is... is it normal to run anything lower than a 45 pilot on this setup?

 

Or do I need a leaner needle or what?

 

Reason I am asking is, I never heard of it, plus my old carbs liked 48's. This doesn't make sense. I am obviously rich on the pilot. Or need a leaner needle. The air screw tells the story. Air screw all the way in took the bog away.

 

42 pilots in a 4mm cub??????? Are you serious?

 

I am running a CEL needle. Tried dropping the needle/raising clip. Nothing. Still have to go down on the pilot size.

 

What the heck?

 

There has to be someone here that can read the above, understand it, and make sense of it. I sure don't understand it.

 

I was told by everybody and their brother jetting would be similar. But it's as rich as can be. Still need smaller on the pilot or leaner needle.

Edited July 4, 2010 by TeamRealtreeHD

[Meat]

at exactly what throttle position is the bog ?

[TeamRealtreeHD]

Right off idle... you pin it, and it dies.

 

I'd say 1/8-1/4 throttle it's dead. And even after.

 

I just never heard of a motor this big needing that small of a jet. Especially since I ran 33mm's with bigger jets.

 

Funny thing is, you can actually see the fuel spraying when you open the slides fast off of idle.

 

I am concerned due to it being jetted great before, and it's not even in the ball park now.

 

Something is wrong.

[TeamRealtreeHD]

As I mentioned above meat, this problem goes away when I turn the air screw all the way in with a 45 pilot. Runs great.

 

I am just confused as to why it's so rich now.

[fastbanshee8]

If you have the air mixture screw turned all the way in, then you're not rich. Turning it in, shuts down the air, and opening it up, adds more, so you are lean on your pilot.

[TeamRealtreeHD]

If you have the air mixture screw turned all the way in, then you're not rich. Turning it in, shuts down the air, and opening it up, adds more, so you are lean on your pilot.

 

It just doesn't make sense, because it still acts the same way when I go up 3 sizes on the pilot.

 

There's oil coming out the exhaust and it's smoking.

 

It's acting rich. But nothing sounds right with the jetting numbers.

 

The only time the bog goes away is when the air screw is all the way in. I tried all the way up to 52 pilots, all the way down to 45.

 

I can try 55's. Time will tell. Just very confusing.

Edited July 4, 2010 by TeamRealtreeHD

[fastbanshee8]

Bigger carbs can be a pain to dial in the first time. I thought I was having jetting problems, and it ended up being a coil that was going bad. Once I changed that out, it was pretty easy to get it jetted right. Just remember, a bigger carb will flow more fuel through a jet, than a smaller carb will. Talk with Jeff, and see what he has to say, about your problem.

[locogato11283]

I just never heard of a motor this big needing that small of a jet. Especially since I ran 33mm's with bigger jets.

 

Bigger motors pull fuel more efficiently. I run 39mm PWK on my 18mm DM and I run 160 mains and 45 pilots.

[Titan up]

When you say you "pin" the throttle, does that mean your stabbing it to WOT? If so, wouldn't that be when your main starts to come into play?

 

Don't rule out that it might be a lean bog.

[TeamRealtreeHD]

Update:

 

First let me thank all of you for the help and input. Always nice to have a place like this to talk with other banshee nuts like me.

 

I went up from the 45 pilot that was in it when I stopped tuning last night, to a 52. My jetting with the last carbs was a 48 pilot.

 

I put that in, started with air screw 1.5 turns out. Instantly felt better than smaller pilots with the bog. But it was still there.

 

So I turned trhe air screw another half turn in. Let it regain itself for 30 seconds.

 

The bog disappeared more. Still a "slight" bog.... something that shouldn't be there. I screwed the air screw in to 1/2 turn out. Went away even more.

 

I am pretty certain I have this figured out. Thanks to you guys. One thing I did yesterday, was put 52 pilots in. But never moved the air screw from 1.5-2 turns out. I never moved it in like I did today.

 

I was lean on the pilot, but it acted like a rich bog for some reason.

 

My goal is to get my hands on 55 pilots today from a buddy. Put them in, and try to get my air screw between 1-2 turns out and have it respond the way I want.

 

I think 55 pilots will do it.

 

Never did I think, just gfoing from 33mm PWK's to 35mm PWK's, would my pilot change 3 sizes. That's pretty insane. But I am pretty certain a 55 pilot will do it with the way it's acting now. It runs awesome, the way I want it to, with 52 pilots and the air screw 1/2 turn out.

 

So 55's should do.

 

I'll update more later. Thankfully I am patient and didn't ride this thing lean on the bottom. I lost a weekend of riding, a big riding weekend where all my friends went out. I didn't knowing it would only do harm if it was lean (which I didn't know of course)

 

I bumped my main from 158 to 165. I will start rich on the main and work down. I was running a 158 main on my 33's and it was right on. I am not taking chances here knowing my pilot circuits were lean with the same settings that were in the smaller carbs.

 

Thanks guys and I'll fill you in when I pin this down for good.

 

I am a firm believer jetting does change when you bump up the size of the carb on the same setup. Atleast it did for me.

Edited July 4, 2010 by TeamRealtreeHD

[TeamRealtreeHD]

Got her all squared away. Never surprises me how finicky a banshee can be, especially one with mods.

 

The carbs are dialed in pretty close right now. I can punch the gas right off idle and it responds. Very snappy. Took it for a ride and the 162 mains were very close. Seems I'll keep it there until the weather gets cooler or I feel a need to change it.

 

Needle seems good. CEL on 3rd clip.

 

Thanks everyone.

[pabansheematt]

Bigger carbs can be a pain to dial in the first time. I thought I was having jetting problems, and it ended up being a coil that was going bad. Once I changed that out, it was pretty easy to get it jetted right. Just remember, a bigger carb will flow more fuel through a jet, than a smaller carb will. Talk with Jeff, and see what he has to say, about your problem.

Thats funny you say that. When I first built my cheetah, I had the same problem. Got a new coil. Jetting it got alot easier.