PWK28 Vents/Bowls running dry?

[stokes77]

Took it out yesterday and it ran good when I was doing some runs for plug chops, but as soon as I got going around the track I would lose all power. The bottom end was reasonable most of the time, but the top end would just disappear and not climb at all after a while. It was to the point where I could barely climb up some of the big table tops. The track had puddles and mud all over it, and It definitely lost some power when I hit them.

 

All my bike has done to it is... FMF SST, Pro Flow Intake with lid on, +4 timing, Coolhead with 21cc domes, PWK28's, Boyesen Reeds.

 

It got worse and worse the more I rode. At first I thought it was a jetting issue, so I changed jets like 5 times trying to get it dialed in. But I was thinking about it some more last night, and I think I may be running the bowls dry.

 

My question is, how many vents do you guys have on your PWK's? Mine have one vent coming off of each side, one vent coming off the top engine side, and two drain lines on the bottom. The right side vent is usable, the left side vent is filled in, the top vent has a rubber cap on it, and the drain valve pointing down is usable, but the drain valve pointing left is filled in.

 

Could the lack of the left side vent cause the bowls to run dry?

 

I have clear fuel line, and it get air bubbles trapped in line sometimes. I've done my best to keep the fuel line as short as possible with the stock T, but it's hard to get them short and running down hill, with the clear fuel line.

 

I also can't get a line on the bottom drain line, because it points straight down and runs right into the clutch arm on the left side and it's still really tight on the ride side.

 

Sorry for the long post, but I am just trying to cover everything... If anyone has any suggestions or has run into similar problems, any help is appreciated!

 

Thanks

-Mark

[hercalmighty]

What is your jetting? Is your tank flowing fuel right? Is the quad getting hot?

[06specialedition]

If it's not jetting then maybe try a Duel Pingle Valve....

[stokes77]

What is your jetting? Is your tank flowing fuel right? Is the quad getting hot?

Jetting was running best at 45 pilot, 150 main, middle clip of JJH needle. As far as I can tell the tank is flowing properly and it never overheated or anything, it just wouldn't pull. Before I put the carbs on, the bike ran great.

 

If it's not jetting then maybe try a Duel Pingle Valve....

 

I've thought about a pingel, but I dont think that is the real problem. The stock petcock should flow enough to support my mods.

[hercalmighty]

What was your jetting with your stock carbs?

When I went from stock carbs to 28 pwks mine didn't seem to run right either. I pulled off my air lid and the thing ran great. I think the air lid chokes it up too much with the 28s. I might be wrong on that but it seemed to work for me. I had T6s, 20cc domes, VF2, open air box with a twin air filter. I had 45 pilot, N68A needle in the middle, 160 main.

[stokes77]

What was your jetting with your stock carbs?

When I went from stock carbs to 28 pwks mine didn't seem to run right either. I pulled off my air lid and the thing ran great. I think the air lid chokes it up too much with the 28s. I might be wrong on that but it seemed to work for me. I had T6s, 20cc domes, VF2, open air box with a twin air filter. I had 45 pilot, N68A needle in the middle, 160 main.

 

I was at 27.5/290/Stock Needle Middle clip.

 

The last time I came in on the bike, it was running really bad. I turned it off and let it sit for a while. I was going to try and run it without a lid, but I couldn't get it to start back up after that.

 

I her home and checked compression on it, which was around 110, which I know is low... but I figure it should still run at that. So i put the plugs back in, and forgot to take the exhaust plugs out, and she still fired up first kick.

 

It's just strange the way it's been acting.

 

I never thought about the carbs being starved of fuel when i was at the track, so I never actually checked them to see if it was the problem.

 

 

-Mark

Edited June 22, 2010 by stokes77

[sandman]

I was at 27.5/290/Stock Needle Middle clip.

 

The last time I came in on the bike, it was running really bad. I turned it off and let it sit for a while. I was going to try and run it without a lid, but I couldn't get it to start back up after that.

 

I her home and checked compression on it, which was around 110, which I know is low... but I figure it should still run at that. So i put the plugs back in, and forgot to take the exhaust plugs out, and she still fired up first kick.

 

It's just strange the way it's been acting.

 

I never thought about the carbs being starved of fuel when i was at the track, so I never actually checked them to see if it was the problem.

 

 

-Mark

 

The first place I would start is the needle. I run these same carbs on mine & when I had FMF Fatties (not SST) they liked N68A needles. I have since switched pipes & have gone to a JJH needle. You will be amazed at the difference the taper/length of a needle can make. My bike reacted the same way as yours when I had the wrong needle with the wrong pipe. You are not running the bowls dry with the mods you have. I've got the same carbs 172 jets to feed a ported motor & 19cc domes & stock pingel & fuel line & have never run the bowls dry. If a N68A needle does not work than try a cel or better yet ask a few builders.

As far as your vents go, the top vent nipple should be a line that runs from one carb to another & for the one hitting your clutch arm you have 2 choices: 1. Get some Boss intakes which will raise & setback your carbs thus gettting that bottom vent off your clutch arm so you can put a hose on it. This may not work in conjunction with your airbox.

2. Remove bowl then CAREFULLY tap the existing hole to a 10/32 thread & put a screw in it with thread sealing tape wrapped around it. Then drill out the nipple on the side that is currently filled in & put your hose on it. These nipples lead into the same 'vent port'.

Good luck,

Chad

[TNTS355]

I would start simple. Pull your pingle and make sure the filters are not clogged.

[stokes77]

The first place I would start is the needle. I run these same carbs on mine & when I had FMF Fatties (not SST) they liked N68A needles. I have since switched pipes & have gone to a JJH needle. You will be amazed at the difference the taper/length of a needle can make. My bike reacted the same way as yours when I had the wrong needle with the wrong pipe. You are not running the bowls dry with the mods you have. I've got the same carbs 172 jets to feed a ported motor & 19cc domes & stock pingel & fuel line & have never run the bowls dry. If a N68A needle does not work than try a cel or better yet ask a few builders.

As far as your vents go, the top vent nipple should be a line that runs from one carb to another & for the one hitting your clutch arm you have 2 choices: 1. Get some Boss intakes which will raise & setback your carbs thus gettting that bottom vent off your clutch arm so you can put a hose on it. This may not work in conjunction with your airbox.

2. Remove bowl then CAREFULLY tap the existing hole to a 10/32 thread & put a screw in it with thread sealing tape wrapped around it. Then drill out the nipple on the side that is currently filled in & put your hose on it. These nipples lead into the same 'vent port'.

Good luck,

Chad

 

I'll have to see if I can find some N68A needles somewhere around me. I don't know if that will fix my problem though, the bike ran decent when I was doing plug chop runs, but when I started running around on the track it ran like ass.

 

I would start simple. Pull your pingle and make sure the filters are not clogged.

 

I'm gonna check that out and see what I find.

 

Thanks!

-Mark

[camatv]

if the bike has mudd all over it like in your pic its probably overheating..

[robert0762]

Sounds rich to me.

I am ported no lid k&n and a 4 mill at sea level pc pipes and I am at 45 pilots and 145 mains n68a needle middle clip

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[RagunCajun]

Isn't the OKO carbs a copy of PWK? If so check the float height! Mine gave me a problem like that. As said drill the tank cap, check pingle screen. You can also drill extra holes before the float needle seats if its like my OKO carbs.

[pittss1c]

I have PWK 28s on a 4 mil.

When doing a plug chop, if I go through all gears and hold it for a bit in the top gear for a few seconds, it will show lean 100% of the time. No matter how big my jets are (even way too rich)

I am guessing that means the bowls can run dry on long runs.