4-mil cutting out

[Master of Faster]

Took my 4-mil, trail ported stock cylinder motor to Silver Lake this weekend for the first time and I was having trouble with it cutting out about 3/4 the way down the drag strip or when making a long pull up the hill.

 

I jetted it all over the place but the problem still persisted. I'm running the 30mm keihin knockoffs with 160 mains currently, bike is running great and will scream through the first few gears but at about 450-500 ft it falls on its face at WOT, sometimes I'll get a little pop.

 

Do you think its possible that its pulling the float bowls dry? I had the petcock out and cleaned it up but I'm still running the stock one. I didn't think I would be pulling enough fuel to warrant a pingel but maybe I am?

 

Here's a horrible pic of the last plug chop I did, I know its on the rich side not so much that it would be causing a problem I don't think, anyways I was all the way down to 152 mains in the dunes and the problem was still there, just took longer to happen and plugs looked lean.

 

Any suggestions on how to get more fuel to the carbs or if you think there is another problem please let me know, I hate to spend the money on a pingel right now if I don't need it, thanks.

 

[blowit]

Took my 4-mil, trail ported stock cylinder motor to Silver Lake this weekend for the first time and I was having trouble with it cutting out about 3/4 the way down the drag strip or when making a long pull up the hill.

 

I jetted it all over the place but the problem still persisted. I'm running the 30mm keihin knockoffs with 160 mains currently, bike is running great and will scream through the first few gears but at about 450-500 ft it falls on its face at WOT, sometimes I'll get a little pop.

 

Do you think its possible that its pulling the float bowls dry? I had the petcock out and cleaned it up but I'm still running the stock one. I didn't think I would be pulling enough fuel to warrant a pingel but maybe I am?

 

Here's a horrible pic of the last plug chop I did, I know its on the rich side not so much that it would be causing a problem I don't think, anyways I was all the way down to 152 mains in the dunes and the problem was still there, just took longer to happen and plugs looked lean.

 

Any suggestions on how to get more fuel to the carbs or if you think there is another problem please let me know, I hate to spend the money on a pingel right now if I don't need it, thanks.

 

 

 

 

There is a plug in that pic?? Drop your plug gap to about .020 If you need more fuel, you can trash the stock fuel filter in the tank, drill the petcock, and install a high flow filter. That should be fine for your setup.

 

Brandon

Edited June 20, 2007 by blowit

[Master of Faster]

Thanks for the suggestions, I'll give it a shot tomorrow.

 

I know the pic isn't worth much, Banshees, snowmobiles and big trucks don't leave much in the budget for a good digital camera, lol. :thumbsup:

[burleybanshee]

Master of Faster, I had the exact same problem two weekends ago at pismo. I have 4mil stock ported jugs 30mm oko, and it was falling on its face 3/4 way down track, no fuel. My petcock was fine. I talked to cpw and they said the jets should not out run the bowls capacity, but they are. the floats are set correctly and I played with jets sizes up and down just like you did. I have a duel line pingel and 35pwk's coming from Jeff at FAST. The 30's are to small for a 4mil ported bike. Go for low end tech. riding, not for wide open dragging. I love the 30's execpt for running the bowls dry. They have to small of an fuel inlet line and not much area inside the bowl cup to hold fuel.

[Master of Faster]

Burley, thanks for the input. Unfortunately funds aren't going to allow for another carb change right now, so I'll figure out some way to keep enough fuel in there. Not drag racing is deffinitely not an option :biggrin:

[badassbanshee479]

my buddys dune ported 350 was breaking up in the higher rpms and it ended up being the flywheel!

Just something else to consider.

I dont think you are running out of fuel but if you are you could always put a fuel pump on it.

Get one off of a twin cylinder snowmobile and plum her in.

Also make sure your floats are set right, check to make sure the needle and seats are clean and not sticky.

You could also gut the stock gas cap, drill the vent line hole bigger, and de screen the stock fuel valve and drill the hole in that bigger.

Make sure you are using big enough fuel line, and that the tee in the line is not restrictive.

Dont count out electrical components also. A bad stator or coil can cause a high rpm miss also!

[J-Madd]

My 4 mil Cub does the same thing, with 38 or 39 mm PWKs. I can run 300 ft fine, but when I get to about 450 ft, it cuts out. I'm gonna get some billet bowls for mine. I already have the dual pingel and gutted cap. Bigger bowls may help you as well, after you try the gutted cap, pingel, etc.

[Master of Faster]

For anyone interested, heres what I ended up doing to solve my problem. I was able to make 6 back to back 500ft pulls with it without it running out so it deffinitely helped.

 

The boss where the needle rides in has two tiny port holes to let fuel flow through, I enlarged them to 3/32" which is about twice as large as they were originally.

 

Here's a couple pics...

 

Before

 

After

[BigRed350x]

Spiffy mod.