Mod sled running out of fuel

[nighthawk285]

Well, I hope this is a good place to start posting, I'll start here because the motor is out of a 98. I have an odd fuel problem, and electrical.....to start with I'll let you know what I'm working with. I have an 03 Polaris ProX 600 Chassis, with a 98 700 RMK engine in it with some mod work done (pipes, reeds, powerpacks, boost bottle, new top end and crank last year).....here's whats going on.....first the fuel

Sled runs like a champ, great throttle response, good idle, burning nice and clean, BUT......at extended trail ride intervals or a couple minutes of WOT, the motor bogs down and leans out (7800 RPM to around 5500).....it runs out of gas.....and if I give it about 30 seconds of idle time for the fuel to catch back up and we're back and off to the races. I've adjusted float height and the jetting is on the money, could it be the fuel pump going out? I've had this problem consistently for the past two years and still haven't been able to figure it out....any ideas?

 

[Jay]

Venting? or lack of.

 

[smashed600]

Ill just throw out, fuel filter?

 

[nighthawk285]

Yeah, tried that.....fuel filter--new vent lines--new

I found out its running out of fuel from the fuel filter, its a clear see through one, so when it would bog down and lose power, I stopped and opened the hood and sure enough, filter'd be empty, but after a couple seconds at idle, it'd be filled back up. Could it be the diaphragms wearing out?

 

[Jay]

I have seen similar problems with a kink in the fuel line, had a tank out one time and didn't realize when I put it back in I had a slight kink in the line from the pump to the tank, did exactly what you are describing.

 

[brushfit]

You may be suprised at how many times I have found the line inside the tank rotted off....9/16 pull the line and see...sometimes just the weighted in tank filter has come off....It has become an important part off routine service for me

 

[smashed600]

Ive never really torn apart the fuel pump but from what a friend told me when the diaphrams go out they actually flood the engine because they don't close. Rebuild kits are cheap though, double checking all hoses as stated should be a pretty quick cheap easy job too. Good luck

 

[nighthawk285]

ill give everything a good going through and see if I can find a problem...

 

[AdrenalineAddict]

I had a similar problem with an 01 800. My solution was to open my fuel screws about a half turn and the issue went away.

 

[nighthawk285]

yeah, that'd work except I'm still running the 1998 Keihins that came on the motor....so no fuel screw.....Speaking of, could this be from the famous Keihin float pin problem that I've read about? Something about how the pins will wallow out the towers and cause problems? If I take off the float bowl and turn the carbs on their sides the pins fall out, I thought this was normal but now I'm reading thats not good correct?

 

[Jay]

I think you found your problem. It is impossible to "adjust" your floats when that pin is pooched. I have fixed that problem by stuffing the worn out holes with JB weld and then redrilling the pin holes. It sounds kinda mickey mouse but it has worked fine for years now. There are a couple of guys selling keihns on here right now. Or throw some 40mm rack mikunis on there.

 

[nighthawk285]

Wow, amazing that they could make THAT BIG of a difference. Ok, so once I take care of the float pin, what are the floats supposed to be set at for this? 98 RMK 700. I think its around 15mm from the gasket surface to the very top of the float correct?

 

[nighthawk285]

If anyone else has a problem like this.....come to find out those float pins were the problem, got them fixed up and set the floats to 16mm, and she pulls hard now with no fuel problems...just FYI for anyone with future problems

 

[X2Freeride]

Id bet money on the float pins being the problem.


****Edit*** Just saw your last post.

 

[bolty16]

Just had the same kind of thing happen to my XLT a couple weeks ago and I got pissed. And started tearing and cleaning carbs and everything I could think of and read this post and looked in my tank and there was the stinkin gas intake line laying in the bottom rotted. Now finding clear gas line is being a pain in my butt.

 

[brushfit]

Just had the same kind of thing happen to my XLT a couple weeks ago and I got pissed. And started tearing and cleaning carbs and everything I could think of and read this post and looked in my tank and there was the stinkin gas intake line laying in the bottom rotted. Now finding clear gas line is being a pain in my butt.

surprised at how often this is overlooked....sometimes you can use a chunk of the vent-line in a pinch, but it is important to have the intank filter because it is weighted to hold the line down in the tank....but it is difficult to find the soft line that was oem,so you have to kind of roll the line to place the natural curve of line down to tank bottom or it will point up and still not pick up fuel unless full tank..

 

[bolty16]

what I did was tightened the fuel petcock in the tank and made a has mark on it with a marker to note the top ( or side up) to that when I put the intake tubing on in curved towards the bottom of the tank.

AFTER i put the tube on and the weight wasnt enough to bend it to the bottom of the tank.