Medical advise

[Wayne S]

Doctors here are the symtoms

• runs ok for awhile
• runs a little faster
• stalls
• no fuel visible in filter
• choke the mess out of her and she pulls gas up enough to see in filter
• finally starts
• runs ok for awhile
• runs a little faster
• stalls
• no fuel visible in filter

Two options I can think of, trash in tank starving out the engine
Just enough vac into the fuel pump to allow it to run until hard throttle

New fuel lines and vac line to the engine (can the vac line be too long?) The parts book calls for 24" from tank to filter, 15" from filter to pump and 10" from pump to carb, but not jack about the vac line.

There is not a part number on the pump, so I can't tell what the flow is suppose to be.

 

[banjo]

The vac line needs to be stiff so as not to expand and contract with the pos. and neg pressure . Are the crank seals ok? you should have about 4 pounds pressure then 4 pounds vacuum on impulse line to operate fuel pump. hope this helps . Dave

 

[minibikedude]

Also check to make sure there is a check valve inside the fuel tank for the pick up line going to the fuel pump and that it is laying flat on the bottom of the tank, Had this happen on a snowmobile before. Check valve was bad.

 

[Fat Boy]

Sounds like the tank vent is plugged :thumbsup:

 

[steven Durham]

The Rupp Centaur has a very small fuel pick-up hose down inside the tank and has a micro screen filter on the end of that flexible tube. Trash in the tank could be blocking that screen
Steve

 

[buckeye]

Oh man, thought I could help. :laugh:

 

[YOOP]

maybe try just pumping out of a gas can and see what happens.

 

[wjustice]

Ok a couple of things. Clean and put a diaphragm kit in the pump. Dont mess with it, the kits aren't expensive. Check for flow out of the tank. The pulse line from the engine should be as short as possible and stiff for better pulse. The mikuni carb choke isnt a choke as some think. It is a separate enrichment circuit. Using it doesnt help to draw fuel. If fuel isnt there then using it does very little. Using a small tank gravity feeding into the carb would be a good test.

 

[minibikedude]

The Rupp Centaur has a very small fuel pick-up hose down inside the tank and has a micro screen filter on the end of that flexible tube. Trash in the tank could be blocking that screen
Steve

The Rupp snowmobiles use that same screen on the pickup tube but there is also a check valve built in to it to keep the fuel from running back into the tank while trying to start the engine and while engine is running.
You can get new ones from any snowmobile site also Manufacture supply has them

 

[Wayne S]

Multitude of sins :doah:
I thought there was a vent in the cap, so I tapped over a hole on the filler neck to keep the dirt dobbers out.
There wasn't a check valve listed in the parts book, but the "weight" that was at the bottom of the line was a filter and yep, it was toast.
The non-flexible flexible line was actually cracked at the top, so it was drawing in air there.
And I picked up some rigid 1/4" line for the pump.

Suffice it to say, I turned the motor over and fuel hit the filter pretty quick.

I will order a kit for the pump and fix that as well

Thanks for the replies...you gents did good :thumbsup:

 

[wjustice]

Great now if I can get this tri-sport engine running right I'd be as happy as you, grrrr