I finished the 440 snowmachine Engine swap into my fl250, from a 78 polaris.

Anyways its been giving me power problems. Sometimes for like 30 seconds it will run great and be able to whip donuts on concrete, but most of the time it is very boggy with little power.

Carbs are clean, I made sure of that. its getting fat spark on both cylinders. Ideas?

compression is good 130-140 on both. Any ideas?


I am using a vacuum fuel pump and the snowmobile tank.

Jetting way off?

Clutching way off?

What fuel filter are you using? Original FL250? Aftermarket?
If your fuel filter is blocked,or an aftermarket too small,even partially,then it's not going to be allowing the new extra demand.Know what I mean?

Are you certain the fuel pump is working correctly? Diaphragm spent?

I will look at the pump closer tomorrow. The clutching is fine, even before it engages it struggles to get up to rpm.

The old pump was bolted to the Engine, I tore that down and just installed a brass barbed fitting into that, pressed and soldered. I then ran some vacuum line to the new external pump I have.

I will check for a vacuum leak, and also get some clear fuel line to route from the pump to carbs so I can see if they are getting enough.


Plugs don't look bad. Not oily.

Hate to say it but crank seals it what it sounds like, if you have torches take the acetaline and spray it around the clutch side seal if the
Engine revs up when its running you have issues.

propane?

I personally use brake cleaner to check for leaks
Works better than ace lane or propane

good I have both. I will try that in the morning. It looks like I am getting good fuel flow.

How hard to replace the seal?

Is the Engine from a '78 TX 440? Figure out the model and go web-hunting for a PDF shop manuel.

78 polaris cobra 440. I had the whole sled.

I just ran the Engine, and sprayed alot of brake cleaner behind the clutch, with NO noticeable rise in RPM. Also checked for leaks using BC around the carbs and found none.

I will pull the main jets and get a no off them.

Okay, it seems that just before it runs out of gas it starts to run great. this would indicate that it needs to be jetted leaner?

Could my fuel pump possible be flowing too much fuel to the carbs and flooding it out, until the tank is dry, and then they run good with just bowl-fuel?

The motor (( Internal Combustion Engine ? )) ran good in the sled before, at about the same air temp. I don't see why I would need to rejet it just because I swapped the motor (( Internal Combustion Engine ? )) into the oddy.



I get that "glimpse of power" and it is sooooo nice.

Do u have a pressure release on the fuel pump. Like a return line to the tank ?

Pressure release? No. There is a pulse inlet, a fuel inlet, and two fuel outlets. How would I make a pressure release?

I don't think it had one before. BTW this is an aftermarket snowmobile pump, not the one that came with it, if that makes a difference.

twin mikuni's btw. I do not remember seeing any sort of "pop-off" inside.

U got a photo of the set up?

What are u using for an air box set up?

This might help


http://www.scribd.com/doc/38755890/1972 ... sterRepair

twin uni pods

Take them off and run it on asfault so u don't suck dirt up and see if it runs better