Poor performance

[Drifter]

Back at her again.  340 drifter. Sled wont idle and bogs through entire rpm range except full throttle where it doesn't want to run at all.  I keep thinking its carb related because when I run it on a stand and pinch off the fuel line after about 20 seconds it takes off and runs well.  This is why I changed the needle and seat.  That and the fuel line would go empty and it always stunk like gas.  I never changed the float level, it looks parallel like it should be.  I don't know, I'm stumped.  Kinda ruled out timing again.

Wanna come for diner Lloyd my wife makes a decent roast beast!

[gixxer6]

Have you checked that the choke is adjusted properly?  It sounds like it might be stuck on...

[Drifter]

Yes I have had the choke plunger out and cleaned it and there is a little slack in the cable.  Even starting cold I just use 1 or 2 primes and that's all it needs. No choke to start.  I thought for sure it was the needle and seat.  The floats float in brake cleaner so I don't suspect a leak.  Seems rich all throttle positions so I think that is all that's common.  I have also had the air box apart-clean, no mice, also flushed the muffler both ways, no mice.  I can't imagine floats would get out of adjustment from sitting 25 years in a barn. 

Good thinking on the choke, maybe I should look closer, is there a seal or something that could deteriorate causing extra fuel always?

[gixxer6]

Yes, the bottom of the choke plunger is rubber.  I have seen the rubber crack and leak...

Other common things that cause excessive rich conditions are:  a bad primer, make sure that there isn't fuel flowing through the primer and into the engine while its running. 

a bad fuel pump, make sure the fuel pump isn't leaking fuel into the crankcase through the impluse line.  You shouldn't ever be able to see fuel in the impulse line...

[Drifter]

On the bottom of the choke plunger the rubber seal has the indentation on it but no cracks.  Could i pull that rubber seal out and turn it upside down for a fresh surface?Could I plug that orfice half way up the intake side to rule that out? 
I have tried a new primer and put the old one back on but that was before changing coils- could have been double trouble there.  I will try new primer back on.

And yes I do see fuel in the impulse line but comes from crankcase not fuel pump side- usually only runs out about 2 inches

[gixxer6]

I have used plungers with dimples without issue. 

You can disconnect the primer and plug the line going to the engine to test.  However, if you have fuel in your impulse line I would suspect the fuel pump.  If it hasn't been rebuilt its time!  A 30+ year old fuel pump is suspect for sure!   

[Drifter]

Alright super!  I will try the fuel pump.  I opened it and cleaned it and put it back together and when fuel line was going empty I put newspaper under it and sure enough there was a small leak.  Tightened the screws and leak externally went away. Maybe leaking through diaphragm.  I think I'm getting close

Thanks for the help!

[Lloyd (ljm)]

 I think Gixxer6 is on to the problem.  Either rebuild that pump or put a new pump on there. Your problem might be solved.

 If there is gas in the impulse line the pump is leaking

 Lloyd

[Drifter]

Got the fuel pump kit on order.  There is and always been fuel in the impulse line but I thought any rich condition would do that.  Thanks guys.  March break is looking a lot better already.

[gavinvader]

I ordered a rebuild kit for my pump and the gaskets and diaphragms are slightly different on a factory pump compared to new style pumps

[Drifter]

Did the kit work?

I'm at work thinking if I can prove this before I get the parts. Here's what I came up with
1 connect fuel in and out line together
2 remove impulse line an block it at fuel pump
3 make sure gas cap on tight
4 use air compressor with reg set about 5 psi , blow air into tank vent to push fuel to carb
5 see if it runs better

I used air pressure to empty the tank quicker when I had to seal the tank fitting.

Part should be here Sunday.

[Lloyd (ljm)]

 You will have to block the impulse line at the motor as well or you will have a lean condition.

 I'm not sure there is much difference in the kits for the Drifter pumps. Invader and Intruder the kits need some tweaking, but the Drifter pumps are a different beast.

[Drifter]

Whoo-hoo! I think we got it.  My buddy dropped the rebuild kit off today instead of tomorrow.  Sled idles well and the oil smoke is no where near as thick in the garage!  Runs good on the stand but unable to take a run in he neighbourhood.  Did still notice a little fuel in the impulse line though but not as much. But this is definitely the best it's ever ran! 

[Drifter]

Tonite I was trying to figure out why still not bang on and easy to flood.  I thought to check the idle air screw and found it all the way in.  With it still idling I turned it out one and a half turns,  idled better, as soon as I took the screwdriver off I watched the screw vibrate rite back in!  I put some T tape on it to hold it.  Anyone ever have this before?  Is it common?  Is there a better fix?

[gixxer6]

There should be a spring under the screw.  This keeps it from turning.