1978 340 Liquifire Intermittent Running Issue

[Wilson Perf.]

Hello,

I am new to the board and have an issue with our families '78 340 Liquifire.

We ran the sled for the first time in two years two weeks ago. It had been properly winterized and fired on the 4th pull. The sled ran perfect for a week with others riding it, then I stepped foot on it and it is now cursed.

Started out last Sunday afternoon pulling the kids on the tube. 15-minutes into it the water pump belt goes. 2 hours later it is running again with a new belt. By now it's dark so I switch on the light. Run around the yard a few times and hook onto the tube again to have some more fun...it dies. I thought well it's not completely warm...flip on the choke, pulled it, it fires right up. Away we go around the field having so much fun...I stop to see how my son is freezing, I mean doing, and bam it dies. Now, this time it refuses to start at all. We tow it back to the shop and try some diagnosing. Immediately we find that the carbs are way out of sync. So that is corrected. Next we check for spark, plenty of nice spark on both plugs. Being a two-stroke guy I'm immediately thinking the plugs may be fouled so we blasted them off and it fired right up. I let it idle for 30-seconds or so and though what if it shuts off will it start again? NO it would not restart.

Well we parked it at that point. I told my brother to get a new set of B9ES plugs just to be safe.

....a week later.

Brother calls and said he popped in the new plugs, pulled it twice and it fired right up. Let it warm up and then buzzed around the field like a striped ape, pulled back up to the shop tried to shut it off with the handlebar kill and nothing, it wouldn't shut off. After two or three pokes on the kill switch it dies. He then tries starting it again and it won't start. Now at this point I know all you all are thinking it's the switch, it's the switch. Well hold on. He then pulls the plugs out and checks for spark, good spark. Still won't run. He then takes a cig lighter and burns off the wetness on the plugs, puts them back in and it fires right up.

So with that that is where we are weird intermittent running. It is likely wiring of ground or something, I would think but given it does have good spark it's just messed up.

Some other background....

- It has good compression 120+PSI
- Running 40:1 ratio fuel/oil
- The key switch is always in the off position and has been for 20 years but it always runs anyway.

Many thanks in advance, but please hurry we're supposed to be getting 10-14" of new snow starting tonight through Wednesday and it would be cool to play. We don't get that kind of snow much here in Missouri.

Regards,
Bill

[JDT]

Bill sounds like you have a couple of things to fix and should put in for some quality garage time.

The ignition switch being off and still have spark.... You either have a defective switch with sometimes makes contact and kills the motor or the switch is unplugged under the dash.
You know the kill switch is bad so replace that.

Flooding and wet plugs... Check the choke plungers and cables. If one or both are sticking open that would explain a lot. A small amount of free play, 1/8", in the cables is needed. A through carb cleaning and resetting would be a good idea. Confirm that the jets are the same in both carbs.

I know this is not what you wanted to hear with snow flying but you must do what you must do.

[harleysportster]

I would like to add that the fuel pump could have a hole in the diaphram causing excessive fuel to enter the crankcase.

[JDT]

Sounds like one more thing to check Bill.

Thanks Pat.

[Wilson Perf.]

Thank you all for the posts. Things I figured would be but you all know more about these old sleds than me.

I'll do some work this weekend and see where it gets me.

This is the first site I've contacted...where can I get a replacement OEM style kill switch?

Regards,
Bill Wilson

[JDT]

ShadeTree Motosports in Big Lake MN may still have them.
They are still out there but no longer made.

[lwb140]

i spent the day getting some of our riders running ,i got 8 sleds out and on some level ready for the incoming snow ,school is already cancelled for tomarrow ,anyway it amazes me what all can does happen to these sleds sitting in the shed , completely plugged sealed over fuel filters pilot jets plugged up on sleds that ran 2 weeks ago etc anyway assume nothing is OK or" well last winter it was ok ", actually it seems to me like .there is more goo floating around in the carbs/fuel systems this winter than last , my guess the solvent [gas] got crap loosened up and moving wade