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Old 01-07-2009, 09:53 PM   #1 (permalink)
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1995 XCR 600 Won't Stay Running

Hello all - first post here, I found the site by trying to troubleshoot my sled and it seems as if there's a lot of good information but not the answer to my problems so far. Here goes.

My XCR will not start and stay running reliably. It ran just fine all last year, I rode it off the trailer and about 500 yards without a problem this year and it quit and hasn't been running since then. It will start and run temporarily if you use starting fluid or pull the plugs and pour a bit of premix into the cylinders but quickly dies. It will continue running at times if you spray a bit more starting fluid into the airbox but not always.

I have cleaned the carbs multiple times, they were spotless from my cleaning last year but I wanted to eliminate that right off the bat. The bowls were full of fuel. Needles and seats are good and I checked the drain ports in the block with almost nothing coming out of them. Carbs are very clean and in the same configuration as last year when it ran just fine. I have disconnected all lines to the fuel pump to check operation. All cylinders are receiving fuel from the pump, the tank to pump line flows just fine, and the impulse line draws a vacuum. Fuel is from last week so it isn't old and gummed up.

All of the cylinders get plenty of bright blue sparks when I pullstart. I have changed plugs several times, using BR9ES gapped to between .018 and.020". I have checked kill and ignition key switch both operationally (multimeter) and by unplugging the white/black wire from the cdi. I have checked the stator resistance at the plugs and all appears to be within spec (I had to use a 1996 shop manual and the wire colors were different but I was able to surmise from the resistances across the different wires that it was ok).

It has backfired a couple of times while trying starting fluid and blown the airbox filter off a couple of times (which I find funny for a 2 stroke). If I pour a bit of gas down the cylinders and start it up it runs just fine for a couple of seconds and sounds plenty strong. It dies as soon as the fuel is used up. I know it sounds like a fueling problem but I can't imagine how if the carbs are clean, pump is functioning properly, and the plugs get wet with fuel after repeated attempts at pullstarting.

Please help if you can, I'm thoroughly stumped. I have all the ingredients (air, fuel, spark) but cannot for the life of me figure this out. I'm wondering if it might be an erratic CDI unit, appears there is no way to check that out either with a multimeter.

Thanks in advance!
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Old 01-07-2009, 11:09 PM   #2 (permalink)
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Fuel pump and fuel filter good?
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Old 01-07-2009, 11:36 PM   #3 (permalink)
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check your intake boots for cracks, this can cause backfiring because the air/fuel mixture is thrown off. you should also do a compression test. In my opinion, Using starting fluid is usually not a good idea in small gasoline engines.. hopefully you haven't done any damage to the top end. then again it could just something stupid like carb. tuning. hope this helps and good luck.
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Old 01-08-2009, 05:08 AM   #4 (permalink)
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From now on use 2 stroke mix in a windex bottle. It is definitely a fuel problem if it only runs when you spray it. Remove the fuel lines from the carbs and pull it over. Does fuel come out of the lines?
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Old 01-08-2009, 01:57 PM   #5 (permalink)
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Fuel filter is a clear aftermarket filter, very clean and no sign of garbage in it. Pulled all fuel lines at the pump. Inlet line from tank flows freely. All 3 outlet lines spit fuel when I pull it over, impulse line draws a vacuum.

Carb boots are still pliable and don't appear to have any leaks in them.

Premix in a windex bottle isn't a bad idea, I'll give that a shot.

Is there any way that the cdi could give good spark while pulling over but drop off quickly when the engine actually starts?
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Old 01-14-2009, 12:11 AM   #6 (permalink)
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Problem solved...tentatively...until I get it slapped back together tomorrow. The how and why of it I don't understand, but I found what I believe to be the cause.

When I pulled the carbs for cleaning last time I was working out in a barn late in the night with a forced gas furnace nearby. I took the carbs off singularly and to drain them, walked outside where it was dark, and turned them upside down to drain the fuel out of the vent holes. Once drained, I took them back inside to clean them. I didn't want to be working with much fuel around because of my proximity to the furnace. I had cleaned them after a 250 mile drive with the sleds on the back of the trailer.

Tonight, I was running through more checks and noticed something funny. Just a little bit of rust on the bottom of the gas gauge unit. Funny...I cleaned that thoroughly last year and sitting in gas, it should have no opportunity to rust. I decided to check one of the float bowls out to look for evidence of water. Bingo...3/4 full of water. The lean backfires through the carbs suddenly makes sense. It won't run on water alone, needs a bit of fuel to go with that.

I drained all the bowls and the tank. I recovered ~1/2 a gallon from the tank - any ideas on how it all got in there? No issues with the fuel cap and the vent lines were clear - a mystery to me. Had I drained the carbs, while cleaning them, in a lighted area I would have probably noted water in the bowls although not to quite the extent that I saw today as it would have been well agitated from the car ride home.

Being that gas is lighter than water, the pickup in the bottom of the tank was collecting almost 100% water. It explains my hardly being able to get it started on starting fluid as the water was certainly causing problems with ignition.

Of course, I filled the tank up completely 2 weeks ago. I skimmed about 7 gallons of good gas off the top (little by little into the car) and the rest with all the water in it can be used to start bonfires. Will update when it is up and running again but I'm 99% sure I have it here.
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