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Old 02-20-2012, 12:05 PM   #1
Cory Lekopoy
Junior Member
Join Date: Dec 2008
Location: Manitoba
Posts: 4
Default 74 340 tnt

Hello All,
I have a 74 TNT that I picked up about a month ago. Really good shape and ran good when I bought it. When I got home I was going to go for a ride and found out I was running on one cylinder and went nowhere with a load on. Decided to give it a new belt, plugs. After that it backfired bad out the carb, exhaust and up the pulse line(?) from the crankcase. Discovered poor spark on the mag side. Installed a new coil. Cleaned points. No more backfire but now won't stay running after it starts warming up(30 sec to a minute, after cold start, fires but won't run) Have set the Tilly carb to spec many times. Any suggestions would be very apreciated!
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Old 02-20-2012, 09:00 PM   #2
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yamacatowner's Avatar
Join Date: Dec 2011
Location: st. croix county WI
Mileage: 2300
Primary Sled: 1994 v-max 600/ 1990 artic cat cougar 500
Where I sled: washburn county WI
Posts: 7

When you cleaned your points you may have changed the gap. When things get warm they expand and may be out of spec now. When it is cold and running is the choke on or off, may be starving for fuel clean the carbs and reset idle screw and float level
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Old 02-24-2012, 05:28 PM   #3
Join Date: Jan 2006
Location: Muskoka
Mileage: 20 000+ km
Primary Sled: mmsrx 700
Where I sled: Muskoka and where ever else
Posts: 68

I had 1 of those. My wireing harness hit the exhaust pipe and melted, the electrical system did not like that. Check it for previous damage. I went through coils and I think it may be because the coils are mounted on the cooling shroud and not enough air gets behind them to cool them. When the coils are cold it will run and when they heat up they stop working. The book I have says your point gap is 0.35 - 0.45 mm or 0.014 - 0.018 inch, The points start to open BTDC 2.8 - 3.3 mm or 0.110 - 0.130 inch. The spark plug is BOSCH W260T1 the gap is 0.5 mm or 0.020 inch. You did not ask for this but yamacatowner could be right.
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