Sputtering 250

[rdrnr]

Hello everyone.  James here who is loving his 74 late model 250 PENTON.  Here is my problem;it sputters from mid to full throttle.   The story is this-it ran great, fast, and hard for about thirty laps (five at a time) then it started sputtering; so I thought the gas was low so I went to reserve.  There was still no change I had almost finished the lap and it tried to die so I killed it.  Then I checked the plug. It looked great but I changed it anyway.  No change. I thought the motoplat might be wet because of the puddles; checked it and dried it, no change. Then I thought maybe the carburator was dirty so I checked and cleaned the bowl (was clean).  No change.[V]   Then I put in a new fuel filter.  No change.  Now I am out of ideas.[?]  Any help from the experts would be great.[8D]  Thanks, James in MO.

[tomale]

Hi James, and welcome.

I had a few ideas and I thought I would pass them along.
Is is possible that you got water in the gas? It does not have to be exposed to the elements to have water in the tank and you did say that you had gone through some puddles. It is not a good ideas to keep gas for very long. It will draw mosture in the tank.
I worked in a chainsaw shop for awile and if a saw came in and was not running right we alway checked the gas first. Try some fresh gas.
HOw about the sparkplug cap is it wet and is it in good shape?
What about the wires under the tank. I had a kill switch wire that was giving me fits for awile. It is more than likely that it is something simple that you have over looked... It is easy to do. Hopes this helps

Thom Green,I own and ride a 76 250 MC5 MX which I bought new.

[Rocket]

James
Does it run badly only after you have run it for awhile and the motor is hot?  If it does, more than likely your motoplat ignition is starting to fail.  If it runs good cold and poorly once it gets hot, ignition failure is happening.
Rocket

[hrbay]

hi james, might retighten or relocate the ground connection(s) and sand the metal to assure good electrical contact, plus all the previous.... GC

GC

[tlanders]

James,

Come over tonight and pick up a spare motoplat and try it out. Great to see you on the POG site!!! Sounds like you guys had a great time in Thayer, I wish I could have been there.

Teddy

[Big Mac]

Hey James,

Is this my old '74 250 giving you fits? Sorry to hear it, the thing always ran like a bat out of hell for me. Keeping the front end on the ground was the biggest problem. In fact, I wish I had the jetting and timing details down so I could get my '73 to run as good.
Hope it's simple like a plugged jet, or loose wire. Or you can get a reasonably priced used Motoplat to replace it if the ignition is going.

Ride on! Mac in Portland

[rdrnr]

Everyone,  thanks for the great advice.  Started with the gas in the tank.  While it was off looked at the wires,  turned out to be a loose wire.  Made sure everything was tight, put it back together,  tried it and up came the front tire again.  Once again a BIG thanks to everyone.  James