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My K has been running like a champ since I got it last July. After a long day at work yesterday, I got in and started it. I gave it a couple of minutes to warm up. But something was wrong. It idled smooth, as it always has. But when I feathered the throttle there was a noticable sputter. Once it came back down to idle again, you couldn't tell that anything was wrong.
The sputter happened all the way through the power band. Needing to get home, I started driving and there was a large loss in power.
After letting it sit all night the same thing happen this morning. So I decided not to drive it today

Now, I presume that this is a carb problem. But then again I don't know much about carbs. Can anyone enlighten me a little. I would like to attack this problem tomorrow. Any ideas or pointers would be greatly appreciated.

Darin

With Pinzies, I like to look at the obvious little stuff first before assuming that it's a carb overhaul. Did you check the plugs, filters, wire connections, etc.. already? How about adjusting the timing? Bad batch of gas?

When mine starts sputtering / backfiring etc. it's usually a sign of tune up time

This past weekend, I changed oil, spark plugs and cleaned K&N.

Might be valve adjustment time?

(This past weekend, I changed oil, spark plugs and cleaned K&N.) Did it run ok before that? if so start there and check thoes items. Are the plugs made in India? check the wires to the solenoids on the carbs (possibly distrubed on putting the cover back on). With the key on and engine not running remove and put back on each solenoid connection and listen for a click. Then with the engine running remove each solenoid wire on at a time and listen for that cylinder to run out of fuel and change the engine rpm.

Next go to the distributer and remove spark plug wires one at a time with the engine running and listen for the change the engine makes when each plug wire is removed. The one that make the least amount of change is the cylinder to start checking. Next Pull that spark plug and check it. Sooty black means plug not firing well or carb is WAY to rich (flooding) that cylinder. If it looks like it did going in then no fuel or absolutely no spark. Start there to begin to find the problem.

If all you did was the Oil, Plugs and Filter thats odd. The Oil change shouldn't change anything. It shouldn't be the plugs if it is idling smooth. I would bypass the filter by removing the boot between the filter can and the air plenum, you may have restricted the airflow with to much oil on the filter. Check the inside of that boot for oil residue. Is it getting hot during the day there? more humid?

Miles

As has already been mentioned, plugs. Whenever I get in my Pinz and it sputters a bit its most always a sign that its time to take out each spark plug and give a good wire brushing to clean them off. 99.9% of the time its good for another 9 months to a year after that until it sputters again and I repeat that procedure.

If you by chance overfilled the crank case any excess oil will come up from the pressure and go through the vent tube right in to foul spark plug number one. Thats been my experience anyway.

Steve

Wow, this is all great info. I am just about to dive in, as soon as I find out what the problem is I'll let you know.

Steve: Thanks for the help. Everytime I change the spark plugs, the #1 cylinder plug has usually got a little oil build up on it. So maybe I did overfill the crank case.

Miles: I don't think it is getting more humid, but we are warming up (70's consisently).

John: Thanks for the step-by-step. That helps me alot.

I'll let you know what I find!!

Alright so here is what I've got so far:

I put the plugs in last week. All of them are very black and sooty. There is equal change in rpm when I disconnect the wires at the dist. I took off the air filter and plenum. When I turn the engine on, and feather the gas I hear a "gasp" out of the rear carb.

So, is the rear carb running rich and turning all of the plugs black. If so, where do I go from here.

Sorry for the ignorance here, but I have to learn so how

Thanks,
Darin

Here are some web sites for plug condition and cause:

http://www.verrill.com/moto/sellingguid ... rchart.htm

http://www.centuryperformance.com/spark2.asp click pics to enlarge

http://www.off-road.com/dirtbike/tech/2002sparkplug/ sparkplug 101

Miles