Losing power at top end

Posts: 238

OK... a little background, I had to drain and clean my tank of crud that was plugging the filter and petcock last night, so while I had it off, I installed a new high output coil and NGK plug. Started great, idled a lot smoother. But when I took her for a spin... acceleration was a bit slower with a little bog off the start, then it climbed RPM's in mid-range really nicely and then completely flattened out at higher speeds with no power at all. Before this, there was still power at high speed and no sputtering at all on take-off.

Could this be a plugged jet? Valves? Bad coil connection? The more I think about the options the more confused I get. I thought if a jet was plugged, it would be sputtering through entire acceleration range. But only a slight sputter on take-off, and very noticeable drop in power at higher speed. Mid range is great. Suggestions?

Posts: 4286

check the connection of the coil, when you had the fuel valve off did you remove the filter and pick up from the inside?

could be more trash in the fuel valve, and make sure the fuel mline and vacumn lines are hooked up correctly

Posts: 238

Glad you mentioned that... for some reason, the filter and pick-up on the inside wouldn't budge. I could unscrew the petcock no problem, but the filter inside the tank was practically glued in place. So once the tank was cleaned out, I filled it with water to test the flow through that filter... and water came streaming out no problem at all, so I assumed there was no blockage. Completely dried out the tank again, reconnected everything, filled with gas and it started up great. Fuel filter filled up fine... all lines including fuel and vaccuum connected properly... but now there's just a slight hesitation at take-off and a total flat spot at top end.

The new coil I bought was too short, so I couldn't bolt it into position where the stock one was, but I double checked the connections and all was fine... started no problem and idled great, so again I assumed there was plenty of spark. Might have to try taking off the carb and giving it a thorough clean. Side note... is it a real pain to adjust the valves? It's never been done up to now, so I should probably get on it. Maybe that will make a difference.

Posts: 1684

Posts: 4286

no its not bad to do, Rick posted a good link,

Posts: 238

Wow... that's an awesome link. I LOVE PICTURES. You could explain it a dozen times and I'd still be confused.... this is a huge help. Thanks guys.

Posts: 24

good topic thanks

Posts: 1684

I recommend having a 9mm box end wrench like in the picture.
Nothing works as well.

Posts: 411

Try the factory coil again and give it a go. Process of elimination.

Posts: 238

The coil was part of the problem, but not all of it. Tightened up the connections to the CDI, it idled a ton better. But the biggest problem was the new MRP intake filter. I had it connected directly to the carb. After I added a short piece of pipe to get the airflow aiming right into the carb, it was a whole new beast. That 6" of pipe between the filter and carb made a world of difference. Changed pilot jet from 35 to 42, and it was even better. I still have just a "slight" hesitation and studder after it warms up a bit, but I'm still planning to adjust the valves one of these days. Overall though, my buggy is faster, climbs better, and sounds meaner then ever before.