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So a friend just purchased a '99 220. It stumbles from the low to mid range. When it reaches the top end it revs out nice and clean. The idle screw has no affect on engine rpm.

Here's what we've done so far...

1. New piston and ring (Wiesco)
2. cleaned Kips
3. cleaned carb...jetted at 145/42 switched to a 40 pilot...no change
4. new jet block gasket
5. New reeds
6. Timing mark is in slightly above the middle line

Everything seems to point to the carb....so we pulled a carb off of a 200, installed it on the 220, and it was the same. The idle screw still has no affect on engine rpm and it stumbles through the rpm range until it gets to the top end and clears out.

What am I missing?

Forgot to include the normal stuff...

new plug
clean air filter
silencer repacked
no obstructions in the pipe

Check for chipped cracked or reeds not laying flat first they sure will cause that

oops sorry you did that already

what position is the needle in should be in 2 or 3 with the stock slide

a stator could be the culprit also as when rpm's go so does voltage just the stator winding is about 35 dollars look and listen in darkness for sparks jumping could also just be the coil all are low cost

We are 3 down on the needle. But again another carb didn't fix the issue. Inspected the coil but didn't put a meter on it.

I also have had spark plug caps go bad as they have a resistor in them that can go bad

looking into the spark plug cap today as well as testing the ignition circuitry.

does anyone know the symptoms of a bad crank seal? I would think...magneto side it would run lean...water pump side it would run rich. It's definitely on the rich side (really rich) but haven't rode it enough to see if its burning any oil.

magneto side would be lean. water pump side would suck trans oil. get it out & run it. make sure the carb has stock jetting for a starting place.

make sure your floats are correctly adjusted.

float is within spec. Waiting to here back about the trans oil level after a 35-40 mile ride today. Didn't get around to checking the ignition circuitry today, but that will be done this week.

100% certain the KIPS is reassembled properly?

I've put plenty of them together through the years and haven't messed one up yet. There's always a first I guess. Rode it 35 miles or so and the oil level stayed.

Also, it was running this way before the new top end.

Kip's appears to function correctly with the large screw in plug removed. Sight window or whatever you call it.

OK, didn't know you were mechanicing on it. :-)

Thinking about tearing into the KIPS just to make sure... anybody ever done it with the top end on the bike? I've always had it on the bench during assembly. Also, think that head gasket can be reused? It's a week old. Not sure if it's a one squeeze and done type of gasket.

I'd start swapping the coil before taking that back apart.

One squeeze & done for me. I second the coil swapping.

IIWM a leak down test would have been first, but should still be done.