I've been chasing a rev limiting fuel problem, it would run up to about 5500 rpm and level off like hitting a rev limiter. First treatment with Seafoam cleared it up just for that tankful, then it was back. Only took about ten miles to clear it up that time.
So today I had about 1.5 gal in the tank and I measured out enough Seafoam for a tankful. Spilled a good bit trying to pour out of the measuring cup, so I just took the bottle and tried to dump about an ounce that way. I may have ended up with 4-5 ounces of Seafoam in 1 to 1.5 gallons of gas. The directions call for 1oz per gallon.
Engine already warm, with the 1.5 gal gas rich on Seafoam, I turn the petcock off and started her up. Held it at fast idle until it started to falter, running out of gas, then I started opening the throttle. I eventually pulled the choke full on too, and ended with it stalling at full throttle and about 6500 rpm.
Next, I opened the petcock and started the engine with the SF rich gas and let the carbs fill up. Squall line of storms rolled through and the ride was postponed about 4 hours, so it sat with the rich mix in the carbs for that period.
Finally got to take off, I filled up with gas and about ten miles out I opened her up. She kept right on revving, like she's supposed to. Great! I thought. Another ten miles and it was back to rev limiting. However, near the end of the 40 mile ride, the problem had cleared up again and I saw 10-11,000 rpm. Full power is also restored, I hadn't really noticed how far it was down on power until it all came roaring back, I just hadn't been cranking on it so it seemed fine for just putting around and quick jets light to light, short shifting.
It acts like it's cured, time will tell, but just a little riding with Seafoam did the trick, twice now. There must be a good bit of hard gunk in those carbs that's dissolving and coming out of there a little at a time. When it's Seafoamed, it can digest the crap, plain gas and it clogs again. Need to pull those carbs, dangit.
It was willing to run as hard as I asked it to when I came back home, have to see what it does next time out, or on the next tank of gas. I definitely don't need to see 11000 rpm, that's just a tool i used to see if it would bog at all. It probably would have pegged the tach if I let it.