AndyMX47

Ok, bought a used 98 superhawk a week ago. Started right up at the guys motorcycle shop, we ran it for a minute or so. No tag on it. Ran it around the parking lot for a minute or so - the guy told me it had sat for several months, but he had cleaned the carbs etc.

Bike has two brothers pipes, K&N filter, 48 pilot jets and 180 (I think - I'm old and its hard to read them) main jets.

I get it home (2 1/2 hour drive) start it up, starts immediately, runs pretty good - but with the occaisional pop from the exhaust.

Go to ride it around the block the next day, here's what happens:

Bike starts immediately, idles for a minute - I ride up the driveway, ANY throttle causes it to fall flat on its face - like the throttle is connected to the kill switch! Idles for another minute or so, dies, will not re-start.

I read several dozen threads on here, check the bike for PVLIR. Nope, its in the right place. I do note, however a couple small drips of fuel from the petcock vent tap on the bottom of the petcock. Order the petcock rebuild kit from Honda, replace it this weekend. Test petcock, works great, no more drip from the vent.

Start bike - starts immediately, seems to have less popping and farting at idle (idles at about 1400 rpm). Moment of glory - I fixed it! Bike will only accept a tiny amount of throttle, when opened very slowly. I'm Wrong. Runs for a couple minutes, then RPM begins to drop over about 20 seconds, from 1400 to 900, then it dies. As it's dieing, I realize it's going to stall - I fiddle with throttle - makes it worse. Pull the choke on - seeems (?) to keep it running better for a few seconds. Quickly open the fuel tank filler to test for a clogged tank vent - no hiss, then the bike dies anyway. Opened float bowl drain screws to see if there was fuel in the bowls - yes, got a nice little dribble of fuel out of each one.

Attempts to re-start result in the occasional semi-firing of a cylinder, but no way will it run. Let it sit for two hours - no re-start - a few semi-productive farts out of the pipes. I predict if I let it sit for a couple days, it will re-start.

Last night I removed the carbs, removed all the jets, sprayed with carb cleaner, blew out all the passageways with compressed air, cleaned and boiled the jets, and re-assembled. Hopefully I will have time to put the carbs back on the bike tonight and try again.

I bought a used R/R from an 08 ZX6, but didn't want to try that yet, as this sounds like it may be a fuel issue - I'm not seeing any signs of electrical R/R trouble - no loss of headlight, gauge lights, etc.

Any other thoughts about what would cause this? Pretty sure it's not ignition related, because my attempt to re-start after two hours should work.

The "mechanic" that had it previously used some type of sealant on the float bowls with a good bit of excess - my theory is that a tiny bit of that rubber crap may be inside a carburetor passage, get sucked into the carb, then starve the bike for fuel, causing the stall. BUT, why would both cylinders cut out, not just one? Why would it run for about the same amount of time, then die?

Shouldn't be a tuning thing - at least the bike should run poorly for a while before stalling.

I did think about loading it into my truck and driving the truck through the wall of his shop, but its about 2 1/2 hours away.

Frustrating - such a beautiful bike!

Jonar

This might sound strange, but the same thing happened with my Astrea 100. Yes I know there's no comparison between these two, but I probably had your "mechanics" soulmate, because he too used some kind of sealant on the float bowls, that most of it got sucked into the carb. Removing and blowing the carb passages solved my problem. But that's my experience with my 100cc moped, not the huge 996 VTR engine.

I just thought I'd mention it because the issues sound really similar. I too had the throttle issue, killing the engine, I too could only open the throttle slowly 1/3 of the way before the bike choked on itself.

Anyways, try remounting the clean carbs before trying anything else, hopefully that will work things out.

AndyMX47

Well, my instincts were rewardingly correct - after re-installing the carbs, with the sealant crap blown out of them, the bike now runs pretty darn well. Idles nice, has a slight flat spot at 3500 rpm when you accelerate (K&N filter, perhaps? - got a stock airfilter ordered and on the way) but other than that runs like a raped ape. This bike is amazing - torque like mad, sounds like a nascar engine. Happy! I swear I'm going to run it every day until my title comes in the mail, then ride the wheels off it.