Help HELP!!! Bike stumbles hard on medium throttle...ALL FIXED, THANKS!!

[valvesprung]

Well I bought it a week ago, rode it for 5+ miles on a test ride, rode it one other time for 5+ miles, no big issues. When I went to ride last night a few blocks from home and it started stumbling hard. To the point that I didn't have enough torque to get rolling without slipping the clutch HARD.

Pushed it home found the thread a few posts down about cleaning the fuel tank vent. I found that the tank vent line was in fact quite plugged with grime. I blew everything out from the hole in the gas spout opening until I had a good flow through the tube. I tossed it back together went for a ride, made it a few blocks and it started again. I popped the gas cap and no help there. Pushed it back, pulled it apart again, recleaned and rerouted the line and tried again...same results, a few blocks away and it starts stumbling...

Where do I go next guys? I've had this bike a week, the sun is about to come out and I need to ride!!!

[Paulcet]

If the bike sat for several months with fuel in it, there may be some clogged passages in the carbs, or stale fuel.  Might need to check the valve clearances, especially if you don't know whether they have ever been checked.

There is the possibility of a heat related electrical problem.  Slim though.

[tt_four]

Did you try riding it on PRI? Sounds like the gas flow is still getting cut somewhere.  

Otherwise something could've been floating around in the carbs and finally clogged something.

The sun thing definitely sucks. I pulled my bike completely apart Friday night because it was supposed to rain all weekend. This morning I check the weather, and it says it's gonna be beautiful all day. What a scam. I definitely won't have it together to ride until tomorrow or Tuesday.

[valvesprung]

Yes, I've tried all three fuel settings with no change. Prime was where I started after the first issue. hoping that would clear it up.

Now that I think about it I DID have this issue on the test ride, but thought the fuel was just off. I turned it all the way up to prime (before I knew what it was, and I did it blind while I was riding) and it settled out. I'm not having the same luck any more though. Maybe I'll start with fresh gas and see where that gets me...

[mister]

How much gas is in it? Did you fill it up after purchase? (just looking in the tank won't tell you cause the tank's deceptive.

Michael

[bombjack]

Is it running on one cylinder only?
Check your spark plugs. If one plug is carb fouled then you have prolly have an electrical problem.
I've just had the same problem. One spark plug wire and the HT coil had poor connection.

[valvesprung]

It's has gas, just poured the old crap out and put fresh gas in, it was pretty discolored and smelly. I have flow through the tank petcock, but am going to verify through the frame petcock as it really seems like it's being starved.

The new gas alone didn't do it, and I could only get it to run choked for a couple minutes (no where near warm) before it starved out and died again.

I pulled apart the frame petcock and it's clean. Next I'll verify proper flow. After that I'll be pulling the carbs to be cleaned properly. The carb boots are looking pretty cracked too, so maybe replace them too?

[Paulcet]

If the boots between carb and engine are cracked, definitely replace.

[valvesprung]

Alright, I'll definitely order a pair. I'm thinking that cleaning of the carbs is going to be needed...I'll check the frame mounted petcock tonight for proper flow at least on the prime setting and go from there.

Any other words of wisdom that might keep me from tearing the carbs apart?

[valvesprung]

It's...



...ALIVE!!!!

Well after all that, I started over with each of the lines and rerouted everything by the book. It would seem that the tank vent was the issue all the time, and at some point a line got crossed up(well that and the garbage gas). I'm going to run a fuel system cleaner through this tank of premium and suspect
I'm good to go.

Now I can finally ride it to the bike shop for some new f*&king rubber! Wahoo!

[jeremy_nash]

in most cases, its cheaper if you take the rims in off the bike, if you have means to do so. 

[the mole]

And definately replace carb rubbers if cracked, else they'll suck air and it'll run lean and maybe burn a piston.

[steitsma]

wish i were that lucky, my vent tube was clear and still hesitates on take off!!  good to hear you got it fixed and keep the rubber side down

[valvesprung]

Thanks guys. I pulled the wheels last night to take for rubber, free install if off the bike.

I'm really excited to get it road bound.