B6 Running like a 2-stroker

[Airmotive]

Okay all you troubleshooters out there....here's one to wrap your brain around:

Well, I just returned last night from my 4000 mile Texas-Canada and back tour de force... And I brought home a sick lil' Bandit. (2001/600 Bone Stock).

If I wasn't within 150 miles of finishing a 1000 miles/24 hours, I probabaly would have parked it for the night and found a shop the next morning. But, I made it home so I'll get 'er done myself....I just need some advice.

Here what I know:
Chain and sprockets are now officially shot...this could be the cause...could be a red herring.
Brand new NGK spark plugs - replaced as soon as this problem began to manifest itself. (Had no affect)
All pipes are equally hot.
Engine runs/revs absolutely normal with no load.
In neutral, on center stand - rear wheel/chain turns freely.

The problem:
When accelerating through the low gears, the engine does not come up smoothly, but rather goes "wawawawa". It still pulls strong, but does so with a bunch of mini "surges".
Engine braking really (really!) exacerbates the problem.....it then becomes more like riding with a teenager who is learning to drive a stick-shift for the first time....you know...rapidly jerking you forward and back. (And the same 2-stroke-ish "wawawawa" engine sound).
There is no backfiring, smoke, etc. Fuel milage stayed the same. Not burning any oil.
The problem gradually worsened over the last 400 miles.

Is this a good enough description to fit a common problem?
I hope this is simply a worn out final drive....but I've never had one go like this.
I am concerned about burned valves....but I've never had one. How do different valve problems manifest themselves?

Blue Skies,
JJ

[PeteSC]

Stupid question......the clutch isn't slipping?
My inexpert thoughts are maybe it jumped timing, or some ignition component went bad.

[Red01]

What kind of shape is the air filter in?

[turbo-bob]

Check your points...            

[chupacabra]

I'm going with a BAD CHAIN, real bad chain.
And maybe some bad rotors on the front brake, stoping it uneven?

[Airmotive]

This is my first chain driven bike in quite a while. The only other chain drive I've had was an '81 GS550L and the first clue I had a chain going south was when it broke on I-10 at 2 in the morning.

The chain is definately worn out...I just though that worn chains made ugly noises...not the symptoms I've described here.

Regardless....chain and sprockets are on order from MAWOnline. I'll let ya know the outcome. Thanks for the input.

[Daytona]

New chain & sprockets. I had a 650 Yamaha that i made do the same thing! After the MPG jumped way up though?? Throw on another carb sinc for good measure!  Man what type seat do you have! and the brand on the bike too? 4k I'm impressed!      Why did U order from MAWOnline?

[mike]

I was gonna say clogged screen filter in the fuel tank , clogged air filter, make sure all the vent hoses are clear of clogs and not pinched..  In other words fuel/air mix related....

Sounds like you already got it mostly figured out, good luck...  Texas - Canada  WOW! that was some road trip ! Kewl!

[Airmotive]

Seat is stock....but I added a cheapo saddlepad from Stateline Tack. Just folded it up a little so it fit nicely on the seat.

I was not riding in the lap of luxury by any streatch of the imagination, but if I wanted luxury, I would have driven.  

Regarding MAWOnline...
I've ordered from them before, good prices, easy to track your order online. For what I ordered (Two sprockets, chain and front tire) MAW came in a full $70 under Dennis Kirk. I had a question about which sprockets I needed, and someone at MAW answered the 1-800 number on a Saturday evening. Good enough for me!

eg:
RX 530xso x-ring chain: MAW: $75.95, DK:$104.99
Battlax BT020 Front Tire: MAW:$74.95, DK: $110.99

[pmackie]

A couple of things you can try, if you haven't already...

First and easiest is to check your fuel. With the run you had from Texas to us up here in the North, you have likely had to run a number of different fuels on route. One option is that you have picked up a little water en route, and/or have some alcohol blended fuels. If you have had some water (or water & alcohol mix) separate and collect in the float bowls, you could be picking up a miss as it sucks in a little water. I would suggest you drain the float bowls via their bottom drains and if you find any evidence of water, then drain the tank as well.

As others have mentioned, change the fuel filter, check for blocked/kinked vent or supply hoses, etc.

Check for loose electical connections and mountings, especially the wires to the coils. Check the plugs and plug caps for any cracks and tight fit. It is not unusual to have a poorly fitting plug cap cause an miss. Check the plugs carefully, especially since you say the bike will run cleanly under no load, but misses when under load. A defective plug can exhibit similar problems.

Good luck, and I hope you have your problem solved.

[tacoman]

I'm with the above post, I would say fuel and fuel delivery is your problem.  Worn drive gear (sprockets, chain) will not make a motor run bad, you'll just get weird noises.  You probably picked up some bad/weird gas somewhere on your journey.  Drain the carbs and see what you get

[Airmotive]

And the answer is......

The Chain!  

(I'm writing from Hong Kong...away on business for a month) but before I left I did lots of replacing of worn parts. Chain and sprockets fixed the problem. I assume the badly worn chain prevented smooth power delivery from the engine to the wheel, resulting in the 2-stroke effect. I'm glad I only had to ride the last 500 miles like that. It could not have been good for the engines/tranny.

...waiting for my Iron Butt award to arrive...