Background: I bought a 2007 S40 a few days ago. It has 131 kilometres on it. Apparently the woman scared herself and it got parked in the garage until her husband decided to sell it.

I've put fresh fuel in it and a large dose of carb cleaner, and driven it about 100 kilometres - just breaking it in.

It idles smoothly and has lots of torque and top end, although I haven't hit the highway, yet.

Problem: It surges when held at a steady speed, as noted in the caption, doesn't back-fire, and gives a quiet puff at shutdown. Is this a dirty / gummed up carb, or a lean mid-range, or will it heal itself with more mileage? I'm at 3500 feet.

Suggestions from the experts are welcome.

Solution: I removed and disassembled the carb. It was spotless inside - no sign of any varnish, and no jet orifice plugged. I was going to do the white plastic washer mod, but was unable to find anything with the correct diameter.

I reassembled everything, drilled and removed the brass plug covering the idle mixture screw, and in so doing, found my problem. The screw was tight. I turned it out three turns. A quick drive to try and duplicate the problem, and 90% of it is gone.

While I was at it, I installed a fuel filter, and checked the plug - a nice tan colour.

Update: I did the .06" white spacer mod, thanks to Serowbot who was generous and mailed one to me when I couldn't find one locally. The mod resolved all the just-off-idle hesitation and the low-throttle / low-speed surging caused by the lean air-fuel mixture. The bike now accelerates smoothly from idle to any rpm. This is definitely the solution to poor low-rpm performance.

Yes, oil change, check the air filter and box, drain the carb and tank, inflate the tires to the proper values, check the torque on all the major bolts, etc., ... all done.

Many thanks for the advice.  

On this bike, ist gear is just to get it moving; I would probably have shifted by 15 mph....2nd gear is for putting around.

and welcome....enjoy the ride.

BillF6531 wrote on 06/27/11 at 21:59:19:


Solution: I removed and disassembled the carb. It was spotless inside - no sign of any varnish, and no jet orifice plugged. I was going to do the white plastic washer mod, but was unable to find anything with the correct diameter. Not much selection of odd parts in Canada, and I tried three large hardware places.

I reassembled everything, drilled and removed the brass plug covering the idle mixture screw, and in so doing, found my problem. The screw was tight. I turned it out three turns. A quick drive to try and duplicate the problem, and 90% of it is gone.

While I was at it, I installed a fuel filter, and checked the plug - a nice tan colour.

If anyone has a spare white spacer in the correct diameter, and would be interested in mailing it to me, I'll buy you a beer.

Thanks, everyone, for your helpful advice.

Best regards,

Bill

BillF6531 wrote on 06/29/11 at 16:17:54:


Nice job solving your problem.

That's great!...  

Ride safe,
Serow ...

Quote:


I don't know if this is a gasahol argument or not...It's a 2007 with less than 500 km on it that after it sat he ran carb cleaner through it before he opened it up, any varnish or other gasahol residue would have been washed away...Also, he lives in Alberta, Canada, do they use ethanol "enhanced" gasoline up there as well?