Help
Honda 250n 1981
I acquired this bike a few years back as a non runner and now got a bit of time to fiddle with it, had to put a new battery on plus petrol.
Bike starts and revs ok on the driveway then I take it down the road get up to 30mph it then starts to die as if its running out of petrol, I ease off on it picks up again .
Have pulled the cabs off and giving it a good clean the float's are made of plastic so there is no adjustment for float level .Bike back on the road still only does 30mph.
Change plugs and caps also put secondhand coil on plus done a compression test, turns out to be very good.
Still only 30mph.
Taken two in one exhaust system off to see if blocked but found to be ok. Still 30mph
Can it be the cdi unit or the timing system at fault?
Any help welcomed--- Bill

Bill, July 2009

check/change your air fillter. check the fuel tap fillter. you have to remove the fuel tap from the tank to do this. also you could do with changing the fuel itself if its been stood in the tank for some time.

barry, August 2009

Took the fuel tank off to check the operation of choke cable and found that it wasn’t shutting off properly, it was on quarter choke also took the air filter out.
Put tank on and took it down the road now it revs up to the red line bike sorted.

Bill, July 2009

Hi Marc
The two plugs are black and sooty ,deposits indicate an over-rich fuel/air mixture or a malfunctioning ignition system. "Looking in the workshop manual,photo of the plugs".
There's no misfire ,bike starts ok just will not go over 30mph . Will take air filter out and see how it goes,but prob get a carb kit .
Thanks

Bill, July 2009

Check the plugs to see if its running rich. Previous owner may have jetted up with the 2 into 1. I cant remember whet the stock jets were but somewhere round 68/102 ish. Also make sure the fuel cap vent is clear as if its blocked it creates a vacuum in the tank and stops the fuel flowing. the fuel tap has filters on it ( 1 for main and 1 for reserve ) so make sure they are clear too and pull out the air filter to see if thats causing it

Marc, July 2009