Swm not revving out?

[hampster]

Hi all,
 
My tf1 250 starts first kick idles fine , till mid throttle than seems to brakes down ? Sound like its electrical the ignition system has been re wound looks a bit average does any body know where I can get a new electric system?

Thanks chris

[Slakewell]

Why not PVL? or similar?

Have you tried it with no Muffler or air-filter? 

[mainline]

Try disconnecting the kill switch, may have a dodgy connection, not earthed properly etc

[bigk]

Don't discount carburetion, check needle & needle jet are not worn.
K

[shortshifter]

Hi Hamster.Seem to remember a rebuilt Husky with same problem,guy tried everything to fix it.Turned out it was the muffler restricting the engine

[Bamford#69]

Hi,
have look at Fuel tank breather , and take fuel line off and check fuel line/tap flow,
cheers

[oldyzman]

Recently purchased a cr250 1989 "race ready" was also weak at high RPM. Changed the muffler and put back to std jetting was a bit rich. Goes really well now.
Once your bike is warmed up does it still blow heaps of smoke mid range?
Brett

[supermotomc]

so what have you touched or did this just appear have you worked on this before you got the earth wire on this 12v to earth ok have you had the disc valve out??

[kim80y]

I had a similar problem for a long time, and it was the HT coil, there was a "bad batch" of aftermarket ones floating around, I had two of them before the importer fessed up........

Cheers
Kim

[hampster]

Thanks All,

Have tried the following,
The bike is running a 34 mm Dellorto have put in standard new main jet , pilot jet , needle , needle and seat. No change.
Run the  bike with the petrol tank cap off seems to have plenty of fuel, no change.
Have taken off the muffler and run , no change.
Have taken out the air filter and run , did make it run worse ?
Have varied the timing,  advanced and retarded , backfired a bit when advanced?
Have tried a colder plug a 9, no change.
Still starts first kick and idle fine till mid-throttle?
The stator has been rewound and looks a bit dodgy?

Yet again any help would be much appreciated

Chris.

[Lozza]

VHSB or PHBE carby?  Can you tell me the main jet, needle, atomiser tube and I'll check the fuel curve

[mainline]

Try disconnecting the kill switch, may have a dodgy connection, not earthed properly etc

[pokey]

Any chance of posting a pic of the plug?
to me it sounds like an air leak . specially seeing as allowing more air by removing the filter makes it run worse.

[Mick D]

Hi Chris, Mid throttle,
Fuel maybe??
Mid throttle = needle jet

Have you completely stripped the carb to make sure?
Removed the emulsion tube?
100% sure that the air draft passage from the bottom of the air horn to the emulsion tube is clear?

Worth verifying, good luck.

[Canam370]

I don't know if anyones asked but was the onset of the issue sudden or progressive? Sudden would point towards electrics (the Bosch CDI's weren't startling). The stators were generally OK. Multimeter checks won't always show up a fault. Send the lot off to be checked dynamically by a professional -  including the kill button -  it'll be cheaper than shotgun solutions to imagined repairs. Particularly if someones already monstered the electrics.
 Progressive deterioration leads down a whole different fault tree analysis.