I've had my k2 crm250 for about 2 years. When I first got it It would easily do 80-90mph on the motorway but now I can only get 70mph flat out!
Just wondered if anyone had any ideas as to what might be slowing it down?
Also need a new front tyre what best compromise for on/off road?

sorry to hear this, there are lots of things that do go wrong and can cause this but most never happen.
An experience mechanic should be able to find the culprit quickly.

When was the last time the bike had a fresh pair of rings, piston or re-bore. One of my road 2-strokes is doing the same and i know that the only thing wrong with it is that the piston and rings are worn out.

possible culprits for the loss in power;
excessive piston &/ or cylinder wear- found by testing compretion pressure or removing piston or cylinder
air filter/ air box blocked with dead mouse- (he he this has happened)
fuel filter/tap blocked- just unplug the fuel hose on the carb and check the fuel flows freely
carb blocked with dirt or petrol crystals -happens if the bike is left with fuel in the carb for more than a couple of months (ie when imported!)
main cranck seals blown
exhaust blocked (amasing how many scooters do this)
weak spark/ damaged coil- a weak spark becomes even weaker under pressure
most of the things mentioned here you can check yourself, but a few need specialist equipment. things like the weak spark, air filter, and fuel flow you can check quickly, others can be spotted by their tell tail signs- blocked carbs dont work well, especialy on idle.

If its broke it can be fixed. if you need more help i can gude you throught some testing procedures.

could be any of the above but i'd be checking the opperation of the power valve. (ask me how i know )
cheers, rikkster.
\" ride it like ya stole it\"

Hi,

Another, more obvious cause, would be the build of carbon in the exhaust port, piston and exhaust, Always worth a look as it costs nothing!

Does the bike have a high mileage? Might be worth running a compression test first...

Barg.

Spark plug was the reason mine got fluffy, slapped a platinum one on and it's like new again - 22k and counting, took the head off and the bore was fine, head had some carbon gummed on, but not too much...

Spark plug was the reason mine got fluffy, slapped a platinum one on and it's like new again - 22k and counting, took the head off and the bore was fine, head had some carbon gummed on, but not too much...

I know when mine needs replacing as its misfires occasionally.

Its a great feeiling to just know that mine will always start, especially when im stuck in the middle of some muddy lane at 10pm...

I'll try the spark plug as thats nice and easy it's been off the road for a bit as it (aparently) needed a lot to get through mot (£160 inc vat!).