Hello all! New to the forums, but was wondering if you could help me with a baffling issue.

I have a 1994 XT350 and have done a bit of work to it as it was a bit of a pig when I bought it and need some tlc.

I have stripped down the carb, replaced the jets with original ones and replaced the diaphragms as the bike wasn't running great. I've also replaced the coil as I suspect the original was on its way out.

The bike now runs great, accelerates nicely with plenty or torque and is no longer running hot. Starts easily and there is no signs or spluttering or struggling through all gears and speeds accept when I hit 50mph and this is where things get baffling.

You will accelerate up to 50 then bam nothing. The bike will not go any faster. There is no struggling or spluttering, just a constant speed of 50.
I have tried dropping it down a gear and giving it some welly, or leaving it in 6th and cranking the throttle, but nothing happens. The rev counter doesn't go up along with the speed.

I have checked the rubber boots as well as the chain and sprockets to see if they have been altered but they are all fine. The bike doesn't struggle at lower speeds and accelerates nicely through all gears otherwise.

I have looked endlessly for a sign of a restrictor to no joy.:confused1:

I'm lost.

The only thing I have left to do on the bike now is to check the valves, but I can't see that fixing this problem. I could be wrong though.
Any help would be great as it would be nice to do more than 50 down the motorway!

Cheers