Top end is a pig

[aarron]

My bike (TC250) has been running very good, starts easily, goes through the gears nicely around town, but is a real pig on the top end. Once I get much above 55-60 MPH, it actually seems to slow down when giving it more throttle in 5th or 6th. It has new seals, plugs, air filter, etc. Not sure where to look first, thinking it's carb related? Any ideas are appreciated. Thanks!

[Alan H]

Blocked exhaust or manky baffles?

[GTandcbr]

http://kawtriple.com/mraxl/carb/carbadj.htm" onclick="window.open(this.href);return false;
May help you with your carbs

[Alan H]

http://kawtriple.com/mraxl/carb/carbadj.htm" onclick="window.open(this.href);return false;
May help you with your carbs

The TC250 is a Suzuki.

[Vintageman]

Is problem related to throttle position or RPM. I know these two things tend to go hand in hand but are different

If you been through engine and all stock. Poor mid range power can be ignition timing is off ... even couple degree makes a difference on little engines.

How was cylinder and piston, nice fresh so good compression? Top end running quiet or a lost of piston slapping noises?

Are "ALL" I mean "ALL" the carb brass parts as new and original Mikuni items?

Someone said exhaust plugged already +1

Ever backfire or pop out exhaust or carb?

Gas cap venting and petcock flowing fuel OK?

[aarron]

Sorry for the slow response, I was called out of town and just got back. These are all great responses and much appreciated. Everything on this bike is stock, but I'll check the exhaust 1st, that sounds like a possibility. The carbs are clean and I have a brand new petcock flowing properly. I'll check the timing to be sure, it could be off a little, but no backfire or popping going on. There's not much slapping either, it's pretty quite. My H1 slaps a lot more than this 250. Thanks again for the replies! I'll post what I find out, probably next week some time.

[rngdng]

If backing off the throttle improves speed, the mains are too big, OR it's not getting enough air.



Lane