I have a Gas Gas TXT 2001. It has recently developed a single sharp tap/knock after the throttle is blipped.

I have owned the bike for three years and it has never done this until this year.

I have never heard the knock at any other throttle position or time (load/no load) when riding.

I run normal unleaded with motul synthetic at 75ml per 5 litres.

I appreciate that at this age the engine is likely to need some TLC I just want some idea of the likely cause and the size/cost of the repair job.

If that's normal unleaded, I would try Super Unleaded or Shell Optimax before you start to worry too much.

I have an 01 TXT also (280) and as BS says its probably just the fuel you are using. Mine knocks too and so does my mates (same bike) when I use normal unleaded but now Im on Shell Optimax and although it has'nt completely gone it is stacks better!

Take BS's advice and get some higher octane fuel!

My sons 2000 TXT after a lot of use developed a knock that was rather harsh and matalic (piston slap) when you blipped the throttle with no load. the knock was only at relatively low rev's and disapeared as the rev's increased.

Bad news is that our problem was caused by the chrome in the barrel starting to peel. I guess just general wear and tare on a well used engine.

Twinnshock

Thanks for the advice.

I'll upgrade the fuel first and hope. After that I'll strip it and see.

Pog

pogbird, keep us informed will you?

I have a new TXT280 from this year. It also give a metallic sound when I shortly give it gas to high rpm. The sounds comes when I let the throtle go back.

Is that normal/okay?

Thomas

Edited April 21, 200521 yr by Thomas

Sadly if neither of the above suggestions helps, then its a matter of stripping the motor, and looking for wear or damage, which can often be pretty expensive, if the bike has been badly maintained in the past.

The motor has only done 4-5 hours so it shoundn't be worn.

I will follow your advice starting with trying a different fuel (we do not have Optimax in Denmark).

Thanks for the advice

Hmm the Optimax is a higher octaine. If you cant get higher octaine fuel maybe you should try some Octaine boost? Silkoline make it but I can not help you with how much you need to add, I have never used it! Maybe the others can advise you on whether or not this is a good idea??