When I do wheelie's on my 99 techno 250, there seems to be a problem with power, it seems to choke a little like it is flooding which makes the power cut out. I also get coolant leaking down from under the fuel tank onto the head, but cannot see the leak source. Any suggestions to remedy these problems?

Yes buy a newer bike

don't do wheelies

And don't bother with the coolant if you only loose it!

Edited April 29, 201214 yr by easytigrrr

Ok I will elaborate as you don't seem to be taking my question seriously. This is my first trials bike, so don't know a great deal yet. The fuel problem happens on big climbs also, like it is running rich. I also notice it loses a lot of fuel sometimes from the overflow? I sometimes do not turn the fuel of when storing, is this a problem? The coolant thing only happens when I wheelie it, so was just asking as maybe you can overfill the coolant?

Yes if you fill the coolant system to the brim it will eject some coolant out through the overpressure valve as the coolant expands with temperature rise.

I'm only guessing here but maybe for some reason your motor is getting hotter than normal when you wheelie, but you haven't given any details of what sort of wheelies you are talking about so it makes remote diagnosis difficult. One thought I had was that maybe your radiator fan runs backwards, and the only time your bike is ridden fast is during a wheelie, so there might be little airflow through the radiator if the fan starts while you are going fast? (fan working against the natural airflow ditection when the bike is moving fast)

Same for "big climbs" are you talking 10 minutes or 10 seconds of continuous climbing?

Fuel coming out the overflow usually means either a passing float needle valve, or the fuel level set too high in the float bowl. If it only comes out when you are riding, the level is set too high, or the overflow standpipe has a problem. If it comes out when the bike is completely stationary ie motor stopped and bike upright and sitting on a stand, it is a passing float needle valve.

If you can leave the bike parked with the fuel tap on, and there is still fuel in the tank (and not on the floor or in the crankcase) when you come back to it, the float needle valve is working fine.

The coolant may be resting in the radiator overflow pipe (most bike blow a bit out now and then), then when the bike is up on end it runs out. I guess if you are doing very long wheelies you may not be getting enough air through radiator and it may be boiling a bit out.

Rich running is almost certainly carb float hight setting or a worn float valve. When the bike is wheelied the petrol in the tank will cause a higher head / pressure on the carburettor and accentuate these faults / misadjustments..

Cheers

Thanks for the replies. The bike gets ridden fast quite a bit, as I use it on the road. The wheelie's are made short by this problem, it's very hard to get even power when it's in this position. Is the carb float problem easy to investigate for a novice like me? I will check out if the fan is working properly.

Carb easy to remove then with fuel line on make sure the float arms, usually brass can be lifted upwards and cease petrol flow thus eliminating float function. Next bend the arms down 1-2mm this will reduce petrol level in carb oh and check the floats are ok.

Rad replace cap as its most likley old, make sure youve not got water in transmission oil it will look milky if so. If fault still persists remove rad and all pipes and check water can flush through, plus remove water pump and check condition.

If this fails refer to my first post

You can replace the float needle with a viton tipped needle and solve many of the overflow problems.

I moved the overflow pipe and it seems better. I discovered the fan is not working though, the bike was overheating, this is what was causing the coolant leak. What should I check to find out why? Cheers.

Smalley250 may have a point in his first post.

My mate has a 1999 TXT. Everything on it works to a point but also every single component is worn including tyres. Badly!

He competed on it for the first time the other week and did well. Goes to show an old dog can run with the hounds.

He needs a newer bike though

I moved the overflow pipe and it seems better. I discovered the fan is not working though, the bike was overheating, this is what was causing the coolant leak. What should I check to find out why? Cheers.

check power is getting to fan, if yes check fan motor on a battery (12VDC)

if no power getting to fan, check fan switch and power supply from rectifier