hello to all i am left hanging with a fault that is a bit strange

basically my bike is overheating,there is coolant coming out of the overflow and the pipes are expanding as if there is a blockage or the prepeller isnt working or thermostat

as of yet i have ripped out the coolant system(radiator,all pipe and also checked the water prepeller on gearbox, i do not have a thermostat fitted either

the bike on revs idles strangly eg 1-3 thousand rpm up and down unsteadily

the bike will ride normally for around 20 mins then overheat and fluid comes out every gap it can find

any suggestions i would be grateful for,thank you in advance

time to start eliminating things, your cylinder you say has no thermostat, so it flows through the head fine, ur rad works as intended, your 'impeller' (not propeller - just me being pernickety) works and spins freely have you looked at your bottom end? between impeller and were it would meet the nicely working cylinder.

i remember on my old dt (bless her cotton socks) when the head gasket went it allowed engine pressure into the water system (fortunately water didnt enter the cyclinder) thus buggering up the water system as the engine pressure was greater. a big tell-tale sign is after 5 or 10 mins of running the waterpipe coming off the top of the head (leading back to rad) would swell to twice its size. if this is the case then swap your head gasket (little tip - using 2 o-ring gasket washers (what ever they called) use these as gaskets to replace the original so you would need 1 approx 60mm diameter and then 1 about 85-90mm these will happily stop water leaking from the head and also seperate the cylinder and water system. much cheaper than a ebay job) hope this helps mate

top bloke yes it has swelled above the cylinder head like you say, today i checked base gasket(while i was there)and removed head and checked gasket seems flat although never trust a pattern jobby they normally warp, my guess is your right and thank you for your support, when you say change the gasket for o rings do you meen without putting another original in? would'nt they melt when temp gets high? or even move with pressure? thank you in advance you've been a great help

you have the same rings (only smaller)on either side of the powervalve, they take the pressure and heat and technically have more area on display to get affected (servo controlled powervalve that is) i have a 125 bored out to 185 and cant get a gasket for it so i use the o-ring setup, its clamped down that tight its almost invisible, works fine. if your unsure about your head and cyclinder warpage dont go pay some1 to do the work, grab your mums or wifes 'marble' chopping board and gaffa tape some 1200grit wet and dry on it, then work either the head or cylinder in left to right motions just to get a wear pattern on them, then have a look and check your wear pattern covers all the area your working (still with me) if your wear pattern covers the whole area then it is not warped (dips and pits etc) if there is a little patch woith no wear pattern, that would be your problem. after you have your wear pattern remember to finish the piece with circular sanding motion.

must be a marble chopping board (perfectly flat) and try no to push to hard when sanding (imagine your playing air hockey, let it glide or you mite bevel it off)

yup i had my dt in bits many times and didnt see the point in buying new! its a DT, indestructable, i ran 1 with 1 ring and a back to front piston (drunken mechanics) and it still pulled 45 ish

have fun fella its the wet season! jelous as hell now.......