Good evening all.

New rider on the block so please be gentle lol

I bought a 97 gas gas JTX 270 about 2 months ago and have done roughly 2 tank full before the bike struggled to idle without a little reving. I took the bike to my local specialist and he stripped most of it down and cleaned it and that still didn't solve the problem. I changed the carb today for a good second hand carb with throttle etc full cleaned and stripped and fresh tank of 70:1 mix. The bike started first kick but the idle was all over so I have adjusted the fuel screw to 3-3.5 tuns out from fully in and tried to adjust the idle screw to suit. The bike idled well for short while and then the fan kicked in for a few mins then a little water via the cap run off and now it won't start at all.

The carb is full of fuel, I have compression on the kick start, and I have a spark at the plug but not sure how strong it should be?

any advise would be really appreciated,

thanks nath UK

Good evening all.

New rider on the block so please be gentle lol

I bought a 97 gas gas JTX 270 about 2 months ago and have done roughly 2 tank full before the bike struggled to idle without a little reving. I took the bike to my local specialist and he stripped most of it down and cleaned it and that still didn't solve the problem. I changed the carb today for a good second hand carb with throttle etc full cleaned and stripped and fresh tank of 70:1 mix. The bike started first kick but the idle was all over so I have adjusted the fuel screw to 3-3.5 tuns out from fully in and tried to adjust the idle screw to suit. The bike idled well for short while and then the fan kicked in for a few mins then a little water via the cap run off and now it won't start at all.

The carb is full of fuel, I have compression on the kick start, and I have a spark at the plug but not sure how strong it should be?

any advise would be really appreciated,

thanks nath UK

crank seals?

The spitting out of coolant suggests one of two things; you overfilled the radiator or the rubber 'O' rings between the cylinder and head have perished and need to be replaced. Its probably a good thing to replace them anyway on a bike of this age so you know they're good.

Other things I'd check is the inlet rubber the carb' fits into and the joints between the inlet rubber and reed block and crankcase. The inlet rubber can split (always at the back where you can't see!) and I use new gaskets and a smear of silicone jointing compound whenever I remove the reed block and inlet; you can check the reeds at the same time but I doubt this is your problem.

The carb' mixture adjustment you are at is about right. Is the float height correct?

I'd be inclined to check these simpler things before embarking on a drastic engine overhaul.

http://www.gasgas.com/Pages/Technical/starting%20problems.html

Follow this link mixture screw should be 1 to 1 1/2 out from lightly seated.

Check all the simple things before you start spending money.