so i replaced the o ring on the needle jet and the bike revs better and pulls through the gears,but if i give it lots of throttle it seems to die ?? i cleaned all the carb components and everything looks ok . can you give me any advice ? many thanks. 

Ok, so 'die' as opposed to 'bogs'. Have you checked the main jet, like taken it out of its holder in the side as can get blocked or restricted from the back side of the jet on that system. Just want to be sure its that before looking further. Is the needle on the middle clip notch as a starting point.

Hi and thanks for your reply. please could you tell me where to find the main jet on the carb i can only see two. one is the idle jet number 25 inside the carb and the other is the long jet that the needle slides in . am i missing something really obvious ? externally there is the air screw set at about 1 and a half turns from seated . and i dont know the difference between dies and bogs , but when i open the throttle more it just seems to slow the engine ?? thanks again. any pictures might help.......

Item number 6 in the attached parts diagram - sits in a banjo bolt at the bottom of the float bowl.

 

i will check that jet i didnt know it was there. also i have just replaced this jet the old one looks like it has been messed with. 

Yep number 6 in the bowl side fitting, that's ya main jet. The idle jet you might be in trouble if it won't come out. Is that a new one you're holding. If it won't unscrew--screwdriver slips over--just leave it & see if a super small strand of wire brush will go through or just compressed air & see if you can see through it up to the light.
By saying dies i meant just shuts off on full throttle & stops, or almost stops, as a blocked main jet would cause. By bogging--a term i've seen used on here--& think it means drowning like its getting too much fuel--that's what i mean anyway lol. First things first & check the main jet for blockage.

i have replaced the main jet for a new one number 200 . the jet in the other photo is the old one being held in the pliers, the hole is bigger than the hole in the new one shown fitted.on the exploded diagram i cant see the screw next to the banjo bolt as in my picture ?

Yes, that little screw is not original.  Supposed to be a brass ball in there I think to block end of drilled passage.  Might be okay if screw is not too long. need to see inside of bowl.

Also, o-ring seal of float bowl to jet setter is critical if you didn't know...  I may have missed if it was mentioned already.

Here's a thread on that hole with the screw in it...  like I said, need to see inside bowl.  If screw is short, should be fine.  If they blocked a critical fuel passage with long screw, it could be an issue.

yamaha-enduros.com/index.php/forums/1972...tor-questions#104376

the picture of the bowl on its side shows the length of the screw, another picture shows how much i have cut off and the last picture shows the end of the screw protruding into the hole that takes the needle slide setter potentially reducing fuel flow ?