holding revs when getting into band!

[muddyfox]

been busy trying to sort the bike, never buy a bike un tested, you live and learn as this was supposed to be a easy project lol
bottom end is nearly perfect, picks up very well only needs very little revs to get moving, however if you rev it just as you get into the band it seems to hold the revs even if you close the the throttle,

if you rev it on the stand under 5k its fine, settles nicly and doesnt hold revs and you can hear the slides snap back, around 1mm play on the cable

its like its got a leak some where, im sure it doesnt as it would play up all round the rev range

things that have been done, since buying it

4l0 blocks, carbon reeds- could this be a issue, i made sure it was sealed, i used my blue gas , it has gaskets between spacers and had some blue between the spacers and boot

reed spacer

rejeted 31k carbs 27.5 pilot, 240 mains, 5l something needle, needle clip 2nd from the bottom

plugs were a bit black and slightly wet

so clip was lifted, now in the middle and plugs is brown and dry

i set the timing as it didnt seem right, 2mm btdc using my dial, i set it to 0 just as you get free play on the dial, then wound it back 2 turns and moved the stator plate till it lined up with F on the rotor, does that sound right, ive not stobed it as i dont own one

could i have timed it wrong? could some one tell me where theres is set to test, seems ive ended up on if you looking at the stator plate, im at the full left on the stator
has any one experianced it, ive never seen this before

thanks in advance!

[muttsnuts]

what bike?

[jackjabba]

Generator side crankshaft oil seal would be my guess. My 250lc use to do it, use to settle nice at low revs, but once you got the revs up it use to come back down real slow. Have a good sniff around the generator and see if you can smell petrol after running it.

[muddyfox]

so i take you replaced it and all was well?

[jackjabba]

Replaced both seals and the problem was gone. I ran the bike without the generator cover and could smell fuel. Pulled the rotor off and you could see it had been weeping. Check there isn't a score on the crank surface where the seal sits as I have seen a few cranks that have been scratched along the bearing surface when someone has removed a main bearing.