xj 900 rough running till hot

[Hahadumball]

xj 900 runs like shit till its super hot

start it on the choke give it about 30 seconds choke off and try rev it gently itll bog down around 3-5k and slowly pick up then run shit 7k -8k

leave it to idle for a good 10 minutes till its pretty damn hot it revs up just about fine and after 15 mins its smooth.

any ideas?

has had new plugs and no change.
has had some carb cleaner thrown in and fuel cleaner shite.
bowls drained and new fuel.
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Fin: no matter how much I look at It I can't understand what was going through my head, all I remember is going about 80 and redlining it to stop it seizing.
360 Deg... Five 1/4 turns. :- Teflon-Mike 18 Jan 2015

[jaffa90]

"leave it to idle for a good 10 minutes till its pretty damn hot"
Not recommended, your bike is running on a weak mixture which could be the pilot jets partly blocked ( work mostly up to 3,000rpm) .
Also it sounds like the diaphragms in the carbs are perished, these c.v. carbs need a vacuum to lift the main jet needles so all 4 lift equally at the same time.
I hope the fuel tap is working correctly and that vacuum pipe leading to it and the correct air filter.
Also no unwanted air going in in between the carbs and engine.

[Draco87]

To throw an idea in there I would also get the cabs re-balanced I had a similar issue on my xj600
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1992 Yamaha SR125, 2005 Honda XR125, 1998 Yamaha XJ600S, 2000, 2004 Yamaha R6, 2002 Yamaha Fazer, 2004 Honda CBR