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Help with a Yamaha YZF600 Thundercat problem


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Im a first time poster here, and i am unsure if this is the right sub-forum for my topic, but this place was the one that made most sense to me. 


I bought a 1997 Yamaha YZF 600 Thundercat project bike this summer, and was hoping I would manage to fix it up.

After some rounds of trial and error im not really getting any closer to fixing the problems with it. So i was hoping there where some Thundercat/Yamaha gurues here that could help me a bit with my problem.


The thing is that when i bought the bike it wouldn't idle, but it could be driven so long as you kept the revs up a bit. My tiny experience with motorcycle repairs lead me to believe that this was a carburetor related problem. So the first thing i did was to take out the carburetors and clean the jets and those tiny bras? parts inside the carburetors. Also, before reassembling the bike i adjusted the air/fuel-mixture screws to stock settings. I noticed that one of the screws was like just 1 revolution out from bottoming, while the stock setting is suppose to be 2,5. The other 3 screws where at about 2,5 revolutions out.


but then i started the bike up again i had this totally different problem. Now the idle was just fine, but the throttle got stuck when reving up the bike. A bit of research on the new symptoms suggested that this was because of an air leak. So i started to look for some of those. I tried the trick with spraying some WT-40 on parts that are prone to air leaks, but now really getting any results, but when taking a closer look at the rubber connection hoses between the carburetors and the engine it looked like they where quiet worn. So i changed them for new ones, but this didnt help either.


So this brings us to where i am today. Can anyone help me figure out that is wrong with this bike.


Thanks i advance.



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6 hours ago, blackhat250 said:

The cable  connection,   it will be snagged, disconect it, see if it cures it ,

Hey. Thanks for the reply. I checked the cable connection and lubed the gap between the cable and the cable hose. The trottle seems to be working very smoothly. It snaps back instantly in all positions of the steering wheel. But still when i turn on the bike and rev it the revs dont come down.

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I would disconect cable to see if revs drop,,what about the  idle screw ,-back it off fully,   then check the choke cable isnt snagged or  fully off, 

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How many miles are on the cat?

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