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Hello, I’m hoping that someone can help me with a mechanical issue I’m having with my 1998 Yamaha YZF 600R (Thundercat)… It has about 11,500 miles on it and has been sitting in my garage here in Colorado for about 8 years… I’ve always had in the back of my head that I wanted to turn this into a streetfighter, but never knew this community even existed. Once I heard, I was all in… So on to the problem, which is just simply keeping it running… I’ve done some work to it (amateur stuff), but I can’t keep it running in an idle or under 2500 RPM’s. To date I have replaced the oil and filter, changed the spark plugs (all gaped correctly and the same brand/model that came out of it), cleaned out the gas tank of sediment and corrosion, cleaned fuel filter (will eventually get a new one, but had to be ordered – Cleaned very well), replaced hose from fuel pump to tank (was crimped), new battery, removed all plastics from the front/side, and cleaned and lubed the chain… All the low hanging fruit… I was able to fire it up by removing the tank and spraying some starter fluid in the tubes (took a while for that to work as well, but now if you spray in the 2nd or 4th tube it fires up every time)… but as stated previously, I have to keep my hand on the throttle and the RPM’s above 2500 for it to keep running… I also have a hard time starting it without the starter fluid… Starter is strong, so no issue there, and sometimes it really wants to turn over, but I can’t tell if that’s from residual starter fluid in there or something… so, the throttle is opening the flaps just fine, but it’s almost like it’s not getting enough gas to keep going…I know the fuel pump is working though because when I twist throttle when it’s running, the bike reacts according… The throttle was sticky at first, but it’s now seemingly back to working as it should with good recovering and not sticking. To that point, at first when I held the throttle steady, it will jump around on the RMP’s… it’s better with that now. I tuned the idle knob on the side to the place where it was almost kicking on (again, not sure if residual starter fluid helped, but at this position, it was almost there compared to not being even close at other positions) and it seemed to be the best position for it. My buddy suggested that it may be that choke isn’t working so it wasn’t opening the vents inside the carb enough. Don’t know if that statement is even accurate… I am thinking maybe the fuel injectors are all gummed up? I don’t know, hope you can give me some new things to try before I pull everything apart and start looking at the carb… Thanks in advance for any help!
 

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The Hell You Say!!
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2,956 Posts
Is it FI or carbed? I would run some seafoam through it if its FI if it is carbed you need to take them out and clean them really well. Sounds like they are gummed up pretty bad.
 

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The friendly Ghost.
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It's carbed... By take them out, do you mean the injectors?
The carb bank

You going to want to clean out the float bowls and jets really well. Also check the status of the float bowl needles, o ring and diaphragms.
 
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