im redoing a 90 cbr 600 (code name ebay junker) how can i tell if the carbs were jetted? it has a slip on pipe and a k&n filter but no idea if it was jetted any ideas

 

Well first, you can ask the seller. Other then that, the only real answer is to actually take the carbs apart. I believe the 90 models has either Keihin 108 or 110 main jets. The needles were non adjustable which means there are no c-clips attached to them. The Dynojet kets made for these bikes came with adjustable needleswhich meansthere would be c-clips attached if they were aftermarket. The Dynojet kit also used Dynojet mainjets. If the mainjets have a DJ stamped on them then chances are it has a jet kit installed. But a better indicator would be if the needles are adjustable or not. I hope that helps.

 

thank you im not going to tear them down just yet it runs to good right now time will tell with my ebay junker

 

Then have no worries and ride on!!

 

Easyest way to tell without tearing things apart is to look at the inside of the pipe. Is it clean or does it have black soot in there? If it's clean your running lean and run the risk of blowing a hole through a piston or two. It would also be pretty flat in the mid-range RPMs if it is running real lean. If it's nice and dirty in there and is easy to cold start then don't worry about it.

 

I would not go by your theory of having soot on your taipipe as an indicator of your air/fuel ratio. A properly jetted bike will still have some level soot on the tailpipe regardless if it's rich or lean. Reading spark plugs is the easiest way to tell if it's jetted corretly other than having it dyno tuned. My bike is jetted fine, and I'll bet you any money I could take a Q-tip and write my name on the inside of my tailpipe tip.

 

I think you mis-read Critter's post. He said that it should be sooty (is that a word?). He said that if it's clean, then you have a problem. I don't know the feasability of this or not. When I was asking the same question about my F4 I was told to get out on the freeway, stop, and shut off the bike. Start the bike andimmediately take offand run the bike at around 8-10k rpms for about a minute then hit the kill switch and coast to a stop. Pull one of your plugs and note the color of it. The color charts around will tell you exactly what you want to know.

 

Yea, you might have misunderstood. Your pipe should be dirty. This is by no means a very scientific way of diagnosing things. It's only an indicator. A dangrously lean bike will have a clean pipe. Didn't seem like he wanted to start pulling things apart, so that is why I mentioned it.