I'm helping a friend out with rebuilding the carburetors off his 1989 crb600. it has a k&n plus some slip on muffler.

I was thinking 2 up on the pilot and 2 up on the main, but I also noticed dynojet makes a kit. Are their kits any good? I was originally just going to have him order some jets from jetsrus, but we are not sure if it has the stock jets in it now. All I know is the previous owner didnt have it jetted correctly.

Anyhow, all suggestions are appreciated. We are rebuilding the entire carbs with new everything. it would be nice if we could nail the jetting the first go, but thats wishful thinking im guessing.

 

I take it the engine is running lean, is that so

 

We were told it wasnt jetted correctly. It was also backfiring a bit. I have a feeling one of the valves is a bit too tight, but we are just trying to get one thing done at a time.

 

Hi , if you suspect valve clearance, then you would have to set those first , and then take a look at the carbs, does it backfire on start up only or generally all the time

 

Man I have zero reference. All I know if my friend road it back for my budy who bought it. He said it was running on 3 cylinders he thought. The owner he bought it from had not jetted it after the slip on or k&n. Who ****ing reall knows,. my buddy bought it off ebay, and paid too much for a bike that ran like ***, but its clean. We, me and my friend are just trying to help him out, because he is over his head. I noticed a small black spot on a otherwise clean k&n on the number 3 carb, I first suspected a torn cv rubber. THat wasnt is. My next guess is either a blown cylinder, but more likely a tight valve im thinking. It's a long slow process, and right now, we made the choise to rebuild the entire carb system as he doesnt plan on selling the bike any time soon. We will address the rest later, but right now its just getting the jewt sizes to order so we can actually do the carbs. I dont plan on going over and messing with valves until the carburetors are finished. There is no point in messing with the carbs until we get the somewhat correct jets. There has to be some sort of freaken documentation. The f2 forum has pages of jetting info... Basically is what I am saying, is I would like a ball park jet setup for my first post. The bike is 30 years old and id assume there is plenty of people on here who have rejetted these things before. I cant fix the rest of the crap, but I have no idea on jetting on this particular machine, and hoping some of you veterans can give me a good starting range.

 

Okey Dokey, heres the jet sizes and what you might need for the carb, have you got the workshop manual?

 

Factory Service manual is up in the sticky on my post at the end. The folder also has a color wiring schematic.

Once you get close on your jetting this link https://cbrforum.com/forum/cbr-600f-...et-kit-127567/ is the best way I have ever seen it written on how to tune it.