Sport Bikes banner

1 - 7 of 7 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
I have a 95 YZF600 that won't idle. With the choke it won't idle lower than 1,500-2,000. Without the choke, it doesn't want to idle at all. It also runs rough below 4-5k rpm. The bike is stock, plugs are new, fuel level in carbs is good, jets are set up according to FSM. Also, if you rev it at idle, rpm fall down quickly. What else should I check? Should I just get used carbs off ebay to see if that helps?
 

·
Banned
Joined
·
293 Posts
Have you messed with your idle screw at all ? Id use that for the time being and get those carbs adjusted.
 

·
Registered
Joined
·
62 Posts
your idle screw is set way too low. you need to raise your idle, you'll find if you have it too high the rpms wont really fall when you rev it up, if its too lowit'll barely run. On my YZF i found that if i set the idle to where it pause briefly after a rev then drop it worked great.
 

·
Registered
Joined
·
62 Posts
hey where'd you p/u your YZF anyway? i'm sorta tryin to track down my old bike, just to see how it's doing. sentimental i know.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #5
Once it gets past 4k rpm it's fine. If I crack the throttle open the revs rise fast and drop when the throttle is released; they don't hang up or bog down when the throttle is opened. It works fine (revving, driving) at anything at above 4k rpm. I don't think it's the jet needle.

And if i set the idle at 1350 rmp, it stalls. I can raise the idle to 2k, but that's not the point, it should idle fine at lower rpm.

And I got it in Gainesville, Fl (i got an orange/black helmet with a jamaican flag on it with this bike)
 

·
No Whammy No Whammy STOP!
Joined
·
1,752 Posts
Its your carb settings. Whats the temperature down there? Probably somewhere in the high 80 up to 100 degrees, right? If thats the case, your carbs are probably dumping in so much fuel that the bike is flooding itself. I had the same problem this season once the weather warmed up to 90 degrees.

First off, take off your carbs, and clean them with carb cleaner and a tooth brush. Pull everything apart.



I suggest you get a manual so you know what to remove and how to put it all back together.

I assume your bike has a jet kit, but if it doesnt, I would recommend you drill out the idle mixture screw covers. If you look at the bottom right carb that is in the above picture you will see the idle mixture screw. It is located right below the float bowl. If yours have a brass cover with a small hole in them, then take a drill with a small bit and slowly drill into that hole until the drill bit kinda gets stuck in the hole. Then you can pull off the cover. Do not drill deep at all. You have maybe 1/8 of an inch between the cover and the screw, so be careful.

So now that that is done, turnthe mixture screws all the way in until it just begins to give back resistance. From there turn them to two full turns out. At two turns out, you should be fine in warm weather. Mine are set to 1.75 turns and I have no problems at all at idle. Most jet kits say to go to 3 turns out, but my bike ran so rich at idle it was off the charts on an A/F graph.

I dont know what size pilot jets you have in there but I would recommend using the factory size. If your bike has a jet kit in it, they may be one size larger. This will cause a big 'ole stumble at the 5000 rpm range at light throttle conditions. I has a #35 pilot jet in my FZR and when it got up to 90 degrees the bike would flood itself if I pulled in the clutch when I was riding. I went down to a #32.5 (stock) and it is better, but I also have a #30 jet that I am thinking about throwing in there to clean it up a little more.

If you do these things and put it all back together, set the idle to something like 2000 rpms, then slowly decrease it to 1250. Then play with the throttle and see how the rpms drop. If you get a small hangup at 1700, and then it drops down to your 1250 setting, thats just fine.

Hope some of this helps and that Im not talking over anyones head here. Carbs are really easy to work on and adjust, but tuning them for changing weather is really annoying and can be a trial and error sort of thing.
 
1 - 7 of 7 Posts
Top