Ok guys. 95 cbr600 f3. I bought this bike about 6 months ago, and havent even ridden it yet. Been trying to figure out whats making it run bad.

I've been through 3 sets of carbs, and my latest set is clean as a whistle. They are absolutely spotless, i ate off them the other night (tasted like gas though).

Ohm reading on ignition packs is 3.6 (manual says 2.5-3.1) and they are hooked up correctly.

Ohm reading at ignition control module is 481 (manual says 460-580).

Ohm reading at ignition pulse generator is 481 (manual says 460-580).

Plugs are brand new, gas is fresh and clean, battery is charged. Fuel pump works.

The slides open perfectly. Choke slides smoothly. Carbs arent synced, but from what i've read around here the past 6-8 months is that it isnt absolutely necessary unless you physically take the carbs apart from each other. Its only after you got everything else working good and right. (basically, your bike will run OK out of sync, but not 100%. I'd say my bike is running at 50% now.)

Basically the bike will not start without choke. I let it do its 4-5k rpm run up while its on choke, then after a couple minutes when it gets warm i can finally take the choke off without it dying and it will bounce around rpms from 1k to 1.5k. I give it a slight twist of throttle and it wants to fall on its *** temporarily and then it climbs up to any rpm you want it to, with a slow fall in rpms back to idle. It will do it even if i only try to get it to 3k with a slight twist of the throttle. If you gradually and slowly twist the throttle, it will climb without a hesitation.

Even with the motor warmed up to operating temp, when i cut it off, then try to start it up one minute later, I cant start it without choke.

I havent even tried to ride it yet because the problem is so bad Im afraid it will stall out in traffic if i try to go into first fast by twisting the throttle too fast and it falling on its ***.

SO hopefully thats enough information to get someones gears turning in their head and hopefully kick out an idea and point me in a direction to go while i have the bike ripped apart right now. My latest theory is that it is a vacuum leak issue. Sorry for the long post, but more info is better when diagnosing a problem!!

 

Well it starts and runs so that's a +. The RPMs bouncing around is prolly part carb sync from what I've seen. You can shelve that for the moment. Carb sync after you finish playing with the jets cause it sounds like an A/F mix issue.

Are you doing this testing with the airbox / filter on?

 

yeah doing all the diagnostic **** with the airbox / filter + gas tank on ready to go with all vacuum lines + electrical hooked up. never messed with the a/f mix, arent there screws on the bottom of the carbs that adjust that?

 

id push it in a creek and try some good old insurance fraud. haha or keep working on it

 

trust me will, ive had it for 6 months and its been sitting in the same place in the garage. the thought of dousing it in gasoline and throwing a match to it is very frequent.

my next bike................. FUEL INJECTED!!!

 

The a/f mix is by adjusting the pilot screws inside the carbs and changing the size of the jets, main and needle. Can't intentionally manipulate it, to my knowledge, from outside the carbs (yuppers, you'll have to crack the carbs open again ). Hard to say, and Idodirt is definitely more qualified than I am to offer an opinion, but it sounds like you have a lean condition. Too much air, not enough fuel.

Since you haven't ridden the bike yet, had it under load, you can't really tell if you need different size jets yet. The main and needle jets really affect how hard the bike pulls with the throttle opened different amounts. So for the moment, you'll be playing with the pilot screws. It was the 'D' shaped screw inside each carb.

If you wanna test to be sure if its idling rich or lean, you can try this. Open the airbox and start covering the air filter in increments with strips of duct tape. if it improves, too lean since you're restricting air to the carbs. If not take the air box off, increasing the air flow. Better bike = rich.

i'm betting lean tho cause of your choke and other symptoms.

 

alright thanks kuroshio. the whole bike is ripped apart right now since i quadrouple checked the jets to make sure they were clean. will be putting it back together tomorrow or sat and try your trick. i cant believe i forgot about that, i used to do that back in the day with cars by restricting the air intake pipe with my hand.

just checked and i see the D shaped screws. should those be cleaned as well when cleaning the jets? ive read on here before about turning them all the way in, and writing down how many revolutions it took before reaching the stop, so you can put them back in that way.

 

That's based on the assumption that the carbs were properly tuned and simply dirty. You replaced the carbs, so whatever the pilot screws are set for atm its prolly not your engine. You're gonna have to tune the carbs Or pay someone to do it

Give this a look too
http://www.musclecross.com/forum/viewtopic.php?id=70

 

thanks.

 

The A/F "D" shaped adjustment screws are accessable with the carbs installed (it's very tight). If you didn't remove them and clean them, then you need to do so. Yes you're right that you should gently turn them in until they stop and count the number of turns for each of them so you can put them back. But, as Kuroshio said, these are not your carbs, they came off another bike, and there is no telling how they were working, if at all. I'd start off by turning them in to see where they are, and if they're much off of where the manual says (I believe 2.5 turns from all the way in, but verify that), then I put them where the manual says to put them. I realize you've cleaned them really well, but the idle circuits have some really small holes that are easily blocked. After you remove the A/F mixture screws, you should be able to spray Carb cleaner into them and get it to come out the small holes that are on the intake manifold side of the throttle butterfly. Those holes (3 of them) are hard to see, and 2 of them are hidden by the throttle butterfly. That's the idle circuit, and just off idle when you initially crack the throttle.

The correct initial setting for the A/F mixture screws is 1.5 turns out. This is a 49 state setting according to page 5-22 of the shop manual.