CBR 600F2 1991 - 1994 CBR 600F2

Cbr f2 runs terribly

  #1  
Old 04-06-2016, 11:34 AM
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Default Cbr f2 runs terribly

-94 cbr f2
-good equal compression across all 4
-cleaned and synced the carbs 4 times I'm certain their clean
-good timing bike starts and runs even though it's poorly and I have the stock timing set right now
-Ngk cr9 sparkplugs .035 gap, they look good not wet or dry no oil no fuel no premature wear if anything its a little lean
-3.1 ohm across both ignition coil posts
-4.2 ohms on icm primary coil (way out of spec)
-icm coil pick up resistance in spec I forgot the exact reading
-can't get a resistance reading on spark plug wires no matter how much contact I feel but the bike starts and I can ground the plugs and see a spark (possibly weak)
-Muzzy exhaust, k&n oil and air filter
-Stock jets (yes I know I should rejet, but i should be able to get it in running condition without rejetting, yes power and efficiency will be sacrificed)
-idle jet set at stock position
-No oil leak

Problem is the bike will start with choke on but will die with choke off. Won't idle under 2k even with partial choke. I feel like I'm getting fuel I know I have timing and compression so the last thing is spark, I have identified some problems with the spark circuit but I'm not sure if they are the root of the problem or what I should do about them. When light throttle is applied the bike studded It might be weak spark is creating problems but with choke it will Rev to 3-4k so the spark is there and can support the rpm under its own power

So a few questions, why can't I get a spark plug wire resistance reading? Why do I have so much resistance at the icm primary coil? And for the icm problem would the high resistance show that the wiring has too much resistance through it and would that relate to the high resistance on the coils?, their within spec but at the very top end of in spec, I'm not really sure where to go with the high primary coil resistance. The connections feel solid on the coils and every other part of the circuit looks good to so what should I look for?

Sorry for the long post and the help
 
  #2  
Old 04-06-2016, 01:14 PM
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When the choke is on, the mixture is rich from the blocking of air. It really should not run that great with it on. Since it is, extra air could be getting in there leading to too much with the choke off. I would be looking for a vacuum leak somewhere, like a vacuum line or intake boot.

To check plug wire resistance, you need to be on the 20k scale.
 
  #3  
Old 04-06-2016, 03:52 PM
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Sorry I remembered wrong, the primary coil has 3.3 ohms so still over but not by much should still run. I just went out and double checked that reading

I did more digging around and I believe now that I have a fuel problem, I found a leak on the fuel t on carb 3/4 it was leaking in a way that it was hard to see but I found it and have removed them just need to go to autozone to get 4 new orings

I looked for a vacuum leak but I recently replaced the vacuum lines with new lines and it looks like their still doing their jobs no leaks that I can find.

I'm going to replace the orings Im thinking that should solve my problems, since the carbs are off I'll go a head and clean them again just to be safe, then resync them once their on again. I'll post back if my problems continue, thanks for the quick help though 👍👍
 
  #4  
Old 04-07-2016, 11:29 AM
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Are you sure you put the synch port plugs back in? You know what I mean, like the one your vacuum operated petcock works from.
 
  #5  
Old 04-12-2016, 12:34 PM
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Originally Posted by coalminer frank View Post
Are you sure you put the synch port plugs back in? You know what I mean, like the one your vacuum operated petcock works from.
Yeah I replaced them with new when I replaced the lines.

Got it started resynced the carbs their all equal and looking good. The orings fixed the major leak and their acting more like carbs again but I still have some problems/questions:

I cant get a solid idle, and especially near 1400rpm I get surging, I've adjusted the pilots I have to be near 3 or 3 1/4 turns out (yes I know I should rejet but I'm not spending that money right now too many other investments and projects) each time I adjust the pilots a 1/4 turn out then restart I get a more consistent idle and I can lower it's idle slightly before it starts studdering again and sounding like it wants to die on me.

Are the pilots still not out enough and it's too lean to idle where I want? Either that or some cyl are rich and some are too lean causing the weird idle and studdering and surging?

My question should i keep adjusting the pilot screws out and try to get a more steady idle right now it's idling best around 1700

To be honest I'm on the edge of welding some o2 bungs in each of the exhaust tubes and using a wideband to tune ( i would have to get one or borrow one)

If I went that route could i just go one by one start the bike with a wideband In one cyl with the others plugged then just adjust the pilot screw until I get the a/f I'm looking for? Since the carbs are already synced all that I would need to do is adjust the pilot then the idle screw back to the right rpm then go to the next cyl?
 

Last edited by tampa_git; 04-13-2016 at 07:26 AM.
  #6  
Old 04-12-2016, 07:50 PM
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Somewhere out there, there is a "hand held tach" that you can see the rpm's change as little a 50rpms or something like that. And thats how you supposed to adjust the pilot screws. Its tells in the Clymer manual. But I've never been able to find such a "tachometer".
 
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Old 04-12-2016, 08:45 PM
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Yeah I've read about it and saw one post somewhere on a forum I can't find again that had a ebay link that went no where but that's the closest I got haha

If I'm going to take it to a dyno I might aswell get a wideband and 5 bungs with the plugs, 1 for each cyl then the one for the combine just to double check and take note of. That way at least I can keep it and use it to tune other projects.

I'm looking at a innovative mtx-l, ok price and innovative seems accurate and reliable any opinions would be great though this will be my first wideband

I have a syncrowave 250dx and can weld the bungs no problem it won't be back purged but honestly I'm not that concerned, the bigger pain will be getting the angle right so they will fit and can stay on when driving not just on the stand

Tomorrow I'm going to run to united speed world and see what they have laying around and see how much their trying to charge I just really want to get it running how it's supposed to be
 
  #8  
Old 04-13-2016, 01:29 PM
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Well I had to order the wideband but I got the innovative wideband I was looking at and they only had 3 bungs and 2 plugs so I had to order a few of them also but they are vibrant performance so their really nicely machined and a breeze to weld so all good

3 bungs are tacked I'll tack the other 2 then check fitment when I get them and the wideband in

I guess I should be shooting for 14:1 at idle?
 
  #9  
Old 04-13-2016, 02:59 PM
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Originally Posted by coalminer frank View Post
Somewhere out there, there is a "hand held tach" that you can see the rpm's change as little a 50rpms or something like that. And thats how you supposed to adjust the pilot screws. Its tells in the Clymer manual. But I've never been able to find such a "tachometer".
Most DVOMs have a tach setting that is that accurate.
 
  #10  
Old 04-13-2016, 04:27 PM
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Originally Posted by 74demon View Post
Most DVOMs have a tach setting that is that accurate.
Yeah I've heard of people trying to tune that way some more successful than others. Heard a big problem was how fast the screen refreshes, it's only 50rpm changes and the rpm is chaging all the time but it's possible. I don't really want to trust my tune to mine though, so that only leave the dyno as a accurate source to use as a tach but I might as well get a wide band if I'm going to spend money to dyno a bike that I know needs a jet kit
 

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