CBR 1000F "Hurricane" 1987-1996 CBR 1000F

Cleaned carbs now won't start back when warm

  #1  
Old 09-13-2017, 11:49 AM
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Default Cleaned carbs now won't start back when warm

Ok, so I found a thread in the f2 forums I thought was close to my problem, so I posted there first (before I realized I was in the f2 forums) but didn't figure much out. I was advised to post here in the hurricane forums with the hopes someone can help me. I cleaned my carbs a few weeks ago and the bike runs great while it's running, I can ride it anywhere as long as I don't shut it off. It will NOT start back after it warms up, didn't even try. Here's a copy and paste of my 2 posts in the f2 forums. The first post I was asked if I synced the carbs after cleaning. Post 1 "I did not. I noticed while I had them off they weren't perfectly in sync by holding wide open and just eyeballing it. But i didn't think it would stop it from running since it was running before hand and I didn't mess with the mixture screws, I just figured I would sync them once I got it back together, but I think I'm going to have to bench sync them first. The reason I cleaned them is it was running rough at low RPM and when just cruising along around 3k it would jump like I was playing with the throttle until I got above 4k. Now after the cleaning it runs great, so much smoother than before but only while it's cool. As it warms it gets worse and worse until it finally dies. I can keep it running by playing with the throttle but if it dies it will NOT start back without letting it cool completely. I don't have much experience with bikes but have been a fabricator and mechanic for a while, and from my experience this is the tell tale signs of bad coil packs or ignition module. So, after triple checking everything I had done with the carbs I replaced both coil packs, wires, plugs, and resistor boots only to change nothing. Thanks for the welcome and the quick reply. I'll bench sync them tonight and go from there." Post 2 (after balancing carbs) "Ok, so I bench synced the carbs, and had a friend of a friend sync them with his tool (carb tune pro I think). Fires right up and runs incredible, so smooth through the rpms, until it warms up. Then it wants to idle a little rough around 1800rpm or lower, not like it has a cylinder down, just rough like a single misfire every few revolutions. Also has a hard time taking off, misfires worse when I start to let out the clutch as it starts to pull, I have to rev it to at least 3k to get moving. As long as I keep it from idling down and dying it runs sooooo much better then it did, so smooth. If it is shut off or dies once it's warm, sometimes it'll start right back as long as I hit the starter within a few seconds of it dying, if it sets for at least about 30-45 seconds it WILL NOT start back until cooling down., Almost like the kill switch is engaged, it won't even try to start, just turns and turns. Using the choke or throttle makes no difference, new plugs, wires, and coil packs, getting fire to spark plugs, getting fuel to carbs. Just a thought that's been banging around in my head, the bike has Vance Hines exhaust and k&n filter but factory 122 jets, do you guys think it's possible that the previous owner, (to compensate for dirty carbs and higher flowing intake, exhaust) could've increased fuel with mixture screws and now that the carbs are clean and flowing better they're flooding the engine? The harder i twist the throttle the better it runs. Also, every time I pull the plugs, there's a sort of yellow film or haze on them, I have cleaned them every time I've noticed it, never seems to make a difference though. I'm completely stumped, this is my only DD so any and all help is GREATLY appreciated. Thanks in advance"
 
  #2  
Old 09-13-2017, 11:53 AM
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BTW it did help with the weird idle a good deal balancing the carbs but still won't start back while it's warm.
 
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Old 09-13-2017, 12:49 PM
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Hi Ricky , what size slow jets do you have, and what colour are the plugs
 
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Old 09-13-2017, 08:50 PM
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Originally Posted by CaBaRet View Post
Hi Ricky , what size slow jets do you have, and what colour are the plugs
I can't recall any numbers on the slow jet, I would assume it's factory and the manual says the pilot jet for my model is 40. The plugs have a yellowish film on them
 
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Old 09-14-2017, 12:53 AM
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Also it's probably worth mentioning, I did not pull the pilot screws when I cleaned the carbs. It was my first time cleaning motorcycle carbs and I didn't want to take anything out that had to be adjusted unless I had to.
 
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Old 09-14-2017, 03:01 AM
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Maybe worth setting the pilot screws to factory specs as they and the slow jets only affect idle (mostly)
 
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Old 09-14-2017, 08:00 AM
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Originally Posted by CaBaRet View Post
Maybe worth setting the pilot screws to factory specs
Ok thanks I'll give that a try this evening after work and post an update
 
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Old 09-14-2017, 09:05 PM
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I pulled the carbs to check the mixture screws. The book says 3 turns out initial setting and 2.5 turns final. They were set at 2 so I moved them to 2.5 it started up fine, I rode down the road and back a couple miles to warm it up real nice. When I shut it off and tried to start it back she fired up instantly. So I shut down again, waited about 60 seconds and tried again, fired right up, shut down, waited about 2 minutes and it started fine again(so far this is the only thing that's made a difference in any way). So I waited about 10 minutes and tried to start it back and it had kind of a hard time firing up, instead of starting immediately it took about 10 seconds of turning over. This time I rode to the store, when I came out she wouldn't start. After about 60 seconds of turning over, while trying different amounts of choke, it backfired and blew a flame out of the exhaust then made a sort of howling sound like the flame was running up the exhaust pipe. The backfire happened right when I let off the starter. After it backfired I tried again and it fired right up, so I got it back home and shut it down. Waited about 5-10 minutes and it won't start again, so I'm going to give it an hour or 2 to cool down and try again. I also noticed while I had the carbs off the #2 carb bowl is just barely barely leaking. Not dripping or anything just had fuel residue on one the cover screws. Could that leak be causing my problems? Sorry for the long post and thanks for any help in advance
 
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Old 09-15-2017, 01:30 AM
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The back firing could be caused by an intermittent spark, check your coils and leads as per manual with your multimeter, and did you put in new spark plugs, carb cleaning can be a b***h to get really clean , and are the slow jets the right size , worth a look when you take them off again, you will probably need a magnifying glass to see the stamp though
 
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Old 09-15-2017, 04:59 PM
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I think I may have solved the issue, but I'm not sure yet which it was. I took the previous owners word for it when he told me the plugs were new because they didn't look very old, probably a bad idea. Also I noticed they were ngk dpr8ea-9 instead of dpr9ea-9 which is a different heat range. So I went ahead and bought new ngk dpr9ea-9 plugs today and replaced the old ones. When I went to the gas station as a test ride I opened the gas cap before I started it because I didn't want to risk shutting it off at the pump and it not starting back. So I went a couple miles to the gas station, got gas and came back, shut her down and she started right back immediately no problem. Shut off and started back a few times with no problems then let it sit for about 10 minutes and it still started back perfect, no problems. Then I realized the gas cap was still open, so, as long as it keeps starting back like it should I figure it was either the spark plugs or the vent in the tank is clogged. The vent being clogged would explain why it runs worse and worse the longer I ride it but doesn't explain why it started doing this only after I cleaned the carbs. I haven't rode any since the trip to the gas station but I'm going to in a few with the gas cap closed to see if that will cause it not to start after shutting off. If it doesn't start back I'll try opening the gas cap to see if it will start. I'll post an update in a little while, I can't thank you guys enough for your help. Hopefully she's fixed
 

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