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

Fuel efficiency

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  #11  
Old 04-05-2011, 09:34 AM
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Just to throw in my 2 cents, I have a V&H SS2R exhaust, K&N filter, Dynojet carb kit, stock gearing, irridium plugs and a V&H power pack(black box ignition). I get 42-44 mpg commuting 85 miles a day. 2/3 back roads, 1/3 interstate.
 
  #12  
Old 04-05-2011, 09:38 AM
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I am not 100% sure, but I am looking in some stuff that the PO gave me, and I think he got #40 for pilot jets, and #125 for the main jets, and #0985e-56r/3 for the needle. I use 3 1/2 turns for the screws. It has a Vance & Hines pipe (SS2), K&N air filter. One more thing, it idles ok but a little bit rough, and while riding it stumbles during low rpms.

I just checked the rear sprocket and says "42T, MA 2". I am not sure which is the right number of tooths for this bike.
 
  #13  
Old 04-05-2011, 10:20 AM
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jajgarcia, do you have a US model or European, Aisian? The pilot srews should be left at the stock position unless there has been radical changes. You seem to be set up similar to my bike. When I put the jet kit in I arbitarily opened the pilot srews 1/2 turn. Not good!
The bike became harder to start, mpg's fell to 35-38. I finally went back to the stock settings on the screws and it made a world of difference.
You say you're 3 1/2 turns out. On the Euro bikes the max. setting is 3 turn out so you probably should turn your srews in at lease 1/2 turn.
 
  #14  
Old 04-05-2011, 10:28 AM
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Bassam, I guess I have a US model. The pilot screws where in the stock position, but the bike was hanging out on the rpms. This is, while shifting, I will have to wait good 2 or 3 seconds with the throttle closed for the rpms to go down and then shift gears. I read somewhere that that is a symptom of the mixture being too lean. I set the pilots to 3 turns and adjust the idle throttle and it got way much better. I thought it could still be a little bit richer, so I gave it half turn. To be honest, I don't think I noticed much difference, so perhaps I should go back to 3 turns. Still it stumbles and there is a little bit of hesitation at very low rpms, which I don't quite understand.
 
  #15  
Old 04-05-2011, 10:33 AM
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3 1/2 turns sounds like alot, I thought it was 2 1/2 to start, or maybe that was for my bike. I will have to consult the manual when I get home. Also when you cleaned the carbs did you check to see if the pilot jet was clean? Because when I tore my carbs apart on Saturday and realized all 4 of my pilot jets were clogged so I had to use a sewing needle to clean em, and now she is on point!!!! I also have a fairly similar set up as yours, and I dont know the pilot screw setting, but I also have #124 main jets and #40 pilot jets, and no idea what the needles are set at.

Also you are saying that the rpms are taking awhile to drop, have you checked your throttle linkage?

From another post by Slowpoke:
check out the following items that the Haynes manual says to check for poor running at idle and low speed. Ignition: Check for low battery, fouled plugs, plug wire shorting, ignition timing, faulty coil and faulty spark unit. For carbs: check for intake air leaks, mixture adjustment screws, carb sync, pilot screw clogged, air cleaner clogged or omitted, choke stuck on, float level wrong, fuel tank air vent clogged, and sticking carb pistons. It also says to check valve clearance. It doesn't say, but we know CBR's, so also check for a stretched cam chain, as that retards valve timing and hurts low end performance.

Another thing is what kind of plugs are you using and what are they gapped at?
 

Last edited by outlawfox13; 04-05-2011 at 10:45 AM.
  #16  
Old 04-05-2011, 10:49 AM
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Yes, I clean very well all my pilots, and make sure they are not clogged. As I said, perhaps 3 1/2 is too much, but for sure 3 turns helped a lot with the hagging on the rpms. The plugs are new, NKG with the recommended gap.
 
  #17  
Old 04-05-2011, 02:04 PM
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Well maybe when we do the carb sync and a valve adjust it will even back out. If not then you may need to get a new jet kit(if the PO didnt get it jetted correctly). Other then that after the sync and the valve adjust, maybe do some plug chops to find out which jet is doing what.
 
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