Choosing Jets
#1
Choosing Jets
Sup guys, Cleaned up the carbs and still have a bogging issue so I've got to repull the carbs and figure I might as well swap the jets this time but I have no clue what to use.
Bike 88 CBR1000f
Altitude 250ft above (below would suck!)
K&N Air filter
Stock Exhaust (would like to future proof for slip ons)
My goal is crisp response, increased power is nice as well. What do you guys recommend? I've read a ton of threads and don't really have an answer that I feel comfortable with. I don't want to do this again (Actually don't really want to rip the carbs off again! ).
This is what I got from an online calculator but from what I've read not all companies use the same numbers?
Bike 88 CBR1000f
Altitude 250ft above (below would suck!)
K&N Air filter
Stock Exhaust (would like to future proof for slip ons)
My goal is crisp response, increased power is nice as well. What do you guys recommend? I've read a ton of threads and don't really have an answer that I feel comfortable with. I don't want to do this again (Actually don't really want to rip the carbs off again! ).
This is what I got from an online calculator but from what I've read not all companies use the same numbers?
Calculated Jet Kits for Your Honda CBR1000F Hurricane 1987-1988!
You are riding at an altitude between 100 and 400 Feet
You are riding at a temperature between 75 and 95 degrees (F)
Only 1 Jet Kit needed for all your carbs!!
for no or light modification
eg. stock airfilter and no exhaust mod, stock air filter and exhaust mod, k&N air filter and no exhaust mod
Ultimate Jet Kit containing a set of larger main Jets, a set of larger Pilot jets and 1 sets of shims
select this jet kit
This Kit contains: four Main jets size 125 , four Pilot jets size 38 and 1 shim for each Slide Needle.
Only $47.95 with FREE Shipping!
You are riding at an altitude between 100 and 400 Feet
You are riding at a temperature between 75 and 95 degrees (F)
Only 1 Jet Kit needed for all your carbs!!
for no or light modification
eg. stock airfilter and no exhaust mod, stock air filter and exhaust mod, k&N air filter and no exhaust mod
Ultimate Jet Kit containing a set of larger main Jets, a set of larger Pilot jets and 1 sets of shims
select this jet kit
This Kit contains: four Main jets size 125 , four Pilot jets size 38 and 1 shim for each Slide Needle.
Only $47.95 with FREE Shipping!
#2
Jetting is really a process, part science and part art.
Stock exhaust and replacement filter should not require rejetting.
The fuel delivery system is segmented into several parts generally starting with the main jets controlling max fuel intake at wide open throttle, max RPM.
The 'midrange', partial throttle/mid RPM is metered by the needles riding on the slides and limiting that max fuel amount using the taper of the needle as a fuel 'curve'.
Below that is the idle circuit yet all these segments do overlap.
If your having a specific issue, you need to precisely as possible establish what part of the system is responsible and then correction can made there. This works best if you know exactly what has or has not been done to the bike from completely stock.
Most stock bikes do not have adjustable needles and would then require a jet kit regardless.
Changing main jets would primarily only affect a fuel condition error from mid RPM mid throttle and on up to WOT, max RPM in a relatively linear manor. Altho a large error in jet size will affect the whole system.
Stumbles and stutters are more difficult, typically include overlapping areas of fuel delivery and could also be related to other carb issues such as slide movement and carb vaccum as well as exhaust anomalies.
Sorry for the long post.
In nut shell, isolate the area as much as possible. Then determine, if you can, whether a lean or rich or 'other' condition exists and then your direction can better be determined.
Stock exhaust and replacement filter should not require rejetting.
The fuel delivery system is segmented into several parts generally starting with the main jets controlling max fuel intake at wide open throttle, max RPM.
The 'midrange', partial throttle/mid RPM is metered by the needles riding on the slides and limiting that max fuel amount using the taper of the needle as a fuel 'curve'.
Below that is the idle circuit yet all these segments do overlap.
If your having a specific issue, you need to precisely as possible establish what part of the system is responsible and then correction can made there. This works best if you know exactly what has or has not been done to the bike from completely stock.
Most stock bikes do not have adjustable needles and would then require a jet kit regardless.
Changing main jets would primarily only affect a fuel condition error from mid RPM mid throttle and on up to WOT, max RPM in a relatively linear manor. Altho a large error in jet size will affect the whole system.
Stumbles and stutters are more difficult, typically include overlapping areas of fuel delivery and could also be related to other carb issues such as slide movement and carb vaccum as well as exhaust anomalies.
Sorry for the long post.
In nut shell, isolate the area as much as possible. Then determine, if you can, whether a lean or rich or 'other' condition exists and then your direction can better be determined.
#3
Jetting is really a process, part science and part art.
Stock exhaust and replacement filter should not require rejetting.
The fuel delivery system is segmented into several parts generally starting with the main jets controlling max fuel intake at wide open throttle, max RPM.
The 'midrange', partial throttle/mid RPM is metered by the needles riding on the slides and limiting that max fuel amount using the taper of the needle as a fuel 'curve'.
Below that is the idle circuit yet all these segments do overlap.
If your having a specific issue, you need to precisely as possible establish what part of the system is responsible and then correction can made there. This works best if you know exactly what has or has not been done to the bike from completely stock.
Most stock bikes do not have adjustable needles and would then require a jet kit regardless.
Changing main jets would primarily only affect a fuel condition error from mid RPM mid throttle and on up to WOT, max RPM in a relatively linear manor. Altho a large error in jet size will affect the whole system.
Stumbles and stutters are more difficult, typically include overlapping areas of fuel delivery and could also be related to other carb issues such as slide movement and carb vaccum as well as exhaust anomalies.
Sorry for the long post.
In nut shell, isolate the area as much as possible. Then determine, if you can, whether a lean or rich or 'other' condition exists and then your direction can better be determined.
Stock exhaust and replacement filter should not require rejetting.
The fuel delivery system is segmented into several parts generally starting with the main jets controlling max fuel intake at wide open throttle, max RPM.
The 'midrange', partial throttle/mid RPM is metered by the needles riding on the slides and limiting that max fuel amount using the taper of the needle as a fuel 'curve'.
Below that is the idle circuit yet all these segments do overlap.
If your having a specific issue, you need to precisely as possible establish what part of the system is responsible and then correction can made there. This works best if you know exactly what has or has not been done to the bike from completely stock.
Most stock bikes do not have adjustable needles and would then require a jet kit regardless.
Changing main jets would primarily only affect a fuel condition error from mid RPM mid throttle and on up to WOT, max RPM in a relatively linear manor. Altho a large error in jet size will affect the whole system.
Stumbles and stutters are more difficult, typically include overlapping areas of fuel delivery and could also be related to other carb issues such as slide movement and carb vaccum as well as exhaust anomalies.
Sorry for the long post.
In nut shell, isolate the area as much as possible. Then determine, if you can, whether a lean or rich or 'other' condition exists and then your direction can better be determined.
Here is the latest thread I have on my issues.
https://cbrforum.com/forum/cbr-1000f...e-road-140722/
So if you guys can give me another avenue to approach I'm all ears. This is the first motorcycle engine I've ever tried myself (I'm old school big v8's) so a little knowledge is probably dangerous for me.
OK just made a vid, the sound is horrible (actually the camera is horrible) but you should be able to see the issue clearly enough.
Last edited by Hueristic; 08-14-2012 at 03:51 PM. Reason: Added Vid
#6
#8
Did you watch the vid? that's the first time the bike ever went through the power band without bogging. I'd say it's all set. After I get some miles on her (got registration headache:lost the bill of sale) I'm putting on the coil mod and do some preventive stuff and then tuck her away for the White stuff.
#9
I meant to say something earlier, but using water to decarbon & clean up an engine is very effective. I learned that trick a few years ago at a shop I used to work for.. most cars that won't pass smog due to carbon buildup will pass with flying colors after running a couple bottles of water through the intake.
If you've ever seen the inside of an engine that was leaking coolant into the combustion chamber(s) it has the same effect. Bright shiny piston and valves with no carbon on anything. Happy to hear you got it sorted out!
If you've ever seen the inside of an engine that was leaking coolant into the combustion chamber(s) it has the same effect. Bright shiny piston and valves with no carbon on anything. Happy to hear you got it sorted out!
#10
I meant to say something earlier, but using water to decarbon & clean up an engine is very effective. I learned that trick a few years ago at a shop I used to work for.. most cars that won't pass smog due to carbon buildup will pass with flying colors after running a couple bottles of water through the intake.
If you've ever seen the inside of an engine that was leaking coolant into the combustion chamber(s) it has the same effect. Bright shiny piston and valves with no carbon on anything. Happy to hear you got it sorted out!
If you've ever seen the inside of an engine that was leaking coolant into the combustion chamber(s) it has the same effect. Bright shiny piston and valves with no carbon on anything. Happy to hear you got it sorted out!