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?

 

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.

 

OK, well here is the deal. Bought the bike and it was not getting over 4k rpms. Found issue with coils (one was not functioning) and since it felt like it literally wasn't running on all cylinders I figured that was the issue. I cleaned up the ignition system and it was still bogging at 4k but was getting past that range with a little coaxing so I figured an Italian tune up would take care of it as I thought the valves hadn't been used in a while and would clean up with some use. But after a few miles the bike would no longer go above 4k rpm and slowly lost power. It felt like it was flooding so i left it for a few hours and came back and it started again and as I got going down the road it croaked again doing the same thing only quicker this time (guessing because it was still heated up). When home I yanked the carbs and found a blockage on the #1 carb (part of the airbox) and the #2 carb was not opening under vacuum. I thin removed the carbs and repaired the airbox and cleaned the carbs but only removed the main jets for cleaning as I couldn't figure out how to remove the others (they are just cylinders). Now I have the bike running synced @ 3k and the bogging was still present from 4-6k (but is fine after that) so I synched @ 1k(idle) and the bogging moved to 7k (and rpms would not go past 7k) and then today I synced @5k and the bogging starts at7-8k but once past will go all the way to 11k (pretty sure I had it at 12k before though. So I figure the high jets are clogged and figured since I have to remove the damn thing again I might as well replace the jets as from what i've read there is extra power to be had from jetting as well as the default jets are intentionally too rich from factory for all altitudes.

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.

 

Bump.

 

When I get home I'll post more but I don't think that's a jetting problem.

 

After WATER DECARBONIZATION.


Click pic for vid. I can't figure out how to embed vids on this board.





Thanks for the help zaqwert6 !!!

 

Well hopefully you got it.

There's an old saying, everything affects jetting and jetting affects nothing.

Good luck.

 

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.

 

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!

 

I wish you had, I was really hesitant about doing this with absolutely "ZERO" feedback from this forum.