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Raptor Pilot
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15 Posts
Discussion Starter · #1 ·
Some background:

Purchased my 1998 BB 3 years ago.
Spent first summer chasing charging issues.

  • Had Dealer replace Chain and both sprockets as part of purchase

  • I did the following myself through first summer
    • Oil change and New Spark Plugs and air filter (not K&N) right after purchase
    • Replaced R/R 3x before ending up with MosFet RR
    • Replaced Stator eventually as well

Work on charging system was based largely on information found on this forum (thanks team)
.

Through out first season of riding experienced performance problem indicating Carb issues. Slight miss at idle, hesitation when at cruise at ~3k RPM regardless of gear, would "bog down" if i tried to get on the throttle from the 3k range, accelerated fine if at higher RPM. Just always felt it was not performing the way it should.

Didn't ride much the first winter, but ran bike a couple times a month and short rides when weather permitted.

In the spring at the start of the second season, took into shop for some work as I needed new tires anyway and didn't have the capability\desire to mount tires myself. Work done by shop was:


  • New Tires installed

  • Rear Brakes
  • Oil Change
  • Carbs Cleaned and Sync'd*******

After shop visit, bike was running really well. Hesitation and rough idle gone, good power, running as expected. Rode all summer with no issues till last ride in late fall, then perf issues re-surfaced one day out of the blue. Parked bike for winter. Turned off fuel and ran till died to drain carbs, removed battery and put on Tender.

Intended to do projects on bike this winter but other issues got in the way. Started putting bike back together for this season in the last couple weekends:


  • New Plugs
  • Changed Oil

Got her back together last weekend and on the road for the first time one evening this week, and perf issue is still there. It's subtle, slight miss at idle, hesitation when in cruise again around 3k like before. Very similar to the way it was when I got it, maybe a little stronger when I get on the throttle than the first season but the perf issue is still there. I was hoping it was just the 2 yo plugs but no such luck. I have a new air filter on the way but not holding out much hope it will fix it.

I think it sat for a while before I bought it. A lot of the problems I had early on seem to be indicative of disuse, but after the shop visit last spring, I was optimistic that I'd worked through all of that but maybe not.

Bike has just shy of 21K miles total, of which I've put maybe 3200 miles on since I got it 3 years ago, most of which is commuting ~40 miles RT to work in the summer weather permitting, with a couple of longer trips each summer.

My question is, could the Carbs be out of sync again after just a year and barely more than 1k miles of riding, or am I looking at something more serious? Manual says carb sync every 8k miles?? I should also point out when the carbs were done last year, they replaced all the fuel lines and vacuum lines to\from carbs\tank as well.

Appreciate any insight.
 

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Had a similar issue with a GPZ900R. If I twisted the throttle (in neutral) really quickly from idle it bogged down before picking up and heading for the red line. Horrible when leant over around a bend because when I initially powered on it would bog down before accelerating. Try that with yours. At a standstill and in neutral - instead of gently revving it, just twist the throttle really quickly to see if the revs drop before picking up.

Anyway, I cleaned the carbs, balanced em etc etc but nothing improved. Took the bike to a Kawasaki specialist who let me try another ecu etc but still the same. They'd never seen the problem before. Some said air leak, some said filter, some said worn carbs.

Anyway, after a few months of trying to ride around the problem (and convinced it was a fueling issue) I stripped the carbs again. Checked everything meticulously and then discovered the problem. The carb floats were set wrong and were too low. So when you revved the bike it took half a second to suck up fuel instead of doing it instantly. Bike cured when I set them correctly :)
 

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When you say cleaned, what was done to clean them. Sounds to me like you have dirt in the primary/low speed side of the carbs. The passages are very small and easily plugged. The best thing to do is pull them down and use compressed air to blow out everything. Another and better option is to have then ultrasonic cleaned.
 

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Raptor Pilot
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15 Posts
Discussion Starter · #4 ·
They supposedly did the ultrasonic cleaning. I'm trying to find the paperwork from the work to be sure but I seem to remember it saying "ultra sonic carburetor clean".

@Steve, From what I've read here on the forums, floats are not adjustable, so if it's a float problem, i think it'll mean new carbs ;-/.
 

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Raptor Pilot
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15 Posts
Discussion Starter · #5 ·
Found the paperwork. Was definitely an ultrasonic cleaning.

That's why it seems strange they'd be having this issue again so soon.

Sent from my SM-G930T using Tapatalk
 

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Found the paperwork. Was definitely an ultrasonic cleaning.

That's why it seems strange they'd be having this issue again so soon.

Sent from my SM-G930T using Tapatalk
The other possibility is that somethings come loose in the lines and gotten into the carbs. The thing that keys that to me is that they replaced all the lines. The low speed jet passages are very small on the order of about .010 thousandths so it won't take much of anything to plug them and cause the issues your seeing. I once had to pull a set of V45 carbs apart 3 times before i got everything cleared out.
 

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Raptor Pilot
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15 Posts
Discussion Starter · #7 ·
The other possibility is that somethings come loose in the lines and gotten into the carbs.
Thanks Bees! I think i may actually have this sorted. Your comment about something coming loose got me thinking. when the issue cropped up again last sumer it was rather sudden, like one minute is was running fine, then next it wasn't.

I got the new air filter, so since i had to pull the tank off any way for that, I went ahead and pulled the whole air cleaner off so I could take a look at all the vacuum lines again, since 'd read on the forums here where others had had similar symptoms as a result of vacuum lines coming loose\leaking, and this is what I found.

20170423_165123.jpg 20170423_165044.jpg 20170423_164821.jpg
 

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Ahh that would explain a bit glad you found it.
I'd go through all of the rest of the lines then as well and look for more cracks and splits. They'll probably show in the same location near the ends.
 

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Yep, disconnected vacuum lines will do it every time.Good eye on the initial visual inspection. To answer your question about carb sync, it mostly affects idle quality...as soon as you crack the throttle it all changes....and by sync the carbs all you are doing is making sure each carb sees the same amount of vacuum and that vacuum is generated by a combination of how far the butterfly is open and intake valve timing...if the intake valve, for whatever reason gets a little loose the intake valves lift is reduced but more importantly the valve opens a little later and closes sooner....which generates a little more vacuum and if you were to sync the carbs you would open the butterfly slightly and that would reduce the vacuum signal to match the other 3 cylinders....problem with that....a cylinder with less intake valve duration is more efficient at idle...efficient means it makes more power....and you just opened the butterfly on that carb....and that increases power.........as long as the linkages on the carbs are good the only thing that affects carb sync is valve adjustment...and as long as compression is within spec.......low speed jets? I dont know how much they are in your world,my local dirt bike had a set in stock...$20...and i went next size up...motor seemed to like the extra fuel, idles fine and off idle response kicks ass....best-est/easiest way to check out proper idle (each cylinder being equal) ...infrared temp gun...anything more than 75* cylinders means something isnt right...if the valve adj is right, carbs sync is good....runs good off idle its either a problem in low speed circuit or idle mixture needs adjustment.......valve adjust/comp test/carb sync and check exhaust pipe temp....and there have been times, for whatever reason...bike needed a blast down the road and back and it ran different/better...........can you buy av gas where you are at? Its the best shit on the planet to put in your tank for storage..50% mix is fine...ive seen bikes stored 2 years that start and run like yesterday...figure light planes sit on the ramp for extended periods of time without problems...
 
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