Topic: my cb650 is holding idle at 4k rpm and wont rev past 6k rpm... please help!

[Spanner 1]

Yep, need to replace them...... should be available 'used' on E-Bay Parts.

[Hush]

Good spotting Spanner, usually these ignitors are OK even with the goo running out of them but if that is capacitor innards hanging out of it I would say yep they are screwed.
Could possibly have happened when that freyed through wiring earthed out on the frame so better tidy taht up pretty good too.
Wonder if this is that other 650's problem also?

[81cb650]

lots of options on ebay, but alot of them have the goo running out already...found a set for 80 shipped that is fully contact no goo running out which is seeming to be a hell of a deal, because they are selling for 125 for one with no goo running out. 70 for one with goo running out. what a rip... tidied up the wires a bit with some soldier and am about to go  for a ride, well see how it goes...

[trueblue]

http://www.davidsilverspares.co.uk/CB650Z/ there are some new ones on dss for 75 pounds

[81cb650]

Thanks for the link true blue. I eneded up going the used route on ebay, I got 2 for $80 shipped, and they are apparently not blown out on the back yet. which is a great deal because most are going for 75 w/o shipping for ONE...They have those aftermarket ones you posted on ebay aswell, which would be $250 to get both! hopfully I went the right way with the used ones and this actually fixes my problem. They should be here tomarow ! if the new spark units dont fix the problem, Im thinking to get my carbs synced next. what do you guys think?

[81cb650]

So I got my new ignition modules, and when I put them in , It did nothing. It kinda felt like it had more power and reved higher for a minute, but was probably just me thinking that it did. I changed the oil today, and cleaned the carbs for the 4th time because everyone I ask keeps saying that, im confident in them now that its not the cleanlyness of the carbs. also The slides on the carbs move freely and are clean, so Its not that. next Im going to get the carbs vaccuum synced. Does anyone think thato It is neccacary to adjust my valve clearences? could that possibly have anything to do with this? Im on the verge of selling this bike, I cant stand watching the summer go by and not being able to use this thing. its saddening. 

[the technological J]

just checking but i wanna make sure.. you have done the 3000 mile tune up?

[81cb650]

Ive never heard of a 3000 mile tune up, But so far I have. installed the correct restriction plate over the air filter, New spark plugs, new wires, oil change with a new filter, air fuel screws at 1.5 turns, carbs clean, idle jets  cleared, new float needles, new battery, choke functioning properly, new ignition modules, checked and lubed the timing advance mechanism. I believe thats it.
What I havn't done- new air filter(bc it looks basically new although I dont know how old it is.) checked the timing,( don't have a light)should I get one? , how important is this to my problem? carbs synched(again, how much would this really help my bike not revving past mid rpm) compression hasnt been checked. And I should add that my spark plugs are black with carbon even tho there only 50 miles or so.
Also I dont know how important this is, but Ive put a few miles on the bike like this and am noticing patterns, first gear will rev to 8.5, sometimes 9.5, 2nd gear, a little less, and a little less throughout the gears until 5th, and the bike tops out at a whopping 60mph, every time, its a consistent flaw at this point. And ive corrected the 4k holding Idle with the black idle nob, but sometimes the bike will just shut off at a stop light. its a very delicate balance.
Again, I really appreciate any help you guys put forth, Without this forum, id be dead in the water.

[w1sa]

Another member (ak58lp )had some success the other day with a problematic 650. There's a link on your thread.  A mechanic isolated the problem (mainly airbox flow-I think)

Might be part of your problem, but could also be poor ignition perf, valve clearances jetting /carbs etc.

I think you should also do the other period service checks including the following,

new air filter
check the valve clearances/chain tension adjustment
check the rotor/pulse generator tip gap/clearance
check each and every spark plug sparks healthy on demand from the ignition (use fresh clean plugs and prop charged batt)
check ignition timing (with timing light) at idle and for full advance.
check the carb jetting......size and condition?......per spec?
bench sync the carbs
check choke operation and control
Recheck float height and function and check fuel level with clear tube(when installed on bike). Good idea (some think) for checking with engine running on centre/back stand.

With a multimeter. you could also check
switched battery voltage level to the coils (as compared to the batt)
resistance thru the pulse generator units (ignition triggers)
ign. coil/lead/cap resistances
other general electrical performance that can also affect ignition voltage

The pulse generator/harness  to spark unit connectors can get cruddy and interfere with good signal switching etc.. etc...................................check and clean all possible connections.
........................if at all possible...............get a manual that covers your specific model ...................

[ak58lp]

Yes it was me that had the same issues. As w1sa mentioned I finally had to take mine to a mechanic to get things sorted out. I looked through your thread and noticed you have the air filter cover back on. Take it off first and try that. Then I would look at these options next in the same order (easy to harder).

-remove air filter cover
-try draining the tubes by the center stand. They are likely full of water and crap
-make sure the air filter box has no holes, cracks, loose hoses etc.
-try running the bike with no gas cap to see if the vent may be the problem
-on the right side of the bike is the round cover that has the ATU behind it. Make sure the springs in there can move freely. My post on your first page has the info on that from Hush.
-when you had your carbs off did you turn them upside down and look at the rubber tees that join the 2 banks together? They hook up to another tee and then to a hose that goes back to the air box. Mine were completely rotted at the bottom. These are not easy to replace but if I can do it you can too.

I feel your pain man but I had mine 85% fixed when I took it to the mechanic. Wires and plugs I think were the sticking points for me.

[81cb650]

So I think I got it, I took the air filter out, and guess what, this thing came alive, imagine that...all this #$%* , and it ends up being the air filter... glad my persistance payed off because I just got off the phone with a few shops that said it would be 100 bucks just to look at it, thats what made me go try everything one more time.... god damn Im glad I did. So now the big question. Is running this bike without an air filter the same as running pods?, because it  seems to be pretty damn wide open. next what is the difference between the stock air filter and a k/n stock replacement. I think the K/n seems like its the best be in this situation because the air filter is the problem. anyone had this problem before wanna tell me what then did? thanks again for all your help everyone this board is a great community

[ak58lp]

Glad to hear it!!! Most of the searching I did forever came all back to one thing..air delivery. My guess is if you have rebuilt the carbs then the rubber tubes are the problem. Mine has the stock air filter back in now and runs perfect. Sorry no idea about the pod filters.

Did you try it with just the air box cover removed and the filter in place?

 Have a look at this (2nd problem with air box pic). This worked for me for awhile. Better than tearing banks of carbs apart until at least the winter.

http://www.myhonda650.com/cb650problems.htm

[81cb650]

glad to hear your bike is working too, I put the filter back in, and my bike came with a modified restrictor plate to begin with so that is on now. its just the ring with the bolts without the restriction part on it.  I had to buy the full plate from someone to get my bike back to normal to my try and get to the bottom of my rpm problems. turns out I needed it to be open all along. but I think the new spark units have alot to do with it aswell because When I put them in I had to completely readjust the air fuel mixture screws and idle knob. now that i have the plate off tho my 4k rpm thing is back and If I adjust my idle low enough for it to go away, the bike dies every once and a while...so still a little touchy on that, But im going to keep working on that just glad I can use it now. looks like im ganna give this 650 a few cosmetic upgrades and sell it on ebay, I think I want a 550, or 750, I didnt realize that the 650s have a raised frame in the back, and I want the flat cafe look... i payed 750 for the bike, and have about 1000 total into it. Id be happy to break even and get into a nice 750 for around a g

[Hush]

My 650 ran like crap too until I put in a new air filter, made unreal difference, pulled my first wheel stand at the lights, quite frightening on a Police bike crossing the intersection on the back wheel.
Best advice I usually give to new owners is throw away the old air filter even though they look good they are clogged with microscopic crud and the bikes are not breathing.

[coldwave007]

Yup, the 650s are very sensitive to airflow.  When I was first trying to get mine tuned, I didn't realized how essential the airbox was.  I was running without the airbox trying to get it "dialed in" but wouldn't rev past 5K.  After some experimenting I noticed that the bike ran better with choke on at higher RPMs.  Realized it was because of air restriction, so put the airbox on after a day of futzing with it.  BAM!!!!  It was like I had a little turbo under my seat.  I seriously didn't not expect the power delivery above 5Gs.

[81cb650]

Lol, its funny to read that hush and coldwave, the same exact thing happened to me, it really does have torq, I was pleasently supprised when i wound it up for the first time once it was running good. The bike is carbon fouling plugs tho and I have the idle mixture screws at 1/2 turn. It fouls them pretty bad, I completely ruined a set already with like 80 or so miles. Any Ideas on this? the floats are not sticking, I know that.

[coldwave007]

Is the choke actually opening all the way (from full choke to open)?  If the cable is too tight or not seated properly, it won't return the flaps to the open position and give the bike a rich condition.

[phil71]

arent they just enrichers, not actual chokes?

[Hush]

You have the 4 butterfly chokes, just flaps that open allowing more air for normal running when the cable is fully depressed and close restricting air when the cable is pulled up and therefore enriching the mixture and the accelerator pump on the 650.
I need to let my 650 idle for a good few minutes before closing the choke and riding away.
If you have trouble seating the choke butterflies, loosen the tiny screws that hold the copper coloured butterfly flaps just a little and then let them snap shut, now tighten the screws again.

[ak58lp]

If you have trouble seating the choke butterflies, loosen the tiny screws that hold the copper coloured butterfly flaps just a little and then let them snap shut, now tighten the screws again.

Agree I had the same problem and this fixed mine.

[81cb650]

well, the way the choke works on my bike is that when i pull it, the rpms go down and it will die if i pull it too far, and it does have a full range of motion, its open all the way when pushed down, and closed when pulled up. my problems are back with the 4k rpm hanging, its realy brief now tho, it will only hang for like 2 or 3 seconds, but its enough that when I go to shift gears, it hangs at 4 and is kinda annoying.

[w1sa]

Check the fuel level in the bowls using the clear tube method......also do it with the bike warmed up......you may then see if the idle hang up coincides with different fuel level