cbxtacy wrote:I had the same problem about 15 years ago on my wire wheeled 79 here http://www.tgprace.com/ at 11,000rpm. Started running on 5 cylinders. I'm pretty sure it was the #5 cylinder connecting rod breaking and acting like a buzz saw. The transmission and cylinder head were still okay, even though one cylinder had a few bent valves.
At least you did the right thing and put something in for your location. Now we can rest easy.
When I read the original post on the 6500 rpm problem, I thought maybe I had hit on a solution for my similar problem. My 79 cbx revs to 8000 rpm and stops, stays there if you hold the throttle open. Operating the choke on does nothing. Carbs have been off twice, 2d time yesterday/today, and cleaned again. I rechecked the floats and they were ok. Checked slides, dropped eye dropers of alcohol in the air bleed holes and it went thru ok, removed jets again and they were clean, blew out all with 120 psi air and cleaner. Now, for the surprising news - this is the second engine in this frame that has done this so it is something common to both motors, ie... the carbs or something electrical. Further, plug wires changed to Taylor, no change in rpm problem. Both 422 and 469A advancers have been tried; pulsar units swapped; two different spark boxes tried. None of these changes/troubleshooting steps has changed the 8000 rpm stall. Bike starts very easy, idles great, runs fine with some cutting out/popping up thru the rpm range but has a strong range between 4000-7000 or so and then pops/cuts out and then stalls at 8000 rpm. Yes, I have also checked the choke and it seems to be operating fine. Gas tank cleaned last week, petcock was rebuilt and it flows fine. I made one other last minute change just in case it is running lean and that was to put in some 105 jets. (I have a K&N filter and dyna coils with the stock pulsar.) I decided to jet up to 105s because the plugs were very light with virtually no grey color, ie... white. Also did an exhaust pipe temp check and found all to be running about the same at 300 degrees plus - hotter than my 81 or 82. I have probably done some other things that I have forgotten to put into this request for help, but hope someone out there may have an idea on what to check next. BTW, I finished the carbs earlier today and have put them back on the bike. Plan to finish bolting engine in tomorrow and take another test ride. Voltage at the coil was 12.5v, pulsar units checked and spark box volts were 11.14 to 11.17; alternator is charging fine. The resolution of this problem will be the last step in an 11 month restoration that has cost me a lot of money.
79, 80, 81, 82 CBX's, 87 Hurr 1000F, 83CB1100F, 87 VFR700, 01 Blackbird
40 yrs of Hondas and still baffled....
yes, tach cable is new and tach seems to be ok. the engine definitely halts at around 8000 rpm, in both sound and performance. it is not mistakable. I have 3 other cbx's, so am familiar with power band and performance characteristics. thanks and keep thinking about it. Sometime today, I hope to finish bolting the motor mounts and get the exhausts back on for another test ride. More later.
79, 80, 81, 82 CBX's, 87 Hurr 1000F, 83CB1100F, 87 VFR700, 01 Blackbird
40 yrs of Hondas and still baffled....
Should be fully on the mainjet by then, I would check cam timing & do a leakdown test if fueling is known to be good.... Check lobe heights while you are at it also....
sounds like you have a "hidden" rev limiter somewhere in the wiring harness since 2 different motor have the same problem ,too bad you don't have another wiring harness you could try
Dan 1995
Triple x owner 79,81,82
Ironbutt member #24745
Coast to coast and border to border on a CBX
My goal was to ride farther and faster than my wife could bitch....
I needed a faster bike....
So I got a BUSA!!!!!
Well, the problem is fixed and the bike will blast up to redline and beyond now. I am not sure what fixed it but here are the two things I did. I changed one wire on the Dyna coils and I know that they are supposed to be non pole specific. I re-vacuumed the carbs (for the 3rd time) and had trouble with # 6 carb. This one was replaced due to damage to the original one. (Mike Nixon replaced it) I screwed the vac adjuster screw all the way in and then backed it out and readjusted to balance with the other 5 gauges. After screwing it back out, there was a noticeable change in the engine sound - smoothed out. After backing the screw out and readjusting, it seemed different. Test rode and all was ok. ?? Mystery to me because I had vacuumed them twice before. Dont know about the coil wire - electric is my worst subject. Any thoughts?
79, 80, 81, 82 CBX's, 87 Hurr 1000F, 83CB1100F, 87 VFR700, 01 Blackbird
40 yrs of Hondas and still baffled....
Congratulations on getting it sorted out John.
My carb knowledge is bad and electrics are worse but would a single carb being out of whack cause the entire engine to stumble?
Coil problems in my past have caused similar symptoms as described by you.
I am no expert either, learning something everytime I go into the garage and fool with these beasts. It is my belief that one carb can mess up the whole bunch of them, screwing up performance. I am going to backtrack in the next week or so, and change the coil wires back to their original positions and then ride the bike. If the problem returns, then the coil wire positions were the culprit and if not, then it had to be the carbs. Guess it could have been more than one of them but #6 is highly suspect because it was the one that was replaced and it was the one that was being non cooperative when I was vacuuming them. More later. Now, on to my 82 for some detailing and restoration work.....
79, 80, 81, 82 CBX's, 87 Hurr 1000F, 83CB1100F, 87 VFR700, 01 Blackbird
40 yrs of Hondas and still baffled....
