The International CBX Owners Association

Under perfect conditions, these will idle at about 500 rpm. But few are in that condition. The easiest thing to do is to gauge sync the carbs and see if that brings a smoother, lower idle. It very well may, and it may not. But there's where to start. If the carbs were properly rebuilt, but never gauge synced, it needs that.

Dave

The previous owner rebuilt the carbs then had them synched at a Honda shop. The fact I can move the enrichener back almost immediately after cold starting, suggests there are some small adjustments required.

For the riding you did on your trip, if the carbs had completely stock jetting and were otherwise in good health, and with taller gearing maybe helping, you should have seen consistently 40-45 mpg. The fact that it warms quickly is nice, but indicates possible tweaked-to-richer jetting.

Dave

Just a little back-up to what Dave said, my 82 will do 40mpg running at about 75 indicated all day.

A high hanging idle, limited need for the choke and won’t idle smoothly at 900 rpm sounds like restrictions in the slow jet circuits and someone has compensated by rich mixture screw settings and or the high idle setting.

The previous owner rebuilt the carbs then had them synched at a Honda shop. The fact I can move the enrichener back almost immediately after cold starting, suggests there are some small adjustments required. The previous owner told me he did the rebuild "by the book" (and even showed me the book) but maybe he used non OE jets or something - or tried to clean pilot jets, rather than replacing them. Clearly some work to be done, in my future.

She got around 40-42 mpg running at an actual (and indicated) 60-65. At an actual 70-80, she returned closer to 35 mpg. This was all with ethanol gas, FWIW.

Not to appear picky, but, just an fyi if you are not aware: the CBX does not have enricheners. It has genuine choke plates. And, high idle cam associated with the plate mechanism. Improper adjustment after a rebuild can be an 'issue'. That goes for someone who 'followed the book'. As such, it appears you just might have a carb overhaul in the near future just to be certain things are as they should be.

Thanks for the clarification. I know a few people hate to hear an enrichener referred to as a choke. I had not considered that the CBX would have an actual choke (six of them, I guess)

On thing at a time. I'm going to get the instruments sorted out (broken needle and a 150mph conversion), then try adjusting and synching the carbs before I resort to a full rebuild. Also noted a bit of noise from the chain. It has a few tight links but no damaged O-rings i could see and doesnt seem worn much, so I'm guessing the front sprocket is on the way out. Need to take a look and see if there's any urgent action required there. Other routine stuff I'll be getting to pretty soon will include a clutch adjust and brake calipers service (which appear fine - but are kind of important.)

Yep, six of them -- one for each carb. As I mentioned, the joint pieces that connect the two banks of carbs can be just a bit challenging when reassembling the carbs. Could the previous owner have gotten something slightly off in his rebuild that has the high-idle piece preventing full disengagement when 'off'. Just something to keep in mind. Honestly, i don't remember the exact configuration. I just seem to recall that even with the choke plates open, the high idle cam could be off.

Dave would know if that's a possibility.

Since it was explained to me, i have considered the possibility that the idle speed was set high maybe because the high idle cam is not engaging at all. I'm not home right now and haven't tried to start the bike again since I turned the idle down. At the very least, I suppose I should pull the tank so I can get a good look at the mechanism. The CBX is to be a retirement "toy" but I'm not retired yet, so it might take me a while to really dig into it.

Something new:

Looks like this has seen it's best days. IEvery search I've done leads to 530 chain & sprockets but I'd like to go with a 525 or 520 replacement. Any suggestions?

525 or 520 will just increase sprocket wear rate. Roller width is narrower. 525 approx 16% less contact area on sprocket teeth; 520 approx 33% less contact area. Otherwise, it should handle stock loads.

I'm not worried about slightly higher wear. 530 just seems unnecessary, given the quality of the lighter chains. Any 100hp bike today would come with no heavier than 525. I'm not hung up on it but don't mind saving the weight or a few bucks either.

Guess I'll have to call one of the specialist suppliers anyway, as I can't find out what other bikes have the same output shaft splines or bolt circle on the wheel.

Devonian wrote: Sat Jul 06, 2024 8:32 pm I'm not worried about slightly higher wear. 530 just seems unnecessary, given the quality of the lighter chains. Any 100hp bike today would come with no heavier than 525. I'm not hung up on it but don't mind saving the weight or a few bucks either.

Guess I'll have to call one of the specialist suppliers anyway, as I can't find out what other bikes have the same output shaft splines or bolt circle on the wheel.

Do you know of any 100 hp bikes running 520 or 525 chains that weigh 550-600 pounds? My’18 Z900RS has around 111 ponies and weighs around 475. It has a 525 chain. I look for a tensile strength of 10,000 or near. My Suzuki and ‘82 use a 530. I changed the 630 my ‘79 came with to a 530.