Mostly solved, Half of engine no longer cold but...

[RJ CB650]

Figured out most:

No idea what is up. I cannot find or think of anything besides carbs that are unique right and left side. Engine starts and runs. What has me stumped is right side 456 are suddenly just stone cold. Fuel in bowls so not an air lock. Plugs and wires good. Batch fire so? I am completely flabbergasted! Only thing I can think is if there is a fuel passage completely separate from float bowls. Maybe that clogged but wouldnt it be bypassed as soon as a bit of rev off idle? All carb linkage moving nice, both sides.

What is worse is they were hot earlier. I had rejetted because it was just too lean with the K&N and whatever exhaust was on the bike. Was warm after since I toastied my thumb.... Or wait... Hand burn is on number three side... Was four hot... Arg... Well, need to pick people brains because aside from an airlock in fuel line, I got nothing... I really dont want to pull these carbs... Again...

[RJ CB650]

Initial issue. The problem was new number 4 wire. I didnt put sheathe on since is a temp til Monday when shop that has high quality wires open. Think it was throwing off other two. That said, number four still cold... Damn... Thinking carb... I gave em a go over while out so once more inspect.

[steve murdoch icoa #5322]

So all cylinders are working now except for #4?
Maybe give it the "quick clean" from Mike Nixon before pulling the whole rack.
http://www.motorcycleproject.com/text/c ... short.html

[RJ CB650]

That is a very cool article and might be needing that soon!

So synopsis, finally found out what was stopping number 4 before I had to dig into the carbs. It was actually the spark plug. For some reason, it was not sparking correctly. I wanted to do a final inspection on the ignition and I spotted something checking for spark. If it grounded further up the threads (as it might when installed) the spark would arc across the inside, not from point to tip. To test, I swapped the plug with number 6, sure enough, number six was cold.

I really dislike whatever modifications were done to this bike. It was just too lean, so I took a chance and put in the Jets that were in the bike and supposedly tuned to. Back of my mind was saying go to a different one, but I did not listen to me. So it runs better now.... at light throttle. There is a throttle position where it is like a switch, engine goes from smooth to rough, but only noticable under engine load. I am thinking it is just too rich now. I can blip it to the rough area, then as rpms increase, smooths. Let it off, and hear a pop. So am sure is just too rich. Because is under load, I do not know which cylinder it is.

All this started from a fill that cause it too run bad. Runs good on that gas now, and added some seafoam... probably an overdose. I want to run this tank down, then refill with the gas I know, and will see. If still rough at that blip, then will decide whether to do that link, or to pull them and get something in between stock and what was in them. I am sure that it is too big, and should never doubt my thoughts. This one was a high number by comparison, and the high speed jet was a lower number than stock.

[daves79x]

I think you need to determine whether you have a complete Stage 3 jet kit or what exactly jets you have. I've fought my last battle with a Stage 3 kit and scrapped it. Just impossible to get smooth running throughout the range. Terrible gas mileage due to being way too rich down low and no way to go leaner with that severely tapered needle.

So on the '79 set of carbs I'm working on (I know yours are an '82), I went with 80/120 on the mains and it's pretty close. Still a bit of a stumble when whacking open at 5K or so (think a bit lean there), but pulls well everywhere else and behaves at low-speed perfectly.

For your VB 64 carbs, the stock main jets are 105 (the only mains those have). I'd go up to about 125 or so. You can also get #38 screw-in pilot jets (yours are #35), but that's not necessary. With pods you have to jet way up, but use stock jets to do it and certainly keep the stock needle.

Dave

[RJ CB650]

That "Stage 3" stuff, never understood it. I mean too many variables to proper carb jetting to be able to have a "kit". From stock, it was a hesitation at the 3500 ish area that made me only change the low jet to start. Top end ran very nice. I agree, I probably misunderstood the jetting range a little. Bigger mistakes was not trusting myself.

Will definitely do a little more on the outside first and see response after the new plugs and wires. If still running not nice, I was figuring similar pilot jet. I do have theory now that if one plug was bad, maybe another isnt running right and as such, getting spark blowout. The problem just seems too consistent for a vacuum carb as it is throttle position, not rpm related. Thanks for the feedback as well. Writing/posting etc I find helps wakes the brain up and clears it.

[daves79x]

Pardon me for being a bit blunt, but this jetting ground had been trod many times and is really not much of a mystery. You need to determine exactly what you have in your carbs now. Do you have the stock 105 mains and #35 screw-in pilot jets, with stock needles? That HAS to be determined. If that's what you have now - the bike will NEVER run right with pods. That is not up for debate - it is a fact. Many guys go the Stage 3 route. I've had little success with them, but I've never put one in VB64 carbs. A much better route to go is up your main jet 15-20 numbers (around 125 for yours). This will get you close. The bike will never run like it did with the stock airbox, but you can get it pretty close.

On the '79 carbs with stock 65/98 mains (2 main circuits in those), going to 80/120 is about right with pods. VB62 carbs ('80 only with stock 110 mains) need to go to about 130 and what I recommended above for yours. Your bike may feel like it's running OK with stock jetting and pods (once you get you spark issue straightened out), but it will be down 15-20 hp on the top end. Upping the jetting is the only way to fix that.

All this still proves my point that the stock airbox is just fine and should be kept.

Dave

[RJ CB650]

Jets, I had reverted to stock. Needle? Who knows. I doubt it is a Keihin.

Why do people say pods? I never mentioned pods... Well, I guess the K&N usually means that in today's modding culture. K&N is just a direct factory filter replacement that came in the bike and I cannot seem to find a quality aftermarket paper filter.

http://www.knfilters.com/search/product ... od=HA-0900

I at current am dealing with stock airbox and the non stock filter but bigger one is the exhaust. Just was too lean in bottom to about 4000. Choke jumped the RPMs bigtime. I am dealing with this because somebody who probably shouldn't even be riding a bike did work on it. My hobby is reviving bikes that others think are dead and gone. These CBX do get on my case based on the simple fact that It is an all day job to pull the carbs on it and a complete pain vs my other 82 where pulling the carbs is as hard as changing the oil. Love the bikes, but just these carbs, completely unservicable.

So I shall be blunt too. I knew that there was a hole with stock jetting since I did full rebuild back to stock settings myself. I did not go and buy new needles because we are not all made of money and the cost of those needles, better invested elsewhere. Slight fuel mileage or performance change? I would not notice or even care. Isn't a dyno queen or some trailer gal that only comes out on cloudless days. I ride regularily my bikes. CBX, no exception. I just dealt with that hickup. So when bad fuel came out the pumps, I took it as a time to replace these jets since was going to be cleaning the carbs anyways. I was just stupid in having thought that maybe whoever had changed from factory jetting possibly knew at least a little. As opposed to buying 200 bucks of new that might not work, I put back in the low speeds that were in the bike when I got it.

Now, it is just pig rich when you open up the throttle, right through the whole rev range. Smooth and quiet idle idle, but even slightest choke, no matter the engine temp stalls it out. It is way too rich and even though I only changed the lowspeed jet, it messed up the entire rev range. Light throttle, smooth and fine, but the more you open it up the more it just richens out. My 650 gets more power. From the start I suspected the needle might not be original, but after initial too stock re-assembly, was running quite well so I didn't worry. Probably needed a 41 or close because of how much effect choke had.

I actually wasn't looking for the bike when I got it. The CBX was just the first bike that I saw that I actually had any interest in from a motoring point of view. Before that, never gave one a second thought. I wanted one, but was not looking for it. One day was chatting with and made mention how the CBX was what got me into motorcycling. Well, in that convo, turns, a very important family friend had gotten it several years ago but did not have the skill to work on it himself and did what any responsible rider would do. Research and find a reputable shop to service it. Well, they messed it up, and it was costing too much money. It was offered to me to buy since they knew I put care and focus into the vehicles I work on. I fully understand these bikes can add up in dollars. We all would love a concourse rebuild. That is just not in the cards for this one in the immediate future.

Doing what I can to get it back to a nice stock operating condition, but only so much stuff one can deal with before it starts getting on me. Hence why I hate with a passion these "stage #" and "Performance" parts since there is no such thing as "bolt on' performance. Lazy work like somebody side cutting off the T-vents just so they could access the adjustment screws easier. It just messes stuff up and the people who installed it messed up and wrecked a bunch of things. So now is a decision, do I go once more back to stock jets, park it for the rest of the year til I can spend 1500 bucks to get a proper OEM replacement exhaust, or now sink a couple hundred and hope I get the correct size up of jet and then come winter, replace the exhaust? Then hope said exhaust works well with the re-jet since they were lean from factory? To have the space to properly pull the carbs, I need to pull my other bike out of the garage hence not something easily done over winter.

[daves79x]

OK - somehow I got from your posts that you had pod filters. With a K&N drop-in, many guys notice a mid-range stumble, many do not. I'd personally get the stock paper filter. Your exhaust has virtually no effect on jetting. Your bike will run best with the stock 105 mains and #35 pilots. If your needles have a gradual taper and are gold-colored, they are probably ones that came in a Keyster kit. OK, but some of them were not to specs and they wear fast. If your needles have a clip adjustment, they are Stage 1 or 3 needles and they have to go.

Your biggest problem is that the carbs do not appear to be completely clean yet. The bike should idle and pull from idle in any gear very smoothly. The old adage holds true - it takes a newbie at least 3 tries to get these carbs close to right. But you can't get frustrated by having to pull the carbs to do this - it has to be done, if you don't want to send the carbs out for rebuild. Otherwise, you will come to quickly despise the bike because it doesn't run right.

Dave

[RJ CB650]

And this is where the topic sort of started, but went a different direction but the same basis. A situation I had not experienced before. The carbs should be very, very clean. Carbs have been working with (from automotive and small engine) since before I could drive. When got the bike on the road last year, they were a full clean. And just last week with the work, same thing. Is why I had pulled them again. In past, I have found that some exhausts if just too open can mess it up. These ones don't seem too open and they have a quite nice volume too them. I mostly dislike them just because instead of the parallel collector, they have a more traditional triangle collector which pushes the down-tube from the inside cylinder extremely close to the oil cooler line. That combined with that I think the mufflers are ugly is the main reason I want to go to a nice fitting, and stylish OEM style. Since bike will never be a 100% original, was looking at the Delkevic setup if no other viables are available when I decide to go shopping. That is a later discussion thought ^.^

So here is the rundown of how it performed and is now:

Then: Last year after rebuild and back to stock, very smooth idle, and holding at all rpm. That midrange is very probable like what you have heard before, a stumble which is a very good definition. The choke, it would seriously spike the RPM, not 500-1000 like other bikes I am used to, but talking 2-3k rpm. Even the slightest choke, RPMs would go up. The two combined plus plugs really hinted me more towards lean. Aside from an ignition issue, a slight leak which I will be looking at when I put new chain on, and that stumble, bike has been doing quite nice.

Now: The bad gas statement. Essentially, I think it had water or? in it. I filled up at an ESSO (normally shell) because I flipped to reserve and my usual shell station pumps were offline. I didn't want to push how far I could go on reserve. Well, about a minute or two later, the whole engine started feeling like a bag of hammers. Made me think extreme lean condition once off idle. Fortunately this was near home, so wasn't an issue getting it back into the garage. Proper maintenance says to pull, flush and clean the carbs, so that is what I did. Because I was pretty lean in bottom, I did what I had been debating and that was richen the pilot jet. Right call am sure since the stumble is gone and under 1/4 throttle is very nice, wrong call was the putting the jets that were in the bike when I picked it up back in.

Taking them off and on, it bothers me only from a design point of view. The proper response, with despite all attitude will be done is that the carbs will be coming off in short order, it is the only proper course of action. But now the question, what size jets? Normally, just do the one step up. Go the 38 like steve mentioned. This is where need expert advice. Giving the "stumble" and choke response, is that enough or would the next step up from the 38 be more correct and what I had been thinking since I first got the bike running, if only for how it responds to full choke. At the cost of the jets, I would rather only have to buy them once unless there is a proper jet sets available? (Example, contains a small range of jet sizes).

Well, will find out tomorrow. Will stop by Dealer since they still have a wide selection of jets in their parts department. Depending on cost, I might get both sizes. Being a little rich running the two steps up shouldn't be that problematic. It is just what everything is telling me, but "gut feelings" and actual on CBX experiences are two different things. What is usual treatment for the stumble? Oh, and the needle is a non adjustable. Trying to picture in my head what it looked like. Not completely certain, but for some reason I am thinking goldish color with silver retain ring? But don't quote me on it.

Oh, and paper filter, I talked to my dealer, and apparently they cannot get a quality one. They have el cheapo listed, but parts recommended against them.

[daves79x]

I'll try one more time - get rid of the K&N - TIMS has a quite fine paper filter. Go with the #38 pilots if you want, but not necessary. Clean idle circuitry with #35 jets is just fine. Stay with 105 mains. Now the needles - if they have an adjusting clip - you have to get rid of them. You can shim the stock needles .020 inch and that will slightly richen the low-mid range. Procedure for doing this is well-documented here on the forum.

Make sure all idle circuits pass fluid through and that the accelerator pump is functioning correctly. Make sure the slides aren't sticking and the air bleeds are open.

I can't help you any more short of rebuilding your carbs for you - good luck.

Dave

[asacuta]

If you're going to use the K&N filter, make sure that the airbox cover is installed. I've run the K&N for years with no issues; however, if you leave the top off the airbox, it will sound great, but bog at mid revs. Other than setting the idle screws and sync screws, my carbs haven't been touched since they left the factory. To me, that suggests the advice above is the way to go: get the carbs back to stock, and it'll probably run right.

[RJ CB650]

Will give it one more go over. They were back to stock on the rebuild. Maybe altitude, may be the fuel? Thinking math, the 38 is a considerable increase on the numerical sid. So will go with those and see how it runs.

Edit: Cancel that for now. Will need to track down some of them first without a 300% markup.... Fiddles... Is there reputable supplier of jets outside of direct from Honda? Will check out carb threads as well to see, but I can do all the work I want, they won't run proper if gone back to how i had it and cannot get the parts needed.

Side point of interest. Was going through the parts taken out and looked at the main jets. Four 110s and two 108s. This really confused me. I know not uncommon on multicarbs to run slightly different jets if they use a common intake. More the confusion of how they got that correct then got way too rich on the other side. I really suspect it had been tuned for pods, then before the gent I got it from bought it, they had put it back to stock.