The International CBX Owners Association

Hi to all you fellow CBXers. I'm a newbie on this board although I'm not a newbie to this site or CBXs. Some of you will know me by my name as I buy and sell a fair bit on Ebay. Not sure if that's a dirty word on this site but I've got a lot of good parts off ebay.
Anyway I've got a problem with my X that I can't solve and I need some collective help from you CBXperts. I've read most of the tech articles but nothing has jumped out at me. Anyway here goes.
I've got a 79 CBX which has had a motor rebuild and as I understand it may have had a fuel lock problem. I know nothing more than that about this engine and no history other than I have a receipt to say the engine was rebuilt. Don't know if it was bored or stock pots.
When I bought this bike it ran rough but that was probably due to it sitting for some time. Anyway I stripped it after I bought it. After 3 years I've totally rebuilt this bike except the engine. All I've done there is to check everything and rebuild the carbs using keihn kits from sirius of Canada. For the carbs I replaced every screw, jet, plug and then some. Refitted the carbs and calibrated to specs. I then sent the bike to the local Honda dealer for carb sync and tune. This was a bit of a disaster. The bike ran OK but the mechanic said that I had an idle jet problem as he couldn't get it to run right. Back to the workshop at home and a complete carb removal and stripdown and rebuild. Nothing I could find was a problem nevertheless I recleaned the carbs, air cleaned the airways etc; but this bike just wouldn't run right.
The symptoms were that the bike would not idle very well and when on the road it would surge except when under acceleration. I finally gave up and bought another rack of carbs off ebay. Cleaned them and fitted to the bike and up to a different Honda mechanic ( a guy who lives 500 miles away but a man I trust) and after he finished the bike actually started to run better. I returned the bike home and refitted the tank etc and then took for the maidem test ride after the second carb rack were synced.
OK, if you are still with me here, this is my problem. Bike starts and like most of the CBX family, takes a while to warm up. Once warmed up I can crack the throttle open to 4 thousand and it will run OK but surges between 3000 and 4000 RPM without load. It's not smooth if you know what I mean. I take it for a run and it accelerates like the clappers and while I'm accelerating it runs sweet as a swiss watch, but once on cruise and at moderate speed it surges like a see saw. Not bad but it surges. Up and down. It's not missing but surging. Initially I thought it was a misfiring plug but it's not. As I say, when I open the throttle it runs sweet. but cruise in any gear it has this unsmooth operation. Pisses me off that's for sure.
Now I've had 3 racks of carbs on this bike and it does the same with them all.
Electrics. I've tested the coil staticially and all three are within specs. Plug caps I've replaced and these are within specs. Plugs are new D8EA NGKs. I haven't got to the pulse unit or the ignitors but not sure if this is the problem anyway. I have read that the pulse units can act up but this bike accelerates fine. Only thing I can think of is that it's running lean on cruise throttle and the needles need to be lifted a touch.
Carbs .... Stock
Airbox ..... Stock
Ignition ......... Stock
Exhausts .......... 1981 CBX Stock (Units with crossover pipe)
Mains, sloww speed jets are CBX ........... stock sizes
Nozzles ..... new stock
Airscrews ........... new stock
Rider ....... Over 50 but still with all the stock items including hair and teeth. Takes me 5 minutes to take a piss but otherwise not in bad order
HELP .......... KP

Welcome kerrycbx, great first post....

Fuel lock problems normally mean bent connecting rod often # 1. I would assume that has been replaced. Quick check is to measure at TDC on each cylinder from the piston crown to the top of a plughole. A knitting needle or the like cut to length is good for this duty.... Don't tell the wife.

OK, 3 racks of carbs & the problem of surging continues....Hmmmm
I would assume the throttle cables are properly adjusted also the choke cable ??

A few ideas not in order of preference:

Air leak on induction, causing lean surging ?
Fuel flow problem, partially clogged fuel filter or partially blocked tank vent ?
Mechanical advance retard unit defective ?
Automatic cam chain adjuster malfunction ? but you would most likely hear that....

Those are a few off the top of my head, let me think this over a bit...

Hi alimey4u2. Thanks for the ideas. I replaced the carb mounts with new ones but these have had carbs on and off a dozen times. I read somewhere on one of the posts to spray some aero start around the carb mounts and see if the rpms increase so I'll try that this weekend. haven't tried the advance retard system yet so this will be another try. Engine internals have been checked. Cam tensioner was also set but I may just check that also. Have always thought this was carbs or lean intake but I haven't given the advance system much thought always assuming it's working OK
Thanks and any other thoughts I'll try.
What's the thoughts on replacing the needles to adjustable types. I don't want to go that route unless I have to but if I must then so be it
KP

I do have my suspicions on the phenomenon of lean surging but then after changing 3 racks it "kinda" points elsewhere. What do the plugs tell you if kept in this troublesome band ?? Yup, spray Ether ( quick start.......I love that smell) around the area of the carbs ( outside, no smoking & make sure you don't have spark leakage IE. Run the engine the dark first)

I need help guys, remember I'm cr*p on CV carbs....

...

Thanks guys. Mmmmm. Ether has a real nice smell indeed. Having worked in the health industry all my life I can actually say I was around when ether was phased out as an anasethetic. Little known fact is it was a safe anasethetic in its day having a wide safety margin but some not so good side effects anyway to the job at hand.
I did say 3 racks of carbs, 2 racks had the same kit installed. When I got the 3rd rack I installed the new kits from rack 2 prior to installation. Float levels were reset to spec on both racks. Rack 1 was changed early as I could not remove the air screw needles and broke 2 carbs trying to remove them. Still have them for spare parts. So the common theme between both good carb sets is the kits. Maybe an important bit of info I omitted. Sorry if it was.
I had been given previous advice to lift the stock needles with washers so will look at that option as well and thanks for the heads up on the type and size hole. As indicated earlier, I got the replacement kits from siriusconinc of Canada. However I said they were Keihn Oops sorry. These were the standard Keyster 422 kits they sell so if anyone has some experience with these kits I would appreciate the comments. I also used their diaphrams, nozzles and plugs they sell. All the bits seemed to fit well and this is understood was a good omen. However, the rubber bowl gaskets are rubbish and swell and are (they said) single use. I've used the original gaskets over and over again without issue so not sure that their advice is accurate. A gasket that swells is in my view an inferior product and companies should listen to their customers. Thanks again guys KP

415ZR1 wrote:
The carb tops can be removed w/o pulling the carbs...or tilting the engine.

OK guys. First thing; I was able to remove all the carb tops without tilting the engine. I did it the way explained in another post on this site. To reiterate for anyone who hasn't read the relevant post. Loosen the carb clamps, undo the 2 frame bolts that hold the aircleaner box and remove the rear engine mounts. Push down on the carbs enough to get #2 and #5 tops clear. Guys it worked a treat and great information.
Anyway, I removed all the needles and shimmed with a washer and replaced all parts, seat and tank. Took it for a test ride and I think it may now be running a little worse.
Before the washers and after the washers if I gave it a little choke it would seem to run better, but with the washers and some choke it really seemed to run a little worse ie: hunted more.
Another thing I noticed is a few crackles from the exhausts. Not a lot but a few at idle. A pop here and there that's all. Open throttle it runs perfectly, accelerating like an X should.
So what next. How do I test the mechanical advance or is this a "get a good one and swap it" type test. I haven't done the aero start bit yet but I really don't think it a leak. Also don't think it's fuel starvation as it accelerates without issue. Alimey4u2, you had some thing you think it may be. I'm all open to any thoughts
KP

kerrycbx wrote: So what next. How do I test the mechanical advance or is this a "get a good one and swap it" type test. I haven't done the aero start bit yet but I really don't think it a leak. Also don't think it's fuel starvation as it accelerates without issue. Alimey4u2, you had some thing you think it may be. I'm all open to any thoughts
KP

Quite simply it can be tested using a timing light ( strobe good for 8000 rpm) & a degree wheel (Honda pt # 07974-4220001 [old number]) but I'm sure a commercial one can be fitted. Oh ! & workshop manual, if you don't have I can send you the relevant pages.
On increasing RPM it should be 23.5 degrees beteween 2200 & 2600rpm & 31 degrees between 6400 & 8000rpm. Do several tests of increasing the rpm to ensure repeatability.Hold it around the troublesome rev range & see if the timing "fluctuates". Don't forget a cooling fan when doing these tests... If you are "minted" Cincycles ( in the States) make an electronic advancer that makes the mechanical redundant.....
Before you do this do the leak test as it's easier & cheaper & check plug readings too....My suspicions are still "lean surging".

EDIT: I have just had a thought>>>>>

If the revs fluctuate (with the engine hot & in neutral) at the troublesome rev range it's very likely an ignition "related" problem. If not......you guessed it.... fuel..

Thanks alimey4u2. Yep I have a manual but I'll take it to the Honda boys to check as I don't have the gear.
Yep bike is at temperature when I test things but no real rev range is noticed, seems to do it from around 2k rpm onwards. I'm starting to suspect an ignition problem. I'm waiting for some new plug caps to arrive and a set of Denso plugs and I'll be satisfied it will be OK from the coils to the plugs. I doubt it's the igniters. I'll look up the sellers of this ignition but was going to go for a Dyna set up if there was/is a problem. I hate these pissey little problems. KP

Kerry the Dyna S is a superb system ( highly recommended) but don't forget it uses the existing mechanical advancer. BUT ! If you slowly increase the rpm of the engine (whilst in neutral) & nothing other than a smooth transition is realised, it's unlikely to be the advance/retard unit...
Good luck & please keep us informed....

kerrycbx wrote: I'll look up the sellers of this ignition but was going to go for a Dyna set up

The Dyna system ( go the full monty) you can get from TIMS & the cincycycle from here http://www.cincycycles.com/domino/cycle ... e?openform

I have no experience with the latter but maybe someone here can advise...

I personally know Jim Zemanek of Cincy Cycles, and would not hesitate to recommend him and his services. He's a straight shooter, and honest as the day is long.

kerrycbx, did you find solution for your problem?
-piit-