CBX 1000 not-so-super-sport

[Mosseltje]

Hello all,

My excuses for the poor grammar and spelling.
But if I tell my story in Dutch nobody would understand.

Responsibility changes the love for bikes throughout my life.
As student I had a CBR1000RR for track use and a GSX1000R for the daily fun.
When I turned 28 I came to my senses and realized I should have died 50 times already.
I sold the bikes and invested the money in a new hobby: Off-road driving.
Nothing gives more fun than 2 wheels, 1 cylinder and a big forest.

This year I turned 35 and have my own company with 17 employees. Responsibility takes away a lot of fun lately. I cannot afford to get injured to badly. It’s difficult to run a company from the hospital or home so I keep the off-road driving to a minimum nowadays. And when I go off-roading I drive like a 80 years old granny.

So I had to find a new hobby again. But luckily the new hobby found me. Since 2 months I am the proud owner of a CBX 1000 Z from 1979.




But here comes the sad part. My CBX is a bit sick. It has nice stickers with super sport on the gas tank but it does not feel sporty at all. This machine produces more decibels then horse power. If I wanted that I would have bought a Harley. But this is a top of the line super sport made in Japan. Luckily I love to solve mysteries and am pretty handy with tools. Only I do not have any mechanical knowledge on motorcycles with more than one cylinder.

Symptoms: Not enough power and farting in 1 or 2 exhaust pipes. This is clearly a carb problem.
Carburetors are scaring me of with too many tiny parts. I tried once to fix one and had to buy a new one as I lost at least 5 microscopic parts in the process.
So I spent some good Euro’s at a specialist who completely cleaned the carbs and fine-tuned the bike on a roller bank.

I was a bit surprised by the outcome:


53hp. . . . Somewhere the bike lost some 30hp. This CBX is not worthy of the super sport stickers.
Hack, even my Grannies electric wheelchair has more power.

The carbs are as new and tuned, the rubbers between the carbs and engine are replaced with new ones and the K&N air filters are clean and properly oiled.
On the roller bank the carbs worked perfect. Even without any air filters. So it cannot be a lack of vacuum due to the open filters.

So the problem must be in the engine. 30% less power must be a wrong timing on the camshafts. (Obvious) So I removed the camshaft cover and took a look inside.

Timing belt is in good shape




Crankshaft on the right position




The back camshaft is okay


The front camshaft is okay.




Perhaps the power loss is caused due to faulty valves . . . ?
So let’s do a compression test on the cylinders.

I measured the following results:
Cilinder 1 : 166,5psi / 11,45 bar
Cilinder 2 : 139,5psi / 9,6 bar
Cilinder 3 : 169,5psi / 11,65 bar
Cilinder 4 : 160,5psi / 11,05 bar
Cilinder 5 : 167,5psi / 11,5 bar
Cilinder 6 : 168,5psi / 11,6 bar

When I poured some oil in cylinder 2 I got the following reading.
Cilinder 2 : 151,5 psi / 10,4 bar

Perhaps a wee bit low but not low enough to explain the power loss.


I love mechanical problems. You can use a hammer when something is stuck and duct-tape when something should stuck.
If a hammer does not solve the problem it must be an electrical problem. And electrical thingies are plain magic for me.
A pulser or transistor are toys for Harry Potter.

So I bought a magic wand, cast some spells and again no improvement on the power…

Luckily I have a neighbor who does know this stuff and he helped me out.
Timing checked with stroboscopic light and timing was perfect



This thingy looks good:

But looking good and working good are two different things.
How can I check if the thinghy above is working properly?



This is as new:


The ignition unit is replaced with an aftermarket mark Tronics MT-3 module




I replaced the battery
When driving the volt meter is between 13 and 14 volts
All electric cable connections (which I could find) are cleaned and fitted correctly
All fuses (on the handlebar) are okay
The gasoline flow is good as well
The bike has fresh oil and filters
I even checked the rear brake

And still 53hp on the rear wheel.

With the current exhaust it is easy to check which cylinder is giving problems.
The exhaust is made by the former owner (and he also lost the original airbox.)
Each cylinder has its own exhaust and no balance pipe between them.
Cylinder 5 is not working (properly).
But cylinder 2 is working good.
Can a coil give problems to only one cylinder? Or does a broken coil always give problems to both cylinders?
Questions I cannot answer.

So by the end of the week I receive some new dyna coils and all the wiring down to the sparkplugs.

This to avoid the same problem as in this topic: viewtopic.php?f=20&t=6970

If this doesn’t solve the problem I am out of options….


Off course I can bring the bike to a specialist but there is no fun in that.
Does anybody here have any idea what I have forgotten to check?

Bike has only 80.000Km (or roughly 50.000 miles)

[EMS]

Welcome, Mosseltje!

You have the perfect set-up to use an exhaust gas analyzer and check the mixture in each cylinder. This would be one additional thing I would do, as I think you still may have a carb problem.

[Mosseltje]

As said before I do not to dare to touch the carbs myself and I have to rely on the information from the company who cleaned the carbs.
According to him the carbs works flawless….

This company is now closed for the summer holidays.
But he already offered to bring the CBX back to his shop and he will do some more testing free of charge.
I will ask him to do a full test on all 6 exhausts.

But if he is right and the problem is not with the carbs, what else could explain the big powerloss?

[Jeff Bennetts]

One other thing you can check is the ignition advancer, make sure the springs are connected and the weights are moving freely, also read the designation stamping on the advancer plate and list it here.

if I understand you correctly you have multiple K&N filters? What is their configuration, 4 singles and 1 for the center 2 carbs, 6 individual or 3 sets of two filters? either way the jetting and needles have to be modified or adjusted correctly by moving the cir-clip position or shimming if they are the stock needles.

Maybe someone else has some other suggestions of what you can check but you need to be very specific about your current setup before people can help you.

Jb

[Mosseltje]

One other thing you can check is the ignition advancer, make sure the springs are connected and the weights are moving freely, also read the designation stamping on the advancer plate and list it here.

if I understand you correctly you have multiple K&N filters? What is their configuration, 4 singles and 1 for the center 2 carbs, 6 individual or 3 sets of two filters? either way the jetting and needles have to be modified or adjusted correctly by moving the cir-clip position or shimming if they are the stock needles.

Maybe someone else has some other suggestions of what you can check but you need to be very specific about your current setup before people can help you.

Jb

A picture of the ignition advancer is in my startpost.
It moves smoothly and looks if new. If I check the picture I can read the following markings on the advancer: Tec and 422

I have 6 single K&N filters. One for each carb.

As for the information about the bits inside the carbs I have to check with the workshop.
They adjusted and replaced some needles and/or jetting. I had full confidence that the shop did a good job with finetuning the carbs.
Now after checking all other possibilities I start to have a little doubt.

[daves79x]

I can tell you that your horsepower deficit is in the main jetting. That is, if you still have the stock 98 mains - if they are VB60 (or maybe 61 in Europe). You have to jet WAY up on the mains if using stock components with pod filters. Or a jet kit. Please verify with your mechanic the main jet sizes. Stock jetting should be 65 primary main and 98 secondary main (or close to that). If that is still what is in your carbs - that's the problem. You need to go up to at least 120 on the large mains and maybe 75 on the small ones. That'll be a good starting point. Your lost hp will magically reappear. Our own beloved Mike C. here found that out. 60-odd HP on the dyno with stock carbs/pods filters (these were on an '80, but still holds true). Put in 120 or so mains and viola! - 80 plus HP.

Your compression is great and barring cams way out of time, carbs has to be the problem. A classic case of not enough fuel at higher rpm. Which brings up another point. If there are ANY restrictions in the fuel delivery system, you'll have high-speed HP issues. The bike literally runs out of gas. Especially on the '79 with the single 1/4 inch inlet.

Your lost HP is likely only some jetting changes away.

Dave

[Mosseltje]

Wow, will it be easy like that?
I just called the workshop but nobody there anymore. Luckily I have his home number as well.
He think that they used the 120 primary but is not sure and he will check the computer tomorrow morning.

Really hope you are right.
But stubborn as I am I still fear not all cylinders are running properly.
My KTM Super Enduro (2 cylinder, 950cc) had almost an identical rollerbank graph.


This was caused by a non working carb and the engine was running on 1 cylinder only..


Between the gastank and the carb is a fuel filter. Could this be a restriction in the fuel delivery you are talking about??

[Mosseltje]

Dave,

Could you perhaps tell me the ideal setting of the mixture screw?
Than I can bring the CBX back to the shop and try the jettings you suggested.

Thanks a bunch for the good insights so far.

[Jeff Bennetts]

Wow, will it be easy like that?
I just called the workshop but nobody there anymore. Luckily I have his home number as well.
He think that they used the 120 primary but is not sure and he will check the computer tomorrow morning.

Between the gastank and the carb is a fuel filter. Could this be a restriction in the fuel delivery you are talking about??

Make sure the shop put the 120 jets in the correct place, people have mixed that up before and have had your symptoms.

I believe Dave is speaking about the main jets as being your fuel restriction not the fuel filter, one reason the carbs could be running out of fuel is the float level being incorrect.

With your setup start at 2 and 1/2 turns from snug closed, and increase by 1/4 turns until the idle hits it's peak and starts to drop, this only affects the throttle from off idle and has nothing to do with WFO.

[daves79x]

Welcome, by the way and your English is near perfect.

120 large main would be a good starting place, may require as large as 130. 75-80 would be good for the smaller one. This assumes a stock needle. If it has a jet kit, like Stage 1 or 3 by Dynojet, then that's a whole other thing. But if the bike has at least 120 mains, then it should be making 80-plus HP. Another thing needed is to shim the metering needle .020 inch. I reviewed all your photos and think cams are fine. Timing I would double check with the new unit. The 422 advancer is correct. These are very sensitive to small timing changes. If you've never been around these before, you probably can't tell if it's running smoothly or not. But if lack of power is due to timing, incorrect ignition wiring or the like, I think it would be evident in rough running or idling. Does the bike seem to idle smoothly and respond to throttle OK?

Back the pilot screw out 2 1/2 turns - I think that was your other question. Jeff is correct about float level being critical.

Fuel delivery issues would be a problem on the dyno. On the street you'd have to be running awfully hard for it to show up, unless you have plugged filters, either the tank strainer or the in-line one that you noted. The first thing I do with any CBX I work on that I don't know the history of, I drain the tank into a white pail (to see just what else beside gas is in there), pull and clean the petcock and screen and thoroughly flush the tank. Then I clean the cap with strong detergent and thoroughly blow out the vent system with compressed air. It could be a tank venting problem as well.

Anyway, everything right now points to a lack of fuel at high rpms, either lean jetting or restricted flow. The 'bounce' I see at high revs on the dyno chart might be a misfire, but also might be an on-and-off fuel delivery. The chart should climb steadily and not have all those dips above 7000 rpm. The pod filters don't help get a smooth HP curve the whole way, but shouldn't look like that.

Keep us posted as we'd sure like you to experience an 85 HP CBX!

Dave

[daves79x]

Just re-read the entire thread and see that you noted a cool #5 pipe only - not #2. Yes, a single coil output can fail, but it's rare. When we see a cool pipe, it's almost always lack of fuel, at idle anyway. Pull #5 plug cap while running and see if you notice a difference in engine sound. A single cylinder not firing at all would give you HP numbers like you've seen. Even if you couldn't tell a dropped cylinder I would think your mechanic could. If that persists and is still now a problem, you need to look into that. Have you installed the new coils yet?

The bike should 'rocket' to redline. If you were down an cylinder, it would be very lazy to get there. Can you ride a known proper CBX to compare? Just some thoughts after reading the thread again.

Dave

[Jeff Bennetts]

You say you're using 6 single K&N's. I have ran the Dyno Jet stage 3 on my 79 CBX for twenty yrs, it has 4 single filters on the two outside carbs and one filter for the center 2 with adjustable needles in the slide.

Dave and I disagree on this but everyone has their opinions and here is mine, you are loosing vacuum by eliminating the airbox and the unequal length runners that are between the airbox and carbs. These are CV carbs and need vacuum the operate properly, when I say properly I mean smoothly without hesitation. Without the airbox you'll get a hesitation when you whack the throttle until the slides have time to react to the additional fuel, this will show on a Dyno sheet.

You're exhaust will also effect your overall performance, mostly midrange and top end.

[daves79x]

Jeff:

I think we're in complete agreement about the use of pods, whatever style. There are for sure jetting issues, whether using a stage 3 kit or jetting up with stock-style jets. I'm not a fan of using pods, that's no secret, but if you must use them, the preceeding post is just my experience in jetting them to work the best. My difference is in what effect pipes have on jetting. I contend not much. Exception is the DG 6-1. Flat spot at 5000-5500 that you can't jet out. Jetting problems are 90% due to using pods, IMHO and experience.

Dave

[Jeff Bennetts]

[Mosseltje]

I wish I had found this forum more early.
You people know your stuff and still able to be friendly as well.
Now I have more confidence I can fix the bike within this year.

The new Dyna coils will arrive end of the week or beginning of next week.
Maybe the original coils are still perfect and not necessary to replace. But let’s call it preventive trouble shooting.

The bike is running smoothly. When hot it idles around 900rpm without any problems.
This weekend I will charge the batteries of my camera to shoot some video’s.
Perhaps the sound of the engine running gives a better idea of the problem.
At this moment I only have this crappy video made with my I-phone.
http://www.youtube.com/watch?v=CePDlgkB ... e=youtu.be

The former owner was a broddler. In his opinion the bike is in mint condition and running perfectly.
After 100km driving the rearlight dropped of the bike. It was bolted on without washers or Loctite.
The front brakes did not work properly. This because both fork seals were broken and had spilled oil all over the disks.
And the rearbrake did not have brake pads.
But he did a good job on the polishing.

Maybe not a bad idea to clean the gastank properly.
This is easy to do and also fits the preventive trouble shooting philosophy.

If I read all the comments above (for which I am grateful) I think the best way to proceed is to search for an original airbox.
Are the air boxes of all years/models the same?
Maybe I can try to make a provisional airbox with tinfoil and duct-tape. To see if more vacuum increases the power.

I would like to keep the 6 in 6 exhaust. I love the looks of those pipes.
Perhaps I can find a real pipemaster for cheap (yeah right) to replace the home made 6 in 6.