Electronics Guru's Needed

[CBX-tras]

I've been using Ignitech programable on DOHC4's and the CBX with great success.

Plug and play. Many features.

KMCarburetor.com is a dealer here in the USA.

You can use the stock advancer or weld the reluctor in place and let the Ignitech do the work.
Even more beneficial if you can install a TPS. (But not necessary).

https://www.ignitech.cz/en/

[Fw66]

Attempted to start the beast today but my bowls were not filling with gas even with a grav fed source. Probably an easy diagnosis for most of you but this is my first carbureted bike so tips appreciated!

Excuse the bootleg gas tank, I didn't want to fill the actual gas tank with gas as metal work is still being finalized.

[512tr]

Maybe your carbs don't like the wine you give it, try tequila

Hard to tell if you have the vacuum driven fuel diaphragm, if so try bypassing it, use a tee to supply both carb banks.

Your wine bottle is not the best to use, you have to vent the bottle to let air in as the fuel runs out, vacuum will prevent the fuel from flowing.

[Fw66]

Haha, absinthe is likely the preferred alcohol.

The bike already has a bypassed T joint for fuel supply, has anyone added a fuel filter before the T joint? I have one on and I don't think it should be an issue...

Thanks for the explanation of why the wine bottle wasnt moving fuel properly. Probably a silly question but I don't remember there being any venting port on the stock gas tank to let air in. Is there enough air volume in the tank to prevent a vaccum or how exactly does that work?

Got the bike set up with a proper aux gas tank, just waiting to start it in the next few days when I have time!

[daves79x]

Every gas tank has an air vent of some sort. It's usually part of the gas cap. Kind of a basic thing. If you did not have any vent in your jury-rigged fuel tank - that was your problem.

Dave

[512tr]

As Dave says, bleeding to the fuel tank is essential.

Your new aux tank arrangement looks good. A fuel filter before the T is OK, you could also use 2 filters after the T (I use a Y connection, looks more streamline than a T )

I also have transparent hoses, then I can observe the fuel flow from the tank to the carbs.
In case of a fuel starving problem it's easy to eliminate some protentional fault sources just by looking at the hoses.

[Fw66]

Well I tried starting the bike but did not get much success- somehow knew it wasn't going to be that easy: the engine turns over, I hear some popping and a few of the exhaust headers feel slightly warm (1/2/4/6) but engine doesn't fully turn over.

Troubleshooting I have done:

1. Confirmed I have spark on all 6 spark plugs when starting the bike- grounded each one and saw an actual spark on each cylinder. I'm using aftermarket spark plugs but based on my research...these should work: 7mm Solid Core spark plugs (non suppression): https://www.amazon.com/gp/product/B07JD ... UTF8&psc=1

2. Confirmed I have fuel in each float bowl, opened the drain screw and saw fuel coming out of each float bowl- no longer using my sketchy wine bottle fuel tank.

Now I'm guessing this leaves me with the carbs: the thing I have the absolute least experience with (all my bikes are fuel injected).

I have installed a dynajet stage 3 kit on the carbs because I am running pods (from Daves) and a high flow exhaust. It was a long while a go but I followed the instructions on the kit and have the new needles/jets installed and holes drilled out based on those instructions. The only difference is for some reason (a buddy who knew carbs did it with me) was my needle clip is at the 5th position as opposed to the 4th (as stated in the instructions). Even with this setting, I don't believe it should impact the bikes ability to start?

Some things I noticed:
1. I found the needle on carb 6 was bent when I took it out for inspection. I straightened it and put it back in but didn't have much impact on the bike starting.

2. Initially, when I opened the fuel valve, before I straightened carb 6's needle, I saw fuel leaking out of the exhaust and bowls down to the lift but that stopped after i shut of the valve. I'm guessing a float needle failed to prevent the carbs from overfilling but I think that has since corrected itself. It took the spark plugs out and let the engine air out but this hasn't made a difference.

3. I started the bike with carb 6 cover and needle off and saw a little fuel coming out of the idle hole so...really stumped as to why the bike isnt turning over.


As always, thanks to everyone for your support and knowledge.

[daves79x]

Are you absolutely sure you have your plug wires sequenced properly. It does not matter which of the two cylinders any one coil fires, but you should have (Left to right) - 1-6, 3-4, 2-5. With aftermarket parts it is very easy to mix these up. It looks like you still have the stock ignition otherwise?

Dave

[512tr]

Agree with Dave....

You have either a fuel or ignition problem…..or both.
Are your spark plugs wet after your start attempt?

Also, since you have rewired the stock ignition, is there a possibility that you have connected the 3 ignition wires to the wrong coils?
You could still have perfect spark on all 6 plugs, but they are not igniting when they should (BTDC on each individual compression stroke).
Check wiring and spark timing… start with pulse generator 1-6 to coil 1, coil 1 to spark plug 1 and 6……

Skjermbilde 2024-11-29 160259.png

Fuel:
As you say, the Dynojet stage3 should not impact cold start.

Remove the air filters, you don’t need them at startup (unless you are starting the bike in a sandstorm)
Ensure that the acceleration pump is working and injecting fuel through all 6 injectors.

My cold start procedure:
- Open fuel supply and let the bowls fill up.
- Apply full choke
- 2-4 fast twists with the throttle (injecting some fuel into the carbs, thus enriching the cold start mixture…… in addition to the choke)
- Push the start button

Works for me, start at first attempt every time.

We can discuss the Dynojet 3 later, in my experience they are “drowning” your engine with fuel, causing higher fuel consumption and reduced performance.

[Fw66]

And to probably nobody's surprise, you both were right- it's really amazing how fast folks can identify the issue based on just the symptoms I described.

After checking my wiring, I realized I had the pulse generator cables mixed up between coils 2 and 3. Luckily this was a quick and easy fix with the connectors I had installed.

Will fire up the bike tomorrow


Many thanks!

[512tr]

Nice to hear

Before you try to start it again, put the piston in and top cover on your carb 6.
Without, it will run very bad on that cylinder due to lean AFR.

The hole you see down the carb is not the idle port, it’s the last of the 3 progression ports

Skjermbilde 2024-11-30 110446.png

Picture1.png

Also ensure that your choke fast idle is working.
When applying full choke, it restricts air and increases fuel to get a rich AFR.
Restrict air by closing the choke plates, full choke also increasing fuel supply by slightly opening the throttle plates (choke fast idle), by uncovering progression port(s) delivering extra fuel at cold start.

When you finally get the engine started and are sure that the ignition is correct, it is highly recommended that you do a complete carb overhaul. There is great carb expertise here (Daves79x is one of the best), so with some advice and guidance you will be able to do it if you work in a systematic, tidy and calm manner.

[CBX-tras]

Here are a couple of photos that may help everyone understand the importance of drilling/tapping/extracting the aluminum plug, near the mixture screw tower.
Crud can/will build up there, and like a ship in a bottle, can't be removed the same way it got in there.

I've found that carbs in general, with age, the worse they get. I've had to do this as a precaution for some time now, on EVERY rebuild.

After ultra sonic cleaning, I reinstall the plug with a thin coat of epoxy to insure sealing.

The cut-away carb is a CB900F example, which is very similar to the CBX

Treat this as gospel.

[Fw66]

Excited to say that the bike starts!!

It starts but definitely not tuned as it has a bit of a rough/unstable idle and opening the throttle kills/stalls the engine.

Carb Specs:

1. Dyna Stage 3 kit ordered directly from Tim's and installed with instructions included. Once again, not sure why, but the clips on the needles were installed with the 5th position from the top.

2. Three sets of double K&N filter pods also ordered from Tim's.

Things I am double checking:

1. I'm pretty sure I installed the accelerator vacuum pump right but I will try to double check. I don't think I would've installed the spring incorrectly when I assembled it but I want to be sure.

2. Bought a 90% screwdriver to adjust fuel air mixture, can't be sure what all the positions are right now but I believe it should be 2.5 turns out.

Observations:

1. Accelerator seems to work with RPM increasing when opening the throttle but only when the choke is on.

2. Seeing what I assume to be unburnt gas droplets around the end of the exhaust (do not have the can installed at the end of the pipe).


As always, let me know what else I should be checking!

[daves79x]

It sounds like you still have idle circuits plugged. But the clip in the bottom position is far too rich. You may be choking the engine with fuel. When rebuilding the carbs, there is no reason to 'think' you have the accelerator pump assembled correctly. You should have wet bench tested the carbs for several hours, while insuring you have fuel squirting out all accelerator pump nozzles

I despise Dyno-Jet kits. Even set to acceptable running settings, the bike runs far too rich. Jetting for pods can be accomplished using stock Keihin jets.

You have some more work to do on these carbs and I'd start with the idle jets/circuits. Did you remove the pressed-in jets? Then get the needle clip in at most the middle position, maybe higher. Test the accelerator pump on the bench. But don't agonize over that - it is not your immediate problem.

Dave

[daves79x]

I see you have an '82 engine - if you have '82 carbs, the idle jets are screw-in and you should have removed them for cleaning anyway.

Dave