The International CBX Owners Association

Wondering if you are getting any further with this. Any progress on having throttle bodies cnc machined?

Like a lot of people, covid put almost my whole life on hold. The focus has been on managing 2 young kids with sporadic school/daycare and 2 parents trying to work from home. The time I had planned to use for scanning & modelling custom TBs gets used up with work and kids, and the money I planned to spend was impacted by multiple leaves from work, and shifting priorities.

I'm really eager to do this, it's at the top of my list of priorities once things get back closer to normal again.

I believe you spoke briefly with Dave north of Kitchener. About his injection system. You should have a good look at it as it works very well. I did a lot of the work and tuning. Let me know if you would like to chat about it, I am local to you as well.

Andrew11 wrote: ↑

Fri May 14, 2021 3:14 pm

I believe you spoke briefly with Dave north of Kitchener. About his injection system. You should have a good look at it as it works very well. I did a lot of the work and tuning. Let me know if you would like to chat about it, I am local to you as well.

That's awesome, thanks! I'm gonna shoot you a PM.

Sent you a pm. Let me know if you got it.

I'm planning to pull the carbs from my bike sometime in the next month or so in order to have them as a reference for designing custom EFI throttle bodies.

My cousin and I will be doing the work together, in a shop that's well-equipped with air tools, hoist, jacks, etc. Neither of us is a pro mechanic but both have worked on cars and bikes for fun. We've both done carb work on old bikes, but neither has pulled CBX carbs before. Is it ambitious to think that we should be able to get this done in ~4 hours? Looking at Mike Nixon's instructions for removal, it looks like this would be doable in 1 hour for someone who's done it before and who knows what's going on. So I'm thinking that 4 hours for 2 guys fumbling a bit should be a safe estimate.

Easy pull in 4 hours. Should be less for 4 hands. If everything is stock, you will need to roll the engine. That means dropping exhaust, etc. Still, two guys and 4 hours -- no problem. Tip: detach the cable at the grip and remove the cables attached to the carbs. Trying to detach cables from carbs while on the engine is a 'challenge'! Have fun. Let us know how the EFI project does.

I don't recall how long it took the first time I did it but it wasn't quick, 4 hours would be a good guess and I was alone. More like 6hrs putting it back together.

I've done it a number of times now, last time and it took about 1.5-2 hrs to tilt the engine pull off the carbs for a quick check then tilt it back up into position and torque everything up. Much quicker but I still don't look forward to doing it.

Pliable intake and airbox rubbers certainly help and a bit of grease. When it comes to putting it back together I'd hold the carbs in one hand and slowly pivot the engine up with a small floor jack tilting it back into position, gently squeezing the carbs between the two sets rubber. When it goes well they almost pop back on but you need to constantly check that they're lined up as you go.

Most difficult part I still struggle with is re-connecting the throttle cables, lots of cursing seems to help.

It's been a while. but I used to pull a rack of carbs from an early model in an hour and a half. Doubt I could do it in 2 hours now. A pair of smaller hands is nice to have helping put the cables back on. I'm lucky that my wife is a willing participant on things mechanical. A light mist of WD-40 on the intake boots helps.

Thanks a lot, gang.

Rick Pope wrote: ↑

Fri Oct 15, 2021 9:42 pm

It's been a while. but I used to pull a rack of carbs from an early model in an hour and a half. Doubt I could do it in 2 hours now. A pair of smaller hands is nice to have helping put the cables back on. I'm lucky that my wife is a willing participant on things mechanical. A light mist of WD-40 on the intake boots helps.

Another pair of smaller hands helping with cables would certainly be helpful, even with the carbs off hooking the cables back up can be annoyingly tricky.

Reconnecting the cables when carbs are in place near impossible, tried it once and unbelievably I got lucky and succeeded but then I disconnected them as I needed to remove the carbs again. Never tried to repeat that bit of luck again, not worth the effort.

Syscrush wrote: ↑

Tue Apr 06, 2021 10:29 am

This week I learned about Saturn's oddball "compression sense ignition":

The waste-spark ignition is part of a unique Compression Sense Ignition (CSI) system that allows the powertrain control module (PCM) to determine proper engine phasing (cam position) without the use of a separate camshaft position sensor mounted near a rotating engine member.

This is such an interesting approach, I can't stop thinking about it, as it would allow me to go sequential without having to have any kind of mechanism for cam angle or phase sensing. Today I found this video, which shows the system in operation using a digital oscilloscope. I'm pretty confident that this would be eminently doable with something like a pair of inductive pickups, each with a Schmitt trigger for edge detection and some timing calculations in a modern ECU. Maybe even in a fairly dumb circuit using an op-amp as a comparator.

I'm going out to pull parts off the bike in just over a week, I can't express how stoked I am about starting to take some concrete steps towards bringing this bike into the 21st century.

Hi Phil, nice to hear you are getting some time for your bike now. Did you try to get in touch with Dave to have a look at his setup? Also, I have a spare head if you need it for bore spacing and mocking up if you want it.

Thanks, Rob! I haven't been in touch with Dave, because my plan is to go a very different direction for the throttle bodies themselves, and that's where I'm focused now - but I wanted to follow up with you about the in-tank pump setup. I remember you said something about choosing a Ducati setup due to clearance issues in the CBX tank, but I don't remember details.

I've ordered a set of used Triumph Bonneville throttle bodies with injectors, and I'm pulling the OEM Honda carbs off the bike soon. My plan is to take apart both and have high-resolution 3D scans done of them and then use CAD to try to come up with a design based on the Triumph approach (in terms of how it places/packages the injector) that looks close to the OEM Honda carbs, and that mounts in exactly the same way as the original carbs.

Once I've finished the first draft of the CAD work and have plastic prototype pieces to fit, I will probably take you up on that generous offer of using the spare head so I can bench-test stuff and refine the design much faster. That's a really kind offer and I appreciate it a lot.