New Member from Texas (former Germany)

[oroepke]

Howdy everyone? I am a happy CBX owner as of yesterday. I am located in Central Texas (last 22 years) but grew up in Germany. Now I have an Autobahn bike but no Autobahn available! Some details about the bike:

1980 CBX,19,000 mls, bought at an estate sale, no service records but a write-up from the late owner
Around 2016: alternator and speedometer rebuilt
Tank and tail section probably repainted, but very high quality
6-1 Supertrapp Exhaust, Corbion Seat, K&N pods (or breadboxes?) one per two carbs
Progressive shocks
Original owners manual
Some chrome covers

It had sat for a year or so but started right up with some starting fluid and I was able to ride up and down the street. My goal is to thourouglky go through the bike, what it needs immediately is oil change, tires, battery, brakes, carb rebuild. The tank has been lined and looks great, inside and out.

Here some pics. Looking forward to digging into this!

[Jeff Bennetts]

Nice bike to do whatever you desire, good luck with the build which ever way you decide go!

[NobleHops]

Great bike!

[Rick Pope]

Looking good!!!

You don't need the Autobahn, with the Hill Country right outside your door. I'll be there in a a couple weeks, in Bandera until last of February. And yes, I'll have a bike with me, though not a CBX.

[EMS]

The exhaust is a combo of two different systems. A Kerker/DG 6-1 header with a slip-on Supertrapp muffler. Supertrapp, to my knowledge, did not make a 6-1 for the CBX, although Supertrapp is a Kerker product.

[oroepke]

Looking good!!!

You don't need the Autobahn, with the Hill Country right outside your door. I'll be there in a a couple weeks, in Bandera until last of February. And yes, I'll have a bike with me, though not a CBX.

Perfect riding weather here now!

The exhaust is a combo of two different systems. A Kerker/DG 6-1 header with a slip-on Supertrapp muffler. Supertrapp, to my knowledge, did not make a 6-1 for the CBX, although Supertrapp is a Kerker product.

Thanks, I wasn't aware. I actually odered a closed end cap and some disks for the Supertrapp, is way too load for me.

[oroepke]

Finally back on the road. Not sure if I can post a video here? I’ll try both, video and pic. Thanks for everyone who helped. Next step -get the airbox on and the carbs rejetted!

[Jeff Bennetts]

Finally back on the road. Not sure if I can post a video here? I’ll try both, video and pic. Thanks for everyone who helped. Next step -get the airbox on and the carbs rejetted!

And find a better exhaust system if you can manage it!

[oroepke]

From what I read the Supertrapp muffler with the 6-in-1 collector can be used with original jetting with something like 8 discs or so.

I may get an original (copy) exhaust later, for now my plan is to keep the Supertrapp, put the air box on with original jetting. What do the gurus say, is that a decent idea?

[Jeff Bennetts]

From what I read the Supertrapp muffler with the 6-in-1 collector can be used with original jetting with something like 8 discs or so.

I may get an original (copy) exhaust later, for now my plan is to keep the Supertrapp, put the air box on with original jetting. What do the gurus say, is that a decent idea?

The muffler is fine, the exhaust headers of your system are D&G and have a midrange flat spot that can’t be tuned out, been that way since they began selling them 35 yrs ago, it doesn’t matter what muffler you use with that D&G header, the results are the same.

[oroepke]

I think I experienced that already, bike runs great up to 5k rpm, then nothing between 5-7 (literally haven‘t ridden anything like this before) then screams from 7k to redline.

So sounds like the airbox won’t cure that? I thought it might be the pods.

[Jeff Bennetts]

I think I experienced that already, bike runs great up to 5k rpm, then nothing between 5-7 (literally haven‘t ridden anything like this before) then screams from 7k to redline.

So sounds like the airbox won’t cure that? I thought it might be the pods.

It could still be a combination of things, just get back to a stock baseline and go from there but that header will always be a problem. I had pods, K&N DJ stage III and always a good breathing aftermarket exhaust systems and my bike ran very well but it took a lot of Dyno time and fiddling to keep it from running fat.

This is my CBX with a Hindle system.

9E527069-DCB2-44E8-9AE1-384F04EE7EAD.jpeg

[oroepke]

I don’t plan to spend a lot of time with this setup, I think I will ride it for a few hundred miles to see if the engine has any issues, then go back to stock jetting and air box and maybe play around with the disks on the Supertrapp a bit.

Would you say the flat spot from the header is because of the less than ideal flow or could it be cured by changing the fueling (different needle, taper, etc.)? I’m not really planning on dyno tuning, I’d rather look for a stock (copy) exhaust then, if I can’t make this work.

[Jeff Bennetts]

I don’t plan to spend a lot of time with this setup, I think I will ride it for a few hundred miles to see if the engine has any issues, then go back to stock jetting and air box and maybe play around with the disks on the Supertrapp a bit.

Would you say the flat spot from the header is because of the less than ideal flow or could it be cured by changing the fueling (different needle, taper, etc.)? I’m not really planning on dyno tuning, I’d rather look for a stock (copy) exhaust then, if I can’t make this work.

Nothing will help that exhaust that I know of.

[daves79x]

Your best bet is to go back to the stock airbox, stock type filter (NOT a K&N drop-in) and stock mains and needles (hope you have them). Not a lot to change on the '80 carbs. You can try a set of #38 idle jets with the exhaust, or Bob's suggestion of drilling out the #35 jets to #36.5. This might give you a little mitigation of the DG flat spot, but perhaps your bike won't be too bad in that regard, some are, some aren't. Do not go up from the stock 110 mains (Keihin, not Dyno-jet) . Set up like this, a set of reproductions exhausts will work just fine without re-jetting again, although the low-end will not be quite as crisp with the #38 jets and stock pipes.

Dave