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OK, let me see if I can put all this together. The CB750 transmission will not handle twice the power, but the weak link is the primary chain, not the gears, or the dogs? So, If I could run the primary chains of each engine to a common jack shaft with a gear in the center, and feed a single...

Yes, UNDER the motors is better. I DO like the look of the Indy Cars that had the headers coming from the middle of the Vee, but UNDER is simpler.

OK, UNDER would be OK. Not as sexy, but....

Thanks for the heads up. (no pun) the overhead space is skyhigh, so, I can just curl the pipes higher over the valve covers.

4 into 2

Well, that's a dumb way to do it. Now that I think of it, you are right! 1-4, and 2-3, would be the way to do it. Since the area above the engines is clear, I would turn the pairs up and over the engines, not to either side. Thanks!

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Ah, the 9-15% power loss. Well, it's back to the cush couplings.

What if I used a cogged drive belt from each engine to the jack shaft. Wouldn't that provide the dampening?

Thank you. I can put something like a cush coupling near the middle of the jack shaft. Don't want to much cushioning, because I want the two engines to stay sync'ed as closely as possible.

I probably will only need high strength chain from the jack shaft to the transmission. The other two chains will only carry the original power from each engine, along with keeping the two engines in sync, although, the trike WILL be heavier.

Yes, you did. Thanks. I DO listen. One CB750 transmission, or one from a more powerful bike? I don't really want to spend the money for that race transmission.

OK, I think I've found a way to do away with the differential and one transmission, and tie the two engines together with the primary chains, without putting extra power through either engine. Split the transmissions off from each engine,and store one. Install high strength primary chains from...

Thank you! I'm not playing a game, just trying to get some information. Please don't be upset if I don't take all of your advice.You have helped me in many ways, for instance, I now think I will move the engines up to on either side of my seat., because they need to be wider apart than my...

There is no reason I can't separate the two engines enough to clear the rear suspension with the inboard pipes. So, where do YOU get your exhaust systems when you buy an old bike?

OK, let me just ask, If I don't change the exhaust plumbing on either engine, where does the 20% loss come in? 'Cause, I didn't plan to make one system crossing both engines. Planned on leaving them as Honda made them.

I mis spoke. Every 180 degrees is for 4 into 1, which gives more power at redline . 4 into 2 is every 360 degrees, which gives more power in the more useful mid range. The 2 into 1 further down wind would send weaker low pressure pulses back up the pipes every 180 degrees, and might be...

Flat plane V8s have no trouble scavenging exhaust pulses efficiently on each side, as each side fires evenly , every 180 degrees. CB750 fours are essentially one side of a flat plane V8. I can go four into two into one on each engine, then maybe connect the two ones with an X pipe.I don't see a...

Each engine has it's own exhaust system. I would keep those separate systems.

Why would that be?

So, two DOHCs through one transmission. No differential.

Post#115 Post#116 I'm sorry. When I opened this thread with the question, I took the following to say that the transmission would NOT handle the extra power. Have I misinterpreted? Post #1 Post#5 Post #6 Post#9

I want eight cylinders, and I'd LOVE to use one transmission, but it won't handle double the power. I'm really after those answers, and they have been answered.

OK, so let's forget the extra ratios. I'll shift both together, and stay in matching gears. The main purpose of the differential is to provide a fail safe in the case of mis matched shifting.

Yes, I've owned a Suzuki 120, Yamaha 400, Suzuki 250,and a Kawasaki 350

Normal driving would be 1/1, 2/2, 3/3, 4/4, 5/5, both paddle gears together. No activation of the spider gears. The differential is there to join the two transmissions safely. The in between ratios would only be useful for full-on interstate entry. In matched gears, the differential acts just...

More accurate chart. I used the numbers from Cycle World Magazine.

It's an RPM to Speed chart, not a horsepower or torque chart. All I added was the 1/2, 2/3, 3/4 and 4/5 ratios in red, and the yellow shift lines. The rest I pulled off the internet. What do you believe is wrong with it?

Why not keep it Honda? A used CBX? What do you see as the biggest problem with my design?

No more than a standard chain driven CB 750,using a double row chain, except when in 1/2, 2/3, 3/4, or 4/5. The advantage of close ratio should be worth it.