Topic: NOS Honda cb750 Engine/Trans.

[BenelliSEI]

Last night I was offered a complete cb750A engine (no carbs). Supposedly ex Honda Canada warranty part, never run, from a dealer inventory. The gentleman that has it wants it gone. Curious;

1. Does anyone desperately need one of these?
2. Is the top end interchangeable with a cb750K. Good source of new parts?
3. Is the camshaft unique to this engine?
4. What else is interchangeable? Crank, rods?

Thanks for your expertise!

[willbird]

I would think it is worth far more as a complete unit than as component parts ??

[BenelliSEI]

I would think it is worth far more as a complete unit than as component parts ??

I agree (see first question). But if not, how useful might it be?

[Gurp]

I'm just wondering if it has numbers to know that exact year. That's insane to find a never fired motor from at least 78 likely before.

Sent from my LE2127 using Tapatalk

[BenelliSEI]

No idea what year. For some reason I think it’s an early one……..

[MauiK3]

I think that you won't know the answers until you get it. There are 750A folks here, I bet someone needs either all of it or some key parts.
Sounds like a great find, love to see photos

[CycleRanger]

I am not an "A" expert but I'm pretty sure the cam and crank are unique to the "A".
Imho a NOS 750A engine would be worth more intact than the sum of its parts.

[BenelliSEI]

I am not an "A" expert but I'm pretty sure the cam and crank are unique to the "A".
Imho a NOS 750A engine would be worth more intact than the sum of its parts.

I’ll bet you are correct. Will wait for more info, but probably make the trip.

[Tracksnblades1]

Crankshaft has Hyvo chain…🤫

[newday777]

I am not an "A" expert but I'm pretty sure the cam and crank are unique to the "A".
Imho a NOS 750A engine would be worth more intact than the sum of its parts.

I’ll bet you are correct. Will wait for more info, but probably make the trip.

Definitely different cam. Head, cam towers and the cylinders are the same though.

[willbird]

The correct answer is once you have the engine you need to find a bike without an engine to go with it :-).

[dave500]

and hopefully its all in good shape internally?like surface rust ect on bores/crank/gear shafts?

[69cb750]

In 1982 Kawasaki was warehouse cleaning and offered z1 and h2 crate engines to dealers for $500.
All engines sold the day they were offered.
In 2019 one of these engines appeared on ebay for $10k, no one bid.

[BenelliSEI]

Been in home basement, always. Will go see.

[PeWe]

Head is 392 if I had got it right.

My K6 has a 392 head.
I bought an old one that my local shop restored and updated.

[Tracksnblades1]

Been in home basement, always. Will go see.

Will you be able to at least flywheel it…🤞

[MauiK3]

Love to see it!

[Stev-o]

John....isn't this the same motor?

http://forums.sohc4.net/index.php/topic,189758.0.html

[HondaMan]

The "A" engine has terrible ports, as Honda wasn't interested in making it breathe better with the smaller 24mm carbs. That said, I've ported them before (takes a while!) for those who wanted to either race them (good bracket racer) or tour extensively with modern speed limits, as it was built for the 55 MPH speed limit era. The cam opens the intake valve AFTER TDC, it is literally that tame! I've installed K4 era cams in 2 of the "A" bikes. It gave better midrange and top end power, but it didn't idle as well when cold, needed some help. Both of those bikes stayed with their "A" carbs because of their idle-booster solenoid when idling in gear.

[BenelliSEI]

John....isn't this the same motor?

http://forums.sohc4.net/index.php/topic,189758.0.html

Yes.

[Tracksnblades1]

The "A" engine has terrible ports, as Honda wasn't interested in making it breathe better with the smaller 24mm carbs. That said, I've ported them before (takes a while!) for those who wanted to either race them (good bracket racer) or tour extensively with modern speed limits, as it was built for the 55 MPH speed limit era. The cam opens the intake valve AFTER TDC, it is literally that tame! I've installed K4 era cams in 2 of the "A" bikes. It gave better midrange and top end power, but it didn't idle as well when cold, needed some help. Both of those bikes stayed with their "A" carbs because of their idle-booster solenoid when idling in gear.

Are the ports only a problem with the CB750A cylinder head?
Does it carry on to the F0, F1, K7, & K8..?
I thought the 392 was one of the better heads..

[HondaMan]

The "A" engine has terrible ports, as Honda wasn't interested in making it breathe better with the smaller 24mm carbs. That said, I've ported them before (takes a while!) for those who wanted to either race them (good bracket racer) or tour extensively with modern speed limits, as it was built for the 55 MPH speed limit era. The cam opens the intake valve AFTER TDC, it is literally that tame! I've installed K4 era cams in 2 of the "A" bikes. It gave better midrange and top end power, but it didn't idle as well when cold, needed some help. Both of those bikes stayed with their "A" carbs because of their idle-booster solenoid when idling in gear.

Are the ports only a problem with the CB750A cylinder head?
Does it carry on to the F0, F1, K7, & K8..?
I thought the 392 was one of the better heads..

The -392- and the F2/3 -410- heads are the best-breathing heads of the bunch! The ones they put on top of the "A" engines looked to be cast from different molds, although the interface (gasket area) seems to be the same. The "A" heads I have seen bear no traces of the "tech's touch" with a grinder, though.

[Stev-o]

Been in home basement, always. Will go see.

So.....did you go?

[BenelliSEI]

Been in home basement, always. Will go see.

So.....did you go?

We had a few days off skiing with the family. Will go this week.

[BenelliSEI]

So the fellow phoned me yesterday. He has a large collection of motorcycles and his “helper” and the guy that constantly cleans and details the bikes and building were both there. They hoisted the engine in the back of our small SUV and I “slid” it into the bucket of my old tractor at this end. It’s on a moving cart for now.

Pictures this afternoon. Not sure how true the “new motor” story is. It doesn’t look like it’s ever been bolted in, the covers are not banged or gouged (very nice points cover). But, the exhaust ports and valves definitely show run time. The intake ports and valves look super clean and unused. Looks like the points plate is in place, it will be interesting to see what the points look like. Photos later today.