CRAZY Honda OVAL Piston Engine

Making it's debut in 1979, the oval piston engine incorporated eight valves, two connecting rods per cylinder, plus an aluminum semi-monococque frame complete with an inverted front fork.

[sahaquiel]

I love ambition, even if you fail, you have no regrets, not mentionning all the innovation that you possibly made along the way, while trying to solve problems.

[billallen]

I had this idea in the mid 80's and my thoughts were decreasing the parasitic drag from less ring-land area against the cylinder! He was a small engine mechanic and he said it would be almost impossible! But with today's materials and machining it could become a reality!..from Wyoming USA 🇺🇸 👋🤠

[keithal]

The piston is not oval shaped. The correct term is obround. Two semi circles connected by straight lines.

[rishikeshraj]

Unique and bold. Honda hats off to you 🙇🇮🇳

[ShaunieDale]

I believe this was a response to the maximum four cylinder rule. They took a V8 and knocked the partition wall between them down!
I remember a Honda press release about the race bike at the time “We have only three problems at the moment, handling, performance and reliability”.

[electricpaisy]

That sounds definitely quite interesting

[phenogen]

a great project for Alan Milyard to replicate

[calvinwong]

This Honda NR750was famous back then with the NSX car..

[SameAsAnyOtherStranger]

Wow. Fifty percent more cylinder bore and a lot less weight since one piston was doing the work of three in the space of two. Maybe if the cylinder was bored at an angle and the rods connected to counter rotating crankshafts.

[markfryer]

Well I just learnt something new for today! Not sure what to do with the information but there you have it! 😂

[leensteed]

I wonder how it would be if the side wasn't straight but had a curve to it so it sealed better

[Thiokol_XLR]

i keep a scale model of a green NR750 on my desk! I was blown away when I found the model, cause of how rare the REAL bike even is. would be an absolute dream to see/ride let alone own one some day

[AbuAusa]

What's the problem with making the motherloving piston just bigger?

[Shubham_man]

Actual problem was inconsistent metal expansion, that led to engine failure in extreme cases, for example, in racing

[haweater]

I've heard about it, I thought the purpose was to create a crazy large displacement engine for a racing category that allowed only 4 cylinder engines.

[Echocompany-]

My question is if they made an oval piston why didn’t they just make it a two valve engine but the valve was a larg oval with two stems to keep it from twisting.

[geoffoliver]

At the time the NR was referred as " nearly ready" as it never ran well for very long, just ask Mick Grant. They even ran Suzuki machines with Honda decals as the engine was NOT READY

[Qui-]

Were they trying to fit more cylinder area into a smaller block this way?

[Jack-wox]

After having reminisce for a minute, harkening back to the good old days of reading all the bike mags and the rest, IT flashed upon me that perhaps it was Honda's way of challenging the 500 2 strokes.?! Perhaps that was the direction they were going in, however, I think it would have been more fitting in the four-stroke category challenging comparable four cylinder 750s. Just my thoughts, welcome to feedback 🙄🧐🤔

[kareldegreef]

Nope => you made a mistake => it had 130 hp but could be easily tuned up to 200 hp for a 750 cc at the time (even now) was mindblowing !