[slr]

What is it??? This Royal Enfield has 4 speed with reverse, single cylinder, bike frame #M&B 4111 and P4551(rear of frame), A serial #G15934 with triangle marking, engine patent plate mfg by The Enfield Cycle Co Ltd Redditch Paten#4930-Year1920. Frame is ridgid, but has telescopic front forks (may not be original front-end?). Any ideas on year & model?

[GlennF]

The Enfield club in the UK has a registry of frame and serial numbers.  Otherwise a photo would really help.

If it has a reverse gear it almost certainly was meant to be used as a sidecar hack.

Pre-war enfields were girder fork and rigid. Late 40's onwards were swingarm and telescopic forks so you are really looking at late WWII or just after I suspect.

One of the more likely candidates is a late 1940's 350cc model G (there is a "G" in the serial number and the 1946 onwards G model was rigid with telescopic forks), or another possibility is a mid 1940's ex-military WWII sidecar hack sold off as military surplus after the war.

[Grabof54]

A 350 single with 4 speed and reverse has most likely been removed from a Pashley manufactured Indian Patrol Car trike.

[Sandgroper]

If this definitely has a reverse gear, it's a weird one. I've never previously seen or heard of  any Enfield motorcycle, with or without a sidecar, with a reverse gear. I'm thinking this is likely a Model G, and is the neutral finder being mistaken for a reverse lever, without this being verified?
The Indian/Pashley Patrol Car trike only has a 3-forward-speed 'box - reverse is where 1st gear would usually be. Idle thought - would a gearbox from an Enfield-powered Berkeley fit?

[rotorwrench]

The Pashley trikes and Indian Patrol cars had a 3-speed with reverse. I have the parts break down that shows the reverse shaft and pinion installation in the Albion type transmission. The shifter gate has the R at one end. These are the only ones I know of that had the reverse gear. Since it is an Albion gearbox, it can be installed on any of the engines with that particular 4 bolt pattern. I don't remember on the Berkley for sure but they used the later Interceptor/Galaxy type 750 engines since they were made in the mid 60s. Somewhere either here or on the Britbike forum , there is some info on the Berkley.