Forum

[Bullet Whisperer]

I agree with Mark M, in fact the crank in my video only required a new floating bush, all else was fine. Regards, Paul.

[John M]

Mark M, my question regarding the plain bush wasn't regarding replacing just the plain bush, (although I am a bit of a tight-ar**), more a case of roller bearing versus plain bearing. I was wondering if the roller bearing is that much better than a plain bearing and if fitting a roller bearing has any knock-on effects on the lubrication system. Particularly considering that the bearing has failed due to my cock-up and you can purchase a plain bush big-end and new con-rod for about £100 less than a roller bearing big end..........Chris Tindal, my reference to a "rare variant" was regarding the make up of the engine, it is a 1956 G2 engine, the crankcases are the pre-56 500 design, but bored for a 350 top end. The effect is that it is like the later 350's with the wider big-end, but has the earlier slim timing chest with the oval oil pump housing but without the auto-advance bulge...... It is not an earlier 500 engine that has been messed with as the engine number is G2 rather than JS and the timing cover has the 1956 onwards oval RE badge rather than the cast in Royal Enfield of the 500's......I have been trying to find out its history, without success and the only other 350 I have seen with the same design is HNP331.... I'm not suggesting that mine is from a works bike, but it is very unusual......https://farm3.staticflickr.com/2565/416 ... babf_b.jpg

[Chris Tindal]

Interesting info about the casing. I recently converted my 59 500 to roller bearing after lots of questions to people with first hand experience. The conclusion I came to was that the floating bush is actually better than the roller and should last longer if good oil pressure is maintained. The only reason I went for the roller was because the only floating bushes available are standard Indian ones. Nothing wrong with Indian, but after shelling out for a steel rod, I wanted a really good quality bearing that I hopefully never have to replace again. If our hosts did a real quality floating bush that didn't dump its white metal after 20k miles then I would have gone for it

[Tim NZ]

John: Uncommon variants and 'specials' turn up from time to time.


The factory also built some 'transition' 350 Scrambles mtrs onto 500 Btm ends where the barrels were flange mounted: base flange studs+nuts, and barrel mounted studs for the head nuts.

[John M]

Tim NZ, mine has a standard post 1956 barrel, but the bottom end is like a 1953-1956 500, with the slim timing case (no auto-advance bulge) but with an oval Royal Enfield badge rather than the cast in Royal Enfield on the 500s. It has always been a 350 as the studs are spaced for a 350 and it has an unmolested G2 engine number. It definitely has full length studs as I had no end of fun getting the head off............Fortunately I have managed to speak to Andy Berry, who as you may know is a font of knowledge regarding Bullets, he will hopefully be doing the big-end replacement for me and should be able to help me identify what is inside my cases.

[John M]

Just to add, the cam-shafts are marked with an R J as well as (I)nlet and (E)xhaust, I have no idea if that are standard or not.

[Chris Tindal]

So it's an early 500 casing machined for a 350 barrel? Could it have been the beginnings of the factory moving towards the common 500 crankcase for both sizes post 55? Maybe the last few 55 350's had the 500 crankcase like all the 56 on ones so it was a gradual change rather than a sudden one, overlapping both early and late casing types, just a thought.

[John M]

Good news, apart from a comprehensively knackered big end the crank appears in good condition.......... The flywheels are, I'm reliably informed, lightened 500 flywheels, and the cams marked "R" are scrambles camshafts, so it appears that I have a scrambles motor, which would tie in with the ported inlet tract and streamlined inlet valve guide.... It would also explain why it goes a lot better than my Indian Bullet............I have decided against a floating bush and think that an Alpha bearing is on the cards.

[Mark M]

A footnote, John gave me the engine number (a while back,) and I asked Graham Scarth to have a look in the Factory Despatch Records to see if it was listed as a competition engine but sadly there is no special note next to the engine number. Which doesn't mean it isn't special, just that if it is they didn't say so! I know Alan Hitchcock bought a similar bike with French plates a couple of years ago at the Netley Marsh Eurojumble and that didn't have anything against the number in the records either although the engine is (externally) the same as John's. I don't know what Alan did with it, maybe worth asking Alan, John?

REgards, Mark

[John M]

A bit of a roller-coaster with this one, Ive had a good look at the flywheels and one appears to be numbered 26699, which makes them 1953 500 Bullet or J2 500 flywheels. I'm confident that they will be the flywheels fitted when the engine was new, The biggest problem with this is that 1953 500s use a different big end than the later Bullets, which is a shame because I've treated myself to a new Alpha roller big end. I don't know what the difference is between the two big ends or if it can be made to fit, so I'm a bit frustrated at the moment, it's all starting to get a bit expensive!