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Long stroke crankshaft for 500/535cc EFI engine including the GT

All English crankshaft for the fuel injected 500/535cc EFi engine including GT

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Big End Bearing

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Big End Bearing
Started at 01:32pm on the 18th September, 2017 by John M
John M Subject: Big End Bearing
To cut a very long story short, I have managed to knacker the big-end bearing on my 1956 Bullet engine...............I have two questions, firstly I intend replacing the existing bearing with a roller bearing big end, are there any short comings in this conversion, or any compelling reason to use the standard type plain bush?............... Secondly, is it practical to attempt this repair at home, I am thinking about truing up the flywheels rather than the disassembly of the engine?
Posted: 01:32pm 18th September, 2017
papasmurf Subject: Big End Bearing
I have tried to find a video on YouTube that would help you. However all of them are accepting crankshaft run outs I would not accept if I were rebuilding a crankshaft, especially on a single cylinder engine. To me 4 thou run out is a mile.
Posted: 02:03pm 18th September, 2017
Bullet Whisperer Subject: Big End Bearing
OK, Papasmurf, I have bitten - here's one of mine, certainly good enough not to cause any problems. Regards, Paul. ... https://www.youtube.com/watch?v=xPyCZZ66WQE
Posted: 04:40pm 18th September, 2017
papasmurf Subject: Big End Bearing
At least the crank "run out" is in the same place both sides in your video;-
Posted: 05:03pm 18th September, 2017
Tim NZ Subject: Big End Bearing
What ever was the cause of the floating bush failure will kill a rolling bearing just the same. Find the cause.
Check the OPR inside the timing shaft....
If you dont have the correct gear to strip and ACCURATELY reassemble the crank shaft you WILL KILL it! Not least if your crank shaft is in need of an oversize crankpin?
IF the crank shaft has been flexing excessively and the 'eyes' in the flywheels have any appreciable TAPER(?) an oversize crank pin will be required.
Nearly every worn out crank-shaft that I have encountered has been in need of an Oversize crank pin, and the fitting of such requires specialist machine tools to re-true the flywheel eyes..
Posted: 10:06pm 18th September, 2017
Leon Novello Subject: Big End Bearing
As they say on TV, don`t try this at home.
Posted: 10:33pm 18th September, 2017
John M Subject: Big End Bearing
Thanks for the replies, decision number 1 has been made and I will get the big-end professionally fitted, it's not worth the risk of making a pigs ear of it myself as the engine is what I believe to be a very rare variant, a 350 with a pre-1956 500 style bottom end............. I'm more than a little annoyed with myself as the cause of the failure was a leak from the oil filter housing and oil starvation, unfortunately I only noticed once it started knocking..........I changed the oil and re-filled with 225cc of oil, but judging by what I drained off it may have got down to 75cc, a very expensive mistake!
Posted: 12:07am 19th September, 2017
John M Subject: Big End Bearing
Just to clarify, when I said that I changed the oil, that was before the big end went, the bike was on the trailer before going to an event and the oil filter housing failed to seal properly. I do know that 225cc of fresh oil doesn't fix big-ends.
Posted: 12:12am 19th September, 2017
Chris Tindal Subject: Big End Bearing
Out of interest, can you explain the rare variant John?
Posted: 07:24am 19th September, 2017
Mark M Subject: Big End Bearing
John, I'm not sure anyone answered the other part of your question, ie, can you replace the bush? I have come across several failed floating bush big-ends that have been successfully repaired with a new bush alone. Obviously it will depend on inspection but this is one of the overlooked advantages of the bush. But I didn't do the work myself!

REgards, Mark
Posted: 08:14am 19th September, 2017
Bullet Whisperer Subject: Big End Bearing
I agree with Mark M, in fact the crank in my video only required a new floating bush, all else was fine. Regards, Paul.
Posted: 08:50am 19th September, 2017
John M Subject: Big End Bearing
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/2565/4166960305_207287babf_b.jpg
Posted: 01:35pm 19th September, 2017
Chris Tindal Subject: Big End Bearing
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 :-)
Posted: 10:56pm 19th September, 2017
Tim NZ Subject: Big End Bearing
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.
Posted: 09:46pm 20th September, 2017
John M Subject: Big End Bearing
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.
Posted: 01:43pm 24th September, 2017
John M Subject: Big End Bearing
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.
Posted: 01:48pm 24th September, 2017
Chris Tindal Subject: Big End Bearing
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.
Posted: 03:50pm 24th September, 2017
John M Subject: Big End Bearing
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.
Posted: 11:13pm 25th September, 2017
Mark M Subject: Big End Bearing
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
Posted: 04:23pm 26th September, 2017
John M Subject: Big End Bearing
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! P1090238
Posted: 12:52am 1st October, 2017

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