Hitchcocks Forum

I purchased my 1992 Bullet 500 in about 2008, it had 17k miles on the clock and was going to be my daily commuter in favour of my trusty Japanese iron which although very reliable lacked character & charisma, and anyway I could make a royal Enfield as reliable as any rice burner. I had bought the Enfield unseen through a well-known internet auction site, I decided to bid on it about 10 minutes from the end of the auction, which pretty much precluded me from seeing it first, but hey, the pictures looked ok and there were plenty of other bidders, it must be ok. This really is an incredibly foolish thing to do and I wouldn’t recommend it, worse still the seller had never run or ridden it, he was a bric-a-brac dealer, God only knows how it had come into his possession but his story was that the previous owner could not get on with the gear change being on the wrong side (yeah right), so he took it in to his local antique dealer and probably swapped it for a couple of candle sticks or a stuffed fox perhaps, anyway the dealer was an honourable chap and delivered it to my home in his rather rickety van, it was at least fairly local. He tried to start it for me, to demonstrate that it would run, this however proved troublesome as he didn’t have much idea, but eventually it was eased into life with a gentle phut, phut, phut.


Despite all this, I was happy enough with my purchase. As far as I knew the Bullet was in pretty standard trim with the exception of an Amal concentric carb fitted by a previous owner. No real issues for the first few hundred miles, although I had noticed that the exhaust valve tappet clearance was in need of regular re-adjustment, not because the gap was opening up, but instead it was closing and the exhaust valve was being held off its seat, this would manifest itself by loss of compression, not a major problem, as long as I checked it regularly, just an inconvenience, although would require further investigation at some point, as advice pointed to valve seat regression. As this was going to be my work horse I decided to fit a BB electronic ignition unit, so that I wouldn’t have to mess around with contact breaker adjustments and settings. This was a good move and has never given any trouble. After about 2,500 miles of trouble free commuting, I was on my way to work one morning, there was a nasty noise from the engine, accompanied by marked lack of power, I was able to complete my journey to work and home again and later carried out a top end strip, I found that the back half of the piston had cracked circumferentially at the scraper ring groove and broken away from the rear of the gudgeon pin , the back half had actually dropped into the engine while the remainder carried on its work. A full engine strip ensued to remove all of the offending bits of piston. I was back on my trusty Japanese steed…


I visited my local(ish) Enfield dealer, proudly showing off my half piston, the dealer was less than surprised at the fate of the item, suggesting that this was probably caused by either an oval bore or an oval piston; he had seen this before on early Indian Enfields, stating that quality had not always been at the forefront of the manufacturing process. The dealer assured me that I needed a new English made Aluminium Barrel and high compression forged piston, which he could order and have in the next couple of days for the princely sum of about £300. I gratefully accepted and awaited their arrival, in the meantime I stripped the engine completely, and while I was there, replaced the main bearings which were absolutely shot , with craters appearing in the tracks through some kind of delamination process. I also did a complete overhaul of the cylinder head, including new valve guides and seats. I then set about reassembling the engine, by this time the Barrel and Piston had arrived so I was able to complete the rebuild, once re-assembled I was mightily impressed by the compression, the like of which I had never before experienced on my beloved Bullet, I had never needed to use the decompressor before! I had ever really found compression. I decided to fit a new oil pump drive a new drive worm and some high capacity oil pumps, based on my misguided opinion that it can’t do any harm…..and would certainly increase oil pressure and flow. I used a good quality engine assembly lubricant and “ran in” the engine carefully, adding a small amount of two stroke oil to the fuel tank at each fill, probably equal to about 100:1, a habit which I have continued based on the fact that it can’t do any harm and acts as an upper cylinder lubricant.


After a very short time on my way to work one morning, the scavenge pump cover gasket failed and blew oil all over my foot and the exhaust, I became aware of this fairly quickly when my foot slid off of the foot rest and I couldn’t get it to stay on. I limped my way back home and out came my trusty jap for work. Once back home I fitted a new gasket to the oil pump cover, comfortable that the failure had been due to a problem during re-assembly (misalignment or bolts not tight enough). I set off for work the very next day and….. yes, you guessed it exactly the same failure. I concluded that there was a problem with the gaskets probably inferior quality, I had some made up at work from proper Klingerite … on the third failure I did two things
i) got the old faithful Jap out again and
ii) checked the internet for problems when fitting High capacity pumps…. Well, it turns out that there are numerous engine internal works you must do when using these pumps to avoid it all ending in tears, these modifications associated with opening up oil ways to prevent over pressurisation (now that makes sense) and fitting an over pressurisation relief valve (the Redditch Bullets have these fitted as standard, but alas Indian ones do not). As I didn’t particularly relish the prospect of going back into the engine again quite so soon, I replaced the original oil pumps and put my lovely new high capacity pumps into storage until the opportunity would arise to increase the oil ways and fit a relief valve.



All was well for about a thousand miles, when on my way home one evening the big end let go, I knew it as soon as it went, a loud knock deep within the engine at the same frequency as the engine speed and rather than stopping the engine and calling for assistance, I limped the bike home for the last 5 miles which it did very well considering The following day it was out with the trusty Jap, which by now was gaining character and charisma by virtue of its unfailing reliability.



I stripped the bullet engine once more and sure enough there was a bag of clearance between con rod and crank pin… I later learned that the floating bush has a life of around 20k miles, mine had managed 22k. I despatched the crank to a local engineering shop and he sourced a new floating bush, fitted it and balanced the crank, I again fitted new main bearings because the ones I had fitted about 18 months earlier were showing signs of wear. I opened up the return oil ways in the cylinder head, fitted a Hitchcocks Pressure relief valve and refitted the high capacity oil pumps.



All was good for the next 15k or so miles, it was sweet and I loved it again, regular servicing, oil changes and all the stuff us tinkerers do all the time just added to the whole ownership experience. I was on my way to work one morning, taking a nice steady pootle when there was an almighty bang and we came to a halt…. Long story short the Con rod had snapped towards the top about two inches below the Gudgeon pin (at 36k miles), furthermore the remaining con rod stub had punctured its way through the crank case in two places, as well as punching its way through the oil tank, the upshot being a written off engine.



I’m fairly convinced that the upgrades carried out earlier in its life High compression piston, Amal Carb, electronic ignition (maybe ?) have led to the failure which wrecked the engine. So what do I do? I would like to rebuild it but don’t want to build in all of the weakness that has been there from manufacture, I want to build a strong, reliable motor that will go on and on. A bike that I can jump on and go anywhere…. Like a Ho**a does. This means spending an absolute fortune to get the bike I always wanted.



I’m going to need :
Replacement Crank cases, roller big end, forged steel con rod, plus all of the other rebuild components totalling something like £2000 which is about twice what the bike is worth, then bear in mind that it has been my commuter for at least 6 years of salty winters and you have a bike that is not overly pretty.



Many people talk at length about upgrades to the 500 to make faster, more reliable, or more ride-able, the fact is that before you take on any of the available upgrades, you really have to start from the bottom end up. The limitations of modifying the 500 classic engines are well documented on the internet, but we (I) really only go looking after the event…



Well done to those of you who got this far.



Should I push on, should I shove a Diesel in it….. Or am I done with Enfields???

Lennie,



ring Paul Henshaw of Performance Classics ASAP, if you get your backside in gear I think he can help you with a much tougher 500 Bullet bottom end. He posts on this forum under the name of Bullet Whisperer. Contact details HERE



http://www.midlandbullets.co.uk/perform ... assics.htm



Sadly the failure of the 500 Bullet alloy con-rod is quite well known if you research a bit, whether Redditch or Indian, as you have sadly found out. This and the fact that the Electra-X has a steel con-rod was one of the deciding factors in my purchase of a new Electra-X in 2005. Yes, the big ends can fail on these too, but you're a lot less likely to have a con-rod let go and wreck the crankcases.



When I finally got the time and the money to go for my dream Royal Enfield - a Fury replica (sort of) I made darn sure that the engine would be built with a steel con-rod from our hosts and a UK needle roller big-end. I'm hoping that that, with a set of lightened, balanced flywheels and a properly trued crankshaft, will at least give the bottom half of the engine as much longevity as anyone could reasonably expect.



Hope this helps.



A.

That's great thanks Adrian, I'll get in touch with Paul.

The OEM 500 piston has long been a known grenade, unless the top land dia is reduced to be NO LESS than 0.028" smaller than the nominal bore size, piston slap causes crown flex, and ring compaction and eventual decapitation. Top land Dia of the OEM piston varies over 0.004"


I inspect every OEM 500 piston at or before every 6000m to check for ring pinching; a sure indicator of impending piston failure. Rings pinched? Replace the piston! (NOW)


Unpolished OEM alloy con rods that look like they have been fettled with an angle grinder are a known nuclear bomb.


Mirror polished (and one with out an offset small-end eye!) they last well for many years unless repeatedly over reved...


Too much Love can kill a Bullet: Oil changes and not primed Oil filter chamber!


Too long between oil changes, run too long with a Low oil level, all contribute to oil cavitation = Dead floating bush -> Blocked rocker oil lines -> Blown return pump cover gaskets.


When a 500 Bullet suffers major piston failure, not only do the main bearings die soon afterwards as a result of running over the shrapnel, but the resultant load on the crank causes the crank pin eyes in the flywheels to distort = Excessive crank flex -> stuffed main bearings (timing side first/worst) -> accelerated crankshaft flex -> potential crank pin snap.


Replacing worn out main bearings? Check the crank pin and fly wheel eyes! (Check crank Truth, and then split the crank to inspect Pin and Eyes)


If the OEM crank-pin is an easy push fit to start into the flywheel eye, the Flywheels and crank pin are NOT SERVICEABLE!


No one stocks over size crank pins!


EVERY Bullet crank that I have inspected/repaired that has suffered piston failure has needed a minimum of a 0.006" oversize crank pin to be fitted to remedy Fly-wheel eye distortion (some 0.010" over size). Which in turn also needs the flywheel eyes specialist reamed True & Square parallel to accommodate the required 0.0025 0.003" interference fit between pin and eye.




Alloy barrels, steel rods, roller big end, forged pistons, high cap oil pumps? All worthy improvements.


But they are all a complete waste of time if the crank pin is not a correct fit in the flywheels.

Wow... Thanks for that Tim, I never would have thought that something so agricultural could become such a mechanism of self destruction.

I have developed a process for priming the filter chamber after filling with new oil, which may be useful to others, I remove the Spark plug and a rocker cover, put the bike on the centre stand, put it into second gear, then rotate the rear wheel until oil appears at the rocker. Could be kicked over but that is pretty long winded.

As Tim says: These things do happen.
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anybody know what percentage of early 1990's 500 bullets go bang in this way?



I knew the pistons could be dodgy, but never really thought about the conrod going astray. I don't want Tornado to suffer this if possible!

Lennie, the cheapest option may be to buy another bike.

My brother has a 1992 Bullet. He rebuilt the engine at around 10,000 miles when the big end bush went West, using British parts. It's been fine since, though it is in stnadard tune. IMHO there's no point tuning these engines unless all the dodgy original bits are replaced with decent British upgrades first. I'm inclined to agree with the previous poster that it may well be cheaper to buy a complete bike of known provenance. Like you, I once made the mistake of buying a bike (a BMW as it happens) before doing the research on the relevant forums. It turned out to be a right money pit and practically all the known faults occurred during my period of ownership. The moral is always check first.

Our host has a selection of engines and bottom ends for sale.