Hitchcocks Forum

Hello,  Haven't been on here for a while.  My 500 has done about 40,000 miles and at the end of last year started showing alloy flakes on the filter.  I have monitored the crank strainer since and the flakes have continued, so today I have decided to finally bite the bullet and change the big-end.


 I can't think that it is anything else.  It does go to show a benefit of the white-metal big-end.  It tells you when it is in trouble and you can continue to use it without too much trouble.  I don't even have problems with smike after starting up.

Does anyone think that 40,000 miles is low for a big-end to go?  Does it fail des[ite good oil pressure, or does it ONLY fail if there is a snag?  Any thoughts?


 I will look for any problems of course.  The feed pump oil flow is good (though don't know pressure of course).

Are you sure it's white metal and not the alloy of the crankcase or the case hardening of one of the main bearings? I had a main bearing failure last year and what was found in the filter was very similar.

Chris, if you are "fortunate" enough to see flakes of metal in your oil STOP running the engine immediately.


There should be no metal in the oil. If you run it then whilst the white metal will continue to break up you are putting the crank pin at risk. Similarly if the metal comes from some other source, main bearings for example, you risk causing major engine failure.


As you have decided to replace the big end shells, I would suggest you do every bearing in the engine at the same time, plus obviously filters etc. Bearings are cheap and rebuilding with another failing bearing surface will only cause further serious damage.


HTH. 


 

 Chris,


  40,000ks is exceptional on these floating bushes.It should be achievable but most of the Indian ones don't cut the mustard. I would like to think you would get the same out of another one, but don't like your chances. One thing to check is the rocker blocks, whitemetal gets stuck up in them and eventually it blocks it off completely and then it stalls the pump because it has no relief and then the end comes quickly. The oil completely blocks the slots in the upper rocker block so check carefully

Thanks for the responses. 


 On the question of the flakes being a main bearing, I would expect them to be magnetic and hard I think.


As to whether it is alloy casing, perhaps, but would there be other symptoms?


I have a WDCO which had a bad big-end from 02 to 05.  When I finally did it, there was about 1/8 inch vertical movement on the con-rod.  It didn't need a new crank-pin.  It was the noise and the black-smoke on starting that drove me to finally do it!!


Perhaps I have too much faith in white metal as a bearing!  I certainly won't use a roller.  I had one of those fail in a Suzuki SB 200 and the engine stopped dead on a hill.


I will certainly look at the innards when I get there.  All comments much appreciated.

Hi guys----------ok, if I'm asking a dumb-one here just kick my old posterior BUT }---- where is white metal used in the floating bush big end ?? Or anywhere else for that matter ?? Perhaps i'm missing something along the way ( OK, OK ---who said a Spinal Tap ??) How about a forged con. rod with cap design from Mr H ?? Or can you get one already ?? 

Alan,  The white-metal floating bush is between the con-rod and the crank-pin.  It's the only place that a white-metal bearing is used in the Bullet as far as I know.


 It is used in a lot of Turbo-chargers too, becauser in theory there is NO metal to metal contact.  Unless pressure fails.


In a Sea King helicopter, the main input shaft to the gearbox (30,000 rpm) used a white-metal bearing, but it was changed to a roller in the early 90's to allow for an oil pressure failure.

Should be OK in an Enfield then.

Hi guys and Chris---well, well---- you live and learn as they say. I thought the floating bush was Bronze !! I've never had a crankshaft apart so it's new territory and a learning curve as well. It must be a white metal lined bush then--- I can't see plain white metal alone taking that sort of punishment. I've worked with both marine and rail steam traction where the axleboxes have a white metal bearing surface and loads of 10 tons typically. But that is an entirely different working envoiroment, loadings etc. Thanks chaps---appreciate that.