Lightweight Big End Failure

Eddison5 · Post by **Eddison5** » Thu Aug 09, 2012 11:44 pm

That looks promising.

borrowashboy · Post by **borrowashboy** » Fri Aug 10, 2012 6:35 pm

very promising if you have a fat wallet
cheers, bb.

SideValve · Post by **SideValve** » Fri Aug 10, 2012 8:34 pm

Still dont think the size of the tank is the problem, worn pumps & dodgy filters look like more likely suspects to me.
Also the crank-pins were never a strong point.

rex.webb · Post by **rex.webb** » Fri Aug 10, 2012 9:13 pm

Still dont think the size of the tank is the problem, worn pumps & dodgy filters look like more likely suspects to me.
Also the crank-pins were never a strong point
These are my thoughts to.
Ride with CARE and LIVE LONG to ENJOY your Bikes and Scooters.
Insured with Peter James.

Eddison5 · Post by **Eddison5** » Sat Aug 11, 2012 12:04 pm

Separated the flywheels and had a look at the crank pin and con rod. Both surfaces are rough and the roller bearings have flats on them. Plenty of residual oil in there so there are no blockages now. Could have run dry under previous ownership I suppose. Thanks BB, I shall get an estimate from Alpha before committing because Pistonbroke in Bristol is also an option.

Ted

Eddison5 · Post by **Eddison5** » Thu Sep 06, 2012 4:00 pm

I gave Alpha the job but now discover that the gudgeon pin is worn. The AMOC site doesn't have the part listed but it seems that (011731) GUDGEON PIN; 500 CC; 1950-60 is a suggested alternative. Anyone know if this bit will fit?

Ted

Ozmadman · Post by **Ozmadman** » Fri Sep 07, 2012 1:00 am

quote:
welcome to the seized big end club, ted. i've had 2 go on me, even after meticulous rebuilds. i'm a great believer in 2 and a half pints being totally inadequate, and looking at an external oil tank conversion for mine. i know it can be done.
cheers, bb.
ps, sorry not to be more helpful

Years ago I built a 1700cc beetle engine with race cams holley carb and all the trimmings and this ran with a standard oil cooler, straight 30 oil and only 3 and a 1/2 pints of it!!!! NO PROBS!! changed it every 1000 miles tho

Paul

GOLDSTAR · Post by **GOLDSTAR** » Fri Sep 07, 2012 9:59 am

information on this topic but not necessarily tbis particular posting, my mate down 'ere in gods country has a 1934 sloper BSA, he required a new crankpin for it and was unable to scource one ,GODDEN engineering Maidstone area made two for from scratch, they actually then rebuilt all the bottom end for him with the new pin rollers etc they also made a couple of gudgeon pins again from scratch, there was a wait of a couple of months so a decent amount of metal could be sent for hardening so as to reduce the total cost, which was I believe extremely good==£400! for it all . kind regards

juanrichardo · Post by **juanrichardo** » Fri Oct 12, 2012 8:54 pm

The late csr engines had a larger crank pin and different roller arrangement to overcome this common occurrence.
Even with this and the later steel flywheels it is very important to press the assembly together fully and not try to pull it up with the crankpin nuts apparently.
My engine was a disaster before I completely rebuilt it with an alpha big end (late type),mains including the later inner roller mains, new oil pump plunger and a new extended filter unit.
So far this has been good with minimal running in and it has been pushed quite hard at times, fingers crossed, touching wood, etc. John

cf160 · Post by **cf160** » Thu Nov 15, 2012 5:52 pm

Alpha is in Netherton down the road from Wolverhampton a k or so..

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