Engine advice (bit off topic, sorry)

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RichieP
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Engine advice (bit off topic, sorry)

Post by RichieP » Tue Jun 19, 2007 8:15 am

Apologies for posing a non B series question, but still - I tried to get to Spain and back on my A50 (thought better of taking my B25SS, I wonder why now?) from northern England, and got within 70 miles of the ferry home before a con-rod popped out through the crank case.

I'm obviously going to need a complete new engine and have decided to get something to work up from scratch, probably a 650 this time. Does anyone have any suggestion as to which of the many variants is the best one to go for. I'm after smoothness (if such a thing is possible with an A65?) and reliability/economy over performance. Any suggestions?

Thanks

Richie

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Post by minetymenace » Tue Jun 19, 2007 10:17 am

A65T (sc), a later one, get SRM to convert the oil feed to end fed (used to be known as a Devimead Conversion), the only real weak point on the engine. This is a wonderful engine, strongly built easy to work on, and if you keep the standard cam/tune with a single carb it will be reliable and economic. It just has the edge on the A50, and well set-up will give a similar aged Bonnie a good run for it money (I'd rather have an A65 than a T120 any day).

Slightly madder an A65L (tc), flowed with a Spitfire cam. You can also take them out quite a bit on the bore, but stronger rods would be good here. Don't you just love the names of this series, Thunderbolt, Spitfire, Lightening etc how poetic is R1 or GPZ (sounds like a bed to me).

If you want to go really mad, and have about £6000, SRM will make it go (by boring and stroking them to 900cc and strengthening all the necessary bits) and stop (by up-rating the brakes etc). This takes them from a parrallel twin to a 90 deg twin, and makes the first two gears redundant, unless you are towing a caravan/plough or having a tug-of war with a Harley (the Harley will come second).

I just love Beesas, they produced some wonderful bikes '68 - '73.

Not sure if you can get the 650 in the 500 frame, from memory the A50 was smaller.

How did you break the rod?

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Post by RichieP » Tue Jun 19, 2007 12:43 pm

With hindsight, the engine had possibly been getting noiser for a while (hard to tell doing 65mph with earplugs in). I'd done about 180 miles that day, and about 80 from my last stop when there was a brief burst of noise from the engine swiftly followed by the front of the crankcase exploding up the road in front of me. Fortunately I got the clutch in quick and emergency stopped safely onto the hard shoulder. So it goes!

Thanks for the advice - I need to find how to fit an A65 to my frame, oh, and find an engine!
Cheers
Richie

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Post by kommando » Tue Jun 19, 2007 6:30 pm

A65 engine pops straight in, no mods needed as it was a common frame to both engines like the B25/B44 and B25/B50 combo.

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Post by beat » Tue Jun 19, 2007 8:31 pm

if you have not overrev`d the engine just wheilst the conrod tryes to shake your hand, I pretty shure your engine had a lubricating problem.
watch carefully the condition of your oil and al your piping and bores in the engine! :cry:

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Post by RichieP » Wed Jun 20, 2007 8:32 am

I spoke to the nice man at SRM who guessed which rod had gone (last part of the system to get oil apparently!), so you're probably right with the lubrication problem. The oil was changed before the trip and all the external pipework in good order, so possibly damage to the oil pump by debris?

The engine's scrap, but anything salvageable is apparently interchangeable with the A65, barring the crank, so at least I can use it for spares.
I've decided that sourcing an A65T engine, starting from scratch and incorporating the SRM mods is the best (if not the cheapest) plan to end up with a reliable touring bike. Anyone got a late pre OIF one knocking around?

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Post by beat » Sun Jun 24, 2007 11:37 am

in my opinion, a oilchange on the twin BSA of this age is a "dangerous" thing.
you have to make very shure to insert exactly the same oil as used bevore, other oils, especialy modern ones workes like a solvent for al the debits in the tank,pipes and engineparts. so this dissolved parts are abel to make a bad engine-lubricating, and as the conrodbearing dos noth like this condition, it advices the rod itselv to change its livingroom, says, to go for a trip outside.... <056

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Post by minetymenace » Sun Jun 24, 2007 9:37 pm

Or maybe the timing side main bearing is worn, through which the oil supply for the main bearings pass. A relatively small amount of wear will cause a considerable loss of pressure to both big ends, this in turn causes accelerated wear in the big ends, it is the drive side big end that is starved of oil, gets hot, and a split runs at 45 degrees across the bottom of the rod, the bearing cap falls of and everything gets very messy....

I still love the A65 motor, this is about its only weakness and the solution is to end feed the big end oil as in the B series.

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Post by beat » Mon Jun 25, 2007 8:30 pm

You are right minety, this motor is a beauty, and his only weakness is the lubricating.
I am shure there are advices around how to get of this troubles. :idea:

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