Timing side main bearing

[Goldy]

Sorry manosound I did not answer your question. The noise was a knock/rattle mostly heard on light load.

[chaterlea25]

HI Goldy,
If thats the case make sure you have the pressure release valve checked
The first items to suffer wear when the oil pressure drops are the cam and followers, Unless the PRV is passing the oil at too low a pressure

HTH
John O R

[Goldy]

Thanks for the advice guys all very usefull. I will let you know how it goes.

[Goldy]

Does anyone know the tolerances for boring out the timing side bearing (standard diameter).

[MG]

I machine them to a radial play of 1.5-1.7 thou.

But make sure the timing side journal is okay, they tend to wear out of round and/or conical. If so, it has to be cleaned up and the bush machined afterwards accordingly!

HTH, Markus

[Goldy]

I did not realise the dimensions are on the BSA sheets and are 1.5 to 0.5 thou. I don,t like the 0.5 that sounds a bit tight to me so I think that 1.5 to 1.7 sounds good. I have taken out the old bush and it,s a two piece bush. Has a steel casing with and bronze liner. I talked to C and D Autos this morning and they say they don,t like those as the bronze centre has been known to turn and block the oil holes. I had not thought of that.

[A10Boy]

I have heard of that happening, thats why I use the solid lead bronze ones from Mike [mentioned above]. BTW T&L will line bore to half a thou.

[A10Boy]

http://cgi.ebay.co.uk/BSA-A10-A7-Main-bearing-crank-bush-Lead-Bronze-/320610888902?pt=UK_Motorcycle_Parts&hash=item4aa5e5ecc6

No connection

[Rocket Racer]

I did not realise the dimensions are on the BSA sheets and are 1.5 to 0.5 thou. I don,t like the 0.5 that sounds a bit tight to me so I think that 1.5 to 1.7 sounds good. I have taken out the old bush and it,s a two piece bush. Has a steel casing with and bronze liner. I talked to C and D Autos this morning and they say they don,t like those as the bronze centre has been known to turn and block the oil holes. I had not thought of that.

I'm running a white metalled bush, which had less than a thou and was hand scraped.
after a 10 minute run on castor oil, it hit the track and we had over 7k on it after a few laps, hasnt failed yet
mind you also on methanol, so doesnt get hot!

[G/F DAVE]

Beware of the solid type timing side bushes these wear out your timing side journal instead of the bush  also in the event of oil starvation they can lock up the crank and wreck the crankcase. Ive never had any problem with the steel lined white metal bushes just make sure they are fitted with a locking screw to retain inner sleeve.I now run a ALPHA steel lined bush on my Flash 20.000 miles later still nice and smooth with no concernable vibrations.The first time I rebuilt this motor I used a SRM solid bush this locked up within 50 miles of running I would never use one again.The original BSA bush was steel lined I still have a few old ones of these that can have a new liner fitted . Your choice I suppose if you dont ride much then its no problem . Dave.


 NOTE SHOULD READ 500 MILES NOT 50. & YES A10 BOY IT WAS ASSSEMBLED CORRECTLY

[bsa-bill]

in the event of oil starvation they can lock up the crank

And the bi metal ones do not ?
Something very wrong if the bush locked up within fifty miles

[A10Boy]

I thought the SRM one was Phosphor Bronze not Lead Bronze? Lead bronze is better on the crank, whatever, any meterial will "lap" the crank if the oil isnt clean.

In any case if it went chest up after 50 miles it was obviously assembled wrong.