Please Help C15

[davet147]

Hi everyone.

It’s been a while since I last posted on here. I have finally got around to splitting my 1960 c15 engine and have found that the conrod bearing is very notchy, so will need to be replaced. I have been reading my Rupert Ratio book and I am a little confused.
I am presuming the bearing that is in my crank at the moment would be the plain bush and on this presumption I want to fit a roller bearing instead. My question is can I purchase a bearing to go straight into my conrod and if so which one would I need or would I need to replace the rod also? If the latter is the case what work if any would need to be done to the cranks?
I have mentioned this in a previous post, but will ask again. I replaced my barrel and piston for  a better one as mine had broken fins, but the one I was able to get hold of was an SS80 piston and barrel. My question is having read my book and the SS80 being of higher compression, would I need to change the spec of the bike i.e. head with bigger valves, carb jets , valve timing etc to compensate for the higher compression ?
Sorry to ask so many questions, but I just want to make sure what I am doing will be done once and correctly. Thanks in advance.

[Goldy]

You will have to replace the con rod as well but then it,s a straight swap and just press the flywheels back on. Bearing in mind that the roller bearing does not usually wear you may be best getting a complete crank assembly from the later B25 from an autojumble. The other option is to take the existing crank to Alpha Bearings and let them update it. You can run the engine with high compression without and other mods although you of course you can fit the SS80 cam and valves if you wish. There is no advantage having high compression so another option would be to replace the piston for the standard compression. There are lots of pistons available at autojumbles and of course E bay. All the best.

[davet147]

Thank you Goldy for your guidance  it is much appreciated.

[johnnyboy-wonder57]

The B25 & C25 if I remember had shell big-ends & put out about 25bhp, there's some good information here but you cannot edit &copy, http://www.classicmotorcycles.org.uk/c15/c15_reviews.htm, In would have thought the higher compression was an advantage with today's fuels & give the bike more punch, incidentally the bore and stroke, is the same on the Rocket 3 & Trident 740cc , the K75 BMW & presumably the 500cc Triumph twin!

Only had experience of BSA singles with a B44, many saw the standard C15 as pedestrian, even in the late 1950s!  OTJ  of Edenbrige, Kent, were experts as was Alan Clews of CCM fame.


Best of luck

Cheers

JBW