Brodie's Bastard BSA

I am thoroughly enjoying the "Frankenstein-ing " going on in this build. Just my style!


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Just a quick update. I went by the engine shop and the new valves are in, new seats installed in to the head.

I was advised to go a 91mm bore for longevity of the cylinder. I am still unsure as 1mm extra is 20cc more.

Sadly the valve collars Modak sent me are the wrong type. I suspect they may be for the b series.
 
I have been searching for new piston in my price range and it looks as if I will be using a 92mm VW piston. I can get a set for $180 and have a few spares for the life of the engine.

Been a bit broke lately due to the new job, rates, water, rego and building a lean to next to the shed so no progress yet.

Still considering using a different rear hub as I am worried about the clearance that the GS hub has.
 
Ohh yeah, I just forgot to post.

Got the cylinder back, had the new valves fitted.

bbd35303f75194972b93268644638455.jpg

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just so im caught up, your not using a hardly ableson top end anymore right?
 
Not for now. The M20 bottom end is better suited due to the shorter stroke. I have the M21. So the plan is to go a 740cc flat head with minor flow work.
 
Brodie said:
Not for now. The M20 bottom end is better suited due to the shorter stroke. I have the M21. So the plan is to go a 740cc flat head with minor flow work.
Click to expand...

Rock on man. gonna be sweet!!
 
I got a head...




Cast iron with a few missing fins but otherwise in good condition. At a bargain price to.
 
who's a lucky boy then

oops, sorry, I only read the first line and jumped to the wrong conclusion

congratulations on the new mechanical parts then
 
glad to see your making progress if you haven't read any on the last flathead harley race bikes its very in teresting reading
i had read it years ago and found the article online for you
it seems higher cr was not a hp maker but shaped piston domes to aid combustion chamber filling was the key
https://books.google.com/books?id=QGMMRS3b0KQC&pg=RA7-PA54&lpg=RA7-PA54&dq=jerry+branch+harley+kr&source=bl&ots=rHv-M29xs_&sig=lxTh_XgW4v71JWQcbAx1AeYxXMQ&hl=en&sa=X&ved=0ahUKEwjlm6uG7NTQAhVRx2MKHZrLCqwQ6AEIXTAM#v=onepage&q=jerry%20branch%20harley%20kr&f=false
 
I think I just found the piston I need in the price range I can afford.

From a Honda GX390..

Which is also a pushrod. Ohh god here I go again with the OHV shit.


I might actually have a source for the parts in Aus. Hmm time to dig deeper.
 
I was starting to wonder if you had given up on 'er. Good stuff, keep it coming! :)
 
Haha no way am I giving up. It is just 40+ Celsius in my workshop at the moment.

Always planning what to do next.
 
Alright I need help from engine gurus regarding valve sizing for this new iteration.

From what I can find this head has a 40mm intake for the "big port" version.

Will this be big enough for a 680-720cc engine?

The other issue is that this head would require me to have a forward facing carby. I understand the issues of ram air on carbs but wanted to know if a decent airbox would prevent the issue occurring.
 
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