Building a less than standard engine!

[Lukey]

Good evening one and all!

Some may of seen my ongoing thread about my caferacer build!

My next job is building up my engine!

I am after building a quick engine BUT not to the limit its unreliable and likely to go BANG!

I plan to fit 9:5:1 Piston's
Spirtfire Cam
Needle Roller Bearing conversion on a Large Journal Crank
Polished conrods
Alloy Head
Thick Flange Barrels

What else should/can I do?

Also I am struggling to source good quality 9:5:1 pistons? anybody recommend a good place to get them?

Many thanks in advance 

[chaterlea25]

Hi, Lukey

What else should/can I do?

Cake st Classics can supply Wiseco pistons, I think they are 9:1
For reliability and todays shit petrol thats high enough, (my opinion)
I know BSA had 10:1's but have not seen 9.5's
Sometimes NOS ones come up on fleabay

I would recommend new conrods, crack testing the crank  and dynamic balancing

A Gold Star valve spring conversion is/was recommended ,
http://eborbikes.com/

A lot depends on you budget, ?? twin carb head/ high flow valves , porting, carb ??  ignition system?

lightweight parts??  polished and lightened rockers / pushrods ??

Have you seen this link ? http://bsa-a10.hailwood.com/index.html

The Skys the limit

HTH
John

[Viking]

I have a Super Rocket with RGS tuned engine, with spitfire cam and 10:1 pistons.

The fuel available today is not in favor of too high compression.
You need octane 100 or octane booster for this.

I had to lower the compression on my RGS engine, to make it stop pinking. ( by installing a spacer under the cylinder !).

Take into account that the alloy cylinder heads we can find today (more than 50 years after end of production) has been shimmed several times in there life !
This rise the compression even more. !

A new high flow oil pump plus new oil pressure relief vale from SRM in Wales is a must today.
The new oil pump benefits with higher oil flow and stop wet sumping.

I use a manufacture new  (from 1998) 389 monoblock 1 5/32” single carb. This setup works very well and has a crisp and quick throttle response.

It is not advisable to use twin carb setup. You can gain a little, but it is very fiddley and you end up with constant adjustment of the carbs.
Finding a good A10 head for twin carb installation, is not realistic today...
   
For valves and guides in the cylinder head, use modern vales with a higher degree of filling, and convert it to lead free in the same go. with oil seals on the inlet valves.
The cylinder headshop in Webley, arranged this for me I 1995, and this setup works sweet… 

Dynamic balance of the crank is a must.

Pay attention to the cam followers, they ware out. SRM can deliver new units.

The SRM oil/ roller bearing conversion is a must on a A10 engine. The turns a good engine in to at strong and very robust engine. 

Ignition:
Magneto is periodic nice, and look right. But it is endless fiddling and troublesome on a 50 year oil bike used only now and then.

Problem I have encounters with rebuild magnetos:
( Rebuild several times by a company in Sheffield and SRM, regardless of cost !)

Uneven ignition on the two cylinders, weak spark from start. Hard to start with the fuel quality available today. Need constant attention.
Last 5-6 years, and need to be rebuild again. 500 £ each time !!

Go for electronic ignition. It is accurate, bullet proof and give a much improved ignition.
Setting up correct ignition time on the magnetosystem is a night mare...

If the dynamo is old and worn: Go for a Alton AC generator unit with chain drive (belt drive give trouble).
This unit works very well and can give you H4 modern light.

Avoid 6V.  Getting long lasting bulbs and equipment is a challenge.
All contactors burn out and last short time with 6 V.

I have BSA, Norton and Triumph. Some with 6 volt and some with 12 volt. All rebuild by me.

I regret my then stubborn attitude in the 90ties and keeping with 6V positive earth.  !

If I was to rebuild again, it would be 12V with negative earth, using a Alton generator and electronic ignition or if possible AC crank mounted generator for my Triumph T110 or my Norton.

With belt drive and dry clutch.


Viking, Denmark.

BSA A10 GF, SR & RGS

[duTch]

 

Take into account that the alloy cylinder heads we can find today (more than 50 years after end of production) has been shimmed several times in there life !

  Hiya biking Viking; at risk of having my own head done... ..I think you mean "more than 50 years after end of production) has been SKIMMED several times"..hence a need for shimming..???
 ..sorry, but that's how it is

[rocker21]

many years ago back in the 60's i built a very quick A10 , it had the needle roller conversion and it was done before Devimead (hope i spelt that correctly) started doing it, 9:1 pistons as that was the safe maximum, the engine ran on needle rollers for the cam, idler shaft etc, there was not a bronze bush in the engine, it also had what was then called a polydyne cam which was made by somerton ( not sure if i spelt that correctly) it it was an animal of a cam , much modified head etc and it was very quick but had no bottom end it was a box of revs and was not really suitable for the road, it took several attemps to get it reliable and i still have that engine in the loft but it would be no good with todays petrol, it used to break the 8000 rpm rev counter and i ended up with a Krober electronic one as that went to 10000 rpm , I am hoping to make a bike for having a go at hill climbs with this engine just for a bit of fun and run it on avgas for compition use. it had so many mods can't list them all here , like crank and conrods modified with shorter rods and bit machined of the top of the block to allow for the short rods, balanced and lightened flywheel  and the list goes on.  it was a lot of fun making it and my local machine shop got to know me well.

[muskrat]

G'day Lukey.
If you do all of the above you'll have the fastest road going A10 on the planet.
A couple of sites for info http://atlanticgreen.com/bsamain.htm  and http://bsa-a10.hailwood.com/
Cheers

[Viking]

I have a BSA A10 with RGS tunes engine.

9:1 compression and BSA A10 spitfire scrambler cam.
Late type alloy head with big valves and 389 mono bloc 1 5/32”
SRM oil and bearing conversion.

Primary gearing changed to 23 tooth, standard solo gearing on gearbox and rear wheel.

Pull like a train, with loads of bottom torque.

Excellent in town driving etc. and quiet on A & B roads around 50-60 mph.

It is the best of my brit bikes. I have a Triumph T110, but it have nothing like the same low down pulling power as my RGS engine…
A proper A10 tuned engine is a treat..


The only issue; if accelerating very hard in 3rd. gear it can jump out of gear.
So a hard tuned A10 engine need a super clutch and a heavy duty gear box.

[rocker21]

never had any gearbox problems, certainly had clutch probs and back in the 60's there was not the options that are about now, i had a modified 6 spring clutch that had solid disc's of friction material rather than steel plates with inserts, still got some in the loft and got a set in my A7ss works well but i don't think you can buy them now. if any knows were they can be bought i will buy some as they make a huge difference to the clutch.

[worntorn]

I have a BSA A10 with RGS tunes engine.

9:1 compression and BSA A10 spitfire scrambler cam.
Late type alloy head with big valves and 389 mono bloc 1 5/32”
SRM oil and bearing conversion.

Primary gearing changed to 23 tooth, standard solo gearing on gearbox and rear wheel.

Pull like a train, with loads of bottom torque.

Excellent in town driving etc. and quiet on A & B roads around 50-60 mph.

It is the best of my brit bikes. I have a Triumph T110, but it have nothing like the same low down pulling power as my RGS engine…
A proper A10 tuned engine is a treat..



The only issue; if accelerating very hard in 3rd. gear it can jump out of gear.
So a hard tuned A10 engine need a super clutch and a heavy duty gear box.

Would thi s engine be any different than a late Super rocket engine? I often see reference to " RGS Tuned" or in magazine reviews of the RGS see the engine referred to as a "Tuned" Super Rocket engine. But isn't it the same engine as the 61 on West Coast US bike, 9 to one CR, same valves, same 1 5/32" Carb and same 357 cam?


Glen

[trevinoz]

Yes Glen, it is the same engine.

[worntorn]

Thanks Trev, it can get confusing. One article suggested that the late Super Rockets produced 46 BHP while the Rocket Gold star could "produce as much as 50 BHP when fitted with the RRT2 close ratio transmission"
I'd love to hear the author's explanation of how the transmission could make the engine proudce more horsepower at the crank!

Glen

[duTch]

 

I'd love to hear the author's explanation of how the transmission could make the engine proudce more horsepower at the crank

yeah, wondered that too..

[trevinoz]

I think that you will find that the increased power was due to the "track silencer", not the transmission.

[chaterlea25]

HI All,
As Trev says, but there should also be a gain from the needle roller equipped RRT2 gearbox ? less friction!

I know Gold Star engines were individually bench tested and had to reach a certain BHP before being fitted to the cycle parts, but there were still engines that comfortably exceeded the required mark
A debatable point is were these engines then put aside for favoured customers/ dealers??
I have often wondered but have not researched whether RGS engines were bench tested /alllocated in such a manner??

Cheers
John

[trevinoz]

John,
                I'm pretty sure that gearbox bearings wouldn't make any difference to engine power output which I think was measured at the crankshaft.
As to the RGS engine allocation, that is an interesting question. Rocket engines were always tested and the test sheet was supplied with the bike.
If you read the original RGS road test, it didn't perform any better than a Super Rocket.
As a matter of interest, a friend bought a Big Valve Super Rocket new in 1962.
It had 10:1 pistons and an output of over 50 BHP. There were two delivered to the same dealer and the horsepower was slightly different on the other, a bit higher than my friend's.
Trev.