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Building a Goldstar engine #510416
10/15/13 4:12 am
10/15/13 4:12 am
Joined: Dec 2012
Posts: 63
S Wales
C
chamber66 Offline OP
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chamber66  Offline OP
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Joined: Dec 2012
Posts: 63
S Wales
Hi, first post on here so hello
I have the intention of Building a goldstar engine for scrambles use. So if you don't mind a few questions, (I have tried the search function) As a donor can i use any of the B series pre unit cases and crank, and conrod i.e B31, B33. Will the barrel, head and cams etc just match up with out any alteration. And are all the year bottom ends the same?
Wasn't sure if i should put this in here or the modified section.
Thanks in advance
john

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Re: Building a Goldstar engine [Re: chamber66] #510432
10/15/13 8:14 am
10/15/13 8:14 am
Joined: Dec 2003
Posts: 352
Oslo Norway
P
Per B - R.I.P. Offline
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Per B - R.I.P.  Offline
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P

Joined: Dec 2003
Posts: 352
Oslo Norway
There is a hornets nest of problems here, if you are planning to do competitive scrambling on a higher level I will advise you not to build a Goldi engine on B33 components, Then you talk to Phil Pearson and purchase a complete engine.

If you are just scrambling for fun, there is some possibilities.
The B series cranks are weaker than the Goldstar cranks, and knowing that the Goldi crank was the weak link in a standard Goldi you are just asking for trouble. The best is to purchase a new made crank from Phil Pearson, NEB or ABSAF, if you are a good mechanics you can modify a Jawa speedway crank to suit. If cost is an issue try to find a Goldi crank, but be aware that most Goldi cranks are beaten to destruction already and you are up for serious money to salvage whatís left. There are many BSA rods out there, here you will find a table
https://sites.google.com/a/bsaoc.no/site/raadelengder-500-encylindret
If you wants to use a BSA rod you have to match piston and rod to get the right length of the whole assembly.

Yes you may use a B33/31 case, but go for a BB or later case as they are stronger than the ZB variants. Goldies has stronger cases.
Cylinders, heads will fit and if you wants a soft docile Goldi you may mix and match parts out of the parts bin, but donít expect any reliability at all if you want a competitive engine made out of B31/33 parts

By the way my Clubmans has a Pearson engine and my Scrambler has modified engine with a Jawa cranck.


best regards

Per
Goldi Clubmans
Goldi Scrambler
Rob North R3
OIF A65
Re: Building a Goldstar engine [Re: Per B - R.I.P.] #510440
10/15/13 10:00 am
10/15/13 10:00 am
Joined: Dec 2012
Posts: 63
S Wales
C
chamber66 Offline OP
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chamber66  Offline OP
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Joined: Dec 2012
Posts: 63
S Wales
Thankyou Per
I have had no luck so for contacting Phill Pearson by telephone or e,mail. I'm just going to be scrambling for fun, although good results would be nice. It's a big single I want, and would have liked a Matchless, but parts arent so readily available unnfortunately. reason i chose the goldie is the amount of people re-manufacturing parts for these, so thought this was the way to go. But after your post i'm not so sure now MMMmmm! decisions decisions
My least favorite choice of engine is the pre unit Triumph twin, but i'm starting to get the feeling it may be the most sensible option?

Re: Building a Goldstar engine [Re: chamber66] #510451
10/15/13 11:48 am
10/15/13 11:48 am
Joined: Feb 2011
Posts: 3,528
Orygone
Boomer Offline

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Boomer  Offline

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Joined: Feb 2011
Posts: 3,528
Orygone
It all depends on your budget. IMO, the bottom end issue with Gold Stars mainly evolves around the stock Gold Star rod. They tended to brake after hard over revving during racing and the stock ones were changed quite often during their heyday. When they broke it was usually right below the pin and the rest of the rod would spin around and ruin the cases and whatever else was in the way. I raced for 10 years with a stock crankshaft but changed the stock rod for a Carrillo rod, (Pearson uses a Carrillo rod in his crankshaft) and never had an issue. Now if you have an unlimited budget then a Pearson crank or engine would be the way to go.
I have also seen a BB34 engined scrambler run very hard and keep up with the pack in scrambles. They aren't as tuned as a Gold Star but are very adaptable to using Goldie parts and are more affordable. When Francis Beart came to Daytona with the Norton race team in the late '40's he said he felt his competition came from the new alloy engined BSA's and not the Harleys or Indians.
That BSA engine was basically the same as a BB34. They have a longer stroke and bigger flywheels giving them a lot of bottom end torque.

Bill


Boomer
Re: Building a Goldstar engine [Re: chamber66] #510457
10/15/13 12:11 pm
10/15/13 12:11 pm
Joined: Aug 2001
Posts: 1,875
California
Ron - in California R.I.P. Offline
In Remembrance
Ron - in California R.I.P.  Offline
In Remembrance

Joined: Aug 2001
Posts: 1,875
California
First, unless Pearson is away on Holiday, he usually answers his phone just before tea time.

Next the BSA flywheels indeed are an issue, the timing side is a softer material than the drive side. The mainshaft is well known to come loose, crank pins break at the oil hole. Now 60 years ago when they were still new, they were fine for a long while.. but no way would I risk catastrophic engine failure with a stock crank today.

All the olde bikes have weak links.. The BSA weak links are well known.. and there are better parts available today than there were 50 years ago.

All the B / BB / etc have the same bore and stoke. Rod lengths and piston pin heights vary by model.

Starting with the BB cases, they have a thicker center "flange" and are much stronger. But if building an engine with BB cases and a Pearson crank, Pearson will machine the cases for an extra main bearing and offer a crank to match. This seems to be the strongest set up I have seen, bottom end wise. Keep in mind the later Goldies have a large inch type roller bearing that is getting very hard to find and expensive. While the smaller double bearing that Pearson can do to a BB case is cheaper and easier to find now and in the future if need be. Yes this may be overkill in an off road scrambler, but done right, it should live darn near forever..! Additionally, Pearson makes each crank to order, thus for a scrambler you would want a heavier flywheel than the later DBD set up. To my knowledge Pearson is the only one that will make what you want... However this comes at a cost... time.. Pearson is usually several months behind as he makes his cranks one at a time and not mass produced..

Re: Building a Goldstar engine [Re: chamber66] #510523
10/15/13 8:15 pm
10/15/13 8:15 pm
Joined: Feb 2003
Posts: 2,951
Ohio
R
Rickman Offline
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Rickman  Offline
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R

Joined: Feb 2003
Posts: 2,951
Ohio
Here John,
take a look at this thread;

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=473979#Post473979

Another option, and you may find parts are MUCH more available? 650 and 500cc variants available... Trials, scrambles, standard, and road race trans ratios factory built and supplied.

Re: Building a Goldstar engine [Re: Rickman] #510563
10/16/13 2:42 am
10/16/13 2:42 am
Joined: Dec 2012
Posts: 63
S Wales
C
chamber66 Offline OP
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chamber66  Offline OP
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C

Joined: Dec 2012
Posts: 63
S Wales
Coincidentley, my dad has an A10 engine sitting there doing nothing. Can theey be made competative? I see lot's of triumph twins being used for scrambles but no BSA's?


Probably sticking with the single plan. I'm going to take your guys advice and invest in a Pearson crank. And make the bottom end as strong as possible. As this is going to take up a big wedge og my engine budget, the head and barrel I will have to source second hand. For the time being.

So the big question, does anyone have a head or barrel that they wish to part with..PLEASE ?

Last edited by chamber66; 10/16/13 5:25 am.
Re: Building a Goldstar engine [Re: chamber66] #510606
10/16/13 9:54 am
10/16/13 9:54 am
Joined: Aug 2009
Posts: 992
gastonia .. NC
L
limeyrider Offline
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limeyrider  Offline
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Joined: Aug 2009
Posts: 992
gastonia .. NC
As I said in my PM to you ... try Chris Williams at Autocycle Engineering.

James

Re: Building a Goldstar engine [Re: limeyrider] #510618
10/16/13 11:31 am
10/16/13 11:31 am
Joined: Dec 2012
Posts: 63
S Wales
C
chamber66 Offline OP
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chamber66  Offline OP
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Joined: Dec 2012
Posts: 63
S Wales
I have, I phoned them this morning. Didn't ask about secondhand parts though. Unfortunately, their parts are a touch more espensive than Phill Pearsons. And he's the man everyone seems to recomend


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