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View Full Version : Making Greeves Motorcycle parts, Could use some UK advice.



oddball racing
06-19-2010, 08:54 AM
Up for discussion here is one of my long term back-burner projects. I have a pair British, Greeves Griffon 380's from the late 60's.
These bikes were one of those "fast in their day, but crudely built one-offs". (Burt Greeves was a small manufacturer making his own csatings for this model of Greeves. Many of his other models used Villiers motors.)They were assembled with many unique and weight saving ideas in their day. But there were many shortcomings as well.
One of those on this particular model was it's inner primary case design. The design permitted adjustment for the primary chain yet left to much flex for the casting to surive the abuse of being a dirt bike. Most are craked in this area. Mine has been cracked and re-welded by what appears to be three different weldors. Finding a used part is kind of out as al I have found are cracked or rewelded as well.

I would like to make a new case.

Although most of these bike were used here as desert racers, Being from the UK you folks probably had most of them at the time. I've been seeing more and more bike enthusiasts from the signnature lines here; anyone remember experiences for this repair that were successful?

1) I could cast a new one. It looks like an easy casting to reproduce, But;

A) I've never tried casting,although this project would be a good candidate
B) I don't know the type of aluminum that I would end up with "alloy wise" as I would be melting various scrap.(auto transmission cases mostly)
2) Second option is to machine it out of a plate of MIC-6 aluminum that I've had for years. (for those unaware, MIC-6 is a cast aluminum plate stock)

The part I have has been rewelded as I said , but who ever the last guy to weld it was, he really made mess out of it and it has so many cracks and damage it's really beyond repair. Any experience out there with this repair?
Alternate suggestions anyone?
Thanks, Mike.

strokersix
06-19-2010, 09:06 AM
A third option might be to break it into sections. Machine each section from solid, say 6061, then weld together, finish machine for geometry, and polish to your liking.

I have no idea what your part looks like.

AD5MB
06-19-2010, 09:48 AM
if Greeves had the option to make it out of billet stock, would he have done that?

TGTool
06-19-2010, 10:03 AM
if Greeves had the option to make it out of billet stock, would he have done that?

Not an option in the 60's with the state of numerical control. NC machines were too expensive and only semi-reliable and manual machining would be way too much labor.

METALARCHER
06-19-2010, 12:19 PM
It seems that cast aluminum aheels provide the best alloy for high strength casting

Oldbrock
06-19-2010, 12:52 PM
The worst aluminium for casting strong parts is bell housings. I always favored melting cast automotive pistons to be sure of getting the best and strongest castings. If you use the original as a pattern be sure to allow for shrink and beef up the weak area. You could just carve out the sand to give a little more beef to the suspect area. I have only done a little casting so my experience is limited so you should take my limited knowledge into account. Peter

aboard_epsilon
06-19-2010, 12:54 PM
wow they are still alive and kicking

http://www.greevesmotorcyclesltd.com/

all the best.markj

tdmidget
06-19-2010, 02:08 PM
http://bbs.homeshopmachinist.net/showthread.php?t=38127&highlight=crankcase

If you elect to cast it forget all the hooey about pistons and other items being the best. Look for items with similar complexity as far as thickness, small features, and such. The biggest difference in cast alloys are the ability to flow and fill a mold. Stay away from alloy 390( think Chev Vega engine Blocks and similar applications) and don't melt rolled products such as plate or structural shapes and extrusions.

John Stevenson
06-19-2010, 05:29 PM
From memory Michael Moore on this site has or had a 380 QUB Greeves.

This was the superfast one that Dr Blair the 2 stroke wizard at Queens University Belfast, hence QUB, helped to develop.

Any chance of pics of the cases ?

The earlier models had cases designed and built by Alpha's the bearing people, I wonder if the 380 was developed / carried on from them ?

gnm109
06-19-2010, 10:38 PM
When I was ridng enduros in Illinois and later racing int the desert in California, Greeves bikes were quite popular. The dirt bikes that I recall had a "backbone" frame made from a large aluminum casting. They were quite fast and well built.

The same company also made a small vehicle for disabled folks called the "Greeves Invacar".

hardtail
06-19-2010, 11:11 PM
You might find some harley primary cases damaged at a bike dealer that could be a donor for your melt??

John Stevenson
06-20-2010, 05:55 AM
You might find some harley primary cases damaged at a bike dealer that could be a donor for your melt??

I think he's in enough trouble as it is.............

.

hardtail
06-20-2010, 06:47 AM
Lol.............

derekm
06-20-2010, 07:17 AM
A curious thing is that its easier to find parts for a 50year old British bike from a company that disppeared 40 years ago than for a 10 year old japanese bike from company that is still going...

John Stevenson
06-20-2010, 07:26 AM
A curious thing is that its easier to find parts for a 50year old British bike from a company that disppeared 40 years ago than for a 10 year old japanese bike from company that is still going...
It's modern marketing, change the design to keep the update path going.
I had a new Honda CB125 for about 4 years as a commuter bike, this was upgraded from the old CB100 and because of this and Honda's used of sintered material for gears the kickstart gear had a nasty habit of rolling a tooth or two off.
First time this happened a new gear was bought no problems, second time they had to order 3 before I got the correct one, last time I gave up and made one.
So in 4 years there were at least 3 mods.

The British being tight wads looked in the stores to see what they had they could use in later models ;) the result was some parts had a 40 year life over 3 models.