Project 2

surfking

So, I have anouther project... well a collection of parts which dosent quite reach the full sum of a bike but its not that far off. Whilst its all tucked away in the spare room I have had to make assurances that the house and Project 1 888/S4RS will be finished first.

Its a retired race bike from the Bott serise early 90s, was once owned and raced by Roy Armstrong. It started out I beleve as a 851 Kit bike, though relations I beleve Roy had with the factory over the years the bike became kitted with some rather nice parts.

Ive managed to get most of the parts but not all, this just to reminde you was a race bike by Roy not a corsa/racing.

I was unable to purchase the cases but strangley most other parts of the engine. However this is the where I seek the advise. I have G&421 cams close ratio box cylinders and pistons & crank and rods with 20mm pins.

I also have a set of race cases period correct (not really wanting to use these), but as its a race bike and not a corsa to restore in all there beauty I am pondering the build for the engine. I have accsess to a new unsed late sp5 cases or should i go for ST4S with 996sps cams. Im not likley to be srceaming it around a track and looking for that 12 thou on the rev counter but would like a strong & fast motor for the eventual track day exploration.

Mr R, Brad anyone with an opinion I would be greatful as Project 1 is nearing compleation. (But alas not the house)

Thanks

dudlington

Project 1 is nearing completion................have I missed something ?????

My tuppence worth.............why not a 996 engine 110 Hp and 70ft/lbs of torque as standard. Plenty around , easily tuneable and won.t cost the earth. Slots straight in , 996 SPS double injection , larger exhaust.

stafford

As I understand you seem to noted cases thorough the ages, in that they got better as they were improved throughout their life cycle.
Whatever you do, balance the crank assembly, 300 miles was the expected life for a race Corsa in 1992.
To summarise I think you need to ask yourself what you are going to use it for and asses the risk of damaging the cases given the use you choose, personally I'd fit the period piece if not for race use.

nine16

Cut the baby in half--use a 996 now, but put a period motor together for the future.

seven4nineR

surfking wrote

Haven't you kinda answered your own question? If you are not going to be racing and constantly exploring the 12krpm mark any of the above options would be fine wouldn't they? It just depends on how you picture the bike in your head.

After much umming and aahing I picked up a rebuilt 999RS engine to replace the cooked unit in my 749R race bike, but only after talking to a couple of RS experts in your neck of the woods. They both pretty much said the same thing: treat an RS like a road engine and it will outlast and outperform a modified road engine treated like an RS. An RS at WSB level makes 190 odd hp at 13krpm (13.5krpm if you are Chili and never look at the tacho, lol), but needs rebuilding every 500km's. I'm happy with my RS making a relatively unstressed 168rwhp at 11.5krpm, should last ages....whereas a 999R built to make that sort of grunt is going to be living on borrowed time.

It's like that "90% of the wear happens on start up" mantra is turned on it's head for race engines: 90% of the stress occurs in the last 10% of the rev range.

Sorry, this is a long winded way of saying if you just run a real world redline rather than a BSB/WSB-spec redline even the old race cases will be relatively unstressed, especially if they are sand cast.

I'm a romantic but it seems kind of a shame to have most of the bits to build a very cool old race bike and put an St4S engine it. But "needs must", what constitutes a "strong fast motor"?

EDIT: apologies for the waffle, it's a quiet nightshift!

brad black

st4s.

surfking

Got NOS late 888 cases sourced, crank with 20mm, waiting for barrels & 94mm pistons with 20mm, close ratio Gears, Cams G/431

So still collecting parts need to start thinking about the heads, I have some notes somewhere for the what he ran when he was racing, i think 37/31 but will have to check.

Nick

surfking

Pistons & Cylinders

Got the heads sorted, late corse type with machined front for clearance. But want to look at making 1 926so need to sort pistons and cylinders, want to remain on 64mm crank etc with 20mm pins.

There is many bits of info on here but just trying to drill down to facts. Has any one used these? or have experience or point of view. Am I on to the right thing? is the pin to the piston crown too high?

Appreciate feed back

Have drawing can't post again!! will try to add

Mr.R

The 96mm 955cc pistons are designed to be run with a 66mm stroke 916 crank.
They have a different deck height to the 96mm items intended for a 64mm stroke 851/888 crank.

Steve R

surfking

Mr.R wroteThe 96mm 955cc pistons are designed to be run with a 66mm stroke 916 crank. They have a different deck height to the 96mm items intended for a 64mm stroke 851/888 crank. Steve R

Thought that was the case, where should I look for 96mm/926 any ideas Mr R? would really like to stick on the original crank & rods with 20mm end.

Mr.R

You could try contacting Pistal direct,
Omega's also made pistons for the 926's,
Kamna in Germany supply Pistal's,
CP's in the States will make a set of four pistons to your design/drawing,
As will JE but the quality's not as good as CP's,
JHP/Coventry Ducati will probably be able to help you, but expect to pay top $ with them.

However you will need a pair of either 916SP or 916SPA barrels for the pistons.
Or...
Fox Engineering in the States can supply steel liners for your bored out 94mm barrels.
But if it comes to that barrel liners aren't that expensive to buy here in the UK, they come it at around £20 each.
I'd go for 916SP barrels bored out to 96mm and replated by Langcourt's in Weston SuperMare.
If you go down this route, ping me a PM as I can give you a few reliability tips for this modification.

Steve R

surfking

Mr.R wroteYou could try contacting Pistal direct, Omega's also made pistons for the 926's, Kamna in Germany supply Pistal's, CP's in the States will make a set of four pistons to your design/drawing, As will JE but the quality's not as good as CP's, JHP/Coventry Ducati will probably be able to help you, but expect to pay top $ with them. However you will need a pair of either 916SP or 916SPA barrels for the pistons. Or... Fox Engineering in the States can supply steel liners for your bored out 94mm barrels. But if it comes to that barrel liners aren't that expensive to buy here in the UK, they come it at around £20 each. I'd go for 916SP barrels bored out to 96mm and replated by Langcourt's in Weston SuperMare. If you go down this route, ping me a PM as I can give you a few reliability tips for this modification. Steve R

Thank. You Mr R. That's where I am at th moment got an email back from Pistal with a drawing for 955 pistons so will try them again tomorrow.

Looking for 916SP Barrels now.

Many thanks updates as when.

surfking

Project Two

So things changed didn't go with the big engine in the end, in fact got the pieces including the 955 barrels but moved them on so as to try and keep the project as near as it was when a racing bike.

So it starts here.

surfking

Forks with 25 degree off Set

Thanks to a member on here I was able to get atop yoke with the 25 degree offset that was on the original bike, I wasn't about to search for anouther two years for the lower Yoke, so used an early Monster Yoke but with these off the shelf Shims from Motowheels.