1960 A7 Shooting Star Sprocket Sizes

[Rocket Racer]

happy to oblige, if anyone wants the spreadsheet because they have different wheel sizes or gearbox ratios, pm me your email address. I work out my circumference from height to axle centre then use the old 2xpi calc. my formula is metric then I convert to mph using the 5/8 miles/km ratio.

[berger]

cheers RR the glance I got was about right, thanks for that

[Rocket Racer]

Nice to know a clubmans trim cafe A7ss can hit the ton, I'm quietly collecting bits to make an A7ss race bike and have visions of matching the 47hp they claim the daytona race A7ss bikes managed, beating the goldstars entered   
and we shouldnt forget the great Chris vincent won the 62 TT on a humble A7ss

[Peter in Aus]

Just a though, could the valve timing be out by one tooth, could be worth a check. also the long stroke crank timing gear will fit but is marked one tooth out, a trap for young players 
Also my 54 A7 I got when it was 6 months old would make the ton, those were the days
Peter

[Rocket Racer]

Just a though, could the valve timing be out by one tooth, could be worth a check. also the long stroke crank timing gear will fit but is marked one tooth out, a trap for young players 
Also my 54 A7 I got when it was 6 months old would make the ton, those were the days
Peter

yes there's something not right other than gearing if a shooting star can only just get to 50-60mph. You'd hope SRM could align the dots but you never know. If the longstroke ones are marked one differently it should be possible to count the number of teeth between dots for a later one... as a quick test. cam timing would certainly also explain it.

I count 49 teeth with a 29/20 split between marks

[JulianS]

Shooting Star road test from 1961, interesting but take with a pinch of salt.

[berger]

RR lost lots of weight on mine and some inlet porting I did years ago, head and block top skimmed and run with tetraboost rocket fuel added in generous doses . the berger build has a head ported [gas flowed etc] by cylinder head shop with super rocket inlets which they say use a 34mm mikuni on it. I don't think I will be getting 47hp but will be putting some ideas and effort into the engine. many ££££££s worth of goodies waiting in spare bedroom then dropping it in a featherbed, it could be interesting, I will have to wait until brother has built his workshop because he is the engineer and I am on the beer haha, when the pubs open that is

[RDfella]

berger - why drop it in a featherbed when a BSA frame handles better?

[berger]

RD I have betsy in one piece and the other frame is lots lighter and came cheap as chip paper with the rrt2

[sheffield steel]

Thanks again everyone for your input
A few people are suggesting cam timing but they have been in and out a few times and it’s always been the same performance wise, I’m confident that the dots are aligned but couldn’t be sure that all the parts are correct for the year / model. I will check valve openings manually but not sure I’d notice if things were one tooth out due to incorrect parts. I’d like to think SRM would have picked up on this though...

I will check carb jetting and restrictions in silences next.

I’ve ordered a cheap 20T engine sprocket so no harm in trying it.

Just a thought....aside from the risk of getting my jeans caught in the chain! Is there any danger running the primary exposed with no oil whilst I trial the new sprocket to save having to seal the cases and recking another gasket.

[berger]

yeah Sheffield steel run it no harm in a few miles like that, wipe primary chain with a rag or you get oil thrown at you

[JulianS]

Some oil will blow from the 3 front chaincase fixing screw holes.

[berger]

oooops forgot about them , but don't put them in the holes you will lock the crank, so just shove the case on without sealed gasket and run it, jobs a good en

[chaterlea25]

Hi All,
In recent months I have viewed two bottom end assemblies that were put together by SRM
For some reason they do not fit the cam pinion or idler,
So unless they built the full engine it would have been the customer who finished the build

John

[Brian]

There is a four teeth difference between the gears. Here is a link to an article I posted some time ago. It deals with the longstroke engine but points out the difference between the gears.

https://www.a7a10.net/forum/index.php?topic=7342.msg51278#msg51278

If you have any doubts about the cam timing put a degree disc on and check it.