Author Topic: A future conundrum methinks. Timing gears: 'long'stroke vs 'short'stroke.  (Read 356 times)

Offline Swarfcut

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 I saw this and thought of you.

https://www.ebay.co.uk/itm/BSA-A10-A7-RGS-GOLD-STAR-TIMING-GEARS-MAGNETO-GEAR-EXCELLENT-CONDITION/224368598136?hash=item343d691c78:g:cd8AAOSwMbxgO5PB

 Swarfy.

Mod edit: moved it back to engine (and edited title), as the discussion evolved into giving much important information and facts.

Offline Swarfcut

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Re: A future conundrum methinks. Timing gears.
« Reply #1 on: 06.03. 2021 16:37 »
Additional.

 The reason for my posting of this ebay find has been possibly mis-understood by those folks who have chanced upon it. Without me commenting further, have a think about why it has been bid up and what future conundrum awaits the successful bidder.

 Swarfy.

Offline JHG1958

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Re: A future conundrum methinks. Timing gears.
« Reply #2 on: 06.03. 2021 17:51 »
Swarfy

The bids do seem very high.  I would be surprised if these wear out, so I cannot think why the bidding should be so hard.  If someone was trying to put an engine together from spare parts, this is going to be an expensive engine.

But and this is a big but, why the conundrum?

John

Offline chaterlea25

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Re: A future conundrum methinks. Timing gears.
« Reply #3 on: 06.03. 2021 21:43 »
Hi All,
Have a look at the sellers other items it will tell the tale  *ex* *ex*

Some sought after stuff there  *????*

https://www.ebay.co.uk/sch/fordwwi/m.html?item=224368598136&hash=item343d691c78%3Ag%3Acd8AAOSwMbxgO5PB&rt=nc&_trksid=p2047675.l2562


John
1961 Super Rocket
1963 RGS (ongoing)

Online Brian

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Re: A future conundrum methinks. Timing gears.
« Reply #4 on: 06.03. 2021 22:20 »
Yes anyone who puts those gears in a A10 are in for a surprise.

Online berger

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Re: A future conundrum methinks. Timing gears.
« Reply #5 on: 06.03. 2021 23:40 »
what would the surprise be?

Online Brian

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Re: A future conundrum methinks. Timing gears.
« Reply #6 on: 07.03. 2021 00:46 »
Swarfy started this so I will leave it to him to explain, but I will give a hint, its to do with numbers.

Offline Swarfcut

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Re: A future conundrum methinks. Timing gears.
« Reply #7 on: 07.03. 2021 13:03 »
 With over 100 views and few comments I can see you're all a bit stumped.

 I'll add that things here are not what they seem, and if you also happen to be bidding for that by now expensive set of crankcases, don't forget to cost in alloy weld repairs to a sump stud hole and the broken off dynamo cradle.  "Good or Excellent" can be considered  subjective descriptions in my jaundiced saddo view, but there is no doubt  the seller is indeed a lucky man today.

 Keep thinking,

 Swarfy.

Offline Swarfcut

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Re: A future conundrum methinks. Timing gears.
« Reply #8 on: 07.03. 2021 18:25 »
Bergs asked the question, and the surprise would be that those gears are no good at all for the models listed in the title. The motor would not run, a mystery conundrum, and worse, possible valve and piston damage.

   Like moths to a flame the words " Gold Star" and "RGS" draw out the bids, which is the only reason I can see for the escalating value. The truth is that the standard engine and more exotic variants share the same basic timing components, and there is no shortage of them at lower prices.

   The clincher here is that with the exception of the fixed magneto gear, at least two of the cogs are for an A7 Longstoke, and if fitted to a later engine, timed by the marks, it won't run, if at all, and the poor punter will be scratching their head for weeks,  entrust it to a specialist and open their wallet.

   Anyone searching for Longstoke timing gears can get by by using the readily available shortstroke gears, marking them with the correct timing marks and in addition repositioning the breather drive peg in the cam gear. They are exactly the same, shaft and toothwise.

 So, if you happen to have realised they are Longstroke Gears, you've bid a bit more than you needed to.

   The Longstoke crankcase here has set a new record pricewise, despite needing remedial action, as has the curious  66mm A7 barrel. The rest of them (no tappet guide, raised spigot for cylinder head location) are 62 mm standard bore.

  If you've bid on the RGS Cam, there's a good chance it won't fit, and the A7/A10 gear cluster and mainshaft are certainly not as described for application.

 Just time to view the listings before they close, laugh, learn, count your blessings. (Or not)

 Cheers.

 Swarfy.

 

Online berger

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Re: A future conundrum methinks. Timing gears.
« Reply #9 on: 07.03. 2021 19:28 »
I wouldn't know that swarfy, I live and learn so they have different numbers of teeth?. but not surprisingly I have been searching everywhere in my places of putting things for a back wheel spacer for the yonda. comparing witness marks etc, I have been at it on and off for 4 days and even picked up the brake caliper mounting piece at least 3 times not realising that it was the missing part, I was lying in bed last night and it finally came to me. what a pillock *pull hair out* *bash* *bash* a bit slow again--- I've been ill, THE TIMING MARKS yipeeee

Offline Swarfcut

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Re: A future conundrum methinks. Timing gears.
« Reply #10 on: 07.03. 2021 19:45 »
   Bergs. Simple  answer is that the gear teeth  are all the same, but timing marks for the Longstroke gears differ in relative position compared with the more familiar gears.  On a Longstroke Cam Gear, the breather drive peg is opposite the keyway.  It's offset on the later engine type.

 It is all on the Forum, as this mistake has been made a few times before! Both ways, as it happens.

 Swarfy

Online Brian

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Re: A future conundrum methinks. Timing gears.
« Reply #11 on: 07.03. 2021 20:16 »
I think it was me some years ago that brought this subject up initially after I had just restored a Long stroke Star Twin.

The bike was advertised for sale locally and I went and had a look at it, was a runner and not too bad but needed a full restoration. When I bought it the owner said he had ridden it a few times and it ran well but he thought it lacked power, I didnt take much notice of what he said and being a genuine Star Twin I bought it.

I duly restored it with all the usual things being replaced, rebored/new pistons, rewound maggy, a pair of new carbies etc.

When I had finished the resto it started first kick and ran perfectly. I went for a ride and it was perfect except it wouldnt go past about 50mph, wasnt missing or doing anything wrong it just wouldnt go any faster. It had me puzzled as I knew everything in the motor was in perfect condition, I let it sit for a couple of days while I thought about it. After quite some thought I was thinking it could possibly be valve timing, I couldnt see how I could have got it worng but maybe I hadnt lined the dots up correctly so I pulled the timing cover off and checked the gear alignment and it was all as it should be.

At this stage I was completely puzzled so just for the hell of it I put a timing disc on checked the cam timing and it was out, at this stage I was completely puzzled as the dots on the gear all lined up correctly. I set the timing up with a degree disc and found there needed to be 16 teeth between the dots, not 20 as my gear had. I put the bike together and it ran perfectly, I didnt ever see what its top speed was but it would run up to 70mph easily.

This is when I found out there is a difference between the longstroke and the shortstroke gears, they are identical to look at except the dot is stamped 4 teeth different.

I would think there have been a few people over the years get caught like I did.

I put a shortstroke gear in a longstroke motor, just what would happen if you did it the other was around I dont know.

Offline chaterlea25

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Hi All
Just out of interest How much did the crankcases go for?
I was watching the long stroke cam followers, they look very like the ones fitted to the mid twenties 350ohvs
BTY does anyone have a long stroke follower and could provide dimensions ?

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Swarfcut

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   For you folks following this, the Longstroke Crankcases also listed were bid  to £197. These required repair to the dynamo cradle and a sump stud thread.

     The timing gears went for £67.65. Lets hope the bidders knew what they were buying, maybe they will be on sale again soon. The RGS cam looked more like a worn Longstroke  type and even at £28 bid I thought overvalued.

      I'm speechless at the values achieved, but reassured that for the short term at least my pile of scraps now have to be treated with a bit more respect.

 Cheers.

 Swarfy. (Cheapskate)