Main difference from G85 vs G80 engine

Discussion in 'AJS & Matchless' started by pierodn, Jan 31, 2018.

  1. pierodn

    pierodn

    Joined:
    Nov 10, 2012
    Hi.
    What they are the main differnces between G85 and G80 engine?.
    Thanks.
    Piero
     
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  2. oldbeezer

    oldbeezer VIP MEMBER

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    Nov 2, 2017
    Not sure but I think to only differences in the engines is tuning. The big difference is the frames. The G80 had an old AMC frame and the G85 had specific frame made for scrambling. If I am wrong I'm sure some one who knows better will chime in soon.
     
  3. grandpaul

    grandpaul VIP MEMBER

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    Jan 15, 2008
    The problem with googling is that there are many photos of many bikes that are NOT the one you type in to the search box! But, from what I could see using that method, the majority look the same

    (it is hilarious that you will find HDs and other modern bikes that way with google)
     
  4. Bernhard

    Bernhard

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    Apr 20, 2011
    and some people don't even know what model they have!..................
     
  5. Bernhard

    Bernhard

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    Apr 20, 2011
  6. oldbeezer

    oldbeezer VIP MEMBER

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    I did NOT google it! I ..... um.......use MetaCrawler
    Just dug up an old issue of The Classic Motorcycle, Oct 2016, and it indicates the G80CS and G85CS uses the same engine. But it occurs to me that, I am fairly certain, the G80CS used an alloy barrel and the G80 used an iron barrel and that all G85s were CSs. The G85 was AMCs last attempt at a competitive scrambler but it was too late against the 2 strokes.
    Again I am not an AMC expert
     
  7. oldbeezer

    oldbeezer VIP MEMBER

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  8. Bernhard

    Bernhard

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    Apr 20, 2011

    You are of course 100% correct. I admit I didn’t check the specs before I posted my reply, I have, not for the first time, been caught out with wrong info on IT . There was of course no single road going SOHC engines from Matchless at that time………..WTF it looks like it has been on the web for some time and NOBODY has bothered to correct it-a swipe of the mouse and a press of the delete button is all it would take!!!
     
  9. oldbeezer

    oldbeezer VIP MEMBER

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    Nov 2, 2017
    Are you saying the internet is not 100% correct 100% of the time?!?!?:rolleyes:
    There was a G50CSR for the road made in 1962, I think. They were made to qualify the bike for American racing, at least 25 had to be made to qualify. don't know how many made it to the streets.
    https://classic-motorbikes.net/wp-content/uploads/2015/10/g50-csr.jpg
    pierodn sorry for hijacking the thread
     
  10. pierodn

    pierodn

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    Nov 10, 2012
    No problem
     
  11. worntorn

    worntorn

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    Dec 22, 2006

    Right, and after that there were a small number of G50 engined Seeley Condors built.

    The Matchless /AJS that interests me is the 600cc Typhoon or G80TCS. I've read that there were only approx 125 built.
    This could be a very useable single cylinder roadbike.

    Glen
     
  12. Jean-Paul ALTAYRAC

    Jean-Paul ALTAYRAC

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    Dec 4, 2017
    Hi,
    The main differences between the G80CS and G85CS (same short stroke) are :
    1) The valve timing : G80CS : 59 - 69 - 74 - 48 / G85CS : 67 - 81 - 69 - 48 and the cams aren't the same...!!
    2) Compression ratio : G80CS : 8.7 to 1 - G85CS : 12 to 1
    3) Power : G80CS : 33 hp at 6200 rpm - G85CS : 41 hp at 6500 rpm
    4) Oil pump : G80CS : old plunger pump - G85CS : Norton oil pump (with gears) with other timing cases
    The short stroke G80CS engine for scrambling was built from 1956 to 1964 and the G85CS engine from 1965 to 1969
    One exception: the factory builted some G80CS for the american market (road and desert races) , between 1965 and 1969, using the G12CS rolling chassis and reduicing the compression ratio (with a G80CS piston) in a G85CS engine -
    The G50CSR (Golden Eagle) is an other thing...!!
    You can find some of the bikes I've built, like that, on www.motos-anglaises.com ------> Motos------>Matchless

    Cheers - Jean-Paul, Helpliner of AJS-Matchless Owners Club, french section
     
  13. Bernhard

    Bernhard

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    Apr 20, 2011
  14. grandpaul

    grandpaul VIP MEMBER

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    Jan 15, 2008
    Excellent info, Jean-Paul.

    Welcome to the forum!
     
  15. oldbeezer

    oldbeezer VIP MEMBER

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    Nov 2, 2017
    Jean-Paul
    Thank you!
     
  16. mdt-son

    mdt-son

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    Jan 19, 2012
    The post'63 G80CS was part of AMC's offering world wide and is featured in every sales leaflet, including those distributed in the UK.

    The G85CS used the very same post'63 engine that was used for the G80CS also. In fact, all heavy-weight single-cylinder roadsters used a common bottom end (85.5mm stroke) and the same oil pump, which was a selling point in AMC's adverts of the time. The G80CS and later the G85CS also featured an alloy barrel while the roadster bikes had iron barrels (which were really heavy lumps, I have to say). The G80CS and the G85CS shared the cylinder heads also, featuring a central spark plug, whereis the roaedsters had an angled spark plug and smaller inlet ports.
    There have been vague reports of the G85CS becoming a six-start oil pump drive for 1967 but I haven't seen this assertion proven anywhere.

    It's important not to compare apples and pies! The G80CS in road trim (1964 on) was a mildly tuned bike, hence the comparatively low compression of 8.7:1. In race trim however, the factory offered different pistons (up to 12:1). I believe this was upped even more for the G85CS as I have seen a 12.5:1 piston for this engine. They were extremely heavy lumps, hardly properly engineered!
    As for camshafts, I don't recall there were differences between race camshafts for the G80CS and those for the G85CS. They all had 030xxx numbers which indicate 1964 model year, i.e., well before the launch of the G85CS.
    The transition between the old engine and the revised engine took place in September 1963 as the 1964-models were launched.

    I hope this helps.

    Regards,
    Knut Sonsteby
     
  17. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    What a load of crap in that text! The top picture shows a 1960-63 G80CS. Why, when the article is about the G85CS? When writing a story, the very least required for an author is to make one's homework.
     
  18. mdt-son

    mdt-son

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    Jan 19, 2012
    Hi Glen,
    yes the TCS is certainly a tractable bike with loads of torque, provided the compression isn't too high, otherwise it will be a pig to start. Except there is now the option of an e-start of course .....

    The TCS was built in 1961 and 1962 only at the request of the Cooper Motors, California. As the saying goes, nothing beats cubes .....
    I think the model was dropped as a result of AMC terminating the distributor rights for Cooper Motors in late 1962.

    There was no TCS offered for post'63, however, that is not to say that one could't be made. In fact, ABSAF of the Netherlands is offering a 600cc version of the later engines, and I believe Jean-Paul has been involved with some big-bore versions of the late single engine also. There are some nice pictures on the net.

    A really desirable bike would be the G50 motor in a G85CS chassis, but I don't think the bottom end fits between the frame rails due to the sump design.

    Regards,
    Knut Sonsteby
     
  19. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Thanks for that info Knut.
    I've read that there were a few TCS built from 59 on, not sure if that is correct.
    This TCS owner says the early bikes had a slightly smaller bore.

    Glen

    Typhoon Numbers
    [​IMG]by Don Madden » Wed Sep 28, 2011 8:10 pm

    The Typhoon, as many know, is a G80CS 500cc bored to 88mm for 1959 & 89 for later years. The stroke is increased as well to give 588 or 598cc. The special pistons are similar but have higher location of the pin to use the same connecting rod. The pistons are relieved around the top edge to fit into the G80CS heads so with the same combustion chamber the CR is increased, 8.7 tp 9.2 for the 1960-up.

    Bill Basset, North American Section member has had these later ones made up by a high quality maker in the past & told me he would have more made to order. The maker is a specialist in modern racing pistons & the same as makes them for PMLI to use in the 500cc late CS. I have been running one in my G80CS & they are superior to the original & weigh about the same, actually, slightly lighter so need no material removed nor rebalancing of the crankshaft. With a properly tuned machine & the standard CR, using 91 octane, (R+R/2), it starts first kick, runs very well & there are no noises from piston or combustion irregularities.

    These pistons must be made in batches of four but the two parties will accept orders of one each & resell the excess. Anyone interested can PM me for more details.

    Cheers, Don. [​IMG]
     
  20. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011

    I knew somebody was going to come back with that OHC model it is listed on the same website;

    http://www.motorcyclespecs.co.za/model/Matchless/matchless_g50 60.htm
     

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