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Performance engine build

Discussion in 'Norton Motorcycles (Modern)' started by Voodooo, Oct 8, 2019.

  1. Voodooo

    Voodooo VIP MEMBER

    Aug 10, 2016
    Has anyone tried milling the head or raising the compression ratio?
    Does anyone offer cams?
    Has anyone ported the head and done a 3 angle valve job or even used titanium valves?
    I’m curious what the maximum horsepower/ torque the 961 is capable of in a race environment.

    What is the bore limit of the stock cylinders? I remember at one time South Bay Norton was talking about a big bore kit for the 961.
  2. Fast Eddie

    Fast Eddie VIP MEMBER

    Oct 4, 2013
    Great questions Scott. I rather suspect you’ll be short on answers.

    Ollie at Thiel Motorsports is one such guy who’s continually developing things for the 961, inc a big bore kit. But he’s very a difficult man to get information out of!

    Stateside, I don’t know of any such outfit. There’s the Cotes boys North of the border, but I’m not sure if they are particularly performance orientated, they seem more focused on reliability and ironing out known issues etc.

    To your points, I would have thought that the cam would be a source of power gains. The stock cam must be designed with a heavy focus on noise / emission reduction plus having to work with the stock silencers. Give the bike open pipes and a programmable ECU and I’d say the cam could definitely be enhanced. But I’m not aware of any off the shelf solutions.

    I would have thought that even Norton’s would already have a half decent 3 angle valve cut these days, but I’ve never looked, so may well be surprised! But I’d also imagine that more work in this area and in the ports may yield some flow improvements. But once again, I’m not aware of any experimentation already done in this area.

    Titanium valve won’t yield any benefit unless chasing much higher rpm, or wanting to lower valve spring rates (in order to reduce losses). Reducing losses by reducing spring pressures would be a good idea, but you’d be venturing out on your own calculating how much to reduce.

    Increasing the CR is an area I’d be cautious about. This is already a fairly high CR for such an old Skool motor and it already runs rather hot. Increasing CR will increase heat, I’d want to satisfy myself that this was safe.

    It might be worth considering leaving the motor alone and grafting a cheeky little supercharger on instead... jus’ sayin’...
  3. TonyA


    Jan 16, 2015
    I know the valve seats are already three angle. You may be able to get Jim Schmidt of JS Engineering to help you. A good valve job will certainly be doable. Would you be willing to send him a 961 Head to look at ? The C.R. is already 10.1 to 1 . I have spoken to him once and I think he may be willing to give the valve job a go . Call him and see , this is the only way we will ever get anything done on the 961 over here. His contact information is on the web , just look up JS Engineering . This way he may be willing to "tool up" for the 961 engine. Don't wait too long , he is not getting any younger !
    Last edited: Oct 9, 2019
  4. BritTwit

    BritTwit VIP MEMBER

    Aug 25, 2009
    I suppose Theil is the only one actually developing performance parts currently.
    With a boutique brand/low production numbers machine there isn't much of a market for performance parts.

    Matt Capri and Carlos Schmidt from Southbay Norton were close to producing kits for the 961.
    Matt went bankrupt at the end of 2016 though.

    Matt was going to offer a 1005 bigger bore kit to owners. 90mm higher compression (11.5:1) pistons
    Would have required his free flowing exhaust, and a power commander.

    He also had another kit - 1108 big bore kit (94.5mm) with custom billet CNC machined replacement cylinders.
    Matt believed that the stock cylinder liners were too small to bore beyond 90mm without warping under use.
    Fitting the custom barrels with larger liners required boring the cylinder spigots of the engine cases.
    The CNC barrels had larger cooling fins, and gave the engine a look like a Commando on steroids.

    The next limitation on bore size was the location of the pushrod tunnels to the cylinder bore.
    They are very close with the CNC cylinders.

    Matt also had a hot cam for the street, not radical just a boost from 4500rpm up.

    Also planned were lightened rockers, and pushrods.

    Sadly, Matt never brought these parts to market before Southbay failed.

    These was a chap from OZ back in 2013 or so who was actually road racing his 961.
    He claimed on the forum that the engine was modified and was producing around 100HP at the crank.
    I tried searching the forum several times to find the thread, but couldn't find it.
    I don't remember if he explained what had been done to his engine.

    Now that I've bored the crap out of everyone about what could have been:

    I'm just waiting for Matt at CNW to introduce the 961 supercharger.
    My California Psychic tells me it's coming.
  5. TonyA


    Jan 16, 2015
    I remember reading when South Bay was still around , 1007cc and 11 to 1 C.R. with his big bore kit.
  6. Panetone


    Nov 1, 2015
    Ollie has a 90mm big bore kit in offer.
    He told me that 90mm is very good, because you can use the standard gaskets.
    The pistons are made from billet an made in Germany.
    In my engine is the BB kit working very well.
    Ollie is working on new push rods and cams in the moment.
    Fast Eddie told you it is not easy to get som Information from him, that`s only the half truth.
    He is only very carefully to offer some parts before they are tested in several bikes for many miles.
    When I visit him there are always bikes from all over Europe in his Company.
    My cylinder head was repaired from him whith new seats and Valve guards.

    richard-7 likes this.
  7. BritTwit

    BritTwit VIP MEMBER

    Aug 25, 2009
    So your Commando is 90mm = 1005cc
    Are the pistons higher compression than stock?
    11:1, 11.5:1, or something else?
  8. Panetone


    Nov 1, 2015
    As I know it is nearly standard.
    With high compression the engine is not good for street riding.
    Ollie is skinnig the head and the Barrels and tha`s enough for street riding.
    All more is not good for the engine "Lifetime"
    Ollie`s own bike is running like hell, but with a lot of problems.
    He has destroyed more than one engine on the dyno.
    A standard Euro 4 bike from him has 80 HP without changing expensive parts.
  9. ntst8

    ntst8 VIP MEMBER

    Feb 14, 2004
    Not sure about Aus but there is one in NZ which has been modded and raced. The 100HP figure has been talked of for that, it has been increased to over 1000cc but i don't know any real detail. He did have a balance shaft break at one stage, ouch. I've only seen it raced once, he was chasing air cooled Ducs.
  10. BritTwit

    BritTwit VIP MEMBER

    Aug 25, 2009
    That sounds about right.
    Any idea who he is, or if he's a member of the forum?
    Bet he would have some great deals on adding steam to 961.
  11. BritTwit

    BritTwit VIP MEMBER

    Aug 25, 2009
    Oooh, now you've whet my appetite!
    Do you know what the weak link was that caused the failures?
    Crank, valve train, gearbox, etc....?
    What kind of HP was he getting from the motors?
  12. ntst8

    ntst8 VIP MEMBER

    Feb 14, 2004
    I can't think of his name for the moment, as far as i know he isn't active on here.
    I do have the number for the performance shop which has worked on his bike, was thinking of having them blueprint my motor since they know their way around a 961. My pot of spare money is a bit bare at the moment so i haven't made the call to discuss it with them just yet.

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