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It's a long way to 920 type(rary)

Discussion in 'Norton Commando Motorcycles (Classic)' started by yves norton seeley, Jan 14, 2018.

  1. yves norton seeley

    yves norton seeley

    Joined:
    Feb 13, 2014
    Hi steve,
    Only fools never change there opinions, the only reason I don't order the gapless rings is that I was afraid that the Alton E start will not pass the compression
    The port work will be down, tomorow I will know more.
    More compression, maybe yes....
    I will ask Bruno to send the mixture graphs
    The riding comparison between the 820 and the 920 is subject to a placebo effect, for sure if you don't ride your bike the last four month and you think that the bike must be faster after all that work, then it will feel faster even it is not.
    BTW: big thanks to everybody helping me on Access
    I was complaining about how difficult it was to me to understand Hobot english, but I am wondering how all of you understand my english
    Keep you posted
    Yves
     
    Nater_Potater likes this.
  2. Jagbruno

    Jagbruno

    Joined:
    Jan 6, 2014
    Hello all, here is the mixture graph, the 920 is about 1/2 point richer throughout than the 850 was, but it may come from different conditions between the 2 tests, air temperature, petrol temperature, air pressure...

    [​IMG]
     
  3. yves norton seeley

    yves norton seeley

    Joined:
    Feb 13, 2014
    Hi There, here are the pics from the LH pistons



    Yves
     
  4. Klaus Monning

    Klaus Monning

    Joined:
    Nov 27, 2014
    Hello,
    I have to interfer here. Yes, I am the cylindeder head man. What I notice here is, that the mixture graph as well as the power graph are both 500 nearly exact 500 RPM offset to the 820cc graphs. Just take the 920 graphs and draw it exactly at the same starting point as the 850 graphs and the picture looks a lot friendlier.

    There is some other point I want to make:
    If you touch a Fullauto head you handle it with greatest respect, which means that these people know exactly what they are doing. If you take material of somewhere you cannot put it back to where it was. So, Yves and I both agreed to leave the port- shape standard as near as possible. For me there was only a bit of blending- work to do. I'm curious to read what Yves found out on the flow bench. Only thing is: has Yves a comparison how a standard Fullauto head will flow?
    Yves, again the question: Can you send me the power graph per E-Mail?
    Best Regards
    Klaus Monning
     
  5. jseng1

    jseng1

    Joined:
    Nov 26, 2009
    Maney cylinders are a good choice for a 920. But you are still getting closer to the bolt holes and the liners are not as thick as the smaller bores.
     
    Last edited: Mar 16, 2018
  6. yves norton seeley

    yves norton seeley

    Joined:
    Feb 13, 2014
    Hi Klaus,
    I don't complain about your work, your job is perfect
    The flow man did flowing on the head when it was new and says that it was close to perfection, with standard valves of course, I hope he still have the records.
     
  7. yves norton seeley

    yves norton seeley

    Joined:
    Feb 13, 2014
    Hi there,
    To day I did the trip to Powerseal in Holland wit the cylinder and pistons, Powerseal is the co. that make the Nicasil on my cylinder, I ask them to make the mesurments and here are the results:
    Bore is 81 mm
    Pistons are 80.89
    Clearence piston/cylinder is 0.11mm
    There is a ovality below the cylinder, lower as the rings come at BDC and it is only 0.02mm.
    So to the man from Powerseal and to me, there is nothing that can explain the power lost...or maybe we must go to 0.15mm clearence.
    The piston looks OK to
    Jim and other specialist, I will be glad to have your comments on this??
    I have a appointment tomorow evening with the flow man and we will see if there is something wrong, and it must be becouse I tchek the ignition, the camshaft timing and now the cylinder and pistons, so there is only one thing left: the flow
    keep you posted
    yves
     
  8. jseng1

    jseng1

    Joined:
    Nov 26, 2009
    Here is the FA port floor moved over for a 5mm larger intake valve (red line), It also needs to be a little wider at the sides of the bowl.

    [​IMG]
     
    Last edited: Mar 16, 2018
  9. yves norton seeley

    yves norton seeley

    Joined:
    Feb 13, 2014
    My intake is only 3mm larger
     
  10. lcrken

    lcrken VIP MEMBER

    Joined:
    Mar 15, 2009
    Liners in Maney 920 (81 mm) cylinders are nominally 1.5 mm (.060"). I've measured several, and got measurements between .060" - .063". The difference is probably due whether they were original or had been honed for more clearance.

    Ken
     
  11. worntorn

    worntorn

    Joined:
    Dec 22, 2006

    Expecting 1/16" of an inch of metal to stay perfectly round for hundreds or maybe thousands of heat cycles in that environment is asking a lot !

    Glen
     
  12. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Is your setup is the 81 mm 920 with alloy barrel and .060" thick cast iron liner?
    If so that is very encouraging.

    Glen
     
  13. jseng1

    jseng1

    Joined:
    Nov 26, 2009
    Worntorn - that was my mistake. I thought you were talking about piston skirt thickness instead of cylinder liners. I'm running a 750 with thicker cylinder linings.
     
    Last edited: Mar 16, 2018
  14. yves norton seeley

    yves norton seeley

    Joined:
    Feb 13, 2014
    Hi there,
    I am just back from the flow bench, you will not believe it but the flow man says: I can do it better but not to close the difference on the graph
    His opinion is that there is some mistake on the 820/920 comparaison on the graph...
    The man from the dyno is in Spain till monday, so no way to call him this week, my proposal is to bring the dyno man and the flow man in relationship on monday.
    It can be that there is something with the dyno graphs, I remember well when I did the first road tests, I was impressed with the power, was it a placebo effect or not....
    Tomorow I will put the cylinder back on the cases and do the cam timing w/o the head, straight on the followers to be 200% sure
    I keep you posted
    Yves
     
  15. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    This is a good argument for finding a dyno hill.
    Approach bottom at some specific speed, then run full throttle up the hill and record speed at top with GPS speedo mounted (any common GPS unit)
    You can do this in top gear as well as one down on a steep hill.
    Make changes and repeat test.
    I've found that my local hill works well with 30- 60 HP vintage MCs, not so much with high horsepower moderns,as the speed at top is too great.

    The GPS does not lie. Sometimes dynos do.

    Glen
     
    Last edited: Mar 15, 2018
  16. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Yves, a few of us did point out that the graphs looked ‘out’ by 500rpm or so. Let’s hope that’s all it is!
     
  17. Brooking 850

    Brooking 850 VIP MEMBER

    Joined:
    Oct 3, 2011
    Yves I have a Full Auto head that has 1.5 mm larger intake Vvs and so far on the flow bench I am seeing the HP potential of 75 + HP using a 34mm smoothbore carb for testing. I tested against a new 34 mm Mk2 Amal and there was a 2hp potential loss compared to the smoothbore. This is at 0.400 " of lift on the intake Vv
    Is your flow man using different stubs and manifolds and carbs to see if there is any change in results?

    My head guy is going to play with some plasticine moulding in the exhaust port , then back to the flow man to see if there are any changes.

    Your FA head should be good for at least 70+ without any big changes.
    Regards Mike
     
  18. yves norton seeley

    yves norton seeley

    Joined:
    Feb 13, 2014
    Yes I know but the dyno man is in Spain for a week, testing some racing bikes, so I can not ask him sonething before monday
    Thanks
    Yves
     
  19. yves norton seeley

    yves norton seeley

    Joined:
    Feb 13, 2014
    Hi Glen,
    good idee, but the problem is that Belgium is a flat coutry, difficult to find a good, long, straight hill here
    Thanks
    Yves
     
  20. yves norton seeley

    yves norton seeley

    Joined:
    Feb 13, 2014
    Thanks for the encoraging info's
    Yves
     
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