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Mikuni

Discussion in 'Norton Commando Motorcycles (Classic)' started by Neil, Sep 9, 2005.

  1. Neil

    Neil

    Joined:
    Jun 3, 2005
    I have a Mikuni 36mm carb fitted to my 850 Commando. Can anyone tell me if the isolastics not being set correct can affect the running of this carb.

    I got rid of the Amals as the vibration was always affecting the carbs by flooding problems etc. They were also worn out.

    I have noticed the Mikuni carb has a slight drip out of the hose overflow when revving the bike to about 2000 - 2500 RPM. I contacted the shop where I purchased the carb and they performed some maintenance but could not find any problems.

    The problem is still happening. Does anyone have any ideas?

    Thanks,

    Neil
     
  2. Geoff

    Geoff

    Joined:
    Aug 20, 2005
    I have single Mikuni carb fitted last 10 years & this fault has not happened so it is not typical. Check float height, manual says 17 to 19mm to activating arm from casting above & needle valve working correctly. IS it mounted on a rubber coupling?
    Incidentally does anyone know if reducing compression ratio affects mixture required as mine now runs rich at low throttle settings following head gasket/valve & compressiln plate job
     
  3. Ron Hulton

    Ron Hulton

    Joined:
    Jul 18, 2005
    Neil
    I have the same problem so hurry up and resolve your issue. I await your prompt reply. I am in a tear down right now so i won't be able to give you much info for a week or two until i am back together
     
  4. Neil

    Neil

    Joined:
    Jun 3, 2005
    Hi,

    The float height was checked when it was sent back to Allen's Performance, they said everything was in spec and there should be no problems. However, when connecting everything back up and running the bike at 2000RPM while on the stand, the petrol is still running out of the hose overflow.

    I have found the economy of this carb probably worse than the worn out Amals and not what I expected. I'm going to ring Allen's Performance first thing Monday morning and request a new carb to be sent out.

    I will keep everyone posted about this issue. Good luck with your tear down Ron.

    Thanks,

    Neil
     
  5. Neil

    Neil

    Joined:
    Jun 3, 2005
    There's been no sign of replacement carb which was supposedly sent Monday 12th September. They originally told me that they didn't think a replacement carb would fix the problem of dripping petrol out the hose overflow, it was more likely vibration. I told the man I thought that a single carb conversion designed for a Norton Commando should be able to withstand the engine vibration that is associated with that type of bike. Given that the bike has been checked over by members of the Norton Owners Club (Northumbria branch) in which it was found that the isolastics are all set correctly.

    I gave Allen's Performance a ring today and they told me my order had been deleted from the system by mistake. I should have a replacement shortly.

    Thanks,

    Neil
     
  6. Neil

    Neil

    Joined:
    Jun 3, 2005
    Received my Mikuni replacement carb thanks to Allens Performance, installed it yesterday and took the bike out for a good 70 mile run. After returning, a thorough check was made throughout different rev ranges and the carb appeared to be perfect.

    No petrol dripping from the hose overflow. Whether this is a problem with some Mikuni carbs that do not like the vibration that is associated with the Commando engine at lower revs or not, I don't know.

    The early stages of running this new carb seem ok and if things stay the same, I will be more than happy as I've no doubt I’ll see an increase in the MPG :)

    Thanks,

    Neil
     

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