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Thread: 1987 CR 500 Carb set up

  1. #21
    Senior Bengt Husky's Avatar
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    Default Re: 1987 CR 500 Carb set up

    Quote Originally Posted by ernie View Post
    Are your reeds ok, if they are fraying a bit could be blowing back in to the carb
    Checked reeds they are fine.

    I'll double check cable condition. Leader of the sunshine band has given me an interesting clue that worked back in the 80's which is to check there is a small hole in the slide approx 1/16".

    I'm going to think about the effect of this and what affect it would have.

  2. #22
    Senior Bengt Husky's Avatar
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    Default Re: 1987 CR 500 Carb set up

    Spoke to Allens and they don't do the PJ 27 carbs any more.

    They offered as an alternative a PWK 38-71 R. Has anyone used one of these as they are going to be 200...

    I will then get a new throttle cable and try again..

  3. #23
    Super Moderator Relic's Avatar
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    Default Re: 1987 CR 500 Carb set up

    Have a chat with Dellorto UK - they might have an alternative carb and they can sometimes be a lot cheaper...
    too late - you missed it...

  4. #24

    Default Re: 1987 CR 500 Carb set up

    Steve, the photos you sent me on facebook didn't download unfortunately, but I think you should try doubling the size of the vent holes and turn the choke knob (which adjusts the fast idle) right down.

    Doing what I suggested to the slide won't affect the carburetion at all but will encourage the slide to drop faster when the engine's doing some rpm's.

    I'm still waiting for a reply from my mate who worked at Ron Humphreys during the 80s but I'm sure he'll confirm the modification.

    Testing it might be squeaky-bum time but it's got to be worth a try and will save you wasting 100s on a new carb!
    Let Brock Bye!

  5. #25

    Default Re: 1987 CR 500 Carb set up

    Quote Originally Posted by LeaderOfTheSunshineBand View Post
    Steve, the photos you sent me on facebook didn't download unfortunately, but I think you should try doubling the size of the vent holes and turn the choke knob (which adjusts the fast idle) right down.

    Doing what I suggested to the slide won't affect the carburetion at all but will encourage the slide to drop faster when the engine's doing some rpm's.

    I'm still waiting for a reply from my mate who worked at Ron Humphreys during the 80s but I'm sure he'll confirm the modification.

    Testing it might be squeaky-bum time but it's got to be worth a try and will save you wasting 100s on a new carb!
    Totally agree with the vent holes. I remember doing the same to my Honda card back then and I remember all my freinds doing the same. Didn't affect the jetting but it did sort out the sticking throttle problems we had.

  6. #26

    Default Re: 1987 CR 500 Carb set up

    Quote Originally Posted by Bengt Husky View Post
    I'm getting the feeling I've wasted my time posting this on here.

    The cable was fine, the throttle snaps shut, it was dry and sunny, it had a clean air filter, the rubber boot holding it on was fine, it wasn't a Gunnar Gasser.

    I've ridden big bikes before, but never have I had a throttle stick open like this before and yes it #ucking hurt hitting the ground in the way I did.

    I was hoping that someone who actually knows something about jetting on these carbs might have posted something meaningful and helpful.

    I'll keep it to myself in future.
    jetting will not cause your throttle to stick, you could try a stiffer throttle spring
    Last edited by Tank slapper; 17th April 2012 at 04:33 PM.

  7. #27

    Default Re: 1987 CR 500 Carb set up

    Steve, this is the reply I got from Nik who worked at Ron Humphreys during the time when the CRs sold like hot cakes -


    "Kev - this was just prior to my time with Ron as I joined him in 88 - but I can remember something about this - in 94 I had a similar problem with the carb on my 250 and we drilled a small hole either side of where the cable goes down into the top ofthe slide - you could try asking Andrew B*** on 07890 102*** as he is the font of all knowledge and definitely not prone to bull*hit - hope this helps".

    RPM who replied earlier was another one of numerous riders in our area to suffer from this - If you want Andrew B's number I'll pm it to you, he did loads of mechanical work for Ron and spannered for Mike Healey when he did a one-off ride for Ron on a CR500 at a Hawkstone GP many years ago

    Kev
    Let Brock Bye!

  8. #28
    Senior Bengt Husky's Avatar
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    Default Re: 1987 CR 500 Carb set up

    Quote Originally Posted by LeaderOfTheSunshineBand View Post
    Steve, the photos you sent me on facebook didn't download unfortunately, but I think you should try doubling the size of the vent holes and turn the choke knob (which adjusts the fast idle) right down.

    Doing what I suggested to the slide won't affect the carburetion at all but will encourage the slide to drop faster when the engine's doing some rpm's.

    I'm still waiting for a reply from my mate who worked at Ron Humphreys during the 80s but I'm sure he'll confirm the modification.

    Testing it might be squeaky-bum time but it's got to be worth a try and will save you wasting 100s on a new carb!
    Cheers mate,

    I've bitten the bullet and bought a new carb and cable (going back to square 1) I will drill the holes in the slide and try it in the old carb when I can go practising. I'm trying to get her (and me) ready for Torrington on Sunday and I don't have enough time to worry whether it will or wont work.

    Having the idle in the position is like having the choke 60-70% open all the time, which can't be right. I'm also going to stiffen the spring up again.

    If it works out I'll keep the old carb as a spare.

    Thanks again for the help

    This is the pic of the slide holes.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  9. #29

    Default Re: 1987 CR 500 Carb set up

    No wonder it keeps sticking, the needle's meant to be pointing downwards!

    Good luck with it anyway, hope it gets sorted out.

    Kev
    Let Brock Bye!

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