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Bike wont rev past 3500k after pamco install

Discussion in 'The Garage' started by IronJim, Jul 11, 2017.

  1. IronJim

    IronJim XS650 Member

    Hey guys

    Having some issues with engine speeds after pamco install. The bike wont rev past 3500k as soon as it hits 3.5 the bike starts to cut out but wont stall. My initial feeling was the advance was kicking in to early. Iv done the timing on the bike and engine runs perfect at idol and all the way to 3.5k then it just cuts out, sometimes it will go past but most of the time it just cuts out.
    Iv check battery and all charging and its all running well. Any advice would be greatly appreciated.

    I have installed -

    PMA charging system

    Basic Pamco High Output Standard Ignition Kit, no electronic advance

    New springs for the advance mechanism
  2. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    Try running with a fully charged battery with the PMA and regulator disconnected.
  3. IronJim

    IronJim XS650 Member

    Just ran the bike with both disconnected and seems to run much better with little to no stumble at all ???
  4. fredintoon

    fredintoon Fred Hill, S'toon.

    Hi IronJim,
    you shouldn't have drunk the PMA koolade, eh?
    If you still have (or can get) the stock alternator & regulator/rectifier, put 'em back in.
    And think about installing the Pamco E-advance. The stock mechanical advancer is most likely worn out so that
    new springs ain't a complete fix and it's claimed the modern replacement advancers are of poor quality.
  5. IronJim

    IronJim XS650 Member


    Looks like iv drank the bar dry currently !!. There was me thinking that upgrading all the stock components was a good idea.... luckily for me i still have everything. Iv spent so much money buying and upgrading different parts for the bike all for it to fail ! Doh don't really want to put all the stock parts back on to be honest but if that's what has to be done then....
  6. fredintoon

    fredintoon Fred Hill, S'toon.

    Hi IronJim,
    upgrades are fine but a PMA ain't one. It's more of a fashion statement and it don't work as well as the stock alternator.
    OTOH, an E-advance Pamco is an upgrade from a points and mechanical advancer ignition.
    Out of interest, what other upgrades did you buy?
    IMHO the best upgrade is modern tyres as they grip so much better than 1970s tyres used to and you gotta buy 'em anyway.
    Perhaps you could sell your PMA on? There's gotta be someone out there who'd want to put one on his XS650 hardtail?
  7. I agree with Fred. PMAs are not an up grade. They are a down grade as you are finding out. You have bought poor quality Chinese PMA parts. The stock charging system is high quality Japanese parts.
    Too many inexperienced lads believing the PMA marketing hyperbole and trash talk about the stock system, when in fact the stock system is a superior design.

    You will survive the koolade, once you re-install a stock type charging system.
  8. IronJim

    IronJim XS650 Member

    Lesson learnt gents... Thank you very much

    I will install the old charging system and let you know how she rides. Before i installed the PMA i had a reg rec which i installed when i first got the bike, do you think i could use that still ? am i right in saying i can still run the pamco and coil with the old charging system ?
  9. If the rec/reg combo unit was working previously, just continue to use it.
    Yes, a Pamco and its coil, work very well with the stock charging system.
  10. IronJim

    IronJim XS650 Member


    Been out of London for a few days seeing family so left the bike at home so i haven't done any work on it dismantling the PMA but thought id give it one more try before i take it all apart.

    Arrived back about an hour ago and gave the bike another run with the PMA disconnected. The symptoms are still there, it still bogs down around 3500k it is a little better at times but still not fixed so it still has the same symptoms weather the PMA is connected or not......Strange !

    Got any thoughts ?
  11. Not reving past 3500 rpm:
    Use a timing light to be sure the timing mark is moving towards the full advance mark.
    Have you confirmed the carb rubber diaphragms have no holes in them. Lift the slides, thumb over the oval hole to confirm the slides only fall very slowly.
  12. IronJim

    IronJim XS650 Member

    I will double check the timing tomorrow, as for the carbs they are TM Mikuni Flat slides so they have no diaphragms
  13. fredintoon

    fredintoon Fred Hill, S'toon.

    Hi IronJim,
    and now you tell us about the flatsides?
    I have always found that any "new" problem one of my bikes developed was caused by whatever I'd last done to it.
    (even the pinched wire that took months to finally earth itself to the frame and stop the alternator from charging)
    So what did you do to your bike just before the not running above 3,500 rpm thing started?
    Most likely that's what's causing it.
  14. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    When testing to see if the PMA and regulator are part of the problem, you should disconnect both the PMA and the regulator as the regulator is a shunt type and can affect the electrical system even without a functioning alternator. Kinda like a snake with it's head cut off.
  15. IronJim

    IronJim XS650 Member

    Yeah apologise gents i did forget about the flat slides only because iv had them dyno'd and they are running great so didn't think they would be part of the problem. The last thing i installed was the pamco and new coil before that the bike was revving and running well. Pamcopete i get what you mean i did disconnect both alternator and reg rec from the bike but the problem still persists.
  16. Have you used a timing light to test that its fully advancing as you rev the engine?
  17. njrmahoney

    njrmahoney XS650 Enthusiast

    I have a similar problem, I have not touched the bike in 1yr since it developed. I want to run it with PMA and regulator disconnected, but seem to recall the unit could be damaged if not disconnected properly. What did you specifically disconnect?.
    Last edited: Jul 21, 2017
  18. fredintoon

    fredintoon Fred Hill, S'toon.

    Hi IronJim,
    the bike revved and dyno'd good with the flatsides on it before you installed the Pamco?
    Can you carefully remove the Pamco, put back whatever ignition it had when it ran OK and do a test run?
  19. Aftermarket advance springs are known to be weak and faulty. Is there any reason you changed them. When i bought a set and installed them the weights wouldn't snap back as hard and as fast as the original springs so i changed them back to the ones that were on there.

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