Grubee 4 stroke gear box chatter

Discussion in 'Rack Mounted Engines' started by cheetoh, Feb 3, 2009.

  1. cheetoh

    cheetoh New Member

    I think Ive solved the Grubee gear box clanking and chatter at idle and take off. The centrifugal clutch springs engagement is so close to the Honda GXH 50 or Huasheng clone engines idle rpm that at idle the clutch is always partially trying to engage creating the chatter ang grabbing. Solution is to lighten your clutch shoes slightly by drilling holes in the metal portion of clutch shoe in an area that wont affect strength similar to swiss cheese or airplane wing spars. I was sucessful with several 5/16" holes. Just drill slowly cooling metal constantly with atf or light oil . Wash shoes after with paint thinner if your running dry clutch. Also carb idle issues. The carbs on these engines were designed to run wide open or nothing. A small slide carb from a pocket bike or scooter will vastly improve idle and drivability. Hope this helps!
     

  2. HoughMade

    HoughMade Guest

    Good tips...I haven't had those issues, but many have. For them, this advice will. be very valuable.
     
  3. fetor56

    fetor56 Guest

    Swiss cheese the clutch.
    Sounds workable IF u have a chatter problem & surely can't do any harm...at the very least you'll lighten your load.
    Now all someone needs to do is Swiss Cheese their entire bike to get maximum lightness.
    Handy tip.
     
  4. HoughMade

    HoughMade Guest

    How about acid dipping the whole thing like they used to do with the body panels on '60s Trans Am racers?
     
  5. Irish John

    Irish John Guest

    It would really help Cheetoh if you included a picture of the centrifugal clutch with holes drilled so we can see the number of holes. This is a great idea of yours if it works because clutch chatter affects almost all Honda or HS Grubees (I would say all!) but wouldn't you think that Grubee woould have got the spring tension right in the first place so the clutch doesn't expand at idle revs. The carb idle problem isn't a problem unless the clutch is expanding and catching the bell housing enough to stall the engine. The problem seems to lie solely and squarely with the spring itself. Grubee got it wrong because Grubee do not test their products in any way that we guys would call testing. A couple of runs around the industral estate in China is not really a good way to test or try out these products. What do people think of Grubee's new belt driven gearbox on their website? That won't have been tested either other than their usual trip around the block.
     
  6. cheetoh

    cheetoh New Member

    Im sorry no pics as bike was sold. If someone could email/post a pic of clutch I could detail locations of holes. But with all the smart folks on this forum Im sure someone could figure out where to drill without affecting strength of clutch. Note probably would be better to drill multiple small holes first 1/4" the progressively enlarge by 16ths to get desired effect. Also a spare set of clutch shoes would be good insurance. As far as the spring is concerned at idle or rest the spring coils need to be touching or retracted but with enough tension left to stay in the clutch slot. Thats why lightening shoes is the easiest way to go. As far as idle quality goes Ive always like my engines to idle down low. I think that the aluminium flywheel affects idle as it has no reciprocating weight.
     
  7. Irish John

    Irish John Guest

    The aluminium flywheel fan is pretty light though and shouldn't be much strain on an idling engine although there must be some. Here's a picture of a clutch without its spring if you want to dot the places to drill holes. I'd like to try this idea cos if it solves the clanging it will be great.
     

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  8. cheetoh

    cheetoh New Member

    Drill holes in the groove or slot in which the spring rides. I believe I started with a 1/4" bit which was the width of the groove and the progressed to 5/16". Drill 5 1/4" holes evenly spaced then enlarge them to 5/16" I know this seems like a lot but the area in which you are drilling isnt very thick. Remember to use plenty of lube for cooling and drill every other hole as not to overheat an area.
     
  9. Irish John

    Irish John Guest

    Drilling 6 x 5\16" holes would be easier given there are 3 clutch segments so that would be 2 for each segment?
     
  10. cheetoh

    cheetoh New Member

    Try 3 holes per shoe. It takes more holes than you think as the shoes are heavy and the area in which you are drilling is thin 1/8" or so. Just try to leave 1/4" more or less between holes. Trust me this will solve the noise issue.
     
  11. Irish John

    Irish John Guest

    That's 9 holes Cheetoh. I'll go strictly by the 1/4" gap between holes & not go closer nor exceed 9 holes. If this works as you say and as it most certainly will I think you have made a great contribution to all Grubee owners and yet again it shows what a truly great forum MBc is. Pity the makers of the kits in China don't benefit from all this incredible knowledge and experience. Well done Cheetoh and conger rats mate!
     
  12. Irish John

    Irish John Guest

    I've reported this elsewhere but I should say it here.....this method of Cheetoh's has worked very well for me but I'm noticing that recent Grubee clutches have a stronger spring as I reported on another thread so might not need this drilling. 5/16" drill bit is too wide to fit in the spring channel so I went a bit smaller 7/32" I think it was and that fitted pretty exactly. Even if you drill the newer clutch with bigger spring it will only improve the clutch because this method cannot harm the clutch but might help stop chatter beginning. Clutch chatter detracts totally from a good bike build and causes onlookers to wince when they hear it. This idea is a great breakthrough I reckon.
     
  13. Irish John

    Irish John Guest

    I think it worth noting that this thread has been moved to the wrong place. This is really about frame mounted kits as opposed to rack mounted and should be in the section for frame mounted rigs. I know the Grubee GB is sometimes used on rack mounts but these postings are all about frame mounted bikes by people with frame mounts.
     
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