Reliability of 4 cycle clutch and gearboxes

Discussion in 'Frame Mounted Engines' started by skyl4rk, May 17, 2008.

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  1. skyl4rk

    skyl4rk Guest

    Can anyone report on the reliability of clutches and gearboxes for 4 stroke 50cc motors?

    The gearboxes that I know of (by name) are the Grubee Skyhawk II type, Dax type and the JL Hoot type. Which ones will last over the long haul?

    I know a few years ago there were some bad gearboxes being offered but this may have been cleared up.

    Are there other gearboxes for the 4 strokers?

    Can anyone confirm long term reliability of the clutches and gearboxes?


    Skyhawk II:

    JL Hoot:

    Last edited by a moderator: Jul 2, 2008

  2. nsideus

    nsideus Guest

    I have probably around 4,000 miles on the grubee gearbox and the only thing replaced has been the clutch spring and clutch bushing at about 2,000 +
  3. The Titan is solid. Remove 4 bolts and you can put that gearbox in your pocket. 500 miles with some hills and some pedaling with the steep stuff but never had to get off the bike like I have to do with MOOP (my Happy Time) so I've given it some slip.
    And when I checked my clutch pack yesterday I see very little wear if any at all. I may take some pics today.
  4. fetor56

    fetor56 Guest

    For the moment the Grubee is the tried & proven contender but i've not heard any bad reports about the Dax either.Let's see how the new Dax in-frame gearbox goes.
  5. HoughMade

    HoughMade Guest

    I the Skyhawk II- no problems, but many less miles than those above.

    To tell the truth, I've not heard anything good about the Hoot. I'm not saying that there are not people who are happy with it, but I have not heard from them.
  6. i have grubee kit and the noise from the gearbox is excruciating.
    once my clutch spring broke apart(i think it's from overheat of gearbox)
    i'm thinking of making my gearbox "oil bath" type as some people seems to have done it already. but i worry if oil is going to leak.
  7. HoughMade

    HoughMade Guest

    Mine is pretty quiet and I use grease, but by using grease, I don't mean some on the gears, I mean a whole lot of a very good, industrial quality grease.

    That being said, in an early thread about the Dax 4 stroke, Augi mentioned trouble with the clutch springs. I think he found that the problem was more that the clutch arms were not rotating freely on the pivots, causing binding. The solution was to disassemble the clutch and lightly lubricate the pivots. There are significant differences between the Dax kit and Grubee, but the clutch looks very similar. I think it's worth checking out.
  8. Proboscis

    Proboscis Guest

    Last edited by a moderator: Jul 2, 2008
  9. That looks like it turned red.
  10. gees i thought JL had better gearbox
  11. HoughMade

    HoughMade Guest

    I've never heard anyone with one give it a good review.
  12. fetor56

    fetor56 Guest

    I've only heard one person say it's fine but that's about it cos he didn't person,not a very good track record.
  13. HoughMade

    HoughMade Guest

    I would love to hear more from people with these gearboxes. I'm an eternal optimist- there has to be more than one person with a good experience.
  14. chuck216

    chuck216 Member

    I've got one, well not the "hoot" itself but the upgraded model with the angle cut gears. The gearbox itself runs fine, have had a problem with the sheer pin on one of the gears inside breaking, but that was what it was supposed to do when the idler pulley got too loose and dropped down causing the chain to wrap around the engine sprocket. Got another and put it all back together, everything works fine.

    Well there is one slight "problem" this GB gets very warm while going down the road, you can feel it against your leg. I'm guessing I need to use heavier grease to cool things off, as the white lithium doesn't seem to be doing the job.

    As far as acceleration, and speed goes, I have a 44 tooth rear sprocket and i'm actually afraid to keep it at full throttle for more than a few seconds at a time I always end up backing it down to half throttle or even less. I don't have a speedo but I know it feels fast. even faster than the electric panterra 750 watt scooter I had that was easily capable of cruising between 25 and 30. (it wasn't a toy type scooter, but a full sized Vespa type electric)
  15. Irish John

    Irish John Guest

    My Grubee Skyhawk 2 is OK after 1400 kms of mostly hard & fast use. I use lithium marine grease and lots of it but any grease will get thrown off the cogs at those revolutions. Doesn't seem to mind not being wet in oil. I think the Titan is probably much better but it's a rear mount. I have read some OK things on this site about JL Hoot gearbox and I will soon know cos I'll be testing one in July. I think the JL Hoot has a fixed drive sprocket - i.e no freewheel which makes it a real danger to ride. Freewheel rear hubs are a pain cos they need a total wheel rebuild. From what I've read and been told on this site the Staton NV (rear mount) seems the best of them all as far as pulling power goes. I see they offer a warranty for life on the NV but I've not had one so can only go on what I read. Anything 4-stroke is better than those HTs in my experience.
    Hang on, Fetor 56 is right, I only saw one report on the JL Hoot but it sounded good from what I remember - wasn't noisy and pulled well. Grubee is a bit gutless on the hills. I would be surprised if the JL Hoot is good cos it looks very HT and it's made in the same factories.
    I'll soon be able to give a report on it.
    Last edited by a moderator: Jun 1, 2008
  16. Irish John

    Irish John Guest

    HoughMade, I'm getting a Huangsheng & JL Hoot garbox at end of June. Will have it mounted on my Merida MTB soon thereafter and will be putting it through it's paces and comparing it to my Grubee 2 rig from In July I'll post a thorough report on it's performanceand on the whole kit. The build will take a long time cos there are all those chinese studs & bolts to replace and the welding on the engine tray looks like it was done by a blind baby. I can see from looking at it that there will be lots of headaches getting it assembled to a decent standard. God knows what size the shaft is on the motor but it's not the one on the other Huangsnengs or the Honda GXH.
  17. chuck216

    chuck216 Member

    It's noisy, though not uncomfortably so. about the same level as the motor itself. just makes a whine while going down the road, the most noise it makes is actually when you let up on the throttle and the clutch doesn't have time to release you get an instant sound of engine braking as it slows the bike down to a crawl. mine may be quieter than other JLs though not "quiet" by any means because I've had it apart and personally aligned all the gears, bearings etc inside so everything meshes. I do like the fact it has the beveled gears, everything fits together better.

    I can't compare it to another GB because I've only owned this one. But If hindsight was 20/20 I would have spent the extra money for a Grubee kit.

    John, about the fixed sprocket, yes it does have that, and letting up on the throttle at speed causes instant engine braking, slows you right down though while disconcerting at first it doesn't seem dangerous, you just have to get used to backing the throttle down gradually instead of just suddenly letting go. And once the revs drop below a certain level the clutch releases anyway and it does "freewheel" albeit with the gears inside the gearbox turning. I'm personally seriously thinking about getting a freewheel rear axle to relieve this problem.
    Last edited: Jun 1, 2008
  18. Irish John

    Irish John Guest

    Thanks for that info Chuck, much needed. Engine breaking is great but my concern was about wheel lock-up in the event of engine seizure which is what nearly killed me once on the HT and another time when the chain tensioner spindle threads stripped and the tension wheel slipped causing the chain to loosen and get sucked into the HT drive sprocket chamber where it kinks and locks up on the first bend and throws me over the handlebars. At 56 years of age I don't take kindly to these things happening.
    BTW didn't your kit come with a rear hub freewheel sprocket? If not then I reckon it will do exacltly what the HT does when it seizes. You don't get time to disengage the clutch (it happens so fast that you just get time to put your hands out to protect your face) and whether the 4-stroke would disengage on seizure I don't yet know. For the price of a freewheel sprocket it really annoys me that they can't be bothered to include one - even as an optional extra. My next purchase will be a Dax or a Staton because they are designed by people with skills who care about the product they are selling.
  19. chuck216

    chuck216 Member

    I can't be sure but engine seizure might not be a factor as it's completely possible to kill the motor while cruising and still have enough free play in the centrifugal clutch to allow it to coast and or be pedaled. the only thing that might prevent this is if somehow the clutch got stuck engaged and/or the gears inside the box got jammed. Even then it would probably just do what mine did when the chain jammed, snap a sheer pin, allowing the rest of the gearbox to act as a freewheel.

    I've actually had the engine die on me while riding with no problems, that's what I get for only putting a few ounces of gas in for the first test run. LOL

    Correct me if i'm wrong but doesn't the HT use a mechanical, manually engaged clutch? if so then there's no release mechanism, which is probably what caused your problem, with centrifugal clutches they release when rpms drop below a certain level. I would think the motor stopping (0 rpm) would definitely be below this level.
    Last edited: Jun 1, 2008
  20. helldog10

    helldog10 New Member

    Last edited by a moderator: Jul 2, 2008