Appraisal of New Grubee GT1 Cruiser Bike

Discussion in 'General Questions' started by Irish John, Aug 21, 2009.

  1. Irish John

    Irish John Guest

    I've seen the new GT1 cruiser bike and I must say that it represents good value for the money. the front forks are telescopic on two triple clamps which give it more of a motorbike look. The crowns are alloy, not steel, which is better quality - (steel crowns are a real give-away of a cheep bike). The alloy is brush finished which is not the best quality finish but better than chromed steel which would rust and blister.
    The double wall alloy rims & wheels with 12g spokes really look good and so do the thornproof tyres. The spokes are gal steel which is a pity and I would much prefer stainless even if only 14g.
    I'm not enamoured with the band brake which seems to get in the way of everything but overall this is a great bike for the price. It isn't that heavy compared to some of the steel electric bikes coming out of China and the pain finish is adequate. If you don't like the paint finish you can respray it another colour because there are no decals.
    The V-brakes look OK - much better than a supermarket bike.
    The G4 Engine tray is much better finished than previous trays and it attaches to the tubes with bolts not studs like before. The clamp brackets are noticeably better quality and the gearbox looks well made.
    The stem is steel with an alloy head - the steel will rust and I would like to have seen a satin finished alloy head and quill stem used like on the Schwinn cruisers.
    The kill switch comes attached to the throttle & double cable brake lever and looks really poor quality and faces upwards where rain will kill it within a month. I'll have to install a Yamaha or Suzuki kill switch on the right side.
    In general the bike is good and its most obvious downer is it has no mudguards and a bike without mudguards is a nightmare in the wet.
    I'd install nice silver plastic mudguards with stainless steel stays and for about Aus $70 it would all look pretty good. The 44T rear sprocket came attached but dished the wrong way around. The 50T that comes with the G4 is yet again the wrong size for the motor and too big by at least 6 teeth which is an improvement on the old kits which came with a 56T that was 8 teeth too big,
    Time will tell what the sprocket size should have been and I'll not know until I ride the bike. These designs are not tested before being sold or they would get these things right.
    I'll add pictures tomorrow but I am impressed so far, Oh yes, the bolt on sprocket to rear hub is a Godsend.

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    Last edited by a moderator: Aug 21, 2009

  2. Irish John

    Irish John Guest

    Closer inspection reveals that the 6 bolts holding the rear sprocket have to be very short because the end of the nut holding them buts up flush against the back of the band brake drum. trouble is they are so short they don't extend to the end of the thread in the nut. This could mean that they strip their thread because they are not fully threaded into the nut. Time will tell. I'm not expecting much braking power from the band brake and if that is the case the lever operating that cable could be used to operate the rear V-brakes which I'm confident have reasonable stopping power. at present both V-barkes are operated by a single lever on the front right that pulls both cables. Double cable levers reduce the braking effect as compared to two single cable levers by bout 25% so unless the band brake can make up for that 25% loss it would be better just having 2 independently operated V-brakes, In theory the 3 brakes philosophy sounds sensible but this bike has not been designed by an experienced rider. I'll know in next 2 days if the 3 brakes and 2 levers is as good , worse or better than 2 independent V-brakes and I'll let people know.
    Not having mudguards is a serious omission and I reckon they were deleted because of the cost of the band brake. The HS motor goes over to the pedal chain side (right side) much further than on the old Grubee rigs - the old ones went as far to the left as possible - and it is quite a nightmare getting the engine tray set up to its best position. There is a lot of intricate work here but I can get the motor to fit and the 1 piece crank to just clear the bottom of the large pulley wheel but I cannot get the tray to be level because the engine won't fit under the top tubes if it is level. I am almost there now and I'll have to mark the final position and then take it all out and threadlock the vital bolts in place. I would never use the Grubee method of screwing steel bolts into aluminium slider bolocks and I will have to use longer bolts with locknuts on the end. This is a real nightmare of a job because you can't access at least 2 of the nuts because they are recessed in cavities and very hard to get at. I grind the roof of the blocks to allow room for the nuts to fit but not to revolve and then I tighten the bolts through them. 4 bolts is all you can ever use and not the 8 bolts they supply with it. Threadlocking the engine base bolts into place requires either using extra washers or using shorter bolts because the bolts supplied are about 2 or 3mm too long. This is typical Grubee lack of real understanding about exactly how it should all be held together. Getting the engine bolts on will also be a nightmare because at least 2 of them will be impeded by the aluminium slider blocks. Getting loctite on these is hard if installed in situ because it is upside down.
    I think it will work out OK but if time cost money this build is expensive.
    Adding to the unnecessary trouble is the fact that the rice farmers have not only got the engine tray plate the wrong way around on the slider blocks but worse still they have installed the 44T sprocket the wrong way around on the hub so you have to dismantle the band brake and take the wheel off to take the sprocket off and unscrew it from the flange and turn it around. Getting the wheel back on necessitates breaking the chain to do it. It is a real pain.
    There's another big problem which I just envisaged but I've forgotten what it is. I'll remember tomorrow when I encounter it but fortunately these carburettors work if they aren't level and whenever I go up steep hills I'll at least know that the motor & carby are exactly level.
    In all fairness a lot of good ideas have gone into this kit but they came from persons who do not ride and it really shows. Here is a picture of the engine position and I've drawn a horizontal line along the top of the chainguard so you get an estimate of the engine tray angle. Hope this helps somebody.

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    Last edited by a moderator: Aug 22, 2009
  3. Will Snow

    Will Snow Member

    Irish john

    I like your belt drive and was going to order one. The dealer I contacted measured the the belt drive and found it 1" wider than my chain drive. I wonder if he could mistaken.

    You had thought your belt drive was narrower than the gear box chain drive. I Like these chinese 4 cycles but the width is a little much for my liking. Maybe you are offered a different setup In your area.

    Any thoughts on this?

    Bill Snow
  4. Irish John

    Irish John Guest

    It's the Grubee G4 that you can buy anywhere. Later today I'll post the exavt width of the engine & GB for both the old Grubee and the new G4. It hasn't been ridden enough to get the sprocket combinations right but you can be 100% certain that Grubee didn't get them right when he put the kit together.
    These turkeys never ride their products. It is left to the likes of us to sort things out. The 48T it comes with is no use and I'm hoping that the 44T will be closer to the right size. Given that Don Grube is normally out by 8 teeth I am thinking it may need a 40T. It's a 5 to 1 reduction GB and then an 11T sprocket to a 44T on a 26" wheel so whatever allows it to get to 33 mph is the right sprocket.
  5. Pablo

    Pablo Motored Bikes Sponsor

    The forks do look nice, how effective is the dampening?
  6. Irish John

    Irish John Guest

    Not sure yet cos I haven't ridden it. They are Zoom which is the bottom of the market brand. If they last 2 years I'll be surprised.
  7. Irish John

    Irish John Guest

    The G4 is 11.5" wide!!

    I have measured the G4 and it is 11.5" wide which is a good 2.5" wider than the Mark 2 or Mark 3 Grubee rig which are 9". It is wider than the 1 piece crank which leaves you less pedal to put your feet on. This is really too wide for my liking and I shall stick with the old gearbox because this will be like riding a draught horse and a draught horse that farts into the dray because the stock exhaust is up front.
    The bolt holes in the aluminium engine tray sliders are all drilled at the very bottom so you have to dremel a dip to get nuts on the end of the bolts. I don't have a dremel so I spend 2 hours filing because without nuts these trays won't hold together and the threads in the aluminium strip so easily over a short time.
    The engine is set up with threadlock on the engine base bolts (those bolts were 2-3mm too long BTW and you need extra washers if you are going to use them. The engine goes as far over to the right as the slots allow whereas the old kits went as far to the left as possible.
    I haven't started it up yet cos it needs a bit of finishing but the chain does interfere with the band brake cable & lever assembly and that will be a problem I'm not sure how to remedy without using brute force. I don't think it can really be bent out of the way anyway. It is a design error that we guys will have to live with.
    All these good ideas (and they are good ideas) just can't be properly realised because of small technicalities that the kit makers don't understand because they don't ride the things.
    The band brake could well turn out to be a real headache on the G4 kit.
    I've had to mount the engine really high to allow for the 1 piece crank clearance which I don't like but I've managed to keep the choke operable if you crouch down and use one finger of each hand to rotate it from the lugs at its base. The top of the choke cannot be reached but with no gear engager I reckon you need a choke to start it quietly because with no choke you need to use a lot of throttle and that could cause the bike to take off without you. It will have to be started on its stand.
    The stand is a great idea and lifts the back wheel off the ground but it is a very light construction and I fear it is made of similar stuff to a TV arial.
    I doubt it will last long.
    Tomorrow evening I should get it operating and I'll report back as to how it goes in comparison to the previous kits it is supposed to replace.
    In summary - nice enough bike but the motor & GB are WAY TOO WIDE and if it can't be made 2.5" narrower I think it will not become popular.
    My advice would be to stick with the old GB but tomorrow might surprise me.
    Here are some pics to illustrate what I've said.

    Attached Files:

    Last edited by a moderator: Aug 23, 2009
  8. Will Snow

    Will Snow Member


    I don't know the designations," GB4,mark 2,mark3". Over the years I have put together a few motorized bicycles with engines of different makes. This will be the fourth Chinese I tried and have not been impresses with any except some things with this last 4 cycle. I see some custom made things made for these little kits that I am begining to like. Between 4cycle and some good parts being made is why I took on this project. However, like you, I don't like the too wide width.

    The bright spot is the little 4 cycle engine, IF only the rest of the kit could measure up to this engine it would be a winner.

    Not knowing what a GB4 is, I am just guessing you are going from a belt drive to a gear drive. Is that correct? If so, I wonder if my chain drive wider than the gear drive you maybe changing to.

    When I finish this project and refresh my memory on how to post pictures I will try to post a couple pictures including the choke lever idea .

    Bill Snow
  9. Irish John

    Irish John Guest

    Will, we're talking about the new Grubee G4 belt driven gearbox that is just released on the market and we are talking about the GT1 cruiser bike that has been specially made for motorising, also made by Grubee.
    I was comparing everything with numerous older style Grubee 4 strokes that I've built, We are also talking only 4-strokes.
    The mark 2 & 3 etc are really all the same old Grubee gearbox with minor modifications. The 4 strokes are wider than the 2 strokes and they needed a wider crank but this G4 gearbox is just way too wide and I think it is so wide it really defeats any advantages the belt drive system may have provided.
    Hope this explains a bit - the bikes in the background in the pics have the older style 4-stroke Grubee gearboxes.
  10. Will Snow

    Will Snow Member

    Ok, so your going back to the old gear box. Too bad, belt drive seemed like a good idea.

    I'll find out if the gear drive you are going to is narrower than this chain drive I have, If so, I may do the same.

    Thank you for clearing that up for me. I see you are well informed on these Grubee kits.

    Several years ago he brought me the first so called 80cc over in his suit case for the sum of $505.00. It was the roughest bike kit I had ever seen. Even the muffler looked like scrap metal. When I called him on it, his answer was:"You know that Chinese quality control is not very good, just take the muffler and get it chromed".

    Thanks John
  11. Irish John

    Irish John Guest

    That would be about what I'd expect from Grubee. Was he wearing a shiny suit as well?
    The big problem with this kit is that they designed it without knowing the small all-important technicalities like, for example, they thought it would be taking a larger back sprocket but it needs to be smaller and this changes so much else because the chain line on a 44T interferes with the band brake lever and it also means that with the engine sitting so high the tensioner has to go too far back along the chain stay and it is then misaligned with the line of the chain and keeps wanting to ride over the tension wheel wall at the back. To remedy this I will have to make a washer that is thicker at the back than at the front to give the tensioner wheel a kick to line up with the chain. They hadn't really got a clue about the proper set-up of the drive train and it is the perfect drive train set up that makes all the difference between a bad ride and a good ride.
    If it in fact needs a smaller sprocket than 44T these problems would become too severe to build the rig. It's all very hit and miss I'm afraid but there are many good things and good intentions with the G4 kit. Sadly it's the detail that brings it all unstuck and the width is actually preposterous! People will hate the width of this thing.
  12. Irish John

    Irish John Guest

    Catastrophic near-death GT1 Steering failure

    Today the GT1 cruisers steering snapped where the head joins the stem. It is a very very dangerous design for a joint between head and stem to begin with but to see how catastrophic the failure was see:
    Put your brown trousers on before looking at the pictures! The rider is lucky to have survived.
    The above appraisal of the GT1 should now be amended pending a total product recall for safety reasons.
  13. Foximus

    Foximus Member

    Perhaps I missed it in your first post, but where do they sell this bike and how much do they cost?
  14. Irish John

    Irish John Guest

    They only sell on Ebay and the guy has gone to Thailand until 29 Sept.
    Until he fixes the stem problem I don't think he'll be allowed to sell any more.
    I forget what they cost but its probably $400.