More Bad News About Grubee G4 Gearbox

[Irish John]

Is the steel CAPABLE of taking a temper, but it just hasn't been tempered ?

Have you considered disassembling one, and tempering the thing, yourself ?

It's not a practical idea Luka - I doubt if it could be dissemled enough & I doubt if it would work, This home blacksmithery is what someone did with that appalling piece of junk the JL Hoot gearbox. There comes a point when you need to walk away from junk and buy something better. I know the EZM belt drive is expensive because it is made in the USA (although my experience of wages in USA factories is that they are very low compared to the rest of the Western economies) but it is a good bit narrower and it surely has to be better than the G4 because it was designed by an MBc member who actually rides bikes. This has to make a BIG difference but I still haven't seen one in the flesh. That would be my advice to Hollbrook above - shell out the extra cash, sleep soundly knowing you aren't subsidising slave labour, and get something that performs adequately for the purposes for which it was designed.
I'll get my friend who I made the G4 rig for to count the teeth but I have really no further interest in this hopeless piece of junk. Suffice to say that the ratios are wrong and their excuse is that they are safer operating less speed given recent hoo-haa about Mbs speeding along roads etc.
Hollbrook, why not call Quenton and ask him to send you the pulley wheels or something so you can build your own. Please don't get the G4 because it only encourages voracious businessmen and rewards them for ripping us off.

 

[Irish John]

I think I'll take your advice and leave the G4 alone right now. I think they had a durn good idea- but ruined it by not doing all their homework. I really appreciate the info.
Thanks.

That's what they are noted for - spoiling good ideas by shonky design, shonky materials and shonky workmanship and most insulting of all they don't bother to listen to their customers, test their shonky products nor do they read these pages. It is unforgiveable that they cannot hear anything over the noise of their rattling cash registers.

 

[biketec]

WOW never ceases to amaze me!!!
The gear ratio is 5:1, 20 drive 100 driven

 

[biketec]

So there's a few minor things wrong with a new setup, hence G4 not G1 you have to keep swingin its evolution!!! Heck I think every Mb on the market has an issue or two ( depending on user ) that could be fixed one way or another and to me, as a rider from day one enjoy the task's and engineering one faces every time we build a bike that's the beauty of it. I dont drive a VW because its some marvelous creation that never works! It's because its a part of me and its what I love to do thats what makes it fun just playin around on your bike.

P.S. your the one selling bikes with kits on them, why do you do it???

If you want my opinion in engineering! Loose the HS clutch go back to the old Gov. clutch (or US made if possible ) loose a half inch or more on the GB by doing that rotate box so its level on bottom, rising on top sell different size gears for all four if you really must and booom!!!! problem fixed

if we could only get all engine kits to mate I think we would be onto something!!!

Can I get a gold star next to my name?

 

[biketec]

SORRY for 3 post in a row but I had another idea, how about multiple mounting holes for different configurations of bikes and applications?

 

[Irish John]

So there's a few minor things wrong with a new setup, hence G4 not G1 you have to keep swingin its evolution!!! Heck I think every Mb on the market has an issue or two ( depending on user ) that could be fixed one way or another and to me, as a rider from day one enjoy the task's and engineering one faces every time we build a bike that's the beauty of it. I dont drive a VW because its some marvelous creation that never works! It's because its a part of me and its what I love to do thats what makes it fun just playin around on your bike.

P.S. your the one selling bikes with kits on them, why do you do it???

If you want my opinion in engineering! Loose the HS clutch go back to the old Gov. clutch (or US made if possible ) loose a half inch or more on the GB by doing that rotate box so its level on bottom, rising on top sell different size gears for all four if you really must and booom!!!! problem fixed

if we could only get all engine kits to mate I think we would be onto something!!!

Can I get a gold star next to my name?

My bikes have very little of the kit on them because anything I can't rely on I can't use. That's how I offer 12 month unlimited warranty. I accept that evolution is a necessary process but the G4 is a big step backwards. Wht fix it if it aint broke? The GB needs to loose 2.5" not half an inch Biketec.
If you look closely at one of my 4-strokes about the only things I use are the tanks (totally repainted, vinyl trim around seam, kreemed and bedded on dense foam; the cables are standard but fully greased; the throttle reel is metal, and the exhaust and gearbox are standard but the rest is all different because I want them to last and I don't want people banging on my door saying I built them a dud and wanting recompense. The engine tray is re-engineered to hold firm and the engines are Honda although I have no beef with the HS my customers don't trust it. The freewheels are standard because I can't find a decent one to replace it but I would if I could because they are seriously sub-standard. If Grubee rode his bikes even for just a week things would probably be very different.
The G4 is wrongly geared and too wide and if I'm being accused of being harshly critical of it that's good because it deserves to be criticised because it was rushed onto the market without adequate testing - without any testing actually. The sad thing is it didn't have to be that way.
For the G4 to work it needs to be made with a different ratio, made narrower, the cover brackets made stronger cos they snap from vibration, the freewheel to be built with hard steel, the engine tray redesigned so it doesn't rely on steel threads into aliminium block, the fuel line made from proper plastic' the Chinese bolts replaced with quality bolts made to a high tensile SI, the correct size sprocket sold with the GB (just for once actually getting that right) and then it might be worthy for sale to the public.

 

[Hollbrow]

Thanks

Biketec, thanks for the ratio info. 5:1- I would have thought it would be a higher ratio than that just looking at it.

My current set up is a rack mount Honda GX35, 78mm clutch drum with a 7 Tooth #25HD sprocket going straight down to a left hand freewheel on the hub with a 125 tooth #25HD sprocket. This gives a straight 17.85:1 ratio. It is very light, and does really well considering the low power of the GX35. It will pull away nicely, and go up a hill, and still has pretty long legs on the straightaways. Of course, I do have mods done to the 35- mild porting, and
a 12mm carb on it. If it weren't for chain management issues with the little 25HD chain (pocketbike chain), I wouldn't be considering changing to a gearbox.
I need something that will positively stay on the sprockets over bumps and whatnot. Even with guides and idler sprockets the system flexes enough that the chain can jump- usually at the worst possible time. I have always wanted to do a planetary drive- but have not hit an anything that would work that is the right size, and they are to complex to just fabricate.

 

[bubbatgs]

I had this same problem!!! I found that it was the retaining nut would back off within ten miles! I used red locktight before installing. Since I found this problem... I have had no more problems

 

[Sean.au]

Hi bubbatgs, my second drive sprocket has just died, a week before the first incident I noticed retaining nut had come off and replaced with high quality lock nut. The luck nut has retained correct position on both incidents.

 

[Irish John]

Hi bubbatgs, my second drive sprocket has just died, a week before the first incident I noticed retaining nut had come off and replaced with high quality lock nut. The luck nut has retained correct position on both incidents.

Sean I thought the freewheel drive sprocket was retained with a small M4 bolt that screwed into the end of the final gearshaft. You talk about using a locnut - how can a nut go into a threaded hole?
I've always used threadloc to hold that bolt in place but maybe the torque from the G4 is causing yours to come loose.
I also recommend undoing the freewheel and installing more grease then using blue threadloc to close the flange. Freewheels should be threadlocked in the factory cos that is standard in the bike industry but these ones are not assembled using standard practice.
I think lowering your motor by using the wide 3 pc crank should definitely help get a better line of drivetrain and the freewheel might last longer.
Ultimately I think we now know that the freewheel cannot stand up to the forces exerted from the G4. It is a product flaw and any recompense must come from the manufacturer but I doubt that will happen. I'd have to recommend buying a Mark 2 or Mark 3 Grubee GB as a replacement but then you'd need a 50T rear sprocket & that might present fitting problems.
You can tell the makers don't ever test these products - no need to when they've got us!