6th gear kit????

[pulsepat]

Hi all.

Whilst looking through old posts I found a 6th gear mod/kit mentioned. Has anyone done it? How much does it cost? Is it hard? Do I just need the gear selector cyinder and sixth gear cogs from a suzuki gs or something? Do I need to split engine? Will it mess with the digital gear screen or just go blank in 6th gear then light up 5 when you change down....? Can somebody please ellaborate or point me in the right direction..... Im very inteterested. Many thanks.

[td_ref]

If you have all it takes probably worth a try. I had the 6th gear thought when I released the upgraded engine had some more power at 5th/last gear. I found a Haojie component, but the real problem was to built it properly. Too much to ask a local technician for. I went for the sprocket option, front add up 1 tooth, rear reduce by 2. Top speed 110km/h (gps) at 11000rpm. reaching 8000rpm at 5th gear was easy, which passes 85km/h.
Let me know the result if you insisted the 6th gear install.

[td_ref]

have you replace 125cc to 150cc bore kit? You probably need to replace a bigger main jet for carb as well.

[pulsepat]

Hi thanks..... So it looks like I might have to hold off on the 6th gear project for now. From what I can tell ill have to split the crank case anyways.... Ill look more into 150 with flat top piston and stronger con rod.... OOOORRRR - Possibly do a complete tear down all at once adding bigger valves, cam, 150 kit, bigger carb and 6 speed gear box..... Who knows..

BUT.!

One thing im very interested in is your sprocket results Td_ref.... I put a 17 tooth sprocket on the front and whilst it lengthened the gears iv gained no top end. Now surely if I go smaller on the back it will lose torque/ bottom end real bad!!!?? Are you getting your speed results with just a sprocket change? Do you have aftermarket exhaust? Bigger jet/carb? 150 kit fitted?
Cheers

[euphonius]

As a lifelong bicyclist, I've been watching these sprocket discussions with great interest for many months. My first bicycle had just one gear (and a coaster brake). My second bike was a Raleigh with the classic Sturmey-Archer internal 3-speed changer, which gave me an amazingly good range of gearing. Next came a 10-speed "racing bike", which I actually raced (without winning). What stuck with me, however, was that the gearing range of the 10-speed was not much greater than the 3-speed; it just had more and finer steps between highest and lowest. Actually, with the 10-speed there was already redundancy. With the small chainring in front and a small sprocket in back, I could achieve roughly the same gear as with the big front chainring and a bigger rear sprocket.

Many racing bikes later, the latter of which had 6 sprocket freewheels in back (there, now I've dated myself), I got a mountain bike that had a third chainring up front, allowing for the "granny gears" supposedly needed for climbing steep hills. Truth be told, those lowest gears were almost never used even on steep pitches; as a longtime road rider, it made more sense to me to select a moderately low gear and stand up and muscle the bike up the hill. (Never won any mountain bike races either, but, well, I never entered.)

During nearly a decade cycling in Manhattan, including long slushy/muddy winters, I came to hate the exposed derailleur gearing, and reverted to internal gearing. By then, Sturmey was finally updating its 100-year-old hub technology with alloy and sealed bearings and, in a nice twist for urban mudbunnies, internal drum brakes. First came a 3-speed set with the same range as the ancient steel hubs, then came a 5-speed, and finally a 7-speed. I built wheels around them all, and loved them all. I could build very robust wheels with straight-gauge 2mm zinc spokes and very strong alloy rims. With the weight concentrated at the center of the hub, rotational inertia was reduced, and the available gearing really came into its own.

Alas, in those years, the cycling mainstream had other ideas, cranking out obscenely stupid cassette freehubs with 10 or perhaps even more sprockets in the rear, and there were probably mountain bikes with four front chainrings. Gullible customers would think: "Wow! A 36-speed bike! That must be even faster than a 27 speed bike!" Most of those bikes disappeared into the garage or basement rarely to be ridden except when Oprah got fat and went on a diet.

Venerable Sturmey lost heart, went bankrupt and the space-age production line was packed up and shipped to Taiwan, sold along with its patents to to SunRacer. This seems to have been a good move. SunRacer canceled the 7, but launched an internal 8 that comes with or without the internal drum brake. This is on my wishlist, to replace the Shimano 3-speed I have in my Shanghai pushbike, a Giant Khan, which is a dual sport bicycle if there ever was one. Not as good as a dirt bike in the dirt, but it'll serve me on most any road or trail, paved or not. It's not a "hybrid" or a "mountain bike" or a "city bike". It's a modern version of the Raleigh 3-speed, one of the greatest bicycle designs ever. With 8 speeds and a modern Taiwan pedigree it'll be the bee's knees, better even than my Beijing Khan with its 15-year-old English-made Sturmey internal 7. But I seriously, seriously digress....

The moral here is that there's actually only limited utility in adding the sixth gear. Yes, when I'm on the expressway (scoffing at made-up local no-motorbike laws) pushing 120kph, my foot always itches for a sixth gear, and sometimes I even pull try to shift, only to remind myself I've maxed out with five. And then I realize that the Jialing, well, she's purring along pretty well at 120kph, and still nowhere close to redline. She won't quite jump if I hit the throttle at that speed, but she does respond, and willingly gives me 130 or 135, which is 80+ mph. I know she'll give more but I've no burning ambition to take her there. Not too bad for 40 horsepower (29 kW) at 6500 rpm.

So I just take a deep breath, and start remembering my lessons from my long history of bicycling. Having five well-spaced gears, with a lowest gear ratio that will help me through tricky or compromised uphill starts on, is surely the moral equivalent of having six gears.

td_ref has said as much in his pithy short post. Get the ratio of your lowest gear to match the engine's power and your riding style, accept that your 200cc qingqi is never going to be a wheelie bike or a drag-race contender, and the top end should take care of itself. More than likely, the addition of a sixth gear, with all the expense and time and technical challenge that implies, might be a big letdown if you end up having to reduce the front sprocket or increase the rear in order for your little powerplant to push that big gear!

cheers!

[MJH]

That's funny I totally agree, I have 15 speeds and only use maybe three and get frustrated having to jump past the others.

I am going to have the 16 tooth put on my motorcycle next oil change, I want to be in fifth with less rpm. In that I will likely be in fourth more often. I do not suspect 1-3 will be much longer but maybe.

If you go the other way it will scream like a banshe and then a six gear would be useful.

[MJH]

The other concern is the ratio of inner gear and the outer gear and stress on the shaft. It can wear and then you could loose alignments and eventually destroy the transmission. The reason I have been reluctant to change the front sprocket, that is the one that matters most. Then the back can impact the rear axel also same scenario.

There are reasons to leave it stock, but when it is Chinese you wonder if they got it correct in the first place? As in was this engineered or was it just configured? Lots of times you think it does not matter and it actually does and eventually the fact that it does will show up…miles later.

[euphonius]

There are reasons to leave it stock, but when it is Chinese you wonder if they got it correct in the first place? As in was this engineered or was it just configured? Lots of times you think it does not matter and it actually does and eventually the fact that it does will show up…miles later.

Very good observation. When bikes are cobbled together from available parts, you don't always get an optimally engineered configuration. All the more reason to cherish this forum and the willingness of members to try things out. We've seen a lot of that kind of ferment in the bobber threads, and the net effect is to improve the performance of those less-than-optimally engineered bikes for everyone.

Round of applause to the tinkerers!


cheers

[td_ref]

One thing im very interested in is your sprocket results Td_ref.... I put a 17 tooth sprocket on the front and whilst it lengthened the gears iv gained no top end. Now surely if I go smaller on the back it will lose torque/ bottom end real bad!!!?? Are you getting your speed results with just a sprocket change? Do you have aftermarket exhaust? Bigger jet/carb? 150 kit fitted?
Cheers

You have to open crank case to access transmission component.
I can't remember the stock sprocket configuration, there is website can help you calculate how many tooth sprocket to reach certain top speed.
In your case you have to do something about the powerplant, otherwise the sprocket modification wouldn't do much top end speed.

[euphonius]

I remember someone posting an elaborate chart somewhere here in MCM about front/rear sprocket sizes and gear ratios.