139QMB Gearbox Upgrade How-To

[Enviromoto]

I installed a set of my Naraku Gear sets for a customer and took pictures to show how its done. We were both very satisfied with the results.

List of upgrades:

Stage 4 Powerpack
NCY Performance Cam
Leo Vince Exhaust
Naraku 72cc Variator Kit
7GDr Pulley Sliders
1500 Pill Springs
High Performance Coil
High Performance CDI
95 Main Jet
Malossi Kevlar Belt
Naraku Gear Set

Before the gear set upgrade this scooter would accelerate very hard and top out around 52 mph gps (still breaking in). After the upgrade acceleration was close to the same but the top end gained about 10% = 5 mph. GPS is now reading 57 mph on a long stretch 50 mph all day long with more power on tap. I wouldnt recommend this upgrade for a stock engine but it is a must have for the 72cc and above engines.

Here is how its done.

Remove CVT components.







Drain gear oil



Remove rear tire



Remove rear brake cable





Remove the 6 bolts holding the gear box to the case. Take note that there is one long bolt in this batch. Make sure it goes back in the right location.



Make sure your drain pan is handy to catch the remaining oil





Stock gears are a 52/15 gear set about 95% of the time

Naraku gears are 52/14 giving you about 10% more top speed without sacrificing acceleration.



The bearings



Naraku Gears





The large drive gear just slides off, easy as pie



The combo gear just slides out of the bearing, easy peachy



Old gears out



Make sure you use this nylon spacer on the new gear







Clean all the old gasket off of the gear box



Install gears the same way they came off, super easy





Add a little gasket maker to the case and install the gasket







Slide the two halves back together, take care to make sure the gears line up with the bearings



Use a little dab of blue locktight on the case bolts





Hand tighten to about 15 ft lbs and fill the gearbox, check for leaks.



Reinstall the tire and CVT components, nows a good time to check your rollers and belt for wear.







Done and done. How easy was that!

The Naraku Gear set is only available at Enviromoto.com

[90GTVert]

Great write up Jermey. Thanks for the how-to info. I was wondering how long it would take for these Naraku gears to show up. Great set, no bearings to press on or any of that stuff.

You think these can take my Sunl from 35MPH to 57MPH? lol

[2strokd]

Good job Jeremy! It does look cake without having to use the press or anything . I will keep those in mind for my gy6 customers that run outta gear.
lol yeah, those should work on Brents Sunl and get er up past 50 no problem right ?

[Enviromoto]

From my understanding these gears offer better top end because they keep your rpms up all the way through to your top speed.

Stock gears = 52/15 3.46 ratio (better for daily drivers)
Naraku gears = 52/14 3.71 ratio (better for the track)

[90GTVert]

I didn;t even pay any attention to the numbers, just assumed they were upgears. Oops. Whatever works. In your customer's scenario, I'd still think the Naraku gears were better for daily driving. Should hold your cruise speeds on hills and against wind a little easier. I guess it depends how you ride. If you wanna ride 35 with max fuel economy, I guess stock is better..

[2strokd]

aahh, i c

[stepthrutuner]

Nice presentation. What brand and model scooter is that?

[Enviromoto]

Thanks guys. That is just your regular ol' Roketa MC-08.

[lackthereof]

From the pictures, it looks like the stock gears have angle-cut teeth and the Naraku gearset has straight-cut teeth. Is that right?

Can you hear much of a whine from the straight-cut gears, or is it just drowned out by all the other noises these things make?

[2strokd]

They whine!
Supposedly there is less drag with the straight cuts...
Makes sense to me

[90GTVert]

The Naraku is angle cut too. I don't hear any whine with mine. The only whine is me crying about my lost MPH. lol

[highmoose]

another GOOD info page

[tj]

I ordered this kit for my taotao thunder 50. Spent 3 hours tearing it all down to find out that its the same gearing... www.scooterdynasty.com/gearsnarakufinaldrivefor50cc4-stroke139qmbscooters.aspx . I sent it back and ordered this kit. I'm going to put it on this week hopefully we will see some improvement www.ebay.com/itm/171650922644?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT . I like the Naruku gear set because you dont have to press off that other gear but again you will and learn.

[katastroff]

You sir just got BOOKMARKED!!!!

[humanshield]

I'm contemplating a final drive ratio change. I guess from reading this thread it's better to open it up and see whats actually in there (if you can't find out from the manufacturer or a reliable source) before ordering.