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 The Definitive Zuma/BWS FAQ 
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Post The Definitive Zuma/BWS FAQ
There are questions that occur on a fairly regular basis. I have prepared this FAQ as a starting point for new or prospective Zuma50/BWS 50 owners. This FAQ is geared towards the North American market, so there might be some things in this FAQ that are inaccurate for the European or Asian versions of the BWS.

PLEASE LIMIT YOUR RESPONSES AND REPLIES TO THIS THREAD. I WANT TO KEEP THIS THREAD FAIRLY "CLEAN".
I SET UP A "DISCUSSION" THREAD SEPARATELY TO PROVIDE COMMENTS, NOTIFY ME OF ERRORS, AND REQUESTS FOR ADDITIONS.
The discussion thread is at viewtopic.php?f=39&t=11751

EACH MAJOR SUB-HEADING WILL BE IN ITS OWN "REPLY" AND WILL BE INDEXED/LINKED IN THE TABLE OF CONTENTS
I will edit this first post periodically as changes are made.

I will alos be creating a downloadable version once things are further along.

Version History
0.2 (May 9, 2010) – Initial FAQ posted on ZumaForums.net. Many unanswered “placeholder” questions and one-word answers.

TABLE OF CONTENTS

GENERAL viewtopic.php?f=39&t=11750#p156363
1. What is the Zuma 50?
2. What is the BWS 50?
3. What is a Bugeye or Prebug Zuma?
4. Besides the looks, are there any differences between the Bugeye and Prebug Zumas?
5. Why don’t I see Zumas from the 2006 and 2007 model years?
6. What are the differences between the 2002-2005 Bugeye and the 2008 and newer Bugeyes?
7. What sort of gas mileage does the Zuma 50 get?
8. How fast does the Zuma 50 go?
9. Can I Take my Zuma 50 on the Highway?
10. Can two people ride on the Zuma?
11. What type of oil does the Zuma use?
12. How often do I need to fill up the injector oil reservoir?
13. My Zuma has smoky exhaust!

MODIFYING A ZUMA viewtopic.php?f=39&t=11750&p=156371#p156371
1. How can I make my Zuma go faster?
2. What should I change first if I want to go faster?
3. Do I need to use premix if I modify my Zuma?
4. Why can’t I just bolt something on?
5. What tools do I need to modify my Zuma?
6. What is this Service Manual I read about everywhere?
7. How reliable are modified Zumas?
8. How do I do the Dual Headlight mod?

JETTING AND CARBS viewtopic.php?f=39&t=11750&p=156376#p156376
1. What is jetting and why is it important?
2. What is a plug chop?
3. What happens when I run my engine lean or rich?
4. What is the Throttle Mod?
5. Can I use my stock carb when I change my cylinder or exhaust?
6. Why are there two lines running between my gas tank and the carb?
7. I took my carb off and now I can’t figure out what line goes where!
8. What are reeds and where are they located?
9. When should I replace the stock metal reeds?
10. What is this raising and lowering of needles I hear about?
11. What is the stock jet size?
12. What is upjetting and how do I do it?
13. How do I adjust the air-fuel mixture on my carb?
14. How do I change from a 2-cable throttle (stock carb) to a one-cable throttle (aftermarket carb)
15. How do I change from a automatic choke to a manual choke?
16. I think I'm running lean so I'm adding a capful or two of oil to each tank of gas. Is this correct?

EXHAUST MODIFICATIONS viewtopic.php?f=39&t=11750&p=156380#p156380
1. What do I need to consider when choosing an aftermarket exhaust?
2. Are aftermarket exhausts loud?
3. Why does my scooter perform poorly after I changed the exhaust?
4. Can I use the stock exhaust on a big bore kit?
5. What is this extra piping running between the airbox and the exhaust on my 2008+ Zuma?

CYLINDER MODIFICATIONS viewtopic.php?f=39&t=11750&p=156385#p156385
1. What is a big bore kit (bbk)?
2. What should I consider when choosing a big bore kit?
3. Can I use my stock carb and/or exhaust with a big bore kit?
4. Can I change to a liquid cooling?
5. Do I need to change my crankshaft when I go to a bbk?
6. What sort of reading should I get when I do a “compression test”?

TRANSMISSION MODIFICATIONS viewtopic.php?f=39&t=11750&p=156387#p156387
1. What is a variator?
2. Can I use my stock variator rollers with my aftermarket variator?
3. My new exhaust pipe came with new rollers and springs. Do I need to use them?
4. Do I need to use a Kevlar belt when I upgrade my Zuma?
5. My transmission is running badly and I have lousy acceleration What happened?
6. My Zuma isn’t as fast as it used to be.
7. What is upgearing (what are upgears)
8. Can I upgear my stock Zuma to get more speed?
9. What is an Over Range Kit. Is this the same as upgears?

_________________
YELLOW 2008 BWs 50 - Zumaforums Member #2057
dual headlight mod, C3 Mirrors, TinyTach, JDM Tail light, Low Canadian OEM windshield
Top Performances Trophy 70 cc, MotoForce 17.5 mm PHVA clone 90 main jet (still tuning) with Stage6 Choke lever next to key
Malossi Variator 6 x 5.5g rollers (still tuning) Malossi Delta Clutch Red springs, (still tuning) Malossi Yellow contra spring (still tuning)
YES Muffler(Canadian, eh)
Stage6 43/13 Primary gears. 10.94 final drive ratio
COMING: STR8 oversized fan, Motoforce Evolution crank


70 cc of scootin' pleasure


Last edited by nifty50 on Mon May 10, 2010 10:52 am, edited 8 times in total.



Sun May 09, 2010 8:41 pm
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Post Re: The Definitive Zuma/BWS FAQ
GENERAL QUESTIONS

1. What is the Zuma 50?
The Zuma 50 is a 2-stroke scooter manufactured by Yamaha. It is called the BWS (short for Big Wheel Scooter) elsewhere in the world.

2. What is the BWS 50?
The BWS 50 is the Zuma 50 as sold in Canada and elsewhere in the world. The Canadian BWS 50 and US Zuma 50 are mechanically identical, with the only differences being cosmetic (stickers) and the speedometer/odometer (the Canadian BWS reads in km/hr to 80 km/h, and its odometer is in km). There are a few subtle mechanical differences between the Canadian BWS50/Zuma 50 and the BWS50 sold elsewhere in the world.

3. What is a Bugeye or Prebug Zuma?
The Bugeye Zuma refers to the configuration of the headlights in the 2002 and newer Zumas. The Bugeye has two large headlights as, hence the “bug eyes”. The Prebug Zuma refers to the older style from 2001 and earlier. Two smaller headlights characterize it.
Attachment:
File comment: A Prebug (left) and Bugeye (right)
prebug+bugeye.jpg
prebug+bugeye.jpg [ 112.58 KiB | Viewed 187779 times ]


4. Besides the headlights, are there any differences between the Bugeye and Prebug Zumas?
Yes. There are two major differences between the Bugeye (2002 and newer) and Prebug (2001 and older) Zumas:
• The Prebug uses an engine with the cylinder in the vertical direction. The Bugeye uses an engine with the cylinder in the horizontal position.
• Because of the vertical engine, the prebug has little underseat storage, and its wheelbase is about 4” (100 mm) shorter

5. Why don’t I see Zumas from the 2006 and 2007 model years?
Yamaha did not manufacture the Zuma in 2006 or 2007, although there were some BWS’s sold in Canada as a 2006. The Zuma returned in 2008 with some mechanical changes compared to the 2002-2005 models.

6. What are the differences between the 2002-2005 Bugeye and the 2008 and newer Bugeyes?
The re-introduced 2008 Zuma included changes to reduce emissions. This included the addition of a catalytic converter to the exhaust, a restricted throttle range, and some internal changes to the carburetor. There was also a change to the gearing in the transmission, making the 2008+ models theoretically capable of going faster than the 2002-2005 models. In general these changes affected performance negatively in terms of both acceleration and top speed.

7. What sort of gas mileage does the Zuma 50 get?
Fuel economy is dependent on the condition of the scooter, where you live, and how you drive. Don’t expect anything near what is advertized. Real-world fuel economy is likely in the 65-75 mpg (US gallons) or 3.2-3.6 liters/100km range (your mileage may vary ;) Most modifications done to increase performance will decreased fuel economy.

8. How fast does the Zuma 50 go?
In stock form, you can expect top speeds in the hi 30’s or low 40’s mph (60-70 km/h). Most modified Zuma 50’s have a top speed in the high 40’s to mid 50’s mph (60-85 km/h), and highly modified Zumas are capable of speeds in excess of 65 mph (100 km/h). Highly modified Zumas are typically not suitable as a daily commuter scooter, due to potential reliability issues, and are usually used for racing only.

9. Can I Take my Zuma 50 on the Highway?
Highway riding on a 50 cc scooter is NOT recommended, even when modified for additional speed. It may be illegal in some jurisdictions.

10. Can two people ride on the Zuma?
Yes. The seating is designed to accommodate two people.

11. What type of oil does the Zuma use?
The Zuma/BWS uses a 2-stroke engine, so ALL of the engine lubrication is delivered through the fuel system. There is no “wet sump” like in a 4-stroke engine. Use a quality 2-stroke oil. Since the Zuma uses an autolube pump to “inject” oil, you must use 2-stroke oils specifically designed for autolube or injector systems, rather than for “premix” only. Full synthetic or semi-synthetic injector oils are preferred: less gumming of engine components and less smoky exhaust.
There is also gear oil in the transmission. Good quality hypoid gear oil, either 10W30 or 85W140 should be used in the transmission. Do not confuse typical 10W30 motor oil with hypoid gear oil. They only happen to have the same viscosity. Use Gear Oil NOT Engine Oil in the transmission.

12. How often do I need to fill up the injector oil reservoir?
A good rule of thumb is that you can go 500 miles/800 km on a single tank of injector oil (1.4 litres). However, it is NOT recommended to run the tank dry! If you run out of injector oil the engine WILL seize, which can be both dangerous to the rider and costly to repair. It is best to top up the injector oil every 3-4 gas fill ups

13. My Zuma has smoky exhaust!
All 2-stroke engines have some amount of smoke in the exhaust. Two-strokes are often quite smoky when cold, but should be nearly smokeless when warmed up. Good quality semi-synthetic or full-synthetic injector oil is usually less smoky than “bargain brand” injector oils

Back to Table of Contents http://www.zumaforums.net/phpBB3/viewtopic.php?f=39&t=11750&p=156360#p156360

_________________
YELLOW 2008 BWs 50 - Zumaforums Member #2057
dual headlight mod, C3 Mirrors, TinyTach, JDM Tail light, Low Canadian OEM windshield
Top Performances Trophy 70 cc, MotoForce 17.5 mm PHVA clone 90 main jet (still tuning) with Stage6 Choke lever next to key
Malossi Variator 6 x 5.5g rollers (still tuning) Malossi Delta Clutch Red springs, (still tuning) Malossi Yellow contra spring (still tuning)
YES Muffler(Canadian, eh)
Stage6 43/13 Primary gears. 10.94 final drive ratio
COMING: STR8 oversized fan, Motoforce Evolution crank


70 cc of scootin' pleasure


Last edited by nifty50 on Mon May 10, 2010 11:04 am, edited 2 times in total.



Sun May 09, 2010 8:47 pm
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Post Re: The Definitive Zuma/BWS FAQ
MODIFYING A ZUMA
1. How can I make my Zuma go faster?
A combination of exhaust, cylinder, carb, and transmission changes.

2. What should I change first if I want to go faster?
Typically, the order of upgrading is exhaust, big bore kit, carb, variator, clutch, gearing, over-range variator. If you have a 2008or newer, the very first thing you need to do is the throttle mod. (See viewtopic.php?f=39&t=2702)

3.Do I need to use premix if I modify my Zuma?
Generally no. Only highly modified racing systems with large carbs need to premix. Typical sports class big bore kits are fine with the autolube system.

4. Why can’t I just bolt something on?
To work properly, you must balance many different aspects of the scooter. There is a ripple effect to modifications. Almost any modification will unbalance something else. In very broad terms, you must balance carburetion (air , gas, oil), CVT (variator weights) and clutch (including clutch springs and contra(st) spring. The 3 C’s of scooter tuning.

5. What tools do I need to modify my Zuma?
The “must have” tools include:
    The service manual (available as a free download at http://www.zumaforums.net/downloads.html)
    Metric wrenches/sockets, specifically 10 mm, 12 mm, and 17 mm
    No 3 Philips screwdriver
    5 mm hex wrench
    Strap wrench
    Large adjustable wrench
The “should have” tools include:
    Impact wrench (electric ones work well and are inexpensive) with 17 mm impact socket (arguably a “must have” tool)
    Torque wrench (3/8” ones are best since they are calibrated to the range of specified torques found in the scooter.
    41 mm (2002-2005)or 38 mm (2008+) to disassemble clutch
    Awl or snap ring pliers (clutch springs)
    Vise grips
    Gear puller
    Digital multimeter
    Electric screwdriver or cordless drill with adjustable torque (removing & replacing panel bolts)

6. What is this Service Manual I read about everywhere?
The service manual is the “bible” of do-it-yourself maintenance and modification of the Zuma or BWS. It explains how to properly disassemble and re-assemble every aspect of the scooter, gives troubleshooting information, provides specifications, and is a MUST HAVE for anyone even contemplating doing their own maintenance or modifications. It is available as a free download at http://www.zumaforums.net/downloads.html

7. How reliable are modified Zumas?
Modified Zumas can be nearly as reliable as a stock setup. Modified Zumas will have increased maintenance requirements compared to stock, with the most notable being are more frequent ring changes and more frequent roller and/or belt changes. If you don’t know what you are doing, modifications can turn out being un-reliable.

Back to Table of Contents viewtopic.php?f=39&t=11750&p=156360#p156360

_________________
YELLOW 2008 BWs 50 - Zumaforums Member #2057
dual headlight mod, C3 Mirrors, TinyTach, JDM Tail light, Low Canadian OEM windshield
Top Performances Trophy 70 cc, MotoForce 17.5 mm PHVA clone 90 main jet (still tuning) with Stage6 Choke lever next to key
Malossi Variator 6 x 5.5g rollers (still tuning) Malossi Delta Clutch Red springs, (still tuning) Malossi Yellow contra spring (still tuning)
YES Muffler(Canadian, eh)
Stage6 43/13 Primary gears. 10.94 final drive ratio
COMING: STR8 oversized fan, Motoforce Evolution crank


70 cc of scootin' pleasure


Last edited by nifty50 on Sun May 09, 2010 10:38 pm, edited 4 times in total.



Sun May 09, 2010 9:02 pm
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Post Re: The Definitive Zuma/BWS FAQ
JETTING AND CARBS
1. What is jetting and why is it important?

2. What is a plug chop?

3. What happens when I run my engine lean or rich?

4. What is the Throttle Mod?
One of the changes done to reduce emissions of 2008 and newer Zumas was to restrict “full” throttle to about half of what it was on the 2005 and earlier models. This restriction severely limits acceleration, and has some impact on top speed. The T-mod involves physical modification of the throttle cam to allow full range of motion, effectively changing it back to the shape found in 2005 and earlier. The T-mod is considered “essential” by many people, and may actually be conducted by the dealer when buying new without affecting warranty.

The T-mod can be done by anyone with only basic tools. A rotary tool like a Dremel ™ or similar is recommended, although it can be done with a hacksaw and a file. Once you have the carb removed, it takes about 20 minutes to complete the t-mod itself, but it will take first-timers about 2 hours from start to finish

An excellent writeup of the throttle mod can be found here: viewtopic.php?f=39&t=2702

5. Can I use my stock carb when I change my cylinder or exhaust?
Yes, but some adjustments will be required to the carb’s jetting (mainjet and/or needle jet position). Typically,

6. Why are there two lines running between my gas tank and the carb?
The larger line is the line that actually carries fuel. The second line runs the vacuum-activated valve at the bottom of the gas tank. The valve only lets fuel flow when there is vacuum applied . The vacuum is created by the crankcase while the engine is running.

7. I took my carb off and now I can’t figure out what line goes where!
There are three (3) lines attached to a stock carb: fuel line, oil line and vacuum line.

Attachment:
File comment: Stock carb from a 2008 BWS
stock carb labelled 1.jpg
stock carb labelled 1.jpg [ 675.82 KiB | Viewed 187783 times ]

Attachment:
stock carb labelled 2.jpg
stock carb labelled 2.jpg [ 763.66 KiB | Viewed 187783 times ]

Attachment:
stock carb labelled 3.jpg
stock carb labelled 3.jpg [ 890.47 KiB | Viewed 187783 times ]


8. What are reeds and where are they located?
Reeds are located in a “cage” at the crankcase side of the intake manifold. They are essentially one-way valves for the air-oil-fuel mixture from the carburetor.

9. hen should I replace the stock metal reeds?
Metal reeds can cause significant engine damage if they fracture and send shards throughtout the interior of the crankcase. They should be replaced in accordance with the Service manual for a stock engine (no modifications) but it is suggested that the stock reeds be replaced with aftermarket carbon fiber or fiberglass reeds if the cylinder, exhaust, or carb is upgraded over stock. Carbon fiber or fiberglass reeds offer slightly better throttle response, but more importantly the softer materials will result in very little engine damage if they break or fracture.

10. hat is this raising and lowering of needles I hear about?
This refers to an ajustment to the eedle valve

11. hat is the stock jet size?
The stock jet size is #80 main jet.

12. What is upjetting and how do I do it?

13. How do I adjust the air-fuel mixture on my carb?


14. How do I change from a 2-cable throttle (stock carb)to a one-cable throttle (aftermarket carb)
With an aftermarket single-cable throttle and the provision of a throttle stop for the second cable

15. How do I change from a automatic choke to a manual choke?
With a short or long aftermarket choke cable. Some carbs may require adapters.

16. I think I'm running lean so I'm adding a capful or two of oil to each tank of gas. Is this correct?

NO! Adding oil to the gasoline actually makes things LEANER. "Lean" and "rich" refer to the amount of gasoline, not oil, in the mixture:

Attachment:
File comment: Adding oil to the gas tank makes things LEANER! Fix lean conditions using jetting, not more oil!
why autolube+premix is leaner.jpg
why autolube+premix is leaner.jpg [ 176.02 KiB | Viewed 187771 times ]

Return to Table of Contents viewtopic.php?f=39&t=11750&p=156376#p156360

_________________
YELLOW 2008 BWs 50 - Zumaforums Member #2057
dual headlight mod, C3 Mirrors, TinyTach, JDM Tail light, Low Canadian OEM windshield
Top Performances Trophy 70 cc, MotoForce 17.5 mm PHVA clone 90 main jet (still tuning) with Stage6 Choke lever next to key
Malossi Variator 6 x 5.5g rollers (still tuning) Malossi Delta Clutch Red springs, (still tuning) Malossi Yellow contra spring (still tuning)
YES Muffler(Canadian, eh)
Stage6 43/13 Primary gears. 10.94 final drive ratio
COMING: STR8 oversized fan, Motoforce Evolution crank


70 cc of scootin' pleasure


Last edited by nifty50 on Mon May 10, 2010 10:59 am, edited 2 times in total.



Sun May 09, 2010 9:17 pm
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Post Re: The Definitive Zuma/BWS FAQ
EXHAUST MODIFICATIONS
1. What do I need to consider when choosing an aftermarket exhaust?

There are 3 general types of aftermarket exhausts: “touring”, “tuned” and “racing”. Touring exhausts are generally close to stock in noise levels, but provide better flow characteristics and low-to midrange RPM power increase. “Tuned” exhausts have expansion chambers and a muffler section connected with a 180-degree connection. Tuned pipes offer increased power gain over stock or “touring” exhausts, but generally in a higher and narrower range in engine RPM’s. Tuned exhausts are louder than stock. “Racing” exhausts are highly tuned expansion chambers for high-revving engines and provide their power at even higher and narrower range in engine RPMs
The aftermarket exhaust should be matched to the cylinder and carburetor that it will be attached to. A racing exhaust would be terrible on a stock cylinder, for example. An exhaust that works well on a 50 cc engine might perform poorly on a 70 cc engine. If you spend much of your time in stop-and-go traffic, you need the low to midrange gains of a “touring” exhaust since you are rarely at high RPMs

2. Are aftermarket exhausts loud?
Depending on the intended performance range of the exhaust, aftermarket exhausts can be from slightly louder to very much louder than stock.

3. Why does my scooter perform poorly after I changed the exhaust?
Because the power characteristics of the engine have changed, and the carburetion, CVT and/or clutch need to be re-balanced.

4. Can I use the stock exhaust on a big bore kit?
Yes.

5.What is this extra piping running between the airbox and the exhaust on my 2008+ Zuma?
The 2008+ Zumas have a catalytic converter. These “cats” need extra oxygen to work correctly, and this is supplied through a line running between the main airbox and the exhaust. The smaller “airbox” located above the CVT belt cover contains a 1-way reed valve to prevent re-circulation of exhaust gasses.

Return to Table of Contents viewtopic.php?f=39&t=11750&p=156360#p156360

_________________
YELLOW 2008 BWs 50 - Zumaforums Member #2057
dual headlight mod, C3 Mirrors, TinyTach, JDM Tail light, Low Canadian OEM windshield
Top Performances Trophy 70 cc, MotoForce 17.5 mm PHVA clone 90 main jet (still tuning) with Stage6 Choke lever next to key
Malossi Variator 6 x 5.5g rollers (still tuning) Malossi Delta Clutch Red springs, (still tuning) Malossi Yellow contra spring (still tuning)
YES Muffler(Canadian, eh)
Stage6 43/13 Primary gears. 10.94 final drive ratio
COMING: STR8 oversized fan, Motoforce Evolution crank


70 cc of scootin' pleasure


Sun May 09, 2010 9:23 pm
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Joined: Mon Aug 10, 2009 8:21 am
Posts: 1016
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Post Re: The Definitive Zuma/BWS FAQ
CYLINDER MODIFICATIONS
1.What is a big bore kit (bbk)?

A replacement cylinder and piston with a “70 cc” displacement. Sport: 2-ring cast iron; midrace aluminum single ring with porting; high ends racing not for daily use.

2. What should I consider when choosing a big bore kit?
Reliability/maintenance requirements vs performance. Cost. Willingness to do additional modifications. Many choose a “sport” bbk, consisting of a (relatively) low maintenance 2-ring cast iron cylinder with 10 mm gudgeon pin (to use the stock crankshaft). Higher performance can be gained by using a single-ring aluminum cylinder, possibly with an upgraded crankshaft.

3. Can I use my stock carb and/or exhaust with a big bore kit?
Yes, but consider a larger carb and highe performance exhaust to get the full benefit of a bbk. You will need to rejet (make richer)

4. Do I need to change my crankshaft when I go to a bbk?
Consensus says that the stock crankshaft is capable of sustained revving up to about 10000 RPM without difficulty. Most sports setups (2-ring cast iron bbk’s) will not rev higher than this, so there is no compelling reason to upgrade the stock crankshaft. Higher performance aluminum cylinders with high-revving exhausts and/or larger carbs should include an upgraded crankshaft to reduce the high potential for (catastrophic) failure of the stock crank. Cylinde kits with a 12 mm gudgeon will need an upgded crankshaft.

5. Can I change to a liquid cooling?
It’s been done, but it’s expensive and not for the faint of heart.

_________________
YELLOW 2008 BWs 50 - Zumaforums Member #2057
dual headlight mod, C3 Mirrors, TinyTach, JDM Tail light, Low Canadian OEM windshield
Top Performances Trophy 70 cc, MotoForce 17.5 mm PHVA clone 90 main jet (still tuning) with Stage6 Choke lever next to key
Malossi Variator 6 x 5.5g rollers (still tuning) Malossi Delta Clutch Red springs, (still tuning) Malossi Yellow contra spring (still tuning)
YES Muffler(Canadian, eh)
Stage6 43/13 Primary gears. 10.94 final drive ratio
COMING: STR8 oversized fan, Motoforce Evolution crank


70 cc of scootin' pleasure


Sun May 09, 2010 9:31 pm
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Joined: Mon Aug 10, 2009 8:21 am
Posts: 1016
Location: Edmonton, AB, Canada
Post Re: The Definitive Zuma/BWS FAQ
TRANSMISSION MODIFICATIONS
10. What is a variator?


11. Can I use my stock variator rollers with my aftermarket variator?
No. The stock roller size is 15 mm x 12 mm. Aftermarket variators for the Zuma usually use 16 mm x 13 mm

12.My new exhaust pipe came with new rollers and springs. Do I need to use them?
In general, yes. However, be careful of the variator roller size. Most rollers that come with exhausts will be sized for the stock variator (15 x 12 mm) and won’t work with aftermarket variators

13. Do I need to use a Kevlar belt when I upgrade my Zuma?
No. The OEM Yamaha belt is very good, even with significantly upgraded engines.

14.My tran smission is running badly and I have lousy acceleration. What happened?
Your rollers are too heavy or too light, your belt is worn, or you have a sticky contrast (or contra or torque) spring
Attachment:
variator setup.jpg
variator setup.jpg [ 555.01 KiB | Viewed 187767 times ]

15. My Zuma isn’t as fast as it used to be.
Flatspotted rollers or worn belt

16. What is upgearing (what are upgears)
Gearing consists of four gears arranged into two sets of two: primary and secondary. The number of teeth in the gear set makes up the gear ratio, and if you multiply the primary and secondary gear ratios together, you get the final drive ratio. THE FINAL DRIVE RATIO IS WHAT'S REALLY IMPORTANT. It tells you how many times the clutch bell needs to rotate (the “input” speed) to make the wheel rotate once (the “output” speed). The SMALLER the final drive ratio is, the FASTER you can go (the clutch bell needs to rotate fewer times to rotate the wheel once or more importantly, for the same clutch bell RPM, the wheel turns faster)
The gearing on stock Zumas are slightly different depending on when it was made. Here is a comparison:

2008 and newer (bugeye): primary gears 52/13 (4.000 ratio) secondary gears 43/13 (3.307 ratio) FINAL DRIVE RATIO 13.231
2002-2005 (bugeye): primary gears 52/13 (?) (4.000 ratio); secondary gears 44/12 (?) (3.666 ratio) FINAL DRIVE RATIO 14.667
1999-2002 (prebug): primary gears 52/13 (4.000 ratio) secondary gears 43/13 (3.307 ratio) FINAL DRIVE RATIO 13.231

When you “upgear” you are lowering the final drive ratio to allow you to go faster. Both primary and secondary gear (ratios) can be changed from the stock configuration, but most people end up changing the Primary gears (you don’t have to fiddle around with the axle and wheel, only the “clutch side” of the gearing.

Primary gear upgear kits for the Zuma/BWS are typically 43/13 (3.307), 42/14 (3.000) or 50/15 (3.333). Here’s how they change the final drive ratio:
For the prebugs and 2008+ bugeyes (secondary gear ratio 3.307):

43/13(3.308) takes you from 13.23 to 10.94 (21% upgear)
42/14 (3.000) takes you from 13.23 to 9.92 (33% upgear)
50/15 (3.333) takes you from 13.23 to 11.02 (20% upgear)

For the 2002-2005 bugeyes (secondary gear ratio 3.666)
43/13(3.308) takes you from 14.67 to 12.13 (21% upgear)
42/14 (3.000) takes you from 14.67 to 11.00 (33% upgear)
50/15 (3.333) takes you from 14.67 to 12.22 (20% upgear)

A conventional primary gear upgrade kit consists of a new primary drive gear shaft and a “loose” gear that will go on the “intermediate” shaft. This involves pressing off the old gear from the intermediate shaft and pressing on the new gear that comes in the kit. Some upgear are advertized with the second gear is already pressed onto a new intermediate shaft, so it sounds like you don't have to press off any gears. Be careful: some of these “pre-pressed” upgear systems will not fit in the North American version of the BWS/Zuma.
Attachment:
File comment: Some gearing info from another source...
Information about the Gearbox.jpg
Information about the Gearbox.jpg [ 514.9 KiB | Viewed 187769 times ]

Attachment:
File comment: Primary gears (removed from the cover)
5 primary gears.jpg
5 primary gears.jpg [ 714.6 KiB | Viewed 187783 times ]

Attachment:
File comment: The secondary gears can be seen here
3 secondary gears1.jpg
3 secondary gears1.jpg [ 722.85 KiB | Viewed 187783 times ]


17. Can I upgear my stock Zuma to get more speed?
No. The stock engine does not have enough power to use the upgears. Top speed might actually decrease.

18. What is an Over Range Kit. Is this the same as upgears?
Different than upgears. Typically one of the last upgrades in the quest for speed. Need to remove the electric starter assembly. Expensive.

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Stage6 43/13 Primary gears. 10.94 final drive ratio
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Sun May 09, 2010 9:37 pm
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Post Re: The Definitive Zuma/BWS FAQ
hi there, i might be missing it but i don't see the answer to
"8. How do I do the Dual Headlight mod?" it seems to stop at number 7 in that section.

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Tue May 18, 2010 1:53 am
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Post Re: The Definitive Zuma/BWS FAQ
EXTREMELY helpful diagrams and explanations. This page has been bookmarked. Thank you.

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Mon Jun 28, 2010 11:40 pm
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Post Re: The Definitive Zuma/BWS FAQ
This needs a bump...

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Mon May 02, 2011 7:03 pm
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Post Re: The Definitive Zuma/BWS FAQ
Whoops!

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i can't wait till i buy my crank! i need more speed!


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Sun May 08, 2011 9:10 pm
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Post Re: The Definitive Zuma/BWS FAQ
Great thread

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Thu Jun 02, 2011 8:14 am
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Post Re: The Definitive Zuma/BWS FAQ
There needs to be a mention of chambering exhaust port in bbk section. The filing of sharp edges on inside of jug....


Thu Aug 04, 2011 7:53 am
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Post Re: The Definitive Zuma/BWS FAQ
Nifty 50, I wish you lived next door to me........your post was fantastic...I'm a stone newbie..but I found your post to be fantastic, and I learned something...now if you just had a used 50cc, 19mm carb for my zuma, I'd cook you the best meal you've every tasted!
C


Sun Dec 09, 2012 10:25 am
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Post Re: The Definitive Zuma/BWS FAQ
:patriot:


Wed Jun 26, 2013 7:07 pm
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