2004 Yamaha Zuma Sport Build

[girldad93]

First time scooter owner here, picked up a non-running 04 yamaha zuma 50cc 2-stroke that needed some work with about 8000 miles. Cleaned the carb, replaced the reeds/reed valve, replaced the spark plug, replaced the battery, and got it running, although it would die while coasting to idle on occasion. From there, adjusted the idle air screw and idle speed screw, and it has been running good ever since.

On to the build, I plan on setting up a mild sport build, low end acceleration is more important to me than high top speed, also hopefully trying to stick with the stock crank for now.

Ordered one of the "Sport" Kits from Scootertuning:

Polini 70cc Sport Cylinder
Polini Speed Exhaust
Polini Hi-Speed Variator Kit (variator with 6.9g rollers, green clutch springs, soft contra spring w/ evo slider)
Stage6 Main Jet Kit 80-102 6mm Kit
NGK BR9ES Spark Plug

I also picked up a pilot jet from a vino (think its a 46) just in case its needed, new pair of michelin boppers, front brake pads, new crank seals and other misc gaskets, a set of 6g rollers, a new oem air filter, and a polini belt.

So far, got the new tires put on, brake pads replaced, and made up a leak check tester to find that my intake manifold/reed valve assembly was leaking pretty bad, 5psi would leak down to 0 visibly in a few seconds. Couldnt get it to seal with the new gasket alone, but sealed fine once I added some grey rtv to both sides. Checked crank seals but they did not leak at all. After letting the rtv cure, the system held 5psi for an hour without decreasing at all. I found that oil would leak into the carb if the scooter sat for a bit, also was some leakage at the pump itself, just went ahead and removed the pump/lines/tank, and will be running premix. Also changed the gear oil.

The plan is to install the parts on the original cylinder, get issues worked out/work on tuning, then swap in the new cylinder and finish fine tuning.

I have been reading on here for quite a bit over the past few weeks and have learned a ton from other people's past experiences, however I do still have a few questions.

I have been trying to get the polini speed exhaust on, but it does not seem to want to fit with the supplied bracket. I dont recall seeing any builds on here with this same pipe. Is it common to have these not fit correctly? Looks like i will have to mount the pipe behind the bracket instead of in front (which attaches to welded on spacers with rubber bushings), and add 2 additional pieces of metal to lower the mounting points about 1.5" from where the original mounting points are, unless I am completely doing this wrong.

Spark plug supplied for the kit is a NGK BR9ES, should I use this or pick up a BR8ES? I guess the 9 just seems like a pretty cold plug for the setup ill be running but maybe not.

I have not ordered a clutch, will the oem 2-shoe clutch be alright to use for now with the polini green springs?

As far as installing the contra spring with the evo slider, how exactly are the slider pieces supposed to be assembled with the spring? Theres a metal perch that goes on one side of the spring, and then a plastic ring that tapers in size, not sure way and what side (clutch or pully) each one of these goes on. Haven't separated the original assembly yet, maybe this will make more sense once I do.

Any other recommendations for a first time build are welcome. Thanks.

[Zino]

Welcome to the forums
I have built a few zumas up .
I have ran a very similar set up to what you are building on Yamaha zumas ,currently I have 2 vinos that are built with sport set ups with street pipes .
It is a very spunky set up for ripping around.
49ccscoot.proboards.com/thread/26756/yamaha-vinos-stealthy-build
49ccscoot.proboards.com/thread/26853/zinos-zuma-sport-build-sold

I have polini greens in my 2 shoe clutch with the vinos and it works well with the malossi wild lion and Malosssi sport bbk .

The wild lion and polini speed are copies of same pipe with different brackets.
I did not have fitment issues with my set up on either the vinos or zuma with the pipe .

Post a picture of how you are trying to fit your pipe.

[Zino]

You are thinking right .
Make your mistakes/learn on stock cylinder.
Go slow change one thing test it and run a few tanks of gas through before making another change .
That way you feel the differences.

I would add a cht temapature gauge to protect your hard work .

[aeroxbud]

Sounds like a good setup. I had the Polini sport on my slider, really liked it for low down torque.
When you have the top end off I would check the crank for play. It's 18 years old if it's the original crank. If it's pretty worn the sport kit might be too much for it.

[pili]

May 5, 2022 2:41:11 GMT -5 aeroxbud said:

Sounds like a good setup. I had the Polini sport on my slider, really liked it for low down torque.
When you have the top end off I would check the crank for play. It's 18 years old if it's the original crank. If it's pretty worn the sport kit might be too much for it.

I've always wondered about the Polini cylinder. I've had so much luck with the Malossi Sport, I stuck with it. 
Aeroxbud, as far as crank play, I noticed what I thought to be a little excessive side to side play on the connecting rod; is that the play you refer to? As I don't have a dial indicator or a spec to refer to, I just ran with it.

[aeroxbud]

You don't want too much play side to side. And there should not be any up and down. It should spin freely to the touch with no binding or sticking.
How many miles has it done?

[65grendel]

May 5, 2022 21:09:26 GMT -5 pili said:

May 5, 2022 2:41:11 GMT -5 aeroxbud said:

Sounds like a good setup. I had the Polini sport on my slider, really liked it for low down torque.
When you have the top end off I would check the crank for play. It's 18 years old if it's the original crank. If it's pretty worn the sport kit might be too much for it.

I've always wondered about the Polini cylinder. I've had so much luck with the Malossi Sport, I stuck with it. 
Aeroxbud, as far as crank play, I noticed what I thought to be a little excessive side to side play on the connecting rod; is that the play you refer to? As I don't have a dial indicator or a spec to refer to, I just ran with it.

The last Malossi rhq crank I ran in my Minnie I thought had a lil too much side to side play but she’s been good 2 years just saying

[pili]

May 6, 2022 2:51:38 GMT -5 aeroxbud said:

How many miles has it done?
Almost 20,000 miles. It has zero play that I can detect up and down.

Girldad93, I would order a variator weight tuning kit. I'm still running 6.5 gram weights but I run the stock exhaust. I think with your pipe it might work better with lighter weights especially since low end acceleration is a priority.

[girldad93]

So with the pipe aatached to the front of the welded on spacers/bushings, the flange sits
about 1-2in to the right of the exhaust port. With the pipe attached to the back of the flange, it is close,
but the pipe starts to come in contact the the bracket/case.

[Zino]

Is the bracket that is welded to the pipe
Does it allow you to for adjust from side to side .
On the wild lion
I can adjust the pipe to slide forward so it fits the short case vino or slide it backward to fit the zuma .
Here is mine mounted on the vino after I took it off zuma and readjusted it

[Zino]

I did not dremel any of the holes on either the bracket that is welded to the pipe .
or the one that attaches to the frame and pipe .
I just shifted back and forth while bolts were loose and then tightened them up on the brackets after she mated right up.

You may have to dremel some slots so you can move it back and forth

[girldad93]

Got the exhaust on, tried several more times to get it to fit as is, but it wouldn't as the pipe (near the outlet) needed to be able to move lower
to be able to rotate the inlet flange upward to meet the cylinder. Ended up dremeling the slots on the frame mounted bracket to allow it to rotate downward a bit more, then mounted the pipe to the cylinder, clamped the welded on pipe mount to the frame mount to see where it would line up in a natural position, then dremeled the holes on the pipe bracket. Has good fitment now.

On to the cvt, got it reassembled with the polini hi speed variator with the 6.9g rollers it came with (anyone know what the stock weights are), also disassembled the rear assembled, cleaned and regreased, installed the polini light contra spring, and put on the new polini belt. Everything went together alright, but it looks like maybe the belt should be riding up a little higher in the rear? I spun the engine over by hand several times, which pushed it outward a bit, but this is still where it ended up. Any thoughts? Worth it to put the original belt back on to see where it sits?

[Zino]

Nice work getting it fitted
Remember to check for exhaust leaks take a wet rag with the scooter running and plug the end of the pipe if it kills quick your good if she keeps runnning check the exhaust gasket for a leak
]Stock rollers are with 6 or 6.5 in stock variator
With the wild lion I like 6 or 6.5 best in aftermarket variators thta pipe will let you be a little above and below that

The polini belt actually rolls out smaller than the stock belt
I had better results with stock belt
Belts measurements are not standard from one manufacturer to the next

[pili]

I'm interested to see how the 0-40 is with that Wild Lion and 6.5 gr weights. I've tried two different pipes on mine and keep going back to stock exhaust as with my commute, 0-40 is key. My '03 Zuma with a Malossi Sport cylinder and an Athena 15/50 upgear is excellent in that range, and I can get to 50 mph if I tuck lol. At that speed I'm pretty sure that's all the revs the stock crank wants to see.

[repherence2]

May 9, 2022 21:03:53 GMT -5 pili said:

I'm interested to see how the 0-40 is with that Wild Lion and 6.5 gr weights. I've tried two different pipes on mine and keep going back to stock exhaust as with my commute, 0-40 is key. My '03 Zuma with a Malossi Sport cylinder and an Athena 15/50 upgear is excellent in that range, and I can get to 50 mph if I tuck lol. At that speed I'm pretty sure that's all the revs the stock crank wants to see.

what kind of clutch are you running and how stiff are your clutch springs?

do you have an aftermarket variator?

roller weights have a relationship with the center spring. maybe you should get a tuning roller set so that you can try different total gram weights in your CVT.  i tune with Motoforce roller weights.  every time i would go to a specific shop to see if he had any new parts, i would always make sure to support these local stores.   i would always at least leave the store with roller weight sets or quarts of oil just to support local business.  now i have weights from 3.5g up to 7g in 0.25g increments.  this allows me to really fine tune my CVT's.  in my experience, 0.25g per roller makes a big difference.  i refuse to tune in 0.5g increments now, those that do will never find the true potential of the CVT and Engine/pipe combination.