Stretching my 2003 Zuma 50cc 2t

[furiousbob]

A little update.

So the Zuma's been leaking fuel for a while. I replaced the petcock, no change. Replaced the fuel level sending unit gasket. No change. Deleted the fuel level sending unit and machined an aluminum plate.




No change.

Pulled the tank. Pumped it up through the breather hose with my fog machine.

Turns out there's a massive crack running through the petcock flange.




Looked online for another tank. No luck so far.

I'm letting the tank air out tonight. Going to take the TIG welder to it tomorrow to see if I can patch it up before I go dropping more cash on it.

Oh also, my buddy was riding the Zuma. Took a left turn through a corner and the front fender exploded to bits. It had a crack where the tire was rubbing through. I'm thinking it caught the crack at a weird angle.

Anyway, another $150 for a new fender and it's all fixed now.

But the petcock issue. I think since the petcock sits right above the carb now, at some point we took a bump too hard and the carb smacked the heck out of the petcock. I've already trimmed the adapter down maybe 5mm. Hopefully that solves the issue.

BUT if anybody has a fuel tank they got lying around. Let me know!

[furiousbob]

It ain't pretty but it's holding up. No more leaks!

[rollingbender]

Any time you weld on a fuel tank and it doesn’t turn inside out is a success in my book.

[furiousbob]

Alright it's been months since my last update. I've finished building the GM 3.4L for my 1990 Trooper. She's in and tuned and ready to go, I think.

Back to scooters!

The metro/reflex swap is under way. Pulled the 250cc out of the Reflex and started tearing down the Metro. I'll start another thread for that when I have enough progress. Edit - Thread here

I'm still not real happy with the top speed on the Zuma. The tank is still sorta leaking. Still scouring eBay for a new tank. Or maybe I'll pull it again and re-weld it.

Top speed is still 45mph. I end up taking my Elite 150 most days.  I'd really like to ride the Zuma though.

Here's my current list of mods:

Polini Sport 70cc BBK
Yasuni R
Polini soft torque spring
Athena 14/42 straight cut gears
Stock carb
3.5g weights at 9500 RPM
Budget overrange kit with a polini belt ( courtesy of Zino, thanks! )
Includes a Malossi fan and variator, Top Performance rear torque driver

Maybe it's time for a Polini CP carb? But that wouldn't net me more speed, right? Or maybe it's time for a new cylinder/piston setup?

[aeroxbud]

I had a Polini sport with a Yasuni R on my slider. I ran it for a while with the standard 12mm carb. It made a real difference though when I went to the 17.5 Dellorto. Top end was much improved.

[furiousbob]

Alright I'm going to do some reading. Thanks for the suggestion! I wasn't sure what size carb I would go with or what type. Dellorto or Polini CP.

I also read that a bigger carb doesn't help top end, only response. Thanks for the input.

[furiousbob]

A much as I hate using scooterswapshop, I spotted this kit:

scooterswapshop.com/products/polini-cp-carburetor-bundle

Seems to do the job. I'll be looking for the 19mm. Given the height of the carb at ~5", I may have to re-machine my manifold. Also, I'll need to re-do my throttle cable YET again. I'm not sure if their 65" cable will work with my setup since my carb is mounted about a foot back so I may have to start from scratch.

Also, their main jet kit ranges from 100-118. I read somewhere that these carbs need a 80-100 range?

Edit - Heck it, I'm going to spring for that 19mm.  If the jets don't work out, I can always order more.  I've got an idea for how I'll re-do my manifold.  Worse comes to worst, I'll relocate the carb to the outside of the scooter.

[bigmatthew86]

I 2nd the dell 17.5. I want as easy as I can get which meant oil injection & auto choke. My Zuma would do around 55 on the flat with it, Street race 70, & yasuni r. I didn’t feel the 17.5mm was limiting me in any way.

[furiousbob]

AW SHOOT. I didn't do my due diligence. The Polini does not come with oil injection. Okay I called scooterswapshop and had them cancel the order.

I think I'll just go track down a dellorto and piece together my own kit.

[furiousbob]

Looking at this one next.

www.dynoscooter.com/products/dellorto-phbg-ds-19mm-racing-edition-carburetor?_pos=7&_sid=661ab41a3&_ss=r&variant=18275836869

Or this one

www.zumasrusstore.com/products/dellorto-carburetor-19mm?_pos=2&_sid=2ecd768d5&_ss=r

I've read that the racing edition carbs do have oil injection. But where does the line feed in?

Edit - nevermind, I found it.  It's right next to the fuel intake tube. 

[Lucass2T]

Its gonna love that 19mm. You can even use your oem intake boot.

[furiousbob]

I think I may have to adjust the boot location or fabricate a new intake tube.

Right now, the carburetor sits directly underneath the fuel tank, with the filter facing rearward.

I've already cracked my fuel tank by hitting a bump in the road too hard. I managed to find another used tank on eBay this morning, thank goodness.

But if the 19mm is the same height as the stock carb, I just don't want to risk it again. I'm tinkering with an idea of relocating the carb the left side of the scooter, in between the left body panel and the CVT case. With the air filter sticking out to the left.

I know on 4 strokes, it's generally fine to extend the length of distance between the carb and combustion chamber. How far can I push it on a 2 stroke? We're talking 2x 90 degree bends and maybe 10" - 12" of tube.

[furiousbob]

Update time!

I am officially relocating the carburetor. I test fitted the 19mm del and there just isn't any way for it to fit under the fuel tank without damaging something again.

Anyway, pulled everything apart, made a new manifold flange out of some precuts



The OD of the carb exit is 1". I have a bender ( JD2 model 3 ) but I only have 7/8", 1.25" and 1.75" dies. I tried bending 1" DOM tube with the 1.25 and it just ended up squishing it.

I ended up buying 1.25", 0.060 wall tube. Please note, the photo below is of the squished 1" DOM. It's just there to give you an idea of the routing.



Since the ID of the 1.25" tube is 1.125", I made an adapter out of a solid chunk of mild steel.





Initial fit-up:





I need to cut the end of the tube another 2" so the carb tucks in closer to the body panel.

Also, I need to notch my stretch kit so the intake tube doesn't contact the stretch kit arm when the suspension compresses.

ALSO, the clear tubing between the intake tube and the carb is temporary. As luck would have it, I work with a lot of car parts companies as part of my day job/business. I spoke with HPS about my issue ( tiny hoses that need fuel resistance ) and they suggested their FKM lined tubing in 1" ID. Regular silicone hoses will eventually degrade when in contact with gasoline and the fuel seeps through the pores in the wall. Anyway, it's on order and I'll get it some time next week.

A throttle and choke cable was included with the del kit but I've yet to figure out if it'll be long enough to route. Initial mock-up indicates it MAY be long enough but I'm not sure yet. I'll need the new hose coupler and then I'll need to weld the adapter on to the intake tube first.

On another note. Maybe someone can chime in here. Are carbs supposed to be free floating? I've seen other custom setups where a custom bracket was made to hard-mount the carb to the CVT case. But I've also heard that carbs need to be free to do it's own thing ( aside from the coupler to the intake tube ).

[190mech]

Let the carb float!

[furiousbob]

So I was doing some test fitting today and the oil feed line isn't long enough. I was debating on either extending it with a coupler and some more hose or running a brand new extended line from the case to the carb.

Upon doing some searching on this forum, I read in one post that the oil pump is controlled by a cable that splits in to the throttle cable. I raised an eyebrow. I don't remember there being any other lines from the throttle housing that goes to the crank case? I remember there being two throttle cables but they both went to the carb. One was pull and the other was push. This was to ensure that the throttle tube didn't roll all the way over, no? I ended up deleting one line and installing a throttle stop in the throttle tube housing.

It's a bit too late to run down to the shop to take a look but am I mistaken? Is there a separate cable that runs from the oil pump?

EDIT - So I answered my own question.  Pulled up the service manual PDF and it looks like the autolube pump is just gear driven.  Nothing else controls it.  It is, however, behind the flywheel and I don't have the tool to pull it.  And I don't want to yank it all apart and attempt it with my automotive gear pullers because... lazy.

So I'm just going to make a teenie tiny 2.5mm coupler out of aluminum tomorrow.