Stretching my 2003 Zuma 50cc 2t

[aeroxbud]

Yes it can be a can off worms. I recently replaced my oil line as it wouldn't fit the bigger carb on my aerox.
Even with the flywheel and drive gear off. I still couldn't clear the cylinder to get the pump off.

[furiousbob]

Actually, it was easier than I thought!

The existing line already had a slip-fit connector on it. I just remove the old line leading to the carb and inserted a longer line. It was a 3.9mm OD line I picked up from the local box store some time ago




Also, here's the carb mounted:





The next issue was that the throttle cable that came with the kit was exactly 1" too short. The custom cable that I made for the existing setup fit the bill and then some. So I snipped off the new cable's barrel end and re-used the carb-side hardware. I made a new cable barrel out of a worn 1/4" drill bit. The barrel size needed to be about 0.145" in diameter and needed a 0.070 hole for the cable to enter. A few minutes on the lathe and the solder pot was on.



Put it all together and she kicks right over! I don't have a choke cable set up yet. Still waiting for one in the mail so I just covered the carb intake with my hand. Runs but smokes. I'm guessing there's too much oil and the motor's not warmed up yet. Set idle to 2000 RPM and it was beer o-clock.

Still waiting for the HPS hose for the carb-to-intake-pipe connection. Also waiting for the new air filter. After that, it should be tuning time.

Short running video: photos.app.goo.gl/fa4WtymtsJoiQwfx5

[190mech]

Carb clear everything at max shock travel?

[furiousbob]

I will be checking that today. I did a bunch of clearance-ing on the main arm so that the intake pipe would clear at full suspension compression. Haven't checked the carb yet but it shouldn't hit anything since it's just sitting out in the open now.

I'm just impressed that the 6-7" intake tube let the motor run. I had spoken to some of my dirtbike buddies about it and they told me that it should result in improved low end. I guess we'll see!

I'll be piecing everything back together today/tomorrow.

I'm just happy to have easy access to the carb now. The setup I had before was a bit tedious. I think that's why I dreaded tuning the carb so much.

[190mech]

I built a long tube intake with a big reed box mounted externally and a 28mm carb for a 103 drag scoot many years ago, it did well!

[furiousbob]

Alright I got her all buttoned up yesterday



Still missing a couple things but it was ready for a test drive. Started right up with no choke. Bogged down as soon as I hit the throttle. Removed the jet that came with it. It was a 75 size jet. Threw in a 95 size.

Runs great! Still.... not enough top speed. Runs about as quick as it did before. Maxed out at about 43mph. Head temps at 230f. Threw in a 97 jet. Ran about the same.

Going to try a lower jet but honestly, I'm a bit disappointed.

Am I doing something wrong here?

I've got all the go-faster bits in there.  Re-geared to 11:1 already.  The only thing I haven't touched is the reed valves and maybe... re-porting the the BBK cylinder?  I don't know what else to do.

[bigmatthew86]

What year is it again? My old 09 would do 50 with a 70kit, Leo Vince @ stock variator & gears. My 05 would do 55 with 70 kit, yasuni r, 15/50 gears. Both of those specs are with 250lb rider sitting up on flat ground. 230 head temps screams way rich to me. I want mine to peak right at 350.

[furiousbob]

It's a 2003. Well I tried dropping the main jet to a 93 yesterday and head temps actually lowered to around 215. Should I keep going further down?

[bigmatthew86]

I don’t want to tell you to keep leaning it & something else is going on & you fry it. But 200ish degrees at full throttle is very cool for an air cooled bike. Your temp sensor is on the spark plug & you removed the plug washer? My last Zuma had a street race 70, Yasuni r, factory air box with snorkel pulled, a Dellorto 17.5 (I forget the jet). At full throttle it would hit over 300 pretty quick & then slowly climb to around 350. Is your choke hanging up by chance? Mine was around 200 not even warmed up. Do you have a tach? What rpm are you running?

[furiousbob]

I do have a temp sensor on the spark plug with the washer removed. I also have a tach. I'm running at just over 9000rpm at full throttle and about 2000rpm at idle.

I did a long test ride today and brought my tools. Started at 93 and dropped 2 sizes until I landed at an 83. WOT temps are now between 260 and 270F. Managed to get to 45mph at the end of the day.

I ran out of time, though. I'll need to keep playing with the jets.

[furiousbob]

Took it on a ride with some buddies tonight. One of my buddies said it's because of the 7" wide wheel. I need a skinnier tire. I'm going to get my stock wheel out of storage and see if that changes anything.

[bigmatthew86]

What is the total height of the tire? If it’s much shorter than stock that definitely changed you’re gearing. I’d also continue with the jetting, I think there’s a few more mph there.

[furiousbob]

Current size is 140/70r12 on a 7" wide wheel. Total height is approx 19.7". Factory tire was 130/90r10 or approx 19.2" diameter

I went to pump up the tires today. Rear was at 28psi and front was at 14psi. Filled it up to 40psi/35psi. Dropped main jet to 81. Went for a rip. Maxed 45mph and noticed fuel dripping out of the air filter.  CHT about 270F after a long stretch of road.



I'm going to take a break from this project and start on my metro/reflex swap.

Any input is appreciated, though!

[bigmatthew86]

If anything I would think with the taller tire it’d be a little faster. Slap the factory tire on at some point & you can at least condor rule that out.

[monsterunderyourbed]

Did you lengthen the actual exhaust at all or did I read that wrong?