View unanswered posts | View active topics It is currently Sat Jul 20, 2019 12:55 am



Reply to topic  [ 11 posts ] 
 2002 Zuma low top speed with 70cc kit 
Author Message
Newb
Newb

Joined: Sun Jul 22, 2012 5:42 pm
Posts: 16
Post 2002 Zuma low top speed with 70cc kit
Helping a coworker out modifying his Zuma. Lately it's not been great on top speed, down from almost 45mph to 30-32mph or so, and I'm running low on ideas as to why.

Current setup:
-generic Chinese 70cc kit, good compression
-stock exhaust, no leaks
-stock carb/airbox, 85 main jet, 1.5 turns on air screw
-Stock reeds and reed cage
-stock variator with 6g rollers
-Teknix Standard 107mm clutch, Polini bell, yellow contra spring, orange Stage6 outer springs
-new OEM drive belt
-BPR8HS plug, chop looks decent to sliiiiiightly rich (tried heat ranges 7 and 9 to no avail)

Acceleration seems fairly normal from my test rides, it just seems to hit a wall at 30 MPH or so. The clutch bell is a bit glazed, but I don't think it's enough to lose 10mph. I can't think of anything that would cause this. Can someone else?


Last edited by thebook92 on Tue Jul 09, 2019 11:23 am, edited 1 time in total.



Sat Jun 22, 2019 10:06 am
Profile
Bronze Member
Bronze Member

Joined: Fri Aug 31, 2018 5:18 pm
Posts: 493
Location: Fox Valley Wisconsin
scooters and mods: 2 2004 Vinos 2004 Zuma
Post Re: 2002 Zuma low top speed with 70cc kit
do the sharpie test
take a permanent marker and make a mark from the center of the variator to out side edge .
warm up the scoot and take a wide open run .
report back with how much marker in mm is left on the variator .

_________________
2004 Vinos Derestricted exhaust and variator stock carb with mikuni 70 main jet needle down 1 clip 40 mph
Athena Sport BBK waiting to go on

2004 Vino Malossi sport 70cc Malossi Wild Lion pipe derestricted stock variator stock carb 72 mikuni main one clip rich
45 mph still breaking in Michelin S1 90/90/10 rear tire Michelin S1 3" x 10 up front

2004 Zuma Malossi sport 70 cc Technigas next r 2008 zuma torque driver polini high speed variator 5.5 grams sliders malossi delta clutch yellow contra yellow clutch springs Stock Carb 82 main jet 46 pilot jet needle 1 clip rich stock athena 14/42 gears 11 to 1 final ratio 56 mph

2005 Eton Beamer (Taiwan Zuma Clone) Airsal sport 70cc 9200 peak rpm top speed 42 77.5 mikuni jet needle 1 clip rich (sold)


Sat Jun 22, 2019 1:53 pm
Profile
Newb
Newb

Joined: Sun Jul 22, 2012 5:42 pm
Posts: 16
Post Re: 2002 Zuma low top speed with 70cc kit
zino18 wrote:
do the sharpie test
take a permanent marker and make a mark from the center of the variator to out side edge .
warm up the scoot and take a wide open run .
report back with how much marker in mm is left on the variator .


After a quick run, there's about 5mm of sharpie left, and the rollers are still in good shape. When we were tuning we found that 6g weights give about 5mm left at the end of the variator, which is the most we've been able to get out of it. Even completely stock, there was a distinct outline of rubber around the inner variator face about 5mm in from the edge. 7g weights don't get it any closer, and going lighter just made everything worse. Of note, the original 45ish top speed was achieved with the same weights that are in it now.


Sat Jun 22, 2019 2:13 pm
Profile
Bronze Member
Bronze Member

Joined: Fri Aug 31, 2018 5:18 pm
Posts: 493
Location: Fox Valley Wisconsin
scooters and mods: 2 2004 Vinos 2004 Zuma
Post Re: 2002 Zuma low top speed with 70cc kit
Can you get ahold of a tach .
To check peak rpms If you are getting high enough rpms then we trace it back to the wheels .
on my 2004 before gears
Stock pipe without a kit i was 8800 rpms or just below 9000
with the malossi kit and stock pipe 9200 ish doing about 45-46 mph .
my belt travel was closer to 3mm .

Try this to see if it helps with speed and travel there is a shim behind the variator fan it is about paper clip thin .
To keep spacing the same take it out put it on the other end of the drive boss behind the movable variator by the starter clutch.
And do a speed run .

When is the last time the rear sheeve was torn down and regreased ?
Is the contra binding holding the rpms down ?
Cltutch shoes are they glazed and slipping ?
Any other black marks on variator besides the edges suggesting belt slippage ?

_________________
2004 Vinos Derestricted exhaust and variator stock carb with mikuni 70 main jet needle down 1 clip 40 mph
Athena Sport BBK waiting to go on

2004 Vino Malossi sport 70cc Malossi Wild Lion pipe derestricted stock variator stock carb 72 mikuni main one clip rich
45 mph still breaking in Michelin S1 90/90/10 rear tire Michelin S1 3" x 10 up front

2004 Zuma Malossi sport 70 cc Technigas next r 2008 zuma torque driver polini high speed variator 5.5 grams sliders malossi delta clutch yellow contra yellow clutch springs Stock Carb 82 main jet 46 pilot jet needle 1 clip rich stock athena 14/42 gears 11 to 1 final ratio 56 mph

2005 Eton Beamer (Taiwan Zuma Clone) Airsal sport 70cc 9200 peak rpm top speed 42 77.5 mikuni jet needle 1 clip rich (sold)


Sat Jun 22, 2019 2:50 pm
Profile
Newb
Newb

Joined: Sun Jul 22, 2012 5:42 pm
Posts: 16
Post Re: 2002 Zuma low top speed with 70cc kit
I cannot get a hold of a tach, but correct me if i'm wrong: would a 25% reduction in top speed would mean a 25% reduction in RPM, variator/carb settings being the same? RPM seems about the same as it was before the issues started, so if my assumption is correct I don't think it's an engine issue at this point.

We tried the variator shim in both positions. No difference.

When we put the clutch springs in (some time ago) we noticed the clutch shoes were slightly glazed, so we just hit them with some sandpaper real quick and ran it. Rear clutch sheave I'm not sure about, I'll have a look in there in a bit. Good chance to look at the clutch shoes and bell too, we'll see how that looks now.

Edit: Upon inspection, the clutch shoes looked somewhat glazed over but the outer bell was glazed to a complete mirror finish. Seems to suggest a good amount of clutch slip, but wouldn't that hurt both acceleration and top end?


Mon Jun 24, 2019 9:14 am
Profile
Bronze Member
Bronze Member

Joined: Fri Aug 31, 2018 5:18 pm
Posts: 493
Location: Fox Valley Wisconsin
scooters and mods: 2 2004 Vinos 2004 Zuma
Post Re: 2002 Zuma low top speed with 70cc kit
Over 10 miles is alot for just a slipping clutch .
That would hurt both acceleration and top speed .
Tachs are cheap and are a great tuning tool very cheap on amazon .
7500 rpms to 9000 rpms sounds close to the untrained ear .
Could the stock exhaust be getting plugged up after the years and need decarbonizing.

_________________
2004 Vinos Derestricted exhaust and variator stock carb with mikuni 70 main jet needle down 1 clip 40 mph
Athena Sport BBK waiting to go on

2004 Vino Malossi sport 70cc Malossi Wild Lion pipe derestricted stock variator stock carb 72 mikuni main one clip rich
45 mph still breaking in Michelin S1 90/90/10 rear tire Michelin S1 3" x 10 up front

2004 Zuma Malossi sport 70 cc Technigas next r 2008 zuma torque driver polini high speed variator 5.5 grams sliders malossi delta clutch yellow contra yellow clutch springs Stock Carb 82 main jet 46 pilot jet needle 1 clip rich stock athena 14/42 gears 11 to 1 final ratio 56 mph

2005 Eton Beamer (Taiwan Zuma Clone) Airsal sport 70cc 9200 peak rpm top speed 42 77.5 mikuni jet needle 1 clip rich (sold)


Mon Jun 24, 2019 3:57 pm
Profile
Newb
Newb

Joined: Sun Jul 22, 2012 5:42 pm
Posts: 16
Post Re: 2002 Zuma low top speed with 70cc kit
zino18 wrote:
Over 10 miles is alot for just a slipping clutch .
That would hurt both acceleration and top speed .
Tachs are cheap and are a great tuning tool very cheap on amazon .
7500 rpms to 9000 rpms sounds close to the untrained ear .
Could the stock exhaust be getting plugged up after the years and need decarbonizing.


I'll see about getting a tach. I may still have one off an old dirt bike that I can at least rig up well enough to work. I didn't think about the exhaust; it's definitely possible that it could be well-carbonated. We'll take a look.


Tue Jun 25, 2019 7:59 am
Profile
Newb
Newb

Joined: Sun Jul 22, 2012 5:42 pm
Posts: 16
Post Re: 2002 Zuma low top speed with 70cc kit
We de-carbonized the exhaust, and went ahead and upgraded the clutch. No change in top end, but it takes off soooo much more smoothly now. A new tach is on its way.

Side note: is this a normal amount of noise to come from the transmission, or is there a bearing that's on its way out? Makes the same noise with the clutch off, so it's nothing to do with that.
https://youtu.be/Mz5vuS3HtLE

EDIT: tach came in. Only pulls 7400 RPM at 30 MPH. Dropping back to 5.5g weights brings it down to 7100 RPM at 29 MPH. Might be on to something here, but what would cause it to rev that low?


Last edited by thebook92 on Tue Jul 09, 2019 12:16 pm, edited 1 time in total.



Fri Jul 05, 2019 12:57 pm
Profile
Bronze Member
Bronze Member

Joined: Fri Aug 31, 2018 5:18 pm
Posts: 493
Location: Fox Valley Wisconsin
scooters and mods: 2 2004 Vinos 2004 Zuma
Post Re: 2002 Zuma low top speed with 70cc kit
Your rpms are too low .
The stock pipe pushes to high 8000 rpms
The stock transmission has very little noise, yours is a little louder than mine .
Do you have the original contra spring .
2 things to try Variator and clutch
use every other 7 gram weight in the variator to see what way too light is like and add 1 gram of aluminum foul to each 6.5 gram and 7 gram weigt to see what going heavire does .
Since you have a tach here is what you want .
With stock pipe power band is 6000ish to 8000ish
When you jump on the throttle the rpms should jump to 7000ish rpms and stay there and gradaully rise if they go to 7 and drop back right away you are shifting too early and need to go lighter on weights .
IF your rpms jump way up and then down shift late you are shifting too late and are running out of power at the top your weights are too light .

Clutch
I Think this is your area that you will improve The yellow contra may not be letting you upshift or you are binding in the torque driver I would take ita ll apart and make sure the guide pins in torque driver are not getting hung up.
the 2002 -2005 has a bad design it has a curve in it that down shifts out of powerband and up shifts at 10-15 mph

_________________
2004 Vinos Derestricted exhaust and variator stock carb with mikuni 70 main jet needle down 1 clip 40 mph
Athena Sport BBK waiting to go on

2004 Vino Malossi sport 70cc Malossi Wild Lion pipe derestricted stock variator stock carb 72 mikuni main one clip rich
45 mph still breaking in Michelin S1 90/90/10 rear tire Michelin S1 3" x 10 up front

2004 Zuma Malossi sport 70 cc Technigas next r 2008 zuma torque driver polini high speed variator 5.5 grams sliders malossi delta clutch yellow contra yellow clutch springs Stock Carb 82 main jet 46 pilot jet needle 1 clip rich stock athena 14/42 gears 11 to 1 final ratio 56 mph

2005 Eton Beamer (Taiwan Zuma Clone) Airsal sport 70cc 9200 peak rpm top speed 42 77.5 mikuni jet needle 1 clip rich (sold)


Mon Jul 08, 2019 10:40 am
Profile
Newb
Newb

Joined: Sun Jul 22, 2012 5:42 pm
Posts: 16
Post Re: 2002 Zuma low top speed with 70cc kit
RPM jumps right up to about 7200 and stays there, but won't go much farther than that. I wonder if it might be the contra spring not letting the belt get all the way down, so it's still trying to "shift" but can't pull enough RPM to actually do it. Might still have the original one, we can try it just for giggles and see what happens. Torque driver is definitely good, I regreased it when we put the new clutch in.


Tue Jul 09, 2019 11:18 am
Profile
Bronze Member
Bronze Member

Joined: Fri Aug 31, 2018 5:18 pm
Posts: 493
Location: Fox Valley Wisconsin
scooters and mods: 2 2004 Vinos 2004 Zuma
Post Re: 2002 Zuma low top speed with 70cc kit
Are your rpms still below 8 after going real light on rollers ?
What do you call good compression with this kit ?

_________________
2004 Vinos Derestricted exhaust and variator stock carb with mikuni 70 main jet needle down 1 clip 40 mph
Athena Sport BBK waiting to go on

2004 Vino Malossi sport 70cc Malossi Wild Lion pipe derestricted stock variator stock carb 72 mikuni main one clip rich
45 mph still breaking in Michelin S1 90/90/10 rear tire Michelin S1 3" x 10 up front

2004 Zuma Malossi sport 70 cc Technigas next r 2008 zuma torque driver polini high speed variator 5.5 grams sliders malossi delta clutch yellow contra yellow clutch springs Stock Carb 82 main jet 46 pilot jet needle 1 clip rich stock athena 14/42 gears 11 to 1 final ratio 56 mph

2005 Eton Beamer (Taiwan Zuma Clone) Airsal sport 70cc 9200 peak rpm top speed 42 77.5 mikuni jet needle 1 clip rich (sold)


Fri Jul 19, 2019 5:42 pm
Profile
Display posts from previous:  Sort by  
Reply to topic   [ 11 posts ] 

Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group.
Designed by STSoftware for PTF.