Acceleration Problem / Yamaha Jog

[tsimi]

Hi all! I am new to your boards and in need of your advise.


About a year ago i got this scooter.

Yamaha Jog R

Year: 2003

BB-SA16J

CV50R (incl. remote)

with approx. 10'000 km

This scooter suppose to have a vicious acceleration at the start.
Well that wasn't the case or at least that is not what i understood as a powerful start.
I started to take parts apart and see if anything needs to be replaced or fixed.
First i just replaced original parts like the Air Filter, the "lightly" cracked Manifold and the Spark plug.
Cleaned the carb and started to do some light tuning.
Here is a list of what i have done so far.
------------------------------------------------------------------------------

Checked and cleaned the carburetor.
(Didn't change the setting of the screws at all. Main Jet is a 68)

Replaced original Air Filter

Replaced Spark plug (BPR7HS)

Replaced the Manifold (that thing where the carburator gets attached to.)

Replaced Battery (FT4L-BS)

Added 6x 5g weight rollers from DWR Daytona (original is 6x 7g)
(original rollers were worn out, flat spots...)

Added Daytona CDI (blue one)

Changed belt to a Kitaco Kevlar Racing belt

Exhaust(Muffler?) B-Moon Factory

Changed rear shock

-------------------------------------------------------------------------------
Before replacing the original belt my scooter drove well let's say decently from the start
it had this small kick start feeling but then lost it's torque and power around 25 km/h and the power came back after i crossead the 40 km/h line.
So i checked the belt and it had a little over 15mm width, original state should be 17mm if i am not mistaken,
so i went and bought the Kitaco Kevlar belt and then the real problem started. Which wasn't there before with the original worn out belt.
Before was like "power" -> "no power" -> "power"
Now is "no power" -> "power" -> "extreme power"

Now until i reach 10-15 km/h (which takes somewhere between 2-3 seconds) the scooter has barely power it doesn't rev up and it slowly moves from the start.
If i stop the scooter on a smaller hill it barely can climb it but as soon it passes the 10-15km/h spot the power kicks in and i get a more decent acceleration.
The top speed is absolute fantastic! Even if i drop the speed down a bit to around 40 km/h and push it again the needle jumps very fast to way over 70 km/h.
The only thing i haven't touch yet is the clutch. So i am suspecting that something there needs to be done/adjusted.
You guys in the U.S. talk a lot about yellow,red or 1500rpm or 2000rpm springs. Here in Japan we have colored springs from Daytona.
White is original, yellow is 3% up, red is 10% up and gold is 20% up.

I would like to confirm that in my case changing the spring will make a difference or not.
Or is there anything that i could do to check/confirm that it is indeed a spring problem?
One more thing i noticed is when i used to change the belt back and forth i pulled the clutch to open a small spacing so that the belt could drop a bit and usually the clutch spring would push right back together but the last time i checked i pulled the clutch and it stayed open and didn't close itself anymore. Make sense? Is this a sign that the spring has lost it's tension?


Kind regards
Lambros

[niz76]

Greetings in Japan!!
90GTVert has a ton of info and videos about CVT tuning. It sounds like yes indeed you could use some new springs in your clutch. The large single spring is the contra/torque spring and most use the "1k" spring- which is one step up from stock. Sounds like the torque driver could use some servicing/grease to be sure it operates freely (opens and closes).
The 3 small clutch springs provide tension for the clutch arms and heavier clutch springs will allow your engine to rev higher before clutch engages providing better takeoff/launch.

[90GTVert]

If the clutch springs don't work, here's more to think about...


The wider belt is probably riding higher in the front pulley, so you miss some of the take off "gearing", but you get to take advantage of the top speed "gearing" better with the proper belt. You could try a spacer on the drive boss or filing the drive face down a little in the center to make up for the width and let the belt ride lower. Using a spacer is easily reversible, although filing the drive face has the benefit of possibly letting the front pulley close even farther as well to squeeze the belt more on the top end.

Spacers and modding info...
49ccscoot.proboards.com/thread/625/vari-tuning
youtu.be/d3cQKYT0ojg?t=6m27s
youtu.be/bAaYJJWvJSw?t=4m22s

[tsimi]

Thanks for the warm welcome guys! I am happy to be here.

@niz76

Thanks for the tip with the torque driver. Didn't thought about that...I will definitely check it out.
I will have to take apart the clutch to replace the contra spring so I will take a good look at it and
grease it up if necessary.
I'll probably go with the 3% up (yellow spring here in Japan) and see how it goes...

@90gtvert

First of, thank you so much for all your effort and time that you put in those videos and topics in the tech library and all over this forum.
Amazing pool of information here...I will have to do some reading in the next few days and gather as much info as I can.

...so you miss some of the take off "gearing", but you get to take advantage of the top speed "gearing" better with the proper belt.

YES! that is what I think is happening. It's like I start in the second gear.
The Dude from the Japanese Bike shop said some similar stuff. He said that some guys cut/sand off some part of
the Variator so that the belt drops full down or they add an additional washer before putting on the outer pulley (front half of the Variator).
The stock belt has also 17mm width same as the Kevlar belt that I bought. That would not make any sense to sell a stock belt that doesn't go fully down unless they intended to do that so that the scooter wouldn't kick off too fast at the start, some sort of restrictor thing? I don't know...

Anyway, I will try to do what I can with the clutch first and see what's gonna happen and then decide what to do next.
I envy you guys over in the US. You have AWESOME home centers with an amazing variety of tools and parts. Here in Japan I am happy
if I can find a normal screw driver.

Thanks again for your help, really appreciated.

[renners]

Today I got the exact same thing now I'm no expert by any means but this was happening to me about a week ago as well so I took off the clutch and cleaned the shoes and housing and it fixed it temporarily. Now I'm getting the same problem as you going downhill its like theirs a turbo attached to my scoot lol revs jump up and its a like a rocket but until I hit flat road its near impossible to get over 30kmh and then the slightest downhill stretch of road my engine sounds like its got a turbo attached lol I have yellow springs in my clutch (I think their after market) but I'm curious to see what happens. My belt is waaay under spec (waiting for local motorcycle shop to get my new one in along with rollers) but for now I suggest cleaning all the gunk out of your clutch. (Like i said I'm no expert) or anywhere near one

[90GTVert]

Oct 22, 2014 11:06:19 GMT -5 tsimi said:

The stock belt has also 17mm width same as the Kevlar belt that I bought. That would not make any sense to sell a stock belt that doesn't go fully down unless they intended to do that so that the scooter wouldn't kick off too fast at the start, some sort of restrictor thing? I don't know...

Could also be so the belt can wear down without being too free. A lot of these won't get maintained or checked regularly so ~15mm wide worn belts are really common. By then I think many will notice top speed isn't what it used to be. Renners said his had a 13mm wide belt in it when he got it, so some get pretty bad or break before anything is done.

[renners]

Yeah that's it mine is currently 13mm wide (closer to 12.5 actually lol)

[tsimi]

@renners

lol 12.5-13mm that is....WOW!

I just wanted to give a small update on the situation.
I went to our famous tuning parts bike shop and bought the 3% up spring and grease.
They really have a great selection over there.
The dude from the bike shop near my place gave me the 41mm wrench for the clutch nut and also
a clutch compress tool (don't know if that is the right expression for it). You can put the whole clutch in that thing
and then just turn the lever to screw/push it together so that I can easy screw the nut back on it.
The only thing I am a bit worried is, how much power do I need to put into it when closing both nuts.
The nut on the clutch bell (24mm) and the big one (41mm) I don't have impact drivers or air pressure drivers
all is done by hand. I have quite some pushing/pulling power in my arms so I'm not worried to loose the nut during driving
I'm more worried to break the shaft or the threads on it.

Anyway off we go....later....

[renners]

Oh god me and you both buddy (no impact driver)

[90GTVert]

Around 40ft-lb or 55Nm for the clutch/bell nuts. I know that's not exactly helpful without a torque wrench though. Get it tight, don't try to break anything.

[tsimi]

@renners

I just found out that you don't need any impact driver or electric tool to take the clutch apart and put it back together.

So repair is done and I took some pictures of it. Both nuts (24mm + 41mm) came off easy no problems there. I used a marker to mark the nut and the shaft so when putting it back together I know until where I have to turn the nut to close the clutch.
There was some black oil like liquid around the torque driver, i guess old grease...
cleaned the parts and put the new grease on it as described in the Tech Library Topic.
After a short test drive here is the result. When the traffic light turned green i cranked the handle but not much power came out. A really small improvement was there i guess but not as I hoped. The overall acceleration is better i get smooth power from 15km/h to very fast 60km/h.
My scooter runs normally 80+ km/h and it used to reach the top speed very fast now I fell like it takes longer to get to the top speed, but that could be just me...need to do more test runs.
One more thing that happened is when push the scooter full at the start i get some sort of kicking like someone would kick the scooter from behind. *kick*, *kick*.....vvrroooomm. something like that. Does that make sense? This also I need to check out again by doing some more testing.
Maybe it is as 90GTVert said, that the belt is not fully down and therefore not in the first gear so to speak.
I'll ask the dude from the bike shop if he still has a worn belt so that i could test it once. And as you can see in the pics below I am in need of new clutch pads.

Work space



Clutch Pad shiny and small crack



Clutch, Bell & Tools



Parts before cleaning



Parts after cleaning



Crack in the clutch pad (close up)

[90GTVert]

Looks like there's still enough "meat" left on those clutch pads. I've had some chip on the edges. I'd just knock that little section off and as long as it's not much more than what we can see it'll prob be fine. Those shoes need to be sanded down though and then cleaned off with brake parts cleaner. If the bell looks glazed, sand it's contact area as well and clean it.

[renners]

Oh cheers mate it took me over two days and about 8 hours to get mine off lol

[54cc]

ok im reading you had a problem when you swapped belts.

so go retune the cvt.

lighter rollers what i hear from about jogs, like 4-5 grams. plus you can also mix and match roller weights.
and also stiffen if its not already on a stock motor, a small amount, to hold off on shifting until a higher RPm. with lighter rollers youll get higher rpms, but what it really is, is itll take off, and start to move at pretty much the same rpms as before. but youll have more power. whatever then figure it out from there. im not even that far yet.

[tsimi]

54cc

Thanks for your advise.
I will do some more testing in the coming days. I did sand down the pads but will do it one more time.
I have all kinds of roller weights and have done quite some testing in the past and 6x5g did the best job so far. But with the new torque spring in place i might have to do more fine tuning with the weights.
As you said it will not improve my starting power though since i believe it to be belt related as 90GTVert mentioned above.