Determining the state of tune on my Yamaha Jog 3KJ

[Rectifier]

Hi all,

I've had a 1990 Yamaha Jog 3kj (edit: "artistic spec") for about a month now. There seems to be very little documentation on these vehicles short of that which is in peoples' heads...

Anyways I'm trying to figure out what state of tune the thing is in so I know how much work it will be to go faster.

I'm in Canada, the bike is a Japanese import. Stock 50cc cylinder for sure.

Acceleration is decent, about the same as a normally driven car in the city, and the speed tops out between 65-70kph on a long flat stretch, with the throttle wide open. I weigh 130lb. Getting about 3.2l/100km efficiency.

I need to get to 80kph as that is the speed limit for a road on which i ride to work. Possible with the 50cc engine? And, do you think there are any restrictions still on this bike?

I'm hesitant to pull the exhaust and look for a washer as everything is quite badly rusted on the flange, so would like to know before I start wrenching.

Thanks anyone,

Alex

 

[melf #50]

if it already runs 65/70 is is possible that is is totally un-restricted , but do you have a picture of the scooter?

and is it an engine with a vertical cilinder or a horizontal engine?

there are other exhausts on the market wich increase your top speed , together with a good Variator Kit this will run very nice , the variator kit is to let the variosystem be more easy to adjust to the exhaust and make it run better too.

 

[ex-racer#2]

Acceleration is decent, about the same as a normally driven car in the city, and the speed tops out between 65-70kph on a long flat stretch, with the throttle wide open. I weigh 130lb. Getting about 3.2l/100km efficiency.

I need to get to 80kph as that is the speed limit for a road on which i ride to work. Possible with the 50cc engine? And, do you think there are any restrictions still on this bike?

Alex

80 kmh is definately possible but it will take some fine tuning and lots of patience. I am in Brampton Ontario and my BWS 50 does 80kmh all day long with a stock cylinder and technigas Next R pipe. (And I weight 190lbs) This is still a very low state of tune and we have yet to "jam" the head and try for more compression.
The keys to getting a little more top end is definately in the small stuff. Opening up the reed stops, cleaning up the casting flaws in the reed block, making sure the pulleys are working to their full range ect ect ect. But be prepared to spend at least $300 to $500 CDN$ to get to 80kmh (pipe, rollers, springs, variator, ect) or just buy a 70cc kit with pipe, carb and variator ect and with some fine tuning you will hit this easily.

The biggest frustration is everytime you make a change to the power characteristics you need to respring and or change rollers in the transmission. Do not assume that your local shop will have the knowledge or experience either. They just don't deal with modified scoots all that often if ever. Almost everything transmission wise is subject to trial and error. I even find that weather and temperature will cause the motor to run different or the transmission to hook up differently. Add to that the issue that you are trying to get it to work over a much wider range speed wise and you will be making some sacrifices. (Mine is a bullet if I go low on roller weight but only to about 65 kmh, if I shoot for 80kmh my speed goes up but the acceleration is definately reduced drastically.)

As a final note while you can hit 80kph on a stock bore add hills or crazy traffic and it will still be a challange. There are some areas here in Toronto I won't attempt to drive during certain times of day or in busy traffic. It isn't worth the risk to my life. If the limit is 80 there is going to be people doing 100 or more and if you are struggling past 70 or 75 to get that last few kph you will get everyone treating you like a speed bump. Choose your route carefully.... your scoot doesn't go very fast when you are in a hospital bed.

 

[BuEn]

The 3KJ has the excact same engine as the more modern Aprilia Sonic, thought far from the same kind of restrcitions on the enigne.
The kph u got from it now is quite decent, thought i would change the exhause, mby even the cylinder to get the 80kp/h. This would still be reachable with a 50cc cylinder.

A new variator would be to prefer to.

 

[melf #50]

80 kmh is definately possible but it will take some fine tuning and lots of patience. I am in Brampton Ontario and my BWS 50 does 80kmh all day long with a stock cylinder and technigas Next R pipe. (And I weight 190lbs) This is still a very low state of tune and we have yet to "jam" the head and try for more compression.
The keys to getting a little more top end is definately in the small stuff. Opening up the reed stops, cleaning up the casting flaws in the reed block, making sure the pulleys are working to their full range ect ect ect. But be prepared to spend at least $300 to $500 CDN$ to get to 80kmh (pipe, rollers, springs, variator, ect) or just buy a 70cc kit with pipe, carb and variator ect and with some fine tuning you will hit this easily.

The biggest frustration is everytime you make a change to the power characteristics you need to respring and or change rollers in the transmission. Do not assume that your local shop will have the knowledge or experience either. They just don't deal with modified scoots all that often if ever. Almost everything transmission wise is subject to trial and error. I even find that weather and temperature will cause the motor to run different or the transmission to hook up differently. Add to that the issue that you are trying to get it to work over a much wider range speed wise and you will be making some sacrifices. (Mine is a bullet if I go low on roller weight but only to about 65 kmh, if I shoot for 80kmh my speed goes up but the acceleration is definately reduced drastically.)

As a final note while you can hit 80kph on a stock bore add hills or crazy traffic and it will still be a challange. There are some areas here in Toronto I won't attempt to drive during certain times of day or in busy traffic. It isn't worth the risk to my life. If the limit is 80 there is going to be people doing 100 or more and if you are struggling past 70 or 75 to get that last few kph you will get everyone treating you like a speed bump. Choose your route carefully.... your scoot doesn't go very fast when you are in a hospital bed.

this is nonsens , tuning reed blochs etc. on A std engine is BS , changing the cilinder head too...

these are ways that are really not neccesary...

most scooters (with minarelli engine)here in Holland already do 80/85 REAL Kilometers just by using a good exhaust , changing the main jet and make sure the variator rollers en clutch springs and return spring are well adjusted..
with a "sport" variator it is easyer to adjust all of this..

so keep your nonsens to yourself...

 

[ex-racer#2]

this is nonsens , tuning reed blochs etc. on A std engine is BS , changing the cilinder head too...

these are ways that are really not neccesary...

most scooters (with minarelli engine)here in Holland already do 80/85 REAL Kilometers just by using a good exhaust , changing the main jet and make sure the variator rollers en clutch springs and return spring are well adjusted..
with a "sport" variator it is easyer to adjust all of this..

so keep your nonsens to yourself...

Getting hot in here.... wait I just got FLAMED!!!!

I simply suggested cleaning casting flaws in the reed block (which are massive FLAWS) and raising the reed stops. Both are simple and STANDARD steps you take BEFORE going much further. You always fix the FLAWS first!!

As far as the head. I made mention that I was hitting 80kph easily and I had yet to modify the head. NOT REPLACE IT but modify it. The stock head simply is not as efficient as it could be and for ten minutes worth of machining it could be made much more powerful.

As far as nonsense...
You keep buying your power out of a catalog and those of us who know how to make power will do it on our own the old fashioned way. You don't need kit parts to make it go fast. You simply need good engineering and the knowledge of what mods affect what and what combinations actually work together. But if you don't know what works buy something that someone else has made and bolt it on.

Here in CANADA we do not have quite the selection of parts readily available except through mail order to the United States or overseas. You can get much better parts much more readily where you live. Maybe that is why people rely far too heavily on catlogues and not on simple mechanics.

 

[melf #50]

why use other parts or tuning when the stock parts can be used perfectly ?

you are changing too much as far as I can see...

further ,parts can be shipped from anywhere at low cost , but if you do not search for parts you won't get any...

 

[adas]

Aloha, 2T tuning is done in stages, ie u will see several sites quoting stage 1, stage 2, stage 3, etc. I think you are looking for stage 1 tuning and that would include, pipe and variator. Stage 2 would be 70cc kit and carb, polini reed block and consulting with someone who has tuned this engine to find the "weak points". All the other stuff about shaving the head should not be done now, except for checking the "squish" for .5-.7mm clearance. All this gas-flow stuff and carter tuning is better left to stage 4-5 as the gains will be minimal and the possibilities of messing it up are large.
frank

 

[ex-racer#2]

why use other parts or tuning when the stock parts can be used perfectly ?

you are changing too much as far as I can see...

further ,parts can be shipped from anywhere at low cost , but if you do not search for parts you won't get any...

LOL

I started to reply then deleted it. NWMT

 

[tiba_karotsu]

hehehe we are very familiar with the yamaha jog artistic spec scooters & the one thing you shouldn't do is to remove the airbox or modify it in anyway at all or you're just gonna fack it all up, for 50cc touring set-up we usually do mild porting, change to higher compression head, use carbonfiber reed petals, change the vario, torquedriver, springs & belt, gearing, CDI, pipe.

you should also make some airvents at the front & rear of the transmission cover to let fresh cool air in & bleed off the heat out the back end, it keeps transmission working better & less wear & tear on the belt & springs.

you can make it go past 100kmh if you can tune the engine properly but of course you need the parts on hand as well but i believe it's next to impossible to find a scooter tuning shop in canada.

 

[MONZAV8]

this is nonsens , tuning reed blochs etc. on A std engine is BS , changing the cilinder head too...most scooters (with minarelli engine)here in Holland already do 80/85 REAL Kilometers just by using a good exhaust , changing the main jet and make sure the variator rollers en clutch springs and return spring are well adjusted...

One thing you might keep in mind is that here in the US and Canada we get alot of asian scoots (including Yamaha) with low compression motors. The Euro ones are much better in that from the factory they come 10:1, so on a Vino,Zuma, etc...upgrading the stock 7:1 compression to 10:1 can get you the extra power to maintain 80kmh.

As an example, I mailed my original Italian Minerelli jug and head to a freind with a Vino. He bolted it on and instantly had 5mph (8kmh) better top end, although he still wasnt hitting 80kmh...

So, for some people, shaving the head to increase squish really helps...

-Paul O.

 

[Rectifier]

Hey guys, thanks for all the info!

It looks like what I will do definately for now is:

tuned exhaust
rejet and change rollers to match exhaust
clutch springs to increase launch rpm

I may get a sport variator but would like to know, what is the real difference between stock and 'sport' variators? Do the sport ones have a wider range of ratios or something? At $100 at the local shop, the sport variator had better give me a good performance boost!

i may also polish the reed block as mentioned since it sounds like not much work and try to find a squish head.

I don't think I will vent the variator case. I ride in a LOT of rain and don't know how the variator would feel about that...

Also, since I do a lot of open-throttle riding, should I premix oil instead of using the lubricator pump? I heard that the pump does not provide enough lubrication for wide-open riding or tuned engines. I'm thinking of going to amsoil at 100:1 for less smoke and better protection, good idea or waste of cash? Vancouver is not a city that approves of smoke much, hehe.

Edit: Adding a question. My air filter is dry. I believe it should be oily. Regular crankcase oil, soak it then wring it out. Right?

The shop I bought the scoot from sells exhausts and some performance parts, and there is an asian scoot tuning shop here that sells parts at what seem to be pretty gratuitous prices... http://www.jiangwayne.com/scooter but they include installation, which is why they are so high, i guess. Nobody wants to do their own work around here...

 

[MikkoR]

hehehe we are very familiar with the yamaha jog artistic spec scooters & the one thing you shouldn't do is to remove the airbox or modify it in anyway at all or you're just gonna fack it all up, for 50cc touring set-up we usually do mild porting, change to higher compression head, use carbonfiber reed petals, change the vario, torquedriver, springs & belt, gearing, CDI, pipe.

you should also make some airvents at the front & rear of the transmission cover to let fresh cool air in & bleed off the heat out the back end, it keeps transmission working better & less wear & tear on the belt & springs.

you can make it go past 100kmh if you can tune the engine properly but of course you need the parts on hand as well but i believe it's next to impossible to find a scooter tuning shop in canada.

And most of the time people here have tight budgets so most just modifies/improves the stock variator, Tiba is right, mild porting, a good pipe, or a taiwan made exhaust is also sufficient for the job.

Carbon reeds, a stiffer clutch springs and main springs works for us, and also a 13/34 or 14/34 secondary gearis also a good improvement.

 

[emo]

The shop I bought the scoot from sells exhausts and some performance parts, and there is an asian scoot tuning shop here that sells parts at what seem to be pretty gratuitous prices... http://www.jiangwayne.com/scooter but they include installation, which is why they are so high, i guess. Nobody wants to do their own work around here...

that shop is really expensive! the 'YMS V8' exhaust cost $299.. here it cost around only $70.

 

[Rectifier]

So any good place to buy online then?

Which exhaust would you guys reccommend, I will be commuting not racing on this, so I don't want to rev too high and kill my engine prematurely. And I most likely will upgrade to 70cc sometime, so a pipe that will run well on both stock and 70cc would be cool.

 

[ex-racer#2]

So any good place to buy online then?

Which exhaust would you guys reccommend, I will be commuting not racing on this, so I don't want to rev too high and kill my engine prematurely. And I most likely will upgrade to 70cc sometime, so a pipe that will run well on both stock and 70cc would be cool.

If you don't want to order online you can try any regular bike shop that deals with Thibault (Les importations thibault). They are out of Quebec but have a Calgary warehouse I believe. Selection is ok but a lot of the brands the guys in Europe are talking about may not be available. For pipes they have technigas and leo vince.