200cc GY6 where's the power? (2024)

I recently upgraded a completely stock 150cc GY6 chinese scooter to 200cc. At the same time I added new air intake and exhaust. The mechanic at the time said i didn't need to change anything else but I'm disappointed with the performance increase which is only max 5-10% more power. Has anyone done this mod before? did you re-jet your carb or change it for bigger one, any other mods you would suggest to specifically suit the 200cc?

anyone else in Shanghai by the way?

Hehe, really cool to see people from all over the world here!

You will proably have to upjet your carb + re-adjust your vario.

ah ok, the mech here doesn't know what a jet is! I'll take a print out with me today.

Well the entire upgrade - 200cc (taiwan), cdi, coil, oil and rear shocks cost 1600rmb so i shouldn't complain.

Has anyone also done the 200cc mod, what size jet are you using?

I have family in shanghai (Zhongtan lu, west of central station) and always buy a ton of stuff when I'm there.

Are you sure its 200cc, because what they call 200cc is actually only 158cc 58,5mm It will fit without any mods and doesn't require a long stroke crank.
Real 200cc requires a long stroke crank and 63mm cylinder. I have never seen those kits on sale in shangai.

In Taiwan you can also get or 62mm 174cc. It requires engine case bore out in most 125cc engines.

Did you go to 'scooter street' JiaoJi Lu? That's a fun place to hang out.
But the mechanics are really quite incompetent as you've noticed, indeed they don't know what a jet is, I also notited it and hoped it was limited to that specific shop .
Well at least on 4stroke most of the time the original jet is good enough. (As long as you don't increase the compression too much).

This is my shop:

http://shop33076546.taobao.com/

Be sure to ask for a discount

By the way my advice for a decent exhaust:
http://auction1.taobao.com/auction/item_detail-db2-2a19c1316e738fad9259d988e1774ad9.jhtml

The really cheap chinese exhausts (those at around 100 yuan) will sometimes make you lose power.

So your next steps are:
-realise it's really only 158cc or 174cc, and you hopefully included a matching!!!bigvalve head. This set will give you maximum 10% or 20% power increase.... Don't put a 61mm head on a 58.5mm cylinder
-Add an A8 sports camshaft (80 yuan)
-Add a bigger carb... But be carefull with the 28mm slide carbs they sell (oko/koso etc...) probably have a 2stroke setup and they don't sell mainjets obviously.

Aidix, I wish I'd talked to you earlier - I just bought and installed an OKO carb today from Jiaoji Lu. Performance has dramatically increased, but mis-fires badly if I throttle on too quickly. Does this suggest that it is a 2 stroke carb?

The cylinder kit was indeed 63mm and matching head but there was no crank changed!? Mine was a 150cc originally...

Cheers for the shop link, my friend just bought a scoot so it will come in handy.

Are there any better places in Shanghai than Jiaoji lu to get work done?

Ok so now you have around 180cc with the stock crank that's ok... the set does not need the long stroke crank unless you 'demand' 200cc.

I'm not sure what parts are in those carbs in standard trim, but adjusting a carb always takes time, money, jets, needles etc... And I can imagine they don't have those parts on the shelve there. Maybe Jason in the other GY6 topic knows what's in those carbs. But they usually recommend a bigger CVK carb.

Here's the lineup of NCY:

http://www.ncy-motor.com.tw/english/products_2.asp?ano=00029&bno=14

Personally id take the 32mm cvk. And don't forget the A8 sports cam, for 80 yuan it's a must have. And a koso sports variator for some extra speed.

JJ Lu has everything, it's the best place for buying parts. It just doesn't have good mechanics.... That's pretty standard in China.

Thanks for the advice Aidix.

My friend was told on Sat that he could upgrade his 150cc gy6 to 250cc by changing the crank, I guess that's actually the 200cc then.

JJ lu doesn't have a good selection of carburetors and jets are non existent. In fact they were highly reluctant to change the carby at all!

How often are you in Shanghai? let me know next time you plan a trip to JJ lu!

Actually, the carb i bought is the 30mm version of this one http://auction1.taobao.com/auction/item_detail-db2-211efb277c197e37f7892b187a5d58a5.jhtml from your taobao shop. Is this suitable for my bike?

That's a 2stroke carb PWK imitation, and basically the reason why it bogs out when you open the throtle. What you need is one of those CV carbs from the NCY website or a 4s slide carb.

Here f.y.i.:

http://www.thumpertalk.com/forum/archive/index.php/t-595079.html

or a 4stroke slider:

PE24 or PE28

http://auction1.taobao.com/auction/item_detail-0db1-c24e1cb6a7b4fde22bc9b9938eb82a7d.jhtml

Also at JJ Lu.

PE24 is probably better at low speed drivability (28 a bit too big), I found one on taobao but not in shanghai.
Those CV carbs are a bit different, they're not as 'effective', so 28 is ok and 24 too small.

How'd you manage to get a scooter license, isn't that restricted for foreign nationals?

Finally it's all working, thanks for the help!

63mm Conclusion for any others considering it - definitely worth it but look into exactly what parts are required including bigger carburetor first. Find a mechanic that knows what they are doing. Mine took 5 days instead of 1 because of incompetent mechanics.

The engine mods increased power but it took a lot of time to get it all working correctly. You definitely need to change the rollers and probably the clutch to get the extra power onto the road. The increased air flow from the filter and exhaust need to be matched by re-jetting or replacing the carburetor. I tried both and found the best performance from a 30mm carby.

Note: if you buy a new carburetor make sure that you buy a 4 stroke model. It is possible to get the 2 stroke working but it is extremely difficult to tune and will most likely lead to problems when you try to open up the throttle too quickly.

My biggest increase in performance actually came from replacing the rollers and clutch - this increased top speed by 20kmph.

Well the clutch can't make any difference in top speed, it's only for takeoff from standstill.

So what carb and rollers did you get ? Do you have Dr Pulley rollers?

Aidix said:

Well the clutch can't make any difference in top speed, it's only for takeoff from standstill.

So what carb and rollers did you get ? Do you have Dr Pulley rollers?

Click to expand...

hello aidix, alby are you in shanghai city? great you got F1 track there
you'll be leader of motor racing in asia nearest future!
taobo website is very interest but not the best parts, the copied Yoshimura ex-pipe, did you get it from xiao-bao of Taiwan?
OKO PWK28, NCY CVK30/32(copied by OKO) all come from JeJiang,
assembly in Taiwan.
maybe your Keihin PE26/28 from Tailand is better, easy tuning,
Keihin CVK32 w/o auto choke power does not compete with PE28
for cylinder displacement 180cc what's ever GY6 or R1
max cyl disp of GY6 is 224cc, bore size 64 x 69.8mm, PE32 carb
correct transmission tuning is of course able to get more speed
nice know you guys here, cheers

I'm in Holland, I just visit shanghai once a year.

The shop from the taobao link is my 'favorite' shop in shanghai. The exhaust is made in china, it's really good quality comparable to taiwanese exhausts but much cheaper. (the yoshimura sticker is not included when you buy the exhaust!)

Aidix said:

I'm in Holland, I just visit shanghai once a year.

The shop from the taobao link is my 'favorite' shop in shanghai. The exhaust is made in china, it's really good quality comparable to taiwanese exhausts but much cheaper. (the yoshimura sticker is not included when you buy the exhaust!)

Click to expand...

the POWER SOURCE w/Japanese words is the Yoshimura sticker, but these canister is not Yoshimura original looking, they should copy it 100% like.
for scooter 4 stroke small engine, disp. under 125cc, it should be made
as back pressure chamber in the canister,and big bore disp. made as
straight exhaust with taper inner tube.
we've a lot of canisters for scooters and I don't know how to post the photos on to quote page

Jason, can you give any suggestions for a good exhaust for my 170-180cc bike? I currently have a 'Beet Japan' exhaust which I have no idea of authenticity or anything.

I ended up changing for a Keihin PE 26mm carb. It turned out the mechanics solution to the OKO carb was punching holes through the air filter with a screw driver. I only found out when the entire filter fell off.

alby said:

Jason, can you give any suggestions for a good exhaust for my 170-180cc bike? I currently have a 'Beet Japan' exhaust which I have no idea of authenticity or anything.

I ended up changing for a Keihin PE 26mm carb. It turned out the mechanics solution to the OKO carb was punching holes through the air filter with a screw driver. I only found out when the entire filter fell off.

Click to expand...

alby, not know what is the Beet Japan ex-pipe, is it straight inner tube?
if so, your bike is poor bottom end to mid range speed, better speed until
high rpm. are you in holland? the closed supplier www.gy6-motor.de
change the very light clutch set, super clutch to raise the engine rpm to forward the power band to improve the bottom to mid speed.

alby said:

Jason, can you give any suggestions for a good exhaust for my 170-180cc bike? I currently have a 'Beet Japan' exhaust which I have no idea of authenticity or anything.

I ended up changing for a Keihin PE 26mm carb. It turned out the mechanics solution to the OKO carb was punching holes through the air filter with a screw driver. I only found out when the entire filter fell off.

Click to expand...

alby if you change the super clutch set, remember the roller weight need to be changed to 13 g, engine rev up fast for your power band.
if you can look the super variator, which is open slide machined for variator ventilating & belt grip tightly, the 2 working together will increase
much transmission efficiency.
machine 1 mm off from the bottom top of your 63mm cyl to get cyl comp
pressure, to get more power for your chinese weak power ex-pipe

He's in Shanghai.

GY6-Motor.de doesn't sell sports exhausts, they are illegal in germany and police is very strict
'Beet japan' is a japanese muffler, well that's what the shop says, but the header pipe is chinese if you ask me.

You can buy a few types of Taiwan exhausts in Shanghai. (Some NCY and RPM).

Aidix said:

He's in Shanghai.

GY6-Motor.de doesn't sell sports exhausts, they are illegal in germany and police is very strict
'Beet japan' is a japanese muffler, well that's what the shop says, but the header pipe is chinese if you ask me.

You can buy a few types of Taiwan exhausts in Shanghai. (Some NCY and RPM).

Click to expand...

yes they have a Tri-Oval canister racing pipe for GY6 150 full mods.
sorry the beet japan never hear before frankly it seems a chinese made
not much craft tech especially the stupid headpipe, if you like let me show
you what is the qualified ex-pipe of taiwan but I don't how to post it