Chinese Scooter Club Forum Index

Home | Forum | Arcade

How increase performance of your 125 - 150cc GY6 engine
Goto page 1, 2  Next
 
Post new topic   Reply to topic    Chinese Scooter Club Forum Index -> Tuning and Modifications
View previous topic :: View next topic  
Author Message
Spanner



Joined: 14 Jul 2007
Posts: 1707
Karma: +64

Location: Port Melbourne...that's the land down under

PostPosted: Fri Nov 30, 2007 2:46 pm    Post subject: How increase performance of your 125 - 150cc GY6 engine Reply with quote

Twisted Evil How to modify and increase the performance of GY6 scooter engines Twisted Evil

A lot of scooters are powered by a 125cc - 150cc engine based on the Honda GY6 scooter engine design.
The GY6 engine with CVT (continuously variable transmission) has decent performance for it's small engine displacement. It surprising how well of a job a small 125 -150 engine can do at moving an adult around on a scooter. Of course, more power would always be nice, but considering the small displacement of this GY6 based engine, it really is impressive. Even so, mod kits for gas scooters are available, and other modifications can be made to increase performance even further.
The GY6 based engine found in our beloved scooters is like any other internal combustion engine - in that it can benefit from some well directed modifications. This is true of just about any mass produced engine which have compromises that are driven because of manufacturing restraints like time and cost. These compromises usually limit efficiency and performance potential of an engine. Increasing airflow through an engine is the goal. More airflow along with the appropriate amount of fuel will result in more power producing potential. With this idea in mind, let's look at some ways that the performance of scooter engines can be increased.

1) Install a high flow air filter system. The stock airbox can be eliminated and a high flow air filter like a K&N style or Uni-foam filter can be used. An intake tube can be made out of aluminium tubing, steel exhaust tubing, probably even PVC or other material that is the right size tube to match the air filter and carburettor intake diameters. A piece of radiator hose from an auto parts store can be used as a rubber connector between the carburettor and tubing. Just be sure to clamp everything together securely and make sure that there are no air leaks where dirt can enter your engine.
When using a foam air filter like a K&N or a fabric gauze filter style, be sure to apply plenty of the proper air filter oil. Without the oil, the foam or fabric filter media will NOT be effective in filtering out damaging dust and dirt particles and you could (probably WILL) wreck critical parts like piston rings and probably scuff and score the piston and cylinder bore. What is good is it to increase power by modifying your engine or installing mod kits for scooters, and then quickly wreck your engine because of sucking in dirty air?!? You won't have much power with a worn out cylinder or rings. Worse yet, a worn engine will burn oil and if you don't keep an eye on your oil level, you can seize and fry the whole engine because of lack of lubrication. The moral of the story is simply: don't neglect your air filter - check and clean it frequently!

2) Another way to increase the performance of a scooter engine is to increase exhaust flow. Stock mufflers can be cut open and gutted out, but beware that this can be loud. In addition, check to see if there is an aftermarket exhaust systems available for your particular scooter. There are mod kits for scooters that come with a high performance exhaust. Some stock scooter engine mufflers can be very restrictive and choke the ability of the engine to rid itself of exhaust gases and as a result prohibit the inflow of fresh air/fuel mixture into the cylinder. As a result, a restrictive exhaust can severely limit the airflow through and engine. An exhaust system upgrade can yield a big improvement in performance as long as the additional flow is combined with properly tuned carburettor...

3) Re-jet your carburettor! Modifying your scooter engine for additional airflow will NOT increase performance, UNLESS you have the appropriate amount of fuel to go along with it to produce more power. Depending on the modifications you make to your engine, you should probably look to re-jet your carburettor with a main jet in the 120 –130 size range (for GY6 150 engines). Many of the GY6 scooter engines seem to use a Keihin style CV carburettor (24mm), so check with a motorcycle shop or motorcycle supply source that sells carb jets. It would probably be best for you to bring in your stock jet so it can be visually matched with the new one that is the right style. Best to error on the rich side (larger jet), because too small a jet and you could run too lean and damage your engine. If someone were to put on a high flow intake filter and also a high flow exhaust, then you'd probably want to look closer to the 130 main jet size if you have the stock 24mm CV carb on a 150cc gy6 engine.

Depending on elevation, a 125, 128, or 130 might work well with a high flow air filter and exhaust near sea level. You might want to buy a few different jet sizes and then experiment with what gives you the best performance. Read your spark plugs to see if you are running lean or rich under wide open throttle conditions. Just remember, that too lean of an air/fuel mixture can increase engine temperatures and cause engine damage. If in doubt, err on the rich side with extra fuel to help avoid engine damage.

4) Eliminate automatic choke. Most of the GY6 scooter engines seem to come equipped with the Keihin style CV carburettor with automatic choke. In theory, this is a nice feature - the choke turns on by itself when needed and then shuts itself off - assuming it all works properly. Unfortunately, the automatic choke on these carbs seems to have a tendency to stick ON at times. As a result, the air/fuel mixture will be way too rich. This KILLS performance. There are a few ways to deal with this... one is to just remove and block off all passages in the carb for the automatic choke. An epoxy such as JB Weld can be used or one of the epoxy putties commonly found in automotive stores.
If you primarily drive in warm weather, then the choke may not be needed anyway. However, if you drive in cooler climates, then you may need a way to richen the mixture so that you can get your engine started easier. Getting a whole new carburettor with a manual choke is one idea.
Mikuni TM24 carburettors can be used as a substitute, but since it's a slide carb then the throttle cable will need to be modified or replaced. The TM24 carburettor (or other manual choke carbs) also may require a spacer on the intake manifold to help the float bowl clear the engine shroud underneath. Another way to get fuel enrichment on a stock carb with choke removed is to add one of the plunger primers that are made for use on snowmobile or ultralight engines. This primer plunger can be pumped and squirt fuel into the intake and help with cold weather starting. A small 1/8" fitting needs to be added where the fuel is squirted into the carburetor or intake manifold. Also, a 1/8" hose needs to be added to supply fuel to the plunger primer. This supply line can be T'ed off the main fuel line or fuel can be tapped off the float bowl or however it works best on your application. Adding this plunger primer is not the easiest method but it does work, and allows the stock carb to be used in cold climates with auto choke eliminated. Just check to make sure that it will fit your particular application. Not all carbs fit all engines! In any case, whatever you end up doing, eliminating the stock automatic electric choke can result in much more consistent performance. If your engines runs consistently well all of the time, then don't worry about changing the auto choke. However, if your scooter engine runs strong one moment and then feel sluggish the next, then it MIGHT be the auto choke sticking on. Just be aware of this as a factor in performance.

Another way that people try to increase performance of a scooter engine is to increase ignition advance. Ignition timing is when the spark plug fires relative to the position of the piston (and crankshaft/flywheel). The gy6 engine has a magnet imbedded in the outside surface, which passes by a pickup sensor that acts as the trigger for initiating the ignition spark. By changing the timing of the spark, it is sometimes possible to increase power and torque of an engine. There are a number of ways that this can be done. One way is to reposition the ignition pickup that is located next to the flywheel. However, to make any significant changes in timing this way, trying to move the ignition pickup may require welding and drilling/tapping of new holes for the ignition pickup mount. This is probably not the best way for most people. Another way is to take a stock flywheel key (that indexes the flywheel on the crankshaft and keeps position secure) and grind an offset so that the flywheel is repositioned relative to the ignition pickup. This is probably also not the most straightforward way of doing this.
A different way that is more convenient is to install a performance CDI (capacitive discharge ignition) module that has additional ignition advance programmed into the ignition calibration. These may be included in some mod kits for gas scooters and go karts, or you can often buy one by itself. The CDI is sort of the brain of the whole ignition system and changing modules is as simple as unplugging the old and plugging in the new. Truly just Plug and Play! Just be sure you get a CDI that actually has a remapped ignition curve with additional ignition timing advance. Some modules might simply have a higher RPM rev limit. If you want to advance your ignition timing, then make sure the unit you get actually has the advance programmed into it!

6) Another way to increasing air flow is to port the cylinder head. This article will not attempt to give specific instructions on the entire "how to" details of porting. Just note that careless or improper porting can HURT engine performance. Even worse, porting done improperly can not only hurt performance, but also result in damage to the engine.
If you are not familiar with porting, then the best way to learn is to research, read up on the subject, watch someone who knows what they are doing, and then get some hands on experience yourself.
Just don't experiment with a cylinder head that you can't afford to scrap. When porting any cylinder head, you have to be very careful not to damage the valve seat-sealing surface. If you make a nick there, then it will at least require regrinding of the seat and if the gash is deep enough, grinding may not do it. In that case, a new valve seat may need to be installed or a whole new cylinder head purchased. In either case, it can be an expensive mistake.

7) One of the most powerful tools to use during porting is the finger! The finger can feel the shape of the port and help find spots that need to be worked on. A smooth airflow path is the goal. No abrupt changes in the flow path - especially where a passage restricts down to a smaller size. That’s bad. If there is a mismatch in ports necessary, then it should be done in such a way that airflow goes into a larger diameter. In other words, mismatches should "step up" in size in the direction of flow. You don't want the airflow along the surface of a passage to slam into an abrupt "wall" (or edge) as it transitions to another passage.
On the exhaust port, the port can be enlarged to match a larger header exhaust if you plan to use one. If you plan to stick with a stock sized exhaust header, then just use a die grinder and sanding roll to clean up the casting surface in the exhaust port. You can shape the valve guide knot as well. On some race engine, builders will completely remove the valve guide knot in the ports to increase flow, but for most engines this is probably not a good idea because much of the valve guide bearing surface is lost, and in the long term the valve stems may then wear the smaller valve guide bearing surfaces too quickly. The valve may also not be properly supported with such a short valve guide.

Hope that helps and that a Moderator maybe makes this post ‘sticky’ ... Wink




_________________


Last edited by Spanner on Sun Feb 03, 2008 1:20 am; edited 1 time in total
Back to top
View user's profile Send private message Visit poster's website
Scootin
Moderator


Joined: 09 Oct 2006
Posts: 7238
Karma: +168

Location: St. Johns MI USA

PostPosted: Fri Nov 30, 2007 3:00 pm    Post subject: Reply with quote

Stickyfied & a big Well Done! Icon_thumbs_up

I am going to try some of those ideas on my 150cc come spring. Especially the Free-flow & upjet job. Smile


K for job well done! Cool



_________________
2005 50cc Taishan Sport XT

2006 150cc Hitong SR-150 (2007-2010)

Member since October 2005
Back to top
View user's profile Send private message
Fox



Joined: 05 Jan 2007
Posts: 7443
Karma: -301

Location: Los Angeles

PostPosted: Fri Nov 30, 2007 3:06 pm    Post subject: Reply with quote

That info was all ready stickied in the third thread in 'Tuning and Mods"
Clic the link and you'll even get pics.


Back to top
View user's profile Send private message
Spanner



Joined: 14 Jul 2007
Posts: 1707
Karma: +64

Location: Port Melbourne...that's the land down under

PostPosted: Fri Nov 30, 2007 4:06 pm    Post subject: Reply with quote

Thanks for the K scootin Wink , as Fox said; it's probably been knocking around for a while, just thought it might come in handy for anyone thinking of tuning their GY6 engines as I've done.

It all worked too Wink I've now got the roadster running with the 175cc engine I'd built after following this guide...Hence it's no longer for sale Exclamation

Performance is something else...totally different animal all together now, loads of usable torque on most levels, and a healthy top speed.

Mike SP



_________________
Back to top
View user's profile Send private message Visit poster's website
NoBike



Joined: 27 Feb 2007
Posts: 3267
Karma: +48

Location: Lancashire, UK

PostPosted: Fri Nov 30, 2007 6:25 pm    Post subject: Reply with quote

You built a big bore kit? Shocked you are God!



_________________
Back to top
View user's profile Send private message
Spanner



Joined: 14 Jul 2007
Posts: 1707
Karma: +64

Location: Port Melbourne...that's the land down under

PostPosted: Fri Nov 30, 2007 6:51 pm    Post subject: Reply with quote

A God Shocked Naaah Laughing Originally planned to build a 180cc, only locating a decent quality piston proved tricky, and the aditional machining wasn’t worth the extra hassles, so I bought the 175cc kit which included ***Head, Barrel, camshaft & Piston, studs & gaskets from scoot's along with the 30mm carb & block, free flow and Twin Shot exhaust system.
***I ported the head myself just to help it to run smoother with the 30mm carb, exhaust; just cleaned off the rough bits.
DRP Variator & HiT clutch mods, KV drive belt.
Hi-Point coil & CDI + vari rpm...and a NGK CR7 HIX Iridium Plug!!

I originally tried fitting a 32mm carb but got nowhere, 30mm worked much better, also I've fitted an electric fuel pump to replace the vacuum one.

Mike SP



_________________
Back to top
View user's profile Send private message Visit poster's website
Yellow Scooter



Joined: 20 Mar 2007
Posts: 7113
Karma: +78

Location: North Carolina USA

PostPosted: Fri Nov 30, 2007 9:11 pm    Post subject: Reply with quote

Darn. Already read it. I Was hoping for a new found secret.
A very well done cut-n-paste though, I must say.



_________________
29997, 98, 99, 30,000 30,002!!
I told ya she'd do it!!

2006 QingQi QM150T-10V
25-Jan, 2007 to 13-Nov, 2011
Rest in peace!
Back to top
View user's profile Send private message Visit poster's website MSN Messenger
Spanner



Joined: 14 Jul 2007
Posts: 1707
Karma: +64

Location: Port Melbourne...that's the land down under

PostPosted: Fri Nov 30, 2007 9:45 pm    Post subject: Reply with quote

It pretty much covers everything you need to know about getting the best from the GY6 engine, and more to the point; it really does work Icon_thumbs_up
Also handy reading for the 'newbies' Wink

Mike SP



_________________
Back to top
View user's profile Send private message Visit poster's website
Qixen



Joined: 06 Jun 2008
Posts: 55
Karma: -2

Location: I live in Bristol-UK / I'm freaky

PostPosted: Sun Jun 08, 2008 2:12 pm    Post subject: Reply with quote

hello, I'm new here and where can I buy big bore kit and Exhaust...ect?
-hard find chinesescooter website Confused
will fit for my Chinscoter? Rolling Eyes



_________________
-

-
Back to top
View user's profile Send private message
Yellow Scooter



Joined: 20 Mar 2007
Posts: 7113
Karma: +78

Location: North Carolina USA

PostPosted: Sun Jun 08, 2008 2:59 pm    Post subject: Reply with quote

Your avatar looks strikingly similar to my current bike Qixen. Where are you from? Is that a 125 or 150cc? Pretty much any GY6 kit will fit.
Try www.partsforscooters.com
also www.scootertronics.com
www.ginospr.com has a nice lookin kit that addresses everything from head to clutch.
http://www.ginospr.com/page8.html is the kit I'm talkin about Wink
Don't forget if top speed is what you are ultimatly wanting, you'll need to have a taller final drive gear pressed into the back end. Keep in mind, it'll make takoffs at stoplights a bit softer, but if it's properly tuned, it won't be too bad.



_________________
29997, 98, 99, 30,000 30,002!!
I told ya she'd do it!!

2006 QingQi QM150T-10V
25-Jan, 2007 to 13-Nov, 2011
Rest in peace!
Back to top
View user's profile Send private message Visit poster's website MSN Messenger
Qixen



Joined: 06 Jun 2008
Posts: 55
Karma: -2

Location: I live in Bristol-UK / I'm freaky

PostPosted: Sun Jun 08, 2008 11:04 pm    Post subject: Reply with quote

hello, thx you :D, I'm Italian -I live in England-UK

my scooter is 125cc.
my scooter is 152QMI will fit it?


EDIT: here - www.Gy6-Motor.De



_________________
-

-


Last edited by Qixen on Thu Jan 29, 2009 6:15 pm; edited 1 time in total
Back to top
View user's profile Send private message
Qixen



Joined: 06 Jun 2008
Posts: 55
Karma: -2

Location: I live in Bristol-UK / I'm freaky

PostPosted: Fri Jun 20, 2008 10:15 pm    Post subject: Reply with quote

-----

EDIT: sorry I post here..



_________________
-

-
Back to top
View user's profile Send private message
fragrance_jane



Joined: 27 Aug 2008
Posts: 12
Karma: -39


PostPosted: Wed Aug 27, 2008 2:47 pm    Post subject: How to Improve the power and look of scooters Reply with quote

A scooter with a GY6 50 engine can be improved with better power and look.

This engine (139QMB) is used in scooters from Kymco, Diamo, Schwinn, Q Link Geely, Roketa, Tank, Avanti, Meitian, Strada Verucci Pep boys and most 50cc four stroke scooters plus many others made in China.

when upgrading your 139QMB GY6 49cc four stroke engine the three main areas to consider are cylinder kit, exhaust and clutch. Build out from these and youwill get results. If doing a clutch do roller weights and belt also, when doing cylinder kits add exhaust, jets air filters ext. To ensure the stable use of the above performance items, air coolers are suggested to use.

When improving the look of the scooter, there are also three areas to consider: change the handle grips with shining chrome handle grip tip; stick night-shining slips on the rims; use a cool or nice bike stand.

For more information, pls add me to your contact list.

Jane
www.highperhz.com
msn:highperhz@hotmail.com


Back to top
View user's profile Send private message
BigCheeseStick



Joined: 20 Aug 2011
Posts: 1465
Karma: +34

Location: Myrtle Beach

PostPosted: Wed Sep 07, 2011 4:27 pm    Post subject: Reply with quote

Probably should'a posted this under this thread to begin with. But, anyway. This may prove useful to anyone looking here! Smile

http://chinesescoots.forumwise.com/chinesescoots-thread18764.html


Back to top
View user's profile Send private message
johnr



Joined: 18 Apr 2007
Posts: 77
Karma: +14

Location: lancashire england

PostPosted: Wed Feb 08, 2012 9:36 pm    Post subject: Reply with quote

oh god, I dont even know where to begin with this topic. lest to say that if you do either 1 or 2 but not 3 then you are a fool. suggesting that improving airflow makes an engine better, faster or more powerful doesn nothing but display your ignorance of simple gas flow dynamics and engine performance. all tuning is a compromise. there is no free lunch. you either tune for more top end, but lose the bottom and mid range or you tune for more mid range but lose the top end. the tricky bit is to work out not what to do, but why what you do affects performance in various parts of the engines performance curve. for example, improving air flow can, note can, be be a good thing for performance. BUT, when you put more air in, you MUST make moves to allow more exhaust gas out. if you dont, then you might as well go and piss into the wind for all the good it will do you. and air alone doesnt make power, you need the right amount of fuel to mix with it, and the fuel needs to be correctly mixed, at the right ratio and to the correct level of atomisation. jets arenot the whole answer. the main jet of a carb on an engine only directly affects the top third to quarter of the engines rev range. therefore upjetting alone will leave two thirds to three quarters of the engines potential fueling problems untouched. I will try and go into a much more detailed, and accurate description of tuning an engine another time, because I could go into many many pages. all I will say is you take the advice above with a huge pinch of salt. sorry to the original poster, because I'm sure they mean well, but ive seen a lot of melted pistons in my time, and ive built and tuned a lot of engines from strimmers and glowplug engines to thumping diesel genny engines right up to 1200cc 16 valve sprint engines with 150+bhp on tap. ive built engines for a long while, and even now I'm still learning. but tuning is a complicated art and theres more to it than just making everything bigger.



_________________
one day you wake up, and all the pain youve given out gets returned.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Chinese Scooter Club Forum Index -> Tuning and Modifications All times are GMT
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
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 vote in polls in this forum


Powered by phpBB © 2001, 2002 phpBB Group
Theme created by Vjacheslav Trushkin
Effex-Media Web Resources

Scooters | Scooter Insurance | Moped Insurance | Direct Bikes | Direct Bikes Reviews


Free Forum Free Top Site List
Make this Forum Ad-Free




31949928