Most Common Mods for gy6 150cc

[SLESTAK75]

I notice that lots of new members come on and ask what they can do in order to get more out of their buggies. Not that I don't enjoy talking with new members; but with a single thread to point new members toward that shows all of the common mods in one place with the explanations of the effects they will have, will save lots of typing and help lurkers to find answers without having to sift through multiple threads. Please feel free to add to this thread, but for the sake of making the info easy to sift thru please keep comments "to the point". Try to keep this to a minimum. This will make things easier for all. Thanks in advance for all of your input.

[SLESTAK75]

First most common mods are to open up the intake and exhaust. This can be achieved by removing the stock air filter box and replacing it with a Uni or K&N type filter attached to a 6-8" piece of 1-1/2" pipe (PVC or similar). This can be attached to the carb with a rubber 1-1/2" to 1-1/4" reducer coupling available in plumbing section of the hardware store. The muffler can be opened and gutted, Or remove the outlet piece and open the outlet hole to around 3/4" to 1". This must be accompanied by an increase in the main jet size. To determine whether your jet size is correct you can "read" the spark plug. Remove the plug, clean well, and replace. Take buggy on a 10 min run at full throttle. Stop immediately and remove plug and inspect. Tan color to dark brown is where you want it. If the plug is white you are running lean and hot and will damage your engine. You will need a larger main jet. If the plug is black you are running rich and need a smaller jet. For basic mods to intake and exhaust, most run better with a 125-128 main jet.

[SLESTAK75]

The ignition will benefit greatly by installing an iridium spark plug and hi output coil. The effect of a performance CDI is debatable. Some say they benefit and others do not. It seems to depend on the engine.

[SLESTAK75]

The CVT transmission can yield nice gains in overall performance with proper tuning. CVT weights and Contra springs are used to tune the CVT. Also the clutch and clutch springs. To understand how each of these parts affect performance it is important to understand what they do and how they interact. First of all it is important to know that tuning the CVT does NOT create power. The CVT transfers the power from the crankshaft to the rear wheels. A CVT that is not tuned properly can rob alot of power, so the objective is to create the most efficient transfer of power possible. The variator is a pulley in two halves. The outer half is stationary and the inner half is moved in and out by weights that run on ramps. The weights are thrown outward by centrifugal force as the rpm's increase. This causes them to ride up the ramps which pushes the pulley halves together. As the halves squeeze together it causes the belt to ride up the pulley faces. This in turn causes the belt to get pulled deeper into the rear "driven" pulley or torque sheave. The tension of the rear pulley is adjusted by the contra spring. Here is a link that shows a CVT shifting so you get the picture.

http://www.google.com/url?sa=t&rct=j...,d.dmQ&cad=rja

After looking at this video I wish I hadn't written so much but oh well. The heavier the weights in the variator, the quicker they are thrown outward and the lower the rpm's needed to shift. If you go too heavy your shift begins almost immediately robbing the takeoff power of the low gear. If you go too light you rpms will be higher as the shift occurs which gives you the benefit of the lower gears power for takeoff and climbing, but it is possible to go so light that the variator never fully closes which robs top end speed. This interacts with the spring on the rear pulley. The stiffer the spring the slower the shift and the more weight needed in the variator to accomplish a full shift. This is desirable when doing lots of hill climbing as the stiffer spring causes the CVT to downshift faster. A lighter spring will speed the upshift and slow the downshift and requires less weight in the variator to achieve full shift. This is desirable when constant cruising speed is your goal( such as in the case of a scooter). Most often a stiffer spring works better on a buggy due to its weight. There is no absolute perfect combination of components for the CVT. The components must be tested and catered to the preference of the owner. There is a range that seems to work best. Ultimately what I look for is the combination that gives the desired rpm thru the shift and still allows the CVT its full range of motion. Slider weights seem to perform better and last longer than roller weights. Most choose either a 1500rpm or 2000rpm Contra spring, and anywhere from 10gram to 14gram weights depending on the contra spring. 10-12 for 1500rpm 12-14 for 2000rpm. This is only a suggested starting point and beyond that the user will have to determine what they want. Higher rpm's = lighter weights. Lower rpms = heavier weights. A clutch with larger pads will grab and hold up better. Different clutch springs will determine when the clutch engages. Lower rpm rated springs will engage the clutch at lower rpms and vice versa. Please feel free to add if I missed anything.

[SLESTAK75]

Also in the CVT there are larger variators 115mm up from 107mm stock this gives the belt more room to travel for a slightly higher top speed. This can be paired with a performance rear pulley that also allows the belt more room to travel. This could be used to increase top speed or allow for lower final gears without losing as much top speed. This could give the benefit of more torque to the rear wheels at takeoff while retaining top speed.

[SLESTAK75]

Next up is the cam. All performance cams have more lift and duration than the stock cam so any that you choose will render better performance. The most common range of cams is A8 to A12. The lower numbers (A7,8,9) have higher lift and have the greatest gain in the higher rpm range. The highest number (A12) has less lift and more duration giving the greatest gain in the low to mid rpm range. The numbers in between shift from lift to duration accordingly. Its hard to find actual data on each one of these cams. For trail riding most will say the A12 is the best choice. If you want a high rpm drag racer go for an A8 or A9. It is recommended that if you decide on the high lift cams you make sure you install high rpm rated valve springs to avoid valve float. Many an engine has been destroyed by overlooking this. This is not meant to start a debate or offer a hard and fast absolute as to what a person should choose. Tailor your cam to your needs. Be aware that changes to the cam will require even more adjustment to carb jets. Here are some links to charts that show lift and duration for each cam A8-A15. It seems that 12-14 are ideal for these buggies.

http://www.scooterchinois.fr/uploads...527980b619.jpg

http://www.scooterchinois.fr/uploads...527b35b439.jpg

[SLESTAK75]

Some choose to replace the stock intake with a 32mm intake. This can actually reduce performance on a stock 150cc. The same can be said for a larger carburetor. If you choose to go for a larger bore then you could benefit from larger carb and intake, but we are talking basic mods here. We will have another thread on advanced mods. There is performance to be had from the stock intake. These are rarely if ever matched to the port on the head. The stock intake can easily be opened up to match the intake port on the head.To do this you will need a dremel or drill with appropriately sized stones to shape the metal. Remove the intake and spacer. Now replace the spacer and feel the underside of it to compare it to the size of the intake opening. Start removing material from the spacer until it matches the intake port. Now use the spacer to match the size of the intake opening. Once the intake opening is matched to the spacer then use your eyes and fingers to judge where material inside the intake has to be removed to give the smoothest and least restrictive path of travel from the carb side to the head side. DO NOT increase the size of the carburetor side and DO NOT smooth out the inside of the intake. It needs to be rough. I used spherical stones designed to fit in a drill to do mine. It took a couple of hours for the whole procedure but alot can be gained from this as these intakes are often extremely mismatched. Depending on what sort of flange you have on your exhaust you could do the same to it. It is recommended however, that the exhaust flange be" slightly" smaller than the exhaust port for best performance. Again, this opens even further the intake and exhaust and must again be accompanied by adjusting the main jet size in the carb.

[SLESTAK75]

The head can also be ported and polished. This is moving out of the realm of "basic" mods. Unless you have skills and tools for this job it is recommended that you have it done by someone who does. Tom at Syc Powersports is a perfect candidate for this. He can be reached by PM to SYCARMS or click the banner at the top of the page and go to the contact tab. The stock head has smaller exhaust valve and ports since 2009 so for best performance some money may be in order to get a large valve, large port head, and have it ported and polished. There is even a 4-valve head for these that could also be p&p'd. This is not to say that you won't get nice gains from porting and polishing the stock head. This will again require adjustment to main jet, but by far is the greatest increase in performance of any mod so far. It is surpassed only by going big bore and in some cases could even surpass a big bore with a stock head. The head can also be milled on the chamber surface in order to increase compression. A combination of all these mods will give you all you can get from this motor in its stock form

[SLESTAK75]

That's all I can come up with for now. If I missed something or messed up a detail please feel free to add. There are other mods that can be done; gearing changes, big bore, stroker crank, shocks....Most of these go beyond simple mods and will be explained further down. Stay tuned.

[Miamieddie]

Bm. Should make this a sticky!! This is good info...Eddie.

[4pullingGM]

Thanks for the info! I've been a mechanic all my life but fairly new to the buggies. My girls have a Carbide 150 which is all stock for now, but they love helping me in the garage. So with all of this info they may not want to leave it stock for long!

[xlint89]

Post #11 helps to show what some of these mods did for my Yerfdog 150

http://buggymasters.com/forum/showthread.php?t=2670

[SLESTAK75]

Thanks for adding that here xlint. Great addition. Is there anything that anyone can think to add?? Basic bolt on mods??

[SLESTAK75]

Originally Posted by 4pullingGM

Thanks for the info! I've been a mechanic all my life but fairly new to the buggies. My girls have a Carbide 150 which is all stock for now, but they love helping me in the garage. So with all of this info they may not want to leave it stock for long!

Glad to help. If you have questions please feel free to ask. We would be glad to help.

[4pullingGM]

Awesome, thanks!

[bear]

How about something as simple as tires?

[x-bird]

Shadetree air intake for improved CVT/belt cooling. Remove stock -4-hole screened cap, insert narrow vacuum cleaner or pool hose, route where you will to cleaner fresh air and use some door screen and prefilter foam.

[SLESTAK75]

Thanks for the input gentlemen. Now we are getting somewhere. Thanks bear. As I recently discovered even bad alignment can REALLY slow down your buggy. And I know that the right tires on any vehicle I have ever owned made a nice difference in ride, comfort, and even fuel mileage. And you know that if your fuel mileage gets worse you are losing power and vice versa. Thanks x-bird for the reminder that keeping ALL parts cool will not only prolong their life but also keep them performing their best. Innovation in cooling can help us all to have better performing longer lasting buggies. Thanks, and keep it coming.

[SLESTAK75]

Need some input here. Should another thread be started for more advanced mods such as big bores and stroker cranks, or should we just add it to this thread? I have no experience beyond what I have posted here so far, and as a result will need input from those of you who have done big bores, and strokers, or any other sort of performance mods such as these. Thanks.

[x-bird]

I'd say keep those here, and keep it to the GY6 engine if it's going to be stickied.

[SLESTAK75]

I'm not sure if it will be stickied or not. It sure would be a good idea though......HINT....HINT.....WINK......WINK.....NU DGE.....NUDGE.........BM

[SLESTAK75]

So next up will be the more involved mods to the GY6. I can tell a bit about what they are but I am hoping that those who have dealt with and resolved some of the issues that can come up with these mods will chime in with that. I will allow some time to pass between each post in hopes that these tips will be posted in order.

[bear]

Just keep throwing them out there Slezman, all info is appreciated!!!

[SLESTAK75]

Heads are a great place to pick up a lot of extra power. The head was mentioned earlier but here is a bit more detail on what can be done. To start with stiffer springs can be installed to compliment a higher lift cam. These will help prevent valve float which can and does put pistons and valves in contact causing major damage. Also lighter stainless steel valves and titanium valve retainers can be installed. This is going to run you nearly $100 and the return in terms of power gained is minimum. The advantage to this upgrade is mostly reliability as these parts are way stronger than stock steel.

[SLESTAK75]

Next up is porting and polishing. Heads are made by casting metal into a mold. This process is very inconsistent as far as the size and shape of the head's passageways. Casting seams and slag will be left behind which will cause restriction and turbulence. A dremel or similar tool and stones or sanding heads can be used to not only remove these defects, but also to improve the shape and open up the inside of the port to allow better flow. Keep in mind the direction that the gasses are flowing in order to determine how best to shape the inside of the port to allow for better flow. It is better to take your time as getting in a hurry could lead to irreparable damage and lead to the need of purchasing a new head. Things to keep in mind: the intake port does NOT get polished, only ported. It must remain rough inside to encourage atomization of the air fuel mix. After porting the exhaust side you should polish to a near mirror finish. The smoother the exhaust port the better flow it will have. Again, most would opt for a professional to do this job. I did and I was not sorry to spend that money as someone who has experience knows the best way to shape the inside of the port in order to get best flow. It is not enough to just open it up. While this will most likely create more power, a poorly shaped port can actually hurt performance. There is plenty of info on porting and polishing on the internet if you chose to do your own. Just be aware that you can damage a head beyond repair. That being said, there is no substitute for a properly ported and polished head. By far the best bang for your buck upgrade there is. Especially if you can do it yourself.

[SLESTAK75]

Along with that a head can also be milled on the combustion chamber side. A special machine is required for this so most will need this done by a professional. This is the process of removing metal from the cylinder side of the head. This squeezes the combustion chamber and piston closer together creating more compression. Gasoline gets more explosive the more it is compressed. More compression=stronger explosion=more power. At this point it should be mentioned that if you are not using high octane gasoline you REALLY should. Also it is a good idea to use 100% gasoline (no ethanol) if it is available to you. This is a good rule of thumb in ALL small engines.

[SLESTAK75]

There is work that can be done to valves and valve seats. 3-angle or 5-angle valve jobs. It has been noted that the gains from this on a 150cc single cylinder engine are very small. If you absolutely need to trim 1/10th of a second off of your run time then by all means get a valve job; otherwise, you should not spend that dime. If this is something you are skilled enough to do on your own then go for it; but if you are considering paying someone to do it for you, your money would be better spent on something else.

[SLESTAK75]

At this point I will allow some time for comments. If anyone has tips on performing headwork at home then don't be shy. Throw it on out there. Every bit helps.

[SLESTAK75]

I added the links to the cam specs back at the cam comment for those who are reading as we go.