Contra Springs Demystified

Rusty Shackleford · Post by **Rusty Shackleford** » Fri Sep 28, 2012 5:48 am

First things first, this info assumes you know how a CVT works.

The job of the contra spring is to maintain appropriate tension on the drive belt, raise the belt up the rear pulley during deceleration, and balance the force of the roller weights to maintain the RPM range in which the gear ratio of the CVT varies. Here's how: When torque is applied to the front pulley, the roller weights cause the belt to rise, increasing the gear ratio of the pulley. Since the belt is a fixed length, the reciprocal action is that the belt must be pulled down towards the center of the rear pulley, raising the gear ratio simultaneously in the rear. The contra spring resists this force, creating a balance at a certain RPM range. Why is this important? The roller weights can't be too light or too heavy in relation to the stiffness of the contra spring. If you go too light on the weights, top speed will suffer. If you go too heavy on the weights, acceleration will suffer.

The contra spring also helps climb hills. As previously explained, torque from the front pulley raises the gear ratio and compresses the contra spring when accelerating. The reciprocal action happens when you climb a hill. Resistance is applied to the rear wheel, the bike slows down, and the contra spring pushes the belt back up the rear pulley until it reaches a ratio that provides enough torque at the rear wheel to climb the hill at that RPM. The engine RPM's change relatively little as the scooter slows down because as the gear ratio decreases, the scooter will travel slower at the same engine speed. If your RPM's drop dramatically and your engine starts lugging, you need a stiffer contra spring.

Here's a YouTube video of a weak contra spring demonstration...

<iframe width="420" height="315" src="http://www.youtube.com/embed/1jK84eI0gHc" frameborder="0" allowfullscreen></iframe>

Contra springs also put you in a lower gear ratio when you roll off the throttle or hit the brakes. The variator is doing the same thing as when you climb hills, only caused by change in throttle input and/or braking rather than change of slope of the road. The "coasting" effect upon roll off comes from the fact that the pulleys are still being turned during deceleration, even though it's from rolling along. This limits how fast the contra spring drops the gear ratio back down. I suspect the reason stiffer contra springs are billed as "performance" items is because the added resistance increases RPM's and theoretically would inherently decrease any lag time in sudden downshifting... say from riding very fast in a high gear ratio, slowing suddenly for a corner, then needing to accelerate hard back out of it. I image the trade off, after a certain point, would be excessive heat/friction losses, belt wear, and limited top speed.

In any event, I hope this has been helpful and clears up some of the mystery on what a contra spring is, how it works, and what it does.

(I have made corrections to this post as it's been discussed, so if the comments in the thread seem to not make sense, that's my fault and not the members of MB.)

thatvwbusguy · Post by **thatvwbusguy** » Fri Sep 28, 2012 10:17 am

Before you write off the contra spring as being of vastly lesser importance than the rollers, please be sure to take into account how design features such as the differently shaped torque drive slots change the behavior of the rear pulley. Racers almost unanimously seem to prefer straight cut diagonal slots, whereas most OEM's prefer a gently curved slot to give a more mellow response when engaging and disengaging.

I would encourage you to put a couple thousand miles on your CVT with different combinations of weights and a couple different contra springs and then see if your views on the matter change at all.

Even if you think you nailed your tune on the first attempt, try a couple other setups and you should easily notice the difference even small changes can make. I think that you will more than likely find that the whole thing is not nearly as simple or linear as it seems on the surface.

Many folks who are much more well versed in the intricacies of scooters than I am ever likely to be advise testing as the only real method to get the ideal balance.

JHScoot · Post by **JHScoot** » Fri Sep 28, 2012 10:21 am

holy cow these scoots are mysterious, indeed!

Rusty Shackleford · Post by **Rusty Shackleford** » Fri Sep 28, 2012 12:08 pm

thatvwbusguy: Point humbly taken. I have removed the opinionated comments in favor of technical explanation. I appreciate the politeness of your critique and hope the quality of the write up has been improved. I welcome your thoughts after this revision.

thatvwbusguy · Post by **thatvwbusguy** » Fri Sep 28, 2012 12:55 pm

Thanks for the edit. I reworked my reply a bit as well, although I think we probably should have left the originals as well for posterity's sake

Once you have the opportunity to get in there and mess around with the various components of the CVT for a while, I think that you will agree that there is actually quite a bit more going on than might seem obvious at first glance. No magic or miracles, but plenty of parameters to play around with nonetheless.

Rusty Shackleford · Post by **Rusty Shackleford** » Fri Sep 28, 2012 1:06 pm

thatvwbusguy: If more people responded with civility the way you and I do on forums there'd be a lot less "flame wars" for people to enjoy.

JHScoot wrote:holy cow these scoots are mysterious, indeed!

Thus is the case with dynamic systems like this. It's much more intuitive with motorcycles where the gear ratios are fixed and shifting them is manually done. CVT's are a constant trade off between "enough for this situation" without "too much for that situation" when trying to tune them.

thatvwbusguy · Post by **thatvwbusguy** » Fri Sep 28, 2012 1:30 pm

As entertaining as flame wars can be, they are generally a waste of people's time and bandwidth. Over the years I have tried to get better at editing my posts and leaving out the really gnarly stuff before hitting the send button. When that doesn't work, I try to just ignore posts from people who I know will get me all fired up (which is not always easy, since I am Scottish on both sides and tend to like a good argument on occasion)...

Doing one part at a time and running it for a while is by far the best way to get a feel for what each modification really does.

When people toss in 2 or 3 new parts all at once, it becomes all but impossible to know what is working well, or troubleshoot what is not working well.

Good luck with your tuning.

JB

Rusty Shackleford · Post by **Rusty Shackleford** » Fri Sep 28, 2012 4:16 pm

I may, in fact, try the next stiffest contra spring at some point and see how it behaves with the new weights. I'm actually interested in how quickly the Buddy would respond to hard-braking-then-accelerating in the twisties with a slightly stiffer contra spring and the 11g sliders. I know scooters weren't originally designed for that type of riding, but I bet it's more capable than it gets credit for being.

Rusty Shackleford · Post by **Rusty Shackleford** » Sun Sep 30, 2012 6:33 pm

Also, on torque drivers...

thatvwbusguy wrote:Before you write off the contra spring as being of vastly lesser importance than the rollers, please be sure to take into account how design features such as the differently shaped torque drive slots change the behavior of the rear pulley. Racers almost unanimously seem to prefer straight cut diagonal slots, whereas most OEM's prefer a gently curved slot to give a more mellow response when engaging and disengaging.

Here's what I have so far...

1st, watch this short video demonstration of Angled VS Straight Torque Drivers.

The more horizontal the cut, the less the upshift (keeping the gear ratio lower). The more vertical the cut, the more the upshift (reducing the rate of change in RPM's). The OEM's curved cut revs to the targeted power range quickly, then reduces the shift rate to hold it there. The diagonal cut would provide more linear power delivery to the rear wheel to continue acceleration since cruising is not applicable to racing. Variator weights and the contra spring will affect the overall change in gear ratio, while the torque driver changes the relative "curve" of the change. Compared to my CBR, the stock torque drive slots are similar to accelerating harder in 1st and 2nd gears, moderately in 3rd and 4th to allow for more range of speed, then becoming biased towards cruising in 5th and 6th. Diagonal slots avoid this bias and gun it in all gears.

Due to the physics of how these parts interact, if I was racing, I'd want a very stiff contra spring to minimize lag in downshifting in corners, and straight cut torque drive slots to scream down straights. To optimize for sporty riding on the street, I'd leave to torque driver stock, get slighter lighter (preferably "slider") variator weights and a slightly stiffer contra spring.

avonpirate · Post by **avonpirate** » Sun Sep 30, 2012 8:06 pm

I 'ditto' JHScoot
And, I am amazed at how good you guys are in documenting these, complicated to me, issues. You aren't just mechanical engineers, but you are also 'word engineers.'
I'm now a little worried ..... Am I smart enough to have a scooter? I certainly do not have a skill set close to similiar, to many of you guys.
w0w...... It's not just 'Twist and Scoot.'

thatvwbusguy · Post by **thatvwbusguy** » Sun Sep 30, 2012 8:25 pm

It's definitely "twist and scoot" for most normal people, some of us just like to obsess about how it all works and how we can make it go faster, accelerate quicker etc. I have a hard time not digging deeper into anything I like. It is in my nature to over analyze anything I am even remotely interested in.

Rusty Shackleford · Post by **Rusty Shackleford** » Sun Sep 30, 2012 8:26 pm

I'm actually web developer/programmer. Physics and engineering are hobbyist interests of mine. The reason I may be explaining it in ways that "demystify" the topics is because while the science behind this stuff makes perfect sense, I'm not actually a mechanic, so I use very "layman" terms and examples. I just have a passion for comprehending exactly how things work. I was fascinated by CVT automatics for their efficiency before scooters actually. I happened to get a Buddy 125 for my GF and started comparing the difference between that drive train and the one on my Honda CBR. The CVT is a very good transmission for a scooter. I predict the automatics in motorcycles will follow Honda's lead towards dual-clutch transmissions (DCT).

In any event, the engineers that design the bikes do a very good job of tuning them for the best all-around performance right out of the factory. If you're content with the way your scooter runs stock, which most people are, then leave it stock and enjoy it. Modding it will bias it towards one particular riding style or another, but not so much that you're missing out big time. There's no free lunch. An increase of X performance is always a decrease in Y performance. It's up to the individual to determine what they're willing to compromise for their preferred balance.

avonpirate · Post by **avonpirate** » Sun Sep 30, 2012 8:42 pm

I get the idea guys. That's what I do with the physics of skiing, ski design, boot design, fitting, etc. with my pals in the locker room. Where and how are we bending the ski. When I move my right hand forward do I accelerate or decelerate and why. and it goes on and on and the conversation lengthens with beer and martini's.
Although sometimes over my head< I enjoy reading your conversation!

Rusty Shackleford · Post by **Rusty Shackleford** » Sun Sep 30, 2012 9:29 pm

Definitely know whatcha mean. The reason I like thatvwbusguy so much is because he respectfully challenges what I write, thus improving the quality of the threads. It's far better for everyone to be "correct" at the end of the day than for 1 person to be "right". I like being challenged, actually. I learn a lot when my initial theories are incorrect, then understand why they were.

jprestonian · Post by **jprestonian** » Sun Sep 30, 2012 9:35 pm

I can only imagine how this thread would be going over at kymcoforum.com. :lol:

Btw, I pointed the ClubPCX folx over here on the rollers thread... very good info, as this one is, as well. Just one of the reasons I, as a non-Genuine owner, consider this the best scooter forum on the web.
.

Rusty Shackleford · Post by **Rusty Shackleford** » Mon Oct 01, 2012 12:01 am

Update: I added a YouTube link to a video demonstrating a weak contra spring to the original post. I hope this clarifies why the spring can't be too weak, and why a stiffer spring would be considered a performance item. It appears to be a trade off between downshifting and level of belt tension.

Rusty Shackleford · Post by **Rusty Shackleford** » Mon Oct 01, 2012 1:33 pm

jprestonian wrote:Btw, I pointed the ClubPCX folx over here on the rollers thread... very good info, as this one is, as well. Just one of the reasons I, as a non-Genuine owner, consider this the best scooter forum on the web.
.

I just looked over on Club PCX. I'm very familiar with who your member "Sendler" is that's trying to get the same info I am. I know him from over at cbr250.net. We both ride Honda CBR250R's and coincidentally both happened to buy scooters recently as well. That dude learns his stuff very thoroughly and is good to have around on a forum. He's frustrated for the same reason I get. It's hard to find any useful technical information on how scooters work in order to tune them. No offense to anyone in any way, but there's way too much mystical-black-art-trial-and-error going on regarding parts that are fundamentally very simple to understand once you physically look at them working. I don't know if the motorcycle community and scooter community are comprised of different demographics, but motorcycle forums are full of passionate debates with dyno charts, gear ratio graphs, 1/4 mile times, lap times, repeated tests of GPS verified speeds, etc.

In the scooter community there's a lot of conjecture and swapping parts out over and over and over to find what "feels right". Not the case with motorcycles. I would never have a pile of sprockets laying around when results can be precisely calculated with online tools like Gearing Commander. Nothing like this exists for scooters to my knowledge, but it's not magic. There's a finite amount of variables at play that will provide very consistent, repeatable results. I understand that as scooterists, riders are at the mercy of the CVT and must find a happy median within their individual range of riding styles, but I would think educated hypotheses can be made, nailing it in a few tries or less by just knowing how what it is you're changing affects the other components of the bike.

Again, I'm not trying to be rude in any way. I'm sure most of you folks who want the information were just as frustrated as I was when your Google searches were turning up empty. I'm referring to the web as a whole, so it's not a knock against Modern Buddy at all. In fact, this is one of the better forums, as are Aprilia, ADV Rider (some how turns up good scooter info believe it or not), and occasionally Modern Vespa. I guess it's on us to dig and curate the information. There may be arguing and correcting each other, but it's worth it to have it all in one place and as accurate as possible.

jartist · Post by **jartist** » Mon Oct 01, 2012 7:14 pm

I think the motorcycle guys like to tinker more where most scooterist are commuters. There are a solid group of scooter tinkerers to be sure, check out a ruckus or Zuma forum to find more. With motorcycles you have way more hp than you'll ever use so people do mods following charts and data and don't even know it when they've gone in the wrong direction. So many of the ECU reprograms make the bikes worst by fowling plugs and lowering usable power but they think they've done it right because they spend money and because everyone else is doing it. Again, though, so much power to begin with the changes are out of range for the butt Dyno to perceive. Go to a low power bike like the royal Enfield or scooters and people following charts and dynos end up going against the theory because there's more to it than a simple chart will tell and the butt Dyno picks up the nuances. Its amazing, too, how much bunk information is out there about simple physics!

Rusty Shackleford · Post by **Rusty Shackleford** » Mon Oct 01, 2012 7:26 pm

jartist wrote:...So many of the ECU reprograms make the bikes worst by fowling plugs and lowering usable power but they think they've done it right because they spend money and because everyone else is doing it... ...Its amazing, too, how much bunk information is out there about simple physics!

Yeeeeeeeeees! I've noticed that too with fuel controllers! Also, the ECU can adapt to a freakin' slip on exhaust, too. I still have the stock pipe on my CBR and Buddy, btw. If you want a pipe because it looks and sounds cool, get the pipe because it looks and sounds cool. It's not going to make anywhere near the amount of performance difference the marketing departments say it will under normal riding. High-flow (loud) exhaust counts on the track where a fraction of a second wins the race, but on the street it's almost purely cosmetic. Even if the dyno'd gains aren't exaggerated, you'd have to run it hard and be in a full tuck at top speed to even think you're perceiving a difference. I had pipes on the cruiser I used to have. You know why? The looked cool and sounded cool. I grew out of annoying my neighbors, lol.

wileythecoyote · Post by **wileythecoyote** » Sat Oct 13, 2012 10:32 pm

how do I know what my factory contra spring rpm is?

2012 BMS Federal 50

Tocsik · Post by **Tocsik** » Sat Oct 13, 2012 11:18 pm

Another great thread for a rainy day (lots of reading!).
I've noticed the last couple of times I ran up Boulder Canyon (which is an uphill grade with some stretches fairly steep) my scooter has been bogging down. My current contra spring has about 15K miles on it so I'm wondering if it could be worn, contributing to bogging on hills. Does this make sense, given your understanding? Also, does the torque converter need periodic re-greasing?

Rusty Shackleford · Post by **Rusty Shackleford** » Sun Oct 14, 2012 2:59 pm

wileythecoyote wrote:how do I know what my factory contra spring rpm is? 2012 BMS Federal 50

It's not always the most available information in the world. The normal tools such as authoritative documentation on your scooter, a call to the dealership, or even Google should yield said information, though. I inquired about this and the roller weights at the local scooter shop to get my info.

Tocsik wrote:Another great thread for a rainy day (lots of reading!). I've noticed the last couple of times I ran up Boulder Canyon (which is an uphill grade with some stretches fairly steep) my scooter has been bogging down. My current contra spring has about 15K miles on it so I'm wondering if it could be worn, contributing to bogging on hills. Does this make sense, given your understanding? Also, does the torque converter need periodic re-greasing?

Contra spring? It sounds logical. As for the 2nd issue, I assume you're referring to the torque driver. Yes, it needs periodic re-greasing. Are you doing maintenance on your transmission in regular intervals? They require it. It's not like the (relatively) maintenance-free world of our more-typical shaft-driven vehicles. The good news is, while the parts wear out, they're much cheaper to replace than you'd think.

Tocsik · Post by **Tocsik** » Sun Oct 14, 2012 6:01 pm

Tocsik wrote: Also, does the torque converter need periodic re-greasing?

Rusty Shackleford wrote:Yes, it needs periodic re-greasing. Are you doing maintenance on your transmission in regular intervals? They require it. It's not like the (relatively) maintenance-free world of our more-typical shaft-driven vehicles. The good news is, while the parts wear out, they're much cheaper to replace than you'd think.

Yes, I do my own maintenance in the CVT but haven't dealt with the torque driver except when installing a clutch and/or contra spring. At each oil/gear oil change (2K interval) I take off the variator and clean all the parts and inspect the belt. I don't undo the clutch nut as it's too much trouble to deal with regularly but I blow out the belt dust from the rear of the CVT; a lot of it can build-up in those clutch arms and pill springs.
General purpose grease OK on the torque driver?
Thanks.

scootERIK · Post by **scootERIK** » Thu Oct 18, 2012 12:05 am

How long do contra springs last before they get weak? I have 12,500 miles on my Buddy 125 and I just did the belt and rollers(went with sliders) and acceleration is about the same as it was before. I am thinking maybe the contra spring is soft?

rick71454 · Post by **rick71454** » Mon Mar 04, 2013 10:29 pm

"If your RPM's drop dramatically and your engine starts lugging, you need a stiffer contra spring."
----Rusty
----------------------------------------------------------------------

After I installed the the 161CC Kit and 14G roller weights on my Buddy 125, I started to ge this lugging effect as Rusty mentioned. At 12,500 miles, I put in a new drive belt 743X20X30 to replace the stock 743X20X30. I got less lugging and an increase in speed 4MPH. I am thinking I need a stiffer contra spring to keep the belt from slipping.

So what size, what rpm contra spring, do you suggest I upgrade to?

Thanks
Rick71454

monnoracing · Post by **monnoracing** » Wed Mar 06, 2013 2:35 am

could the contra spring be the reason for belt slap on the case?

rick71454 · Post by **rick71454** » Wed Mar 06, 2013 5:28 am

Hello Monnoracing:

I believe that if the contra spring was not strong enough to take the slack out of the drive belt, the drive belt could slap inside the case.
I am also thinking that the drive belt slips on the pulleys a little when reaching high enough rpms.
I watched the CVT in operation with the case cover off from idle to full throttle. The drive belt does bounce around some at higher speeds.

Rick71454

rick71454 · Post by **rick71454** » Mon Mar 11, 2013 5:42 pm

Hello Buddyland:

I think that a stiffer Contra Spring makes it more difficult to get top end speed. This is because the drive belt would tend to stay on the outer circumferences
of the driven pulley, unless you have heavy enough roller weights.

So does a stiffer Contra Spring also reduce drive belt slippage on the pulleys?

Rick71454

lancerman · Post by **lancerman** » Tue Mar 26, 2013 2:46 pm

the contra spring is what applies friction to the belt. the front pulley is always in a fixed position relative to what rpm the engine is at. with increases in power there should be a corresponding increase of spring tension. otherwise you may get more belt slip.

also the contra spring tension changes what rollers are needed. so you will need to retune roller weights with a change in contra tension.

sad thing is there isnt many choices of contra springs available. usually 1000 (stock) 1500, and 2000. where 1500 is a big jump from 1000 where a 1200 is ideal. you dont want too much tension on the belt. that just creates heat, belt wear, and loss of mileage.

if I were tweaking i would get a second stock spring and stretch it a little and start there.

rick71454 · Post by **rick71454** » Thu Mar 28, 2013 8:04 pm

Hello Lancerman:

I agree with what you said.

My Buddy 125 has the 161CC cyclinder kit installed. More power, but not more speed. I think the drive belt is perhaps slipping. What does drive belt slip feel like? To me it feels like as if the brake was applied very slightly and the scooter micro jerks. Is that a sign of belt slip?

If I put on the 1500RPM torque spring, I imagine that might tighten up the drive belt enough to reduce and or elimiate belt slip. Would I need to change the clutch springs too?

Rick71454

BuddyRaton · Post by **BuddyRaton** » Thu Mar 28, 2013 8:38 pm

Rusty Shackleford wrote:I still have the stock pipe on my CBR and Buddy, btw. If you want a pipe because it looks and sounds cool, get the pipe because it looks and sounds cool. It's not going to make anywhere near the amount of performance difference the marketing departments say it will under normal riding. High-flow (loud) exhaust counts on the track where a fraction of a second wins the race, but on the street it's almost purely cosmetic. Even if the dyno'd gains aren't exaggerated, you'd have to run it hard and be in a full tuck at top speed to even think you're perceiving a difference. I had pipes on the cruiser I used to have. You know why? The looked cool and sounded cool. I grew out of annoying my neighbors, lol.

I agree if the pipe is the only mod...especially for a 4T. Letting more flow out does nothing if there isn't more flow in!

However if installing a BBK, opening the air box and bolting on a bigger carb a bigger pipe is going to be needed. Not so much to increase the power on it's own, but to allow increased flow for all the components to work together.

With a 2T it is a completley different story. Changing the pipe and a simple carb rejet can make a huge difference. I run a custom expansion chamber on my 67 GT...yeah...it's loud...but when I hit the resonate sweet spot that thing is a freaking rocket!

BuddyRaton · Post by **BuddyRaton** » Thu Mar 28, 2013 8:43 pm

rick71454 wrote:Hello Lancerman:

I agree with what you said.

My Buddy 125 has the 161CC cyclinder kit installed. More power, but not more speed. I think the drive belt is perhaps slipping. What does drive belt slip feel like? To me it feels like as if the brake was applied very slightly and the scooter micro jerks. Is that a sign of belt slip?

If I put on the 1500RPM torque spring, I imagine that might tighten up the drive belt enough to reduce and or elimiate belt slip. Would I need to change the clutch springs too?

Rick71454

What else did you do besides the BBK? Jets? air box? Carb? pipe?

I have not heard of anyone getting huge top end increases in the top end with a BBK swap unless you start going with the big head, polishing the valves, adjustable timing.etc...etc.

Why? Read all the stuff above...if you don't increase your rpms you will not increase your top end...but you will get there A LOT faster.

I run the BBK with an air box mod, upped carb and ncy pipe. The transmission...pure stock. That thing has incredible torque...it will wheelie right out from undeer you if not careful!

The first question to ask before starting mods is "what do I want to get out of it"

rick71454 · Post by **rick71454** » Thu Mar 28, 2013 9:40 pm

Hello BuddyRaton:

Thanks for your input about achieving higher top end speed.....

Other than the BBK, I put in a Main Jet size 102 to replace stock size 92.
Don't know what difference if any it made, but I am thinkin of puttin in a size around 120 after reading the many BuddyLand post. Is that a good try out idea?

Can you suggest a better carburetor or is that needed?

I will also see about the engine timing, get an engine RPM check, exhaust, air intake, compression test, leak down test.

Rick71454

BuddyRaton · Post by **BuddyRaton** » Thu Mar 28, 2013 11:23 pm

You can't always get what you want...but if you try sometimes...you may find...you get what you need.

Are you going for a touring set up or a 1/4 mile street racer?

My goal was not a big increase in top end...I was going for an increase in torque to eliminate the bogging down on long climbs...I can cruise right up a long climb now. When it's time for a variator and rollers I'll probably go with a DR and 12 gram sliders. I changed to a 26 mm carb.

I did not go with the big head because I think that on a long run (touring) heat build up could become a problem. If I was going for a street racer...hell yeah... big head, polish valves, change cam. Heat isn't as much a problem for a light to light bike...hammer the snot out of it...let it cool down...repeat.

Whatever...more ccs need more air, more fuel and more flow.

The first question to ask before starting mods is "what do I want to get out of it"

rick71454 · Post by **rick71454** » Fri Mar 29, 2013 12:05 am

Hello BuddyRaton:

I am looking for more top end speed.
I will likely switch to 12 gram sliders.
26MM Carb sounds good. I think a 30MM carb is available too.

What are your further suggestions?

Rick71454

BuddyRaton · Post by **BuddyRaton** » Fri Mar 29, 2013 12:45 pm

We are really getting off topic here, again...read what has been posted above by others. REALLY good information there.

Are you doing the work yourself?

Honestly...it sounds like you need to do more homework first. There is a ton of information on mods...but it is very difficult to set up a bike over the interwebs. This is especially true for dialing in the carb which is half science, half trial and error, and half voodoo.

I hope you also realize that with modifying also comes a degree of risk. I went pretty easy (for me) on my Buddy mods in order to help maintain reliability. Always remember that if you get into mods there is a chance...sometimes large...sometimes small...that you can blow your motor up.

I heavily mod vintage 2T motors and have blown up one 3 times. Is that a risk you are willing to take? We run them...if they blow up...take them apart...put them back together a bit differently and see what happens.

I could give you a recipe for high top end...but mods are not just plug and play...you need to develop a "feel" and an "ear" for what is going on. No two major mods are ever exactly the same...too many variables. Altitude, weight, height, riding style etc etc.