What cam for a CVT?

#1
What cam should I get for a 6.5 clone with a CVT? The CVT engages at 2200rpm and accelerates at 3900rpm (soon to be 4300rpm). I'm getting a +0.020" billet rod, 8 degree timing key, Mikuni, P+P, and tuned header. I'm curious what cam I should get being I don't rev over 4500rpm. I thought the NR Racing 280-0211 would be nice, but I'm not sure about the lift being too radical for longevity. I want this engine to last and [MENTION=55159]BWL[/MENTION]'s Predator (RIP) doesn't make me so sure about this.

Thank you in advance for all your help.

Tyler
 

CarPlayLB

Well-Known Member
#3
#4
X2! Build off a solid foundation!

OldMiniBikes has the PVL flywheels
https://www.OldMiniBikes.com/pvl-flywheel-for-clone.html
and rod
https://www.OldMiniBikes.com/billet-rod-3_303-billet-rod.html

I like this cam for that application
https://www.OldMiniBikes.com/cs-grind-clone-core-cam-clone-and-predator-hemi.html
.265" lift, and not a lot of duration at 237 @.050. Gives you good mid range and revs to 7000
I'm getting that rod in the +0.020 length (unless that's a bad decision). I'm not getting a billet flywheel because I'm only revving to 4500rpm and I trust the stock flywheel. I've been using it in stock form at 4500rpm for 2 years now.

That cam seems like a goodie. I've never seen that much difference in intake and exhaust duration before (not that I have much experience). It's also half the price of the 280-0211. As I said, I don't rev over 4500rpm, so I'd be missing out on half the powerband and have little torque at engagement.

What do you think about the CL1 grind? Not enough lift?
 

CarPlayLB

Well-Known Member
#5
CL1...why bother? Stock lift? Fuggetaboutit!

I had a friend running the stock flywheel too. I won't ride with him. He called the other day and thanked me for harping on him about the billet flywheels. He took his off and it was starting to radiate cracks from the center out. He trusted it too! But don't worry, it's your leg and private parts!:thumbsup: after all, those are made from the best recycled materials by Chinese professionals!
 
#6
CL1...why bother? Stock lift? Fuggetaboutit!

I had a friend running the stock flywheel too. I won't ride with him. He called the other day and thanked me for harping on him about the billet flywheels. He took his off and it was starting to radiate cracks from the center out. He trusted it too! But don't worry, it's your leg and private parts!:thumbsup: after all, those are made from the best recycled materials by Chinese professionals!
Yeah, I didn't like the sound of stock lift either.

As for the flywheel, it's my leg, my :asshole:, or my thin wallet. Plus, the engine is 3 feet behind me and off to the side so I'm not in the direct line of fire. Maybe after a year of wearing a bubble wrap jacket I'll splurge for the PVL. Just get ready to laugh at me in the hospital.:lol:

As for the cam, has anybody had success with the 280-0211? Maybe a 252 series?
 

SAS289

Well-Known Member
#7
What if all the benefits of the cam you are thinking of getting are in an RPM range your engine will never see? The question I would be asking is how does this cam perform off idle to 4500? Or from clutch engagement RPM to 4500. After all, that's the range you intend to run in.
 
#8
What if all the benefits of the cam you are thinking of getting are in an RPM range your engine will never see? The question I would be asking is how does this cam perform off idle to 4500? Or from clutch engagement RPM to 4500. After all, that's the range you intend to run in.
That is exactly what I'm asking. According to the NRracing website, the 280-0211 is a special marine high torque cam for 2000 to 5000 rpm. That seems like my optimum cam, but I'm a bit skeptical with such a radical lift. This is not going to be a racing engine. I just want to squeeze a little more HP out of a reliable off road kart.
 

BWL

Active Member
#9
Man, most of these engine don't open up until 5,000 RPM. A Mikuni just for 4,500 RPM? Talk about a waste of money on a thin wallet. If you're not going over 4,500 RPM just stick wit ha bone stock Ruxing and rejet it, man. That's where you'll save money.

8 deg timing key just for 4500 RPM? Na, man. Better ways to spend you money. better combos are available at this RPM range than advanced timing, Mikuni carbs, tuned exhaust, 280 lift cams just for 4,500 RPM. It's just not worth your time, man. Of course you can do whatever you like, but most everyone here is pointing you in a different direction.

Unless you're turbocharging getting tons of torque on a low displacement motor is just a bad idea. A happier balance of RPM, carburetor, cam and compression will give you a better performing engine. I don't build race engines either. Hate to burst bubbles, but if reliability is the main goal run a bone stock motor and never change it: maybe stage 1 to make the motor easier to work on.

If you just bumped it to > 5,000 to < 6,000 RPM, rejet carb, good old MOD2 or the 265 cs dyno grind, maybe 9 to 9.5:1 compression, you'll have a nice little engine that won;t win any races, but will get you out on the dirt and having fun without too much wrenching..
 
Last edited:
#10
Man, most of these engine don't open up until 5,000 RPM. A Mikuni just for 4,500 RPM? Talk about a waste of money on a thin wallet. If you're not going over 4,500 RPM just stick wit ha bone stock Ruxing and rejet it, man. That's where you'll save money.

8 deg timing key just for 4500 RPM? Na, man. Better ways to spend you money. better combos are available at this RPM range than advanced timing, Mikuni carbs, tuned exhaust, 280 lift cams just for 4,500 RPM. It's just not worth your time, man. Of course you can do whatever you like, but most everyone here is pointing you in a different direction.

Unless you're turbocharging getting tons of torque on a low displacement motor is just a bad idea. A happier balance of RPM, carburetor, cam and compression will give you a better performing engine. I don't build race engines either. Hate to burst bubbles, but if reliability is the main goal run a bone stock motor and never change it: maybe stage 1 to make the motor easier to work on.

If you just bumped it to > 5,000 to < 6,000 RPM, rejet carb, good old MOD2 or the 265 cs dyno grind, maybe 9 to 9.5:1 compression, you'll have a nice little engine that won;t win any races, but will get you out on the dirt and having fun without too much wrenching..
Good point with the carb. I'll have to rethink that.

I hoped to up compression with the +0.020 rod and maybe shaving the head a few thou.

The timing key was just a thought to make a little extra power. I have about 1.5-2 degrees advance now from a mod to the coil pack and it seems to like it.

I maybe I could bump the rpm to 5000rpm, but it would be pushing it for my TAV2, unless I'm wrong there too.

Finally, don't feel bad for telling me I'm wrong. The whole reason I joined this forum was to get good advice about this build. I've done a couple GY6 150 builds but I'm completely new to the 6.5 clone world.

Ty
 
#11
I don't see the problem or issue with a TAV2 and 5-6000 rpm.
What is your concern?
A lot of people, me included, use a torque converter at that rpm with zero issues.
My advice is to get the billet flywheel to go along with your rod, raise your rpm limitation to 6000 to 6500 THEN ask about what cam to get.

JMO Danford1
 
Last edited:
#12
I already have the stock green contra spring in the third, high rpm hole and I get 3900rpm acceleration. Do you think a yellow spring could get me to 5k?

Also, how good are high ratio rockers on a stock cam?
 
#13
Just learned something today that would have been common sense to anyone else. The garter springs on the TAV2 affect engagement AND acceleration rpm:facepalm:. My neighbor let me borrow a set of white springs from his Yerf Dog and HOLY:001_9898: it opened up. Never realized how bogged it ran with the blue springs.

Now I see how a TAV2 can run 5k-6k. That being said (and understood for the first time), what cam? CS? MOD2?
 
Last edited:

BWL

Active Member
#14
First things first: billet flywheel. After that MOD2 if you don't want to custom cut pushrods. CS if you're willing to cut them and make sure the valve train is perfect.

MOD2 = longer duration
CS = higher lift
Billet flywheel = keep your a** safe
 
#15
First things first: billet flywheel. After that MOD2 if you don't want to custom cut pushrods. CS if you're willing to cut them and make sure the valve train is perfect.

MOD2 = longer duration
CS = higher lift
Billet flywheel = keep your a** safe
The MOD2 is the winner. Since it's half the price of the 280 series, I can get the PVL flywheel. The PVL has 28 degrees BTDC with a stock key so that should be a good start.

This engine should be my learning tool. Do the easy mods now and in the future try some crazier shit. Thanks for talking me out of doing more than I could handle.

I'm even more excited after running those white springs for a day. If 4500 rpm can rip so good, imagine 5500 rpm with a MOD2!:scooter:
 
#16
Do you still have your governor hooked up? I'm wondering why you are only revving to 4500 rpm.

Do you have a GPS app for your phone? How fast is it going at 4500 rpm?

Danford1
 

CarPlayLB

Well-Known Member
#17
First things first: billet flywheel. After that MOD2 if you don't want to custom cut pushrods. CS if you're willing to cut them and make sure the valve train is perfect.

MOD2 = longer duration
CS = higher lift
Billet flywheel = keep your a** safe
Why do you think you need to get custom pushrods? It is the same base circle as the MOD2! These are welded cams, including the MOD2.
 
#19
Do you still have your governor hooked up? I'm wondering why you are only revving to 4500 rpm.

Do you have a GPS app for your phone? How fast is it going at 4500 rpm?

Danford1
Yes, I still have my governor hooked up and my throttle spring is cut. I will remove it as soon as I throw the billet rod in it.

Second question, I GPS'ed it to engage the TAV at 6mph with blue garters and top out at 40mph. I also found a 7-inch driven hiding in my stash so I'll be experimenting with that also. Right now I run a 6-inch.

Why do you think you need to get custom pushrods? It is the same base circle as the MOD2! These are welded cams, including the MOD2.
So the question goes on...Do I go with the stock-lift MOD2, or do I go all out and get the CS?

And a question of my own: What's the difference between the CS and CM? They seem the same to me. 265 lift, 235 duration.
 

BWL

Active Member
#20
Poor fellow, I feel your pain. Someone proposes an error in my reasoning but doesn't offer confirmation, thus leaving the thread completely unresolved. From my experience I'd go with the MOD2, a known quantity. If you want to know more about the CS, then contact Dyno for more information to confirm the valve train question.

It's easy to sit here and say it has the same base circle. It's easy when it doesn't cost you anything in time, money or frustration. As an astronaut once said,

"It's great to fantasize...It's another when the nuts have to fit the bolts."

Dr. Edward Weiler
NASA Space Science Administrator
Based on my experience, I'd go with the MOD2. You may go on the learn something new. The CS may be a better camahaft for you, but you'll have to do the math on your own, as it goes beyond my experience. I know the MOD2 works as a drop-in replacement without question. For my level as an engine builder, that's all I want. You may be willing to go beyond that. That's a decision only you can make.
 
Last edited:
Top