196 cc clone won’t rev under load

[Robertominibaja]

Hey everyone new to the forum and need a little help. I have a 196cc clone engine with the following done to it:

Remove governor
New flywheel
New mod2 cam
22lb valve springs
1.3 ratio rockers
Exhaust header
Intake
Bigger jet in stock carb (91 or .38 is the size)
Billet connecting rod
Torque converter

before I took the engine off to rebuild I had the centrifugal clutch and just the carb jet, intake, exhaust header, 18lb valve springs and the new flywheel with no governor. With this set up I could reach about 60km/h and about 6200 rpm under load. With the new set up above under load I can’t get it to go past 4000rpm but not under load she revs all the way up to 7500rpm easily. Anyone have any ideas why it won’t rev under load?

 

[madprofessor]

The big changes you made from the previous mods are the billet rod (in a tie with the flywheel for "shoulda dun it firstest"), the ratio rockers, the new cam, and the TC (I call them CVT's).
The rod wouldn't change your performance if it still revs freely. It's the pin for your ungoverned grenade.
The CVT can drastically change your gear ratio, what's that ratio before/after adding it on? and is it a 30 or 40 series CVT?
............and the pushrods. No new pushrods? Likely your main problem right there. Changing to ratio rockers dramatically changes the valve lash, and the different cam would have also. Between the two of them, especially because of the ratio rockers, it becomes really important to have the right pushrods length to work with the the new lobe curves and the increased extension of the valves. I recommend to folks to do a squish test (Play-Doh seems to be popular) anytime they change how the valves move toward the piston. What did you set the valve lash to?

 

[Robertominibaja]

The big changes you made from the previous mods are the billet rod (in a tie with the flywheel for "shoulda dun it firstest"), the ratio rockers, the new cam, and the TC (I call them CVT's).
The rod wouldn't change your performance if it still revs freely. It's the pin for your ungoverned grenade.
The CVT can drastically change your gear ratio, what's that ratio before/after adding it on? and is it a 30 or 40 series CVT?
............and the pushrods. No new pushrods? Likely your main problem right there. Changing to ratio rockers dramatically changes the valve lash, and the different cam would have also. Between the two of them, especially because of the ratio rockers, it becomes really important to have the right pushrods length to work with the the new lobe curves and the increased extension of the valves. I recommend to folks to do a squish test (Play-Doh seems to be popular) anytime they change how the valves move toward the piston. What did you set the valve lash to?

Hey thanks for the reply, sorry if I missed mentioning it but the flywheel was part of the initial upgrades. Also the CVT is a 30 series and to be honest I never checked the gear ratios. The valve lash spec that came with the cam card was .003 which I did. For the push rods I never changed them still stock so ya your probably right about that! How do you check for the length you need? I never had to check push rod lengths I’m still learning hahaha. Thanks again for the help and reply much appreciated .

here are pictures of the CVT and rocker arms I purchased

 

[Robertominibaja]

The big changes you made from the previous mods are the billet rod (in a tie with the flywheel for "shoulda dun it firstest"), the ratio rockers, the new cam, and the TC (I call them CVT's).
The rod wouldn't change your performance if it still revs freely. It's the pin for your ungoverned grenade.
The CVT can drastically change your gear ratio, what's that ratio before/after adding it on? and is it a 30 or 40 series CVT?
............and the pushrods. No new pushrods? Likely your main problem right there. Changing to ratio rockers dramatically changes the valve lash, and the different cam would have also. Between the two of them, especially because of the ratio rockers, it becomes really important to have the right pushrods length to work with the the new lobe curves and the increased extension of the valves. I recommend to folks to do a squish test (Play-Doh seems to be popular) anytime they change how the valves move toward the piston. What did you set the valve lash to?

Hey thanks for the reply, sorry if I missed mentioning it but the flywheel was part of the initial upgrades. Also the CVT is a 30 series and to be honest I never checked the gear ratios. The valve lash spec that came with the cam card was .003 which I did. For the push rods I never changed them still stock so ya your probably right about that! How do you check for the length you need? I never had to check push rod lengths I’m still learning hahaha. Thanks again for the help and reply much appreciated .

here are pictures of the CVT and rocker arms I purchased

 

[madprofessor]

Here's your TC from Amazon at different price, $87.99, your pic says it was $129.99, same ad, different spot, same time. You need to contact Amazon Customer Service, and tell them to refund the difference, or else pay for the return shipping for an unsatisfactory product with full refund. Then you can buy it again for $42 less money.
Amazon.com: Bravex Torque Converter Go Kart Clutch Set 3/4" 10T 40/41 and 12T 35 Chain for Manco Comet TAV2 (30 Series): Automotive
Or one like I use from ebay for less than that. Last one was $51.99, now I see them for $62.45 and up. All have free shipping, but you need to check estimated delivery dates.
I trust your Predator is not a hemi? Those rockers are non-hemi only. Hemi is part #60363 or very similar.
Do you know what a squish test using Play-Doh is?

 

[Robertominibaja]

Here's your TC from Amazon at different price, $87.99, your pic says it was $129.99, same ad, different spot, same time. You need to contact Amazon Customer Service, and tell them to refund the difference, or else pay for the return shipping for an unsatisfactory product with full refund. Then you can buy it again for $42 less money.
Amazon.com: Bravex Torque Converter Go Kart Clutch Set 3/4" 10T 40/41 and 12T 35 Chain for Manco Comet TAV2 (30 Series): Automotive
Or one like I use from ebay for less than that. Last one was $51.99, now I see them for $62.45 and up. All have free shipping, but you need to check estimated delivery dates.
I trust your Predator is not a hemi? Those rockers are non-hemi only. Hemi is part #60363 or very similar.
Do you know what a squish test using Play-Doh is?

Could also be that I’m in Canada? But I’ll check it out thanks!! Also no it’s a 196cc clone engine.

 

[madprofessor]

Forgot you said that from the start. Soon I'll be forgetting my own name, it's .....................uhh..........hmm............
Meanwhile, I'm messaging my performance guy in N.C. about the 1.3:1 ratio rockers in conjunction with a Mod 2 cam. Will probably hear back by midweek, he's pretty quick about that, will let you know. If you can get the right performance with just a lash adjustment he'll say so. Got a feeling he's going to recommend a squish test (piston/valves clearance test).
What is the timing advance on the new flywheel, and are you adding an advance key to that? The .038 jet's going to feed a lot of fuel, you'd want to fire it off early enough to burn it all. You didn't mention a fuel pump, are you still gravity-feeding the carb?
Is your billet rod over-length, or still stock length? Did you use a thinner performance head gasket? Both improve compression. For example, I'm currently running a .020" over-length rod and a .012" SS head gasket.

 

[Robertominibaja]

Yup I’m using a .020” over length rod and a thin head gasket. The timing on the flywheel was spec’d at 28 degrees which I used a timing key to advance the timing a little to 32 degrees. Also yes the fuel is still gravity fed coming from a real fuel tank mounted to the bike frame instead of the one that sits on the motor. The jet now that I checked again is actually a 91 or .036” jet. Thanks again for the reply and help! Much appreciated, looking forward to hearing from you and your friend

 

[Robertominibaja]

Oh and I forgot to mention, no I’ve never done a play-doh test but I did buy some over the weekend hahahah.

 

[madprofessor]

Starting to sound like my brother from another mother. Besides the same rods and head gaskets, in my current 212 hemi I'm also running a .036" jet, 22 lb. springs, a .265 cam, and a 28 degree flywheel with advance key like you. Only diff there is my key's a #6 (7.2 degrees) for a total 35.2 degrees advance.
I am running a pulse fuel pump, but remounted the gas tank above the pump to still gravity feed also. Didn't know if pumps required several starter pulls to fill lines or not, gravity keeps the lines full.
So you're basically done with big changes on that motor, for more big changes it's time to look at gear ratios. 30 series TC's usually come with a 12-tooth sprocket for #35 chain, and a 10-tooth for #40 chain. I just regeared for a 9:1 ratio from my CVT to turn my 16" tall tires because my 520 lb. "gokart" couldn't wind up enough rpm's to reach the point where all the horsepower is. You would likely do plenty well enough with a 5:1 ratio as long as you're not trying to turn 20" tall tires.

 

[Robertominibaja]

Hahahaha ya pretty close build sheet. I’ve gotten some feedback from others, they say my issue could also be not enough fuel at the higher rpms?. Also would me re-gearing my bike would I just swap out the 10 tooth sprocket for a 8 tooth?

 

[madprofessor]

No idea how well a chain's going to wrap itself around just a 8-tooth sprocket, but I don't like it anyway, just a personal thing with me. The physics just looks and seems so wrong, even though it may be perfectly fine for all I know.
More of a fan of playing with the final drive sprockets' sizes, on both minibikes and gokarts. Only drawback is that a larger axle sprocket gets closer to the ground. Built the DragginBallz minibike with 6" rims (largest possible split rims of 4", 5", 6") solely for ground clearance of that sprocket. Got a full 2" off the ground with a 60-tooth #35 sprocket. Plowing a chain through sand is like shoving a wood baseball bat into a meat grinder.

 

[bob58o]

The 8 tooth sprocket is a game changer. Anybody who uses it will tell you. No other part can give you 20% increase in torque for $15