79cc Predator with Tav 2 CVT

jeffreykogan

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Mar 1, 2021
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Jeffrey, I run a 79cc pred., and just did The AGK port, polish, and head deck fifty thou.
(5) Bike builders that have machine tools/shops | Motorized Bicycle Engine Kit Forum (motorbicycling.com)
Starting at #191 (4) 79cc Sportsman Flyer build | Motorized Bicycle Engine Kit Forum (motorbicycling.com)
Don't waste time and money on a reworked carb.
Just get a 19mm Mikuni clone on Amazon mostly $20. Needle set middle notch AGK sells them too for much $.
Follow my two links you will see and learn alot. I did.
Lastly if you have the coin, a billet flywheel #6671 from ARC Racing is useful too. 5-7hp from a 79cc (^)
Jerry is telling you straight.
Tom
Thank you, this is very helpful. And yeah I was going to get a 19mm carb from AGK, but I think they have the same thing on amazon. The billet flywheel is definitely on my wish list.
 
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jeffreykogan

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AWESOME JOB, Jeffrey! One bit of tinkering you can try is switching the Driven Spring to the tighter hole on your TAV2. If you Google that, you'll find all sorts of step-by-step info. The issue is, STOCK, a TAV2 is designed to hold the engine it is bolted to at 3500-3600 rpm... since we know these little motors will make more HP if they were allowed to rev around 4000 rpm, it would probably improve things on the top-end by putting the Driven Spring in the tighter position. You will not suffer ANY loss of torque on the bottom end by doing this. It'll just let the motor rev up a little higher before advancing the ratio.

I'm going to take "The Walk Of Shame" and admit that the flathead Lifan just won't swing the TAV2 very well. There's little potential to be gained from it by it's design, even with the better carb and exhaust. The 79cc Predator seems to be a much better candidate, as you're on the road to proving. I took my Lifan off and am transitioning (SLOOOOWLY!) to a Predator 212, because that's what's sitting in my garage right now.

Just to give you an idea of the Lifan 152's limits... before I pulled it off, I gave it One Last Chance to redeem itself and the best I could pull on level ground was 30mph. I slapped on a Huasheng Knock-Off 53cc engine and geared it for a potential of 33 mph at it's stock hp peak, and without ANY tuning or tomfoolery, I hit 32mph. Same Red Cranbrook, same Fat Old Guy.
Me-Thinks the Lifan isn't even 2.8 hp, but I have no dyno to prove anything. ()My Butt-Dyno speaks volumes, though.)

IF I had spent $$ and got the 79 Predator, I would stick with it as it seems to be a manageable size and still puts out good power. At the time I was standing in Harbor Freight, the 212 was on sale for cheaper.

Now to find that shoehorn....
I did actually mess with the spring on the TAV2. I can easily reach 30, and my acceleration is quite good. I basically have no need for pedals. I am hoping the 19mm mikuni carb clone will give me a bit more power.
 
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jeffreykogan

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Tav2 is a 200-class motor transmission. There will be no mods you can make with the driven or driver to make it faster with a 79. It sucks the power... even on a 200 a clutch is better. just leave it at, “it sucks”
So I did actually try the centrifugal clutch transmission. I got about 35 mph, but my acceleration was terrible. Like non-existent. I could've just geared down, but then my top speed would have really suffered. The tav2 is also pretty much hassle-free. I slapped it on there and I have made no adjustments since.
 

JerryAssburger

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Mar 11, 2017
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I did actually mess with the spring on the TAV2. I can easily reach 30, and my acceleration is quite good. I basically have no need for pedals. I am hoping the 19mm mikuni carb clone will give me a bit more power.
Was it any noticeable difference? I wanted to try the same for mine, but I took the easier route of pitching the Lifan. (The 212 was where I was heading anyway.)
INQUIRING MINDS WANT TO KNOW!

I'm guessing, ultimately, that a person will just have to order one of the stiffer springs to get any real difference.

...and now to go read Tom's thread about the 79!....
 

jeffreykogan

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Mar 1, 2021
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Was it any noticeable difference? I wanted to try the same for mine, but I took the easier route of pitching the Lifan. (The 212 was where I was heading anyway.)
INQUIRING MINDS WANT TO KNOW!

I'm guessing, ultimately, that a person will just have to order one of the stiffer springs to get any real difference.

...and now to go read Tom's thread about the 79!....
There wasn't any super noticeable difference, but I think I did manage to squeeze out an extra mile an hour or two. I think the bigger the engine you have, the bigger the difference is going to be.
 

jeffreykogan

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Mar 1, 2021
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#31 Lynn a MBrebel stocks a 56t, I bought one to go with a EZQmatic I never did use.
Mounting hole pattern is for 1 1/2" sprocket adapter.
Tom
What even is the EZQmatic? Does it use a centrifugal clutch? I have seen pictures, but I haven't had a chance to try it out since it was too expensive.
 

Tom from Rubicon

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What even is the EZQmatic? Does it use a centrifugal clutch? I have seen pictures, but I haven't had a chance to try it out since it was too expensive.

It's a up-dated Whizzer transmission.
Primary is a crankshaft mounted v-belt sheave to a centrifugal clutch powered jackshaft. Final is chain sprocket.
Whereas Whizzer used a belt final drive.
If the torque converter works for you, do it. But as has been said they work best with a 212.
Tom
 
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jeffreykogan

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What even is the EZQmatic? Does it use a centrifugal clutch? I have seen pictures, but I haven't had a chance to try it out since it was too expensive.

It's a up-dated Whizzer transmission.
Primary is a crankshaft mounted v-belt sheave to a centrifugal clutch powered jackshaft. Final is chain sprocket.
Whereas Whizzer used a belt final drive.
If the torque converter works for you, do it. But as has been said they work best with a 212.
Tom
Although it would be nicer to have an EZ Q matic, it is almost 3 times more expensive than the CVT I have now. I'm hoping to squeeze a bit more horsepower out of my 79cc motor in order to get more use out of the TAV2
 

Tom from Rubicon

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I'm hoping to squeeze a bit more horsepower out of my 79cc motor in order to get more use out of the TAV2

I guess I will find out soon enough. AGK claims 5-7hp from the mods I am doing. Hope so.
I got my Q matic intending it to be a work around not using a Bully clutch. A Bully is slow off the line but once locked it
provides excellent engine braking.
Tom
 
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jeffreykogan

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I'm hoping to squeeze a bit more horsepower out of my 79cc motor in order to get more use out of the TAV2

I guess I will find out soon enough. AGK claims 5-7hp from the mods I am doing. Hope so.
I got my Q matic intending it to be a work around not using a Bully clutch. A Bully is slow off the line but once locked it
provides excellent engine braking.
Tom
Doesn't engine breaking hurt the engine? And yeah, I was also going to try and use the modified parts from AGK to get a bit of a performance boost.
 

Tom from Rubicon

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Jeffrey, the only things I purchased from AGK were 18lb springs. If you read my threads, porting, polishing, and increasing
compression by milling the head. I did my self, which is the AGK stage 2 + billet flywheel.
My purchase parts add up to $250-$275 whereas Shane is asking $650. Granted his service is his living.
Your profile says you are 21, are you a machinist or mechanic?
When I was your age I was a Tool and Die apprentice and the foreman let me do machining for myself.
These days, I have my own shop. If I need it, I make it.
Do you have a second engine? One that can be worked on while you can still ride? That's how I'm doing it.
If you want. send me a stripped head. For $125 you will get a ported, polished, and head decked 0.050".
You would have the pleasure of doing an engine tear down including governor removal. ( Done twice and did nor pull the crankshaft per AGK.) And then reassemble as per AGK and ARC you tubes.
Tom
 
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Tom from Rubicon

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As an aside Jeffrey, one is not breaking the engine, it is off throttle deceleration using the unenergized engine compression.
All racers use it. Hopefully you have a long life ahead of you learning as you go.
Tom
 
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jeffreykogan

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Jeffrey, the only things I purchased from AGK were 18lb springs. If you read my threads, porting, polishing, and increasing
compression by milling the head. I did my self, which is the AGK stage 2 + billet flywheel.
My purchase parts add up to $250-$275 whereas Shane is asking $650. Granted his service is his living.
Your profile says you are 21, are you a machinist or mechanic?
When I was your age I was a Tool and Die apprentice and the foreman let me do machining for myself.
These days, I have my own shop. If I need it, I make it.
Do you have a second engine? One that can be worked on while you can still ride? That's how I'm doing it.
If you want. send me a stripped head. For $125 you will get a ported, polished, and head decked 0.050".
You would have the pleasure of doing an engine tear down including governor removal. ( Done twice and did nor pull the crankshaft per AGK.) And then reassemble as per AGK and ARC you tubes.
Tom
Can you dm me your email so we can further discuss sending you my head for porting and polishing?
 
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Tom from Rubicon

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Done Jeff,
I am not good at PM's either. I am about ready to close up this engine.
(35) 79cc Sportsman Flyer build | Motorized Bicycle Engine Kit Forum (motorbicycling.com)
Before I put this engine in the Sportsman Flyer, I think a couple hours runup/ break in are worth the trouble. Break in oil from my first 79 cc engine was very cloudy.
The metal grunge in this new engine crankcase, pre run in. Is a WTF! Factory does not clean the engines.
Tom
 
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