New predator 212 with TAV stock 40mph?

[robcantplayhockey]

My wife bought me a predator for Xmas and I put it on my green bastard gokart. I’ve seen several posts with similar setups and they report a top speed of around 30-35mph. All I have done is back out the throttle limiting screw so the arm can fully extend. It still has the governor and everything is stock. I took it out for a spin and was very surprised when it reached 40 mph in about a quarter mile. I’m thinking either my gps isn’t accurate, I’ve messed up something with the gov, or I just have a great setup. I’m currently running 30 TAV on 12 t and a 54 T sprocket to live axel. Medium tread tires I think 18” in rear. I’m so impressed of the capability, I probably won’t mess with mods.

So, is something askew? I can record audio and get some top revs out if needed.

 

[bob58o]

54 /12 = 4.5
With a 30 series TC (6" driven pulley) there is a 0.9 :1 overdrive ratio.
So if the TC is fully shifted, you'll have a ratio of 4.05 :1 (4.5 * 0.9 = 4.05).
With 18" Tires, 3600 RPM should be ~47 MPH.

If the TC is fully shifted, 40 MPH means you are only turning around 3000 RPM.
Or it is possible that the TC isn't fully shifted and you are getting more RPMs. If the engine is running at 3600 RPM, then the final ratio is ~4.8 :1. That would mean instead of reaching the fully shifted overdrive ratio of 0.9 :1, you are only getting ~1.2 :1.

So IMHO, that setup is not ideal. Either you are not reaching RPMs where your engine is making peak HP, or your TC is not shifting out fully. It is possible that you burn through belts quickly with that sprocket ratio and tire size. If you find this to be true, you might consider a #35 10T replacement sprocket for the TC.
https://www.bmikarts.com/TAV-Replac...Up-rnT_BeNr_BpcOR2uov-ERxbnJFbfRoCwqwQAvD_BwE

 

[robcantplayhockey]

I’m not concerned about getting over 40 honestly. The low end power is a dream, it goes right when you hit the throttle. I just want to be sure I’m not over revving and that 40mph was attainable with a pure stock motor such as mine. If I were to slam the throttle, the chain skips which means I should tension the chain some more. I’ve also thought about using 420 chain instead of the 40 I use now. I feel like 35 chain would break easier?

Just trying to be safe with my new engine, the old one was a Tecumseh that topped out around 22 so this new motor has been incredible.

 

[bob58o]

Oh I assumed you were using #35 chain since you said you had a 12T sprocket. The TAV kits come with 12T #35 or 10T #40/#41/#420. They make 12T #40 sprockets, but those aren't included with the kits and need to be purchased separately. Are you positive that the 12T sprocket you are using is the correct pitch?

But no you shouldn't be over revving , like I said... If the TC is fully shifted, you are only turning about 3k RPM at 40 MPH.

I wasn't suggesting a way to make your top speed higher. I was suggesting a way to make your TC and belts last longer, get the TC to function properly, and get your engine to operate in its powerband.

 

[anickode]

My little kart has an Intek 190 and a tav2, with a 4.8:1 ratio and 15" rears... Just touches 40mph as well with a 200# rider. Engine is slightly modded, but overall, real similar numbers. My overall drive ratio (including tires) is a little shorter, but the top speed is the same.

You aren't quite realizing the full potential of your kart. A bit smaller TAV sprocket, or a bit larger axle sprocket likely wouldn't cost you any top speed since your setup is already not reaching it's theoretical top speed. It would however, improve your acceleration, belt life, and performance on hills and soft ground.

 

[robcantplayhockey]

Oh I assumed you were using #35 chain since you said you had a 12T sprocket. The TAV kits come with 12T #35 or 10T #40/#41/#420. They make 12T #40 sprockets, but those aren't included with the kits and need to be purchased separately. Are you positive that the 12T sprocket you are using is the correct pitch?

But no you shouldn't be over revving , like I said... If the TC is fully shifted, you are only turning about 3k RPM at 40 MPH.

I wasn't suggesting a way to make your top speed higher. I was suggesting a way to make your TC and belts last longer, get the TC to function properly, and get your engine to operate in its powerband.

I misspoke. It is a 10T with 40 chain. Another question though, the engine sits pretty close to the axle teeth which made the chain pretty short. However I’m not sure if that is limiting my tensioning abilities with moving the engine forward or backwards. I just painted it so it might just be getting stuck on paint but I have had some problems with the chain skipping when I give it more than moderate throttle from a dead stop. I considered lifting the engine with spacers but I think this is just user error and I need to do a better job tensioning the chain.

 

[mckutzy]

I think we're going to need to see some pics as to what this might be...

 

[robcantplayhockey]

I've got pictures galore, Tony Schiavone!
Tried to get some of everything. The chain is probably a link too loose.

It's a tight fit

Alignment...the chain is a bit loose and I can't fix it right now. The more I look at it, the more it looks wrong.

You can see some of the teeth on the 10T. I thought this alignment looked ok.

A look at the sprocket and the teeth

 

[ezcome-ezgo]

My 2 cents...

 

[KartFab]

in my limited experience with predator engines, if you back out the throttle stop screw too much, it basically "bypasses" the governor and you can rev to 5500 rpm, even if you dont touch the governor mechanism at all. Pretty fun though haha.

 

[itsid]

in my limited experience with predator engines, if you back out the throttle stop screw too much, it basically "bypasses" the governor and you can rev to 5500 rpm, even if you dont touch the governor mechanism at all. Pretty fun though haha.

...until the governor explodes inside the engine and
the small metal pieces get stuck in the cam gear,
then that fun abruptly stops and you open up the swear word box

but for all I know you can't do such with the throttle stop screw..
at least on true clones and hondas you can't open the butterfly past 90°
anyways (even if .. you'd just close it again)
and the governor can handle that fully opene throttle
IF the governor arm is properly conencted.

BUT some bypass the governor arm entirely.. in which case a wide open throttle can and will cause the above trouble eventually
in case the governor isn't removed properly.

'sid

 

[KartFab]

...until the governor explodes inside the engine and
the small metal pieces get stuck in the cam gear,
then that fun abruptly stops and you open up the swear word box

but for all I know you can't do such with the throttle stop screw..
at least on true clones and hondas you can't open the butterfly past 90°
anyways (even if .. you'd just close it again)
and the governor can handle that fully opene throttle
IF the governor arm is properly conencted.

BUT some bypass the governor arm entirely.. in which case a wide open throttle can and will cause the above trouble eventually
in case the governor isn't removed properly.

'sid

with the hondas, they actually have a legitimate governor linkage and the right spring pressures, so even if you back out the throttle stop screw all the way, the governor still works like it should. It hunts extremely fast though when you do this.

On the predators, they dont have the exact same springs and linkage lengths, so when you keep that throttle arm at "full rabbit" , the governor wont hunt, it just cries and threatens suicide if you don't show it more love by using the throttle stop bolt as you should (to pysically stop the throttle lever from overcoming the opposite force created by the governor arm).

 

[J.S.@SMS]

I've never had that problem on my three clones. Two of them are predators with the governors still in them and no stop screw, and the other is a 196 clone with no governor. My non-hemi predators neither over rev, nor hunt, so which predators are you talking about, the hemi of the non-hemi?

 

[robcantplayhockey]

Mine (in question) is a non-hemi bc it has the shinier aluminum valve cover.

 

[KartFab]

I've never had that problem on my three clones. Two of them are predators with the governors still in them and no stop screw, and the other is a 196 clone with no governor. My non-hemi predators neither over rev, nor hunt, so which predators are you talking about, the hemi of the non-hemi?

non hemi, but it is with stage 1 mods so it gets more flow. Im sure it wild be a different story bone stock. The engine just floats the vavles at aroudn 5500 rpm with the throttle stop screw backed out all the way at wide open throttle. The governor still moves the throttle butterfly but there is so much more flow that it doesnt make much of a difference.

 

[robcantplayhockey]

I’ve purchased a tach that will be here Thursday. I’ll do some testing with the bolt in and out.

 

[J.S.@SMS]

None of my engines have a stage 1 kit. They all have stock intakes and two have stock exhausts. The other has a rather sketchy muffler made from a wd-40 can.

 

[robcantplayhockey]

Got my tach. Did 0%, 33% 50% throttle restriction, out of order. Did a lot of idle samples. Took a video which will be at the end but I didn't pay attention to my screen orientation so it's not fun to watch but the data is there. Here are some screenshots of the stuff:

Tach install

Throttle limiter screw out

Idle

Full throttle with screw all the way out

Throttle screw halfway in as stock

Idle

Throttle screw 2/3rds out

Idle

Full throttle 2/3rds out

data video
https://www.youtube.com/watch?v=IjWF8UJcxDs&t=237s