Pred 670 RPM to MPH?

[dpalacio1]

Hey all,

I just completed my 670 swap from 295 robin to the predator 670 in my 2000 EZGO TXT. Used Vegas carts kit and it works great. I just wanted to ask about RPM to MPH. Below is what I am running an want to know if this seems about right?

Engine = 670 Predator
Drive Clutch = CVT Heavy Duty (VC)
Govenor removed inside engine
Tires = 22's (thinking of going to 23's)
Stock Driven Clutch
RPM - 4100 => 25 MPH
Rear end govenor on cart only has shaft but nothing connected.

There is still more to go but didn't wanna push it too much. IT still has all stock internals and I know valves start to float after this 4100 + RPM range on stock motor.

I see folks on here getting 30 to 35 MPH after installing the Pred 670 just curious how that's being achieved.

@Slonomo - you seem to have pretty good experience with this?

Thanks all!

Does all this seem about right or am I missing anything?

Thanks, Dean

[kgsc]

If the rpm hasn’t changed then speed should be close to what it was. Will just get there faster with more attitude

[dpalacio1]

Thanks kgsc!

What I am trying to understand is if others using 670 on EZGO stock rear end gears, no engine governor, no rear end governor if this is about normal speed to RPM ratio?

I know some with bigger tires will get a bit more top end with lower RPM. Just trying to get a pulse on if this looks about normal?

Thanks,
Dean

[kgsc]

Yep that’s normal. 4k rpm, 23” tires, 12.7 or 13:1 = 21mph.

[dpalacio1]

is the 12.7 and 13:1 referring to rear gear ratio? I am new to this sorry for the questions ...

[dpalacio1]

Also, I have seen different answers as to what RPM on the stock 670 valves start to float?

[kgsc]

Yes the 13:1 is the gear ratio. As for valve float on the 670 I don’t know but you are in the right place.

[doo dah]

I have 25" tires, no transaxle governor and no engine governor on a stock 670 with 8:1 gears and run mine 3500-4200 quite a bit. Have likely been over 4500 a few time but haven't seen ill effect yet. I think if you keep it around 4k everything will be fine.

[slonomo]

If people are reporting 35mph on stock gearing with 22" tires.....they are about to blow the engine up

Safe speed with your setup is 25mph. Stay at that speed. And yes that sounds about right. If you rev that engine up past 4500 rpm it will likely damage the engine. If you want that much rpm you need to build the engine to handle it. A good rev kit will get you to 5000 safely. The rev kit will eliminate the valve float.

Past 5000 you'll want billet rods with replaceable bearings, that will get you to 6000. Revving that high you'll surely want to get a new flywheel. My 2 cents.

Bigger tires will give you more mph for sure. Going up to 25" tire will give you 5-10 mph at the same rpm. I did this on my last cart. Didn't affect low end pull at all with the 670.

Swapping gears in the transaxle to 8:1 will also give you 5-10 mph at the same rpm.

If you do the rev kit and 8:1 gears....you'll like the results. I just hope you also get front brakes.

[dpalacio1]

Great reply Slonomo! Thanks for your advise! I get it … didn’t want to do a whole lot more than keep it stock and have some more power! I have a tach and keep it no more that 4k and don’t keep it there long! We just cruise the neighborhood and it doesn’t need to be going that fast all the time.

I may go to a 23” tire for more meat. But I think I’ll leave the rest alone.

Thanks for your input!