Changing gear ratio after big block swap

007ojitos

Hello,
Im starting my big block swap to a 23hp briggs in my 09 ezgo st express....my question is: do i need to swap my gear ratio in the rear differential after swapping to a big block? If so, what ratio??

BGW

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1989Marathon

You don't need to swap gear ratios(gears).
You will want to lighten the secondary clutch.

007ojitos

Cpp advertises machining the stock clutch. Is that what ur refering to?

slonomo

I think he's talking about the tension on the spring in the secondary clutch. If it's too tight/stiff it will not be ideal for the Vtwin engine's power characteristics.

Some guys like it "stock", some will machine the sheaves. It really depends on what you want to do with the cart. What kind of use. If you will be doing a lot of hauling/towing with it, then the machining will benefit you. If you want to make it faster unloaded then keep it stock, it will shift out quicker in the stock configuration.

raydhd

Another factor is the diameter of your tires.This is a fairly simple way of trading the extra torque for more speed and a lower cruising rpm.But again it depends on whether your cart is raised and what your end goal is.

007ojitos

Ah ok...thanks...well some more info if it helps, yes my cart is lifted with a jakes long travel kit, and currently 23's although i was thinking maybe 24's soon. Its an ezgo st express so it sits higher being lifted anywYs....however my cart is also a 6-Seater. I mostly drive it on the streets(street legal) but rarely/occasionally i will cruz it on a trail or desert. Its kinda too pretty to thrash.

All that being said, after the big block swap, should i keep the secondary clutch stock? Or machine it for the compensation low end??

Field6565

With a 23hp Vanguard I doubt you will need anything to compensate for low end torque.

Dave in VA

I've got the 23 and I'm quite satisfied with the stock Yamaha clutch. I don't know if the EZGO would be any different.

slonomo

If the stock clutch is in good condition, give it a try first. If you still need/want more low end pull after the swap, you can do it then. But the guys are right, I doubt you'll have any lack of torque if you are going with a Vanguard...

007ojitos

Im running the stock 23in tires that clme with the st-express. It has a comet clutch, and a vanguard big block with the high speed rev kit, and performance cam.

Currently cart has 11.42:1 gears (or something like that), but im still not clear if i should swap gears or keep stock ones, verdict seems kinda mixed thus far