34 MPH Cushman

kzunell

Ok just took my Cushman Industrial for a test drive and got a 34 MPH on the phone GPS. It has the stock 18" tires and tach was reading 2900 rpm. The motor is a 16hp Blue Max (Honda clone). Modifications to motor are a Honda Carburator bored out to .925" by AGK and a spacer with a fuel pump pulse fitting and a Uni air filter and adapter.
Welded up the Exhaust, bought a flange and a few 1 1/4" 90 elbows, and welded them together. Used an old Golf cart muffler from a 295cc Robin engine out of an EZ-GO?
I also removed the governor from the engine and added stiffer (30 lb) valve springs.
I think the muffler tailpipe is limiting engine RPM on the top end. I am going to try removing the 5/8" tail pipe that exits the muffler and replacing it with a 1.25" like the rest of the exhaust.

BGW

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csason

cool !

fstg21

You mean 3900rpm right? Assuming you have 6:1 gears 2900rpm puts you at 25mph. Unless you have a 30% overdrive clutch.

kzunell

Nope 2900 on the tach. The rear axle has 15.67 to 1 gears. It actually still has the gear ratio tag on the rear axle. I do not know the the gear ratio in the forward/reverse/neutral box but I bet it is 1 to 1. The clutch I would bet is about 1 to 3.5 when closed (driven clutch turns 3.5 times to every revolution of the drive clutch/engine). This gives an over all gear ratio of 4.5 to 1 when clutch is in "high gear" mode (drive clutch squeezed shut and belt at bottom of driven clutch groove). I have an ez-go drive clutch and a Cushman driven clutch, so I do not know if this is normal.

sc3283

4000rpm in 3rd gear(1 to 1 ratio) with 4.71 gears = 44mph in my Cushman

kzunell

You have one of those strange Cushmans with an 18 or 22hp engines and an actual 3 speed manual transmission and a foot operated clutch I bet. I have the one that originally had a 8 or 10 or 12 HP single cylinder motor and a simple belt drive. Tire size plays a role also I have the stock 18.00/8.50x 8.00 tires. Cushmans are so varied, they made everything from motor scooters to mail vehicles, to industrial vehicles to golf carts. Both electric and gas. 1,2,3 and maybe even 4 cylnder engines were in their gas vehicles.

sho305

Most CVT like used in a golf cart are around 10% overdrive at full shift. The belt only drops about half way in to the larger secondary so it is only slightly smaller pulley circle than the primary....making a small overdrive in the CVT ratio.

In my G9 iirc it is around 13:1 trans plus the overdrive at .9 makes 11:1 total, so at ~5K rpm it runs 30mph on 22-23" tall tires. It will run 30mph Garmin GPS on pavement, but most of the time only can get to 28 on dirt/gravel it gets run on. But my tach broke so I don't know exactly what rpm. On a calculator it shows about 5K and I think it used to get very close to that on the tach, a digital clamp on.