Difference between Kohler CV730 (25 hp) and CV740 (27 hp)?

[olde_blue]

My CV730 25 hp Kohler needs a new camshaft (somehow one of the exhaust lobes has lost all it's lift--don't ask me how!); I was wondering if replacing it with a CV740 cam would boost the horsepower.

Both engines are the same displacement (725 cc). The carb is used on both engines (as well as a few smaller diplacement engines); the parts catalog even specs the same miniblock as a replacement for both engines, as well as the same oil pan.

The camshaft numbers are different, however. Anybody know if this is the main difference?

Thanks.

[Sharpcut 1]

Does your 25 have a SAM box?? (black box on side of engine)

The timing curve may be different because of the spark advance module.

Blame the goverment on your cam wiping out. Ever since they took Zink out of our motor oil, we've seen a lot more cam failures, not just on Kohlers, but briggs and Kawasaki. Ususally all 3 other lobes on the Kohlers are in perfect shape.

The problem you may encounter if you just replace the cam on an engine that has some hours, is the cam and crank have a distinct wear pattern. Throwing in a cam, you take a chance of the crank gear spinning. I had a customer who did'nt believe it, and less than a week later spun the crank gear. Most new Kohlers (v twins) are pressed on, no keyway in crank. Good Luck!!

[olde_blue]

My engine doesn't have a spark advance module. The engine is almost brand new (less than 3 hours), so there shouldn't be much wear on the crankshaft. All the rest of the cam lobes are great; any idea what could have happened to the fourth? Hopefully the zinc-free motor oil would not do-in a camshaft in that little amount of time--I was thinking there must have been a defect in the casting. I'm replacing one lifter as well, since it was scored from grinding down the cam nice and round.

[Sharpcut 1]

Did you just rebuild this motor??

Years ago, back in 2003 or 2004, Kohler did have an issue with some soft cams, but they are long out stock. If you rebuild, make SURE you coat the cam lobes liberally with break in lube. That is the #1 reason new cams fail, also when firing up, let run at a constant 2000 rpm,s for 30 minutes to break in.

[65t]

The CV730 (25HP) never had smart spark. The older CV25 did. The difference between the 730 and 740 is the camshaft and ignition. The early 740s had smart spark, the newer ones do not. The newer ones have what is now called DSAI. The 740 cam is designed to make more power at 3600, but looses some of the backup torque at lower speeds. The 730 cam will not make as much at higher RPM, but will have a little more low end grunt. That with the more advanced timing on the 740 helps to get the extra power.

If you replace the cam be sure to use the lube that Kohler recomends (looks like peanut butter), and not to exceed 1800 for the first 90 sec, or until all the lifter rattle goes away. The first 90sec is the most critical.

[olde_blue]

I didn't just rebuild the motor. It is a NOS engine, used as a replacement engine, bought with no manufacturer's warranty. I ran the new engine for about 4 hours before the cam gave out. It may very well date from five years ago, and have one of the soft cams. . .

The 740 cam is designed to make more power at 3600, but looses some of the backup torque at lower speeds. The 730 cam will not make as much at higher RPM, but will have a little more low end grunt. That with the more advanced timing on the 740 helps to get the extra power.


While the torque curve isn't as flat on the CV740 as the CV730, the actual amount of torque produced by each engine appears to be relatively similar at low rpms: the 740 peaks at a higher rpm (about 2800 vs 2400), but has similar lower range torque (as illustrated by the attached superimposition of the torque curves of the CV730 and CV740--at below about 2300 rpms the curves merge). The spark advance may help somewhat, but additional high-rpm power could prevent it from being needed.

Thanks for all your help, and advice on preserving the new cam.

[Sharpcut 1]

If I was a betting man, I would say your serial # starts with the #'s 34