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CV740 rpm drop

#1

smalltimerpm

smalltimerpm

Having issues with rpms dropping under a load. It runs great but it is sluggish getting up to high idle. It runs great and doesn't miss. Once I move forward or backwards the rpms will drop dramatically and pick back up. It gets worse with pto engaged.
I've pulled each plug wire off while running but both have same effect and it almost dies... if not does die out. I haven't put a compression gauge on it I just did the old blow the thumb off the hole trick. It seemed to have good compression. I've been thru the carb, even replaced it with one I know works great. Has good fuel flow. The spring travel seems to be the same on all valves but the lifters are hydraulic. Any help would be great. Also the motor does have about 940 hours on it and not sure if it's been gone through or not.


#2

Fish

Fish

What is the spec. number?


#3

smalltimerpm

smalltimerpm

Cv740-3141


#4

Hammermechanicman

Hammermechanicman

If it has a manual choke try adding some choke when it bogs down. If it does carb problem. Try NEW spark plugs. If you have 2 inline neon testers install them and see if there is any spark miss under a load. The neon testers won't show a bad plug, just a bad coil.


#5

smalltimerpm

smalltimerpm

Ok I'll give it a try. Oh I also forgot mention it does seem sluggish. It acts like it is out of time but it isn't sputtering or missing


#6

B

bertsmobile1

Check the exhaust pipes and see if one feels hotter than the other
A twin running on one cylinder will do what yours is doing .


#7

H

hlw49

Intake manifold gasket blown?


#8

smalltimerpm

smalltimerpm

bertsmobile1 said:
Check the exhaust pipes and see if one feels hotter than the other
A twin running on one cylinder will do what yours is doing .
Click to expand...
Oh Bert! Your a very smart person and some would learn a lot of information you have to offer! I'll touch it and see what happens.


#9

smalltimerpm

smalltimerpm

hlw49 said:
Intake manifold gasket blown?
Click to expand...
I'll check to see


#10

smalltimerpm

smalltimerpm

I'm gonna try to pull the lifters and see what the cam looks like the best I can without tearing down the motor. I'm leaning more towards cam or timing but I'm not really sure.


#11

Tiger Small Engine

Tiger Small Engine

smalltimerpm said:
I'm gonna try to pull the lifters and see what the cam looks like the best I can without tearing down the motor. I'm leaning more towards cam or timing but I'm not really sure.
Click to expand...
Check the governor. Over time (years and hours of operation), they can slip on the shaft where it is tightened by bolt. Governors rarely need adjustment, but it is possible. In the last month, I had two that needed to be reset. Hook up a tachometer and it should be reading around 3200 rpm on a mower. If it is dropping 500 rpms under load, that is a problem.


#12

Hammermechanicman

Hammermechanicman

smalltimerpm said:
I'm gonna try to pull the lifters and see what the cam looks like the best I can without tearing down the motor. I'm leaning more towards cam or timing but I'm not really sure.
Click to expand...
If the flywheel key is intact the ignition timing is correct.
You can remove the valve covers and measure rocker arm travel to see if a cam lobe is worn. They should all have the same amount of lift.
It is possible a cam lobe has moved on the camshaft but not likely.
When you say "pull the lifters" do you mean the lifters inside the engine?


#13

smalltimerpm

smalltimerpm

Hammermechanicman said:
If the flywheel key is intact the ignition timing is correct.
You can remove the valve covers and measure rocker arm travel to see if a cam lobe is worn. They should all have the same amount of lift.
It is possible a cam lobe has moved on the camshaft but not likely.
When you say "pull the lifters" do you mean the lifters inside the engine?
Click to expand...
Yes I do. This particular model has hydraulic. I believe It's possible to pull the valve covers and rocker arms then use a magnet to retrieve out the lifter. With that giving me a small window to see the lobes on the cam or have a look at the back side of a lifter. Normally I've seen I worn lifter come with a worn cam.


#14

H

hlw49

Pull the valve cover and check the valve lift 0.3177 on both valves


#15

G

geelee

check for wiped cam lobes, sheared flywheel key and does it have the right ignition coils on it


#16

smalltimerpm

smalltimerpm

geelee said:
check for wiped cam lobes, sheared flywheel key and does it have the right ignition coils on it
Click to expand...
Yes it still has the original DSAI speed advance coils on it but ordering directly from dealer they did away with the original and updated.


#17

H

hlw49

smalltimerpm said:
Yes I do. This particular model has hydraulic. I believe It's possible to pull the valve covers and rocker arms then use a magnet to retrieve out the lifter. With that giving me a small window to see the lobes on the cam or have a look at the back side of a lifter. Normally I've seen I worn lifter come with a worn cam.
Click to expand...
Remove lifters from lifter bores. Use a hydraulic lifter tool. Do not use a magnet to remove lifters. Mark lifters by location, as either intake or exhaust, and cylinder 1 or 2. Hydraulic lifters should always be reinstalled in same position. Right out of the Kohler repair manual for this engine.


#18

Turbodriven

Turbodriven

smalltimerpm said:
Having issues with rpms dropping under a load. It runs great but it is sluggish getting up to high idle. It runs great and doesn't miss. Once I move forward or backwards the rpms will drop dramatically and pick back up. It gets worse with pto engaged.
I've pulled each plug wire off while running but both have same effect and it almost dies... if not does die out. I haven't put a compression gauge on it I just did the old blow the thumb off the hole trick. It seemed to have good compression. I've been thru the carb, even replaced it with one I know works great. Has good fuel flow. The spring travel seems to be the same on all valves but the lifters are hydraulic. Any help would be great. Also the motor does have about 940 hours on it and not sure if it's been gone through or not.
Click to expand...
Did you ever solve this?
I'm experiencing the same problem with a Kohler CV740 on a Gravely 260z. Runs fine with a new carb/filters/fuel pump/spark plugs/etc etc but as soon as I push the sticks forward the motor (rpms) start to slow down. With PTO engaged it's even worse. It winds down to about 20-30% and barely stays running until I disengage the PTO and pull the sticks back to neutral. Compression is good (170-175psi), as is the gas. Sounds very similar to your issue. Hunting for answers here. 😭


#19

B

bertsmobile1

Turbodriven said:
Did you ever solve this?
I'm experiencing the same problem with a Kohler CV740 on a Gravely 260z. Runs fine with a new carb/filters/fuel pump/spark plugs/etc etc but as soon as I push the sticks forward the motor (rpms) start to slow down. With PTO engaged it's even worse. It winds down to about 20-30% and barely stays running until I disengage the PTO and pull the sticks back to neutral. Compression is good (170-175psi), as is the gas. Sounds very similar to your issue. Hunting for answers here. 😭
Click to expand...
Think I may have answered this previously but that is typical of running on one cylinder
Down side with kohlers one bad magneto coil usually requires both to be replaced .


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