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FS651V No High RPM

#1

H

Hayward51

I have just rebuilt this Kawi FS651V and all test good except I can't figure out the high idle on this engine. I have rebuilt a few FH engines and they are different. The governor arm has a link attached to it where the linkage connects.?? Moving the plate did not effect the RPMs. Adjusting throttle cable helped some. I'm up to 3450 RPM on hand held tach, 3250 on machine (Dixie Chopper) tach. I can finger the throttle on carb and get 3750. I'm thinking it's a linkage issue but, I can't get it. Any suggestions would be welcome.


#2

A

Auto Doc's

Have you adjusted the governor? There are some good videos online about how to do this properly. When you rebuilt it the sump gasket could have been thicker or thinner and that would affect the governor.

Also, there is a tension spring for the governor arm some models have multiple holes for the spring location and that dictates the top governor limit. Other models had a tab that the spring attached to, the tab could be bent slightly to increase or decrease the spring tension.

Do not exceed 3600 RPM or internal engine damage may result.


#3

R

Rivets

This manual will tell you how to hook up, test, and adjust the governor. https://www.mymowerparts.com/pdf/Ka...ASAKI-SERVICE-REPAIR-MANUAL-99924-2093-01.pdf


#4

H

Hayward51

Rivets said:
This manual will tell you how to hook up, test, and adjust the governor. https://www.mymowerparts.com/pdf/Ka...ASAKI-SERVICE-REPAIR-MANUAL-99924-2093-01.pdf
Click to expand...
Thank you very much for enlightening me on this 'new to me' type governor arm. I have this manual downloaded already but had not read thoroughly enough. I'll try to adjust this today.


#5

H

Hayward51

I tried the governor adjustment by the book. I'm evidently doing something wrong. I have the same problem. I hold the gov. arm and throttle lever on carb while tightening and throttle is wide open. When I start the engine and go to WOT, the gov. is pulling back from being full throttle. I still get 3450 RPM. There's no other holes to move spring nor a tab that I see to bend (except throttle stop). Could it be that I still have the gov. spring attached while adjusting ??


#6

A

Auto Doc's

Does the control plate have a top speed limiting screw?


#7

H

Hayward51

Auto Doc's said:
Does the control plate have a top speed limiting screw?
Click to expand...
Yes, it's 1/4" from touching with throttle wide open. I tried moving throttle cable to limit screw and after I pull lever down then back up, it's not touching again. ??


#8

T

txmowman

What is the spec code of your FS651V?
It may have a lower governed high idle spec. Having the throttle at the rabbit position is not WOT. The only time a governed engine achieves WOT is when the engine is under full load.


#9

A

Auto Doc's

Hayward51 said:
Yes, it's 1/4" from touching with throttle wide open. I tried moving throttle cable to limit screw and after I pull lever down then back up, it's not touching again. ??
Click to expand...
You don't want the actual throttle to go to full wide open; the engine will exceed the maximum safe RPM of 3600 RPM and blow itself apart.


#10

H

Hayward51

txmowman said:
What is the spec code of your FS651V?
It may have a lower governed high idle spec. Having the throttle at the rabbit position is not WOT. The only time a governed engine achieves WOT is when the engine is under full load.
Click to expand...
fs651v-DS07-R I'm just trying to get a little more top end. It was showing 3600 on the machine's tach before I replaced wore out rings. Now it shows 3250 RPM. I can definitely tell the difference mowing.


#11

H

Hayward51

Auto Doc's said:
You don't want the actual throttle to go to full wide open; the engine will exceed the maximum safe RPM of 3600 RPM and blow itself apart.
Click to expand...
I only want the rpm's up more than 3450 . 3600 would be good if I can get it there with adjustments.


#12

A

Auto Doc's

Have you broken in the engine and changed the oil yet? The new rings have to wear in properly.

Next question is: Are you sure the cylinders are both firing properly? Put a spark gap type tester on each plug wire and confirm they are firing good all the way through the operating range. Ignition coils do breakdown with age.

V-twin engines do not shake or vibrate with a coil breakdown; they just lose power especially under load.


#13

H

Hayward51

I have been mowing to break-in the rings and haven't got enough time (2 hrs) to change oil yet. I have checked the firing on both cylinders, though not under a load.


#14

A

Auto Doc's

A quick method is with a spray bottle and shoot a stream of water on each exhaust outlet near the head to see if the water instantly burns off. If one side is slow, you have a weak combustion problem.

Check at idle, then at high RPM.


#15

H

Hayward51

Auto Doc's said:
A quick method is with a spray bottle and shoot a stream of water on each exhaust outlet near the head to see if the water instantly burns off. If one side is slow, you have a weak combustion problem.

Check at idle, then at high RPM.
Click to expand...
'a weak combustion problem' ? What does that mean ? I'm not new to this but that term is new.


#16

A

Auto Doc's

Hello Hayward51

On these small single and V-twin engines, coils do not often totally fail totally open circuit, but the resin insulated windings rub together. When that happens, spark for combustion is not complete or consistent.

The next thing to check is to verify your valve lash adjustment is correct.


#17

T

txmowman

Hayward51 said:
fs651v-DS07-R I'm just trying to get a little more top end. It was showing 3600 on the machine's tach before I replaced wore out rings. Now it shows 3250 RPM. I can definitely tell the difference mowing.
Click to expand...
The high idle spec for this engine is 3600 +/- 100. I am thinking that when you are adjusting the governor, you are using the throttle control lever to achieve WOT. Try this:
Loosen the black left-hand bolt in the center of the governor link
Have someone hold the throttle shaft in the WOT position.
With your right hand, gently lift the part of the governor link that is attached to the governor shaft until it won’t move any more. But, do not over force it.
Tighten the LH bolt back down.


#18

T

txmowman

Auto Doc's said:
Have you adjusted the governor? There are some good videos online about how to do this properly. When you rebuilt it the sump gasket could have been thicker or thinner and that would affect the governor.

Also, there is a tension spring for the governor arm some models have multiple holes for the spring location and that dictates the top governor limit. Other models had a tab that the spring attached to, the tab could be bent slightly to increase or decrease the spring tension.

Do not exceed 3600 RPM or internal engine damage may result.
Click to expand...
Exceeding 3600 rpm will not cause internal engine damage. You can run the engine without the governor and will float the valves at around 4200. Ask anyone racing lawnmowers. They modify the valve train and are running 6000-7000rpm easily with stock internal components. These engines are very tough. They fail mostly due to the very poor maintenance that they receive.


#19

H

Hayward51

Auto Doc's said:
Hello Hayward51

On these small single and V-twin engines, coils do not often totally fail totally open circuit, but the resin insulated windings rub together. When that happens, spark for combustion is not complete or consistent.

The next thing to check is to verify your valve lash adjustment is correct.
Click to expand...
I will check the valves and spray the exhaust today.


#20

H

Hayward51

txmowman said:
Exceeding 3600 rpm will not cause internal engine damage. You can run the engine without the governor and will float the valves at around 4200. Ask anyone racing lawnmowers. They modify the valve train and are running 6000-7000rpm easily with stock internal components. These engines are very tough. They fail mostly due to the very poor maintenance that they receive.
Click to expand...
Thanks for that. I'm leaning toward me not getting the linkage right.


#21

A

Auto Doc's

Hello Hayward51,

3600 RPM has been the industry "safe" standard for many years, anything much beyond that is asking for trouble. Yes, it can be done but why take the risk.

I managed to blow up a few "racing mowers" in my youth, several were rather explosive with internal parts finding their way out of the engine.


#22

T

txmowman

Hayward51 said:
I will check the valves and spray the exhaust today.
Click to expand...
Don’t waste your time. If the engine otherwise runs smoothly, valve lash will not increase rpm.


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