Kaw Power Up

[NickTF]

I believe the throttle shaft in the fx651 is the only difference limiting this motor to 20.5 hp when compared to the fx730 which is rated at 23.5 hp, just like in the above discussed FH motors. Can anyone confirm this? Does anyone have a good link I could check out regarding any adjustments to the governor which would be needed when swapping shafts or is it just as simple as swapping the shafts with no adjustment to the governor necessary? Thanks.

Also, is anyone aware of oil cooler equipping on these different motors within the fx line? i.e. does the fx 730 have an oil cooler while the fx 651 does not?
Edit: looks like the FH motors have the oil cooler added to the higher hp model. The fx line do not seam to have this. Debating on whether or not to simply cut the tab/restriction or replace it. Replacing it would be less susceptible to any potential warranty fowl ups but cutting the tab/restriction would likely be easier given I wouldn't have to remove as many parts. Any thoughts...???

 

[Mad Mackie]

No oil cooler added to the FX line until the next model larger than the FX730V.
I'm going to say that if you had identical machines next to each other with the only difference being that one machine had an FX651 and the other an FX730, it would be very difficult to put them thru the same load and speed to become aware of the difference in rated horsepower. If you replaced the throttle shaft or removed some of the throttle stop material, I doubt that you would see any difference in power level produced. On a governed engine of this type it is almost impossible to load the engine to where the throttle stop would limit throttle opening when the governor is trying to push for more throttle. With an engine in a test cell that has the capability of measuring and varying torque load and monitoring horsepower, then you may see a slight difference. On most governed engines at 3,600 RPM and high loads, the throttle plate will not be open very much. Several years I had a 10,000 watt continuous rated generator in my shop for service. This machine had a 50 AMP plug on it and I plugged my AC/DC welder into it. I shorted the leads together and with low amps I turned the welder on. As I was cranking up the amps on the welder, I was observing what the engine governor was doing with the throttle plate. The throttle plate would quickly cycle to a fairly wide setting and then drop back as the engine RPM would increase to 3,600 and stabilize. I slowly increased the amps on the welder until the throttle plate opened more and to the point where the governor quickly pushed the throttle plate to full open at which point the engine quit. I did this after a complete service of the engine and a replacement of one of the large capacitors in the generator field excitation. The owner wanted me to test demonstrate it for him and this was the only way that I could accomplish a test. I still don't really know just how many amps load I put it, just guessing based on the amp calibration on the welder. This generator is still used as power outage backup in a pizza shop to keep the large coolers going and has been doing a fine job.

 

[dnewton3]

Regarding the FX motors, it's entirely possible that the power ratings are limited in the same or similar fassion as the older FH motors. It is, after all, a very easy and simple method of restricting max power.

The best way to tell if this is true is to go to their website and research the parts numbers as I did. Yes, it's tedious and boring. But as often is true, the answers lay in the details. That is how I confirmed my suspisions. And the icing on the cake was the photos from the other website, where folks posted the two parts side-by-side.

Find your specific model and series of FX motor, then look up the parts for the larger models in that same series. Drill down to the carb, and the throttle shaft of the carbs. If the jets stay the same and the throttle shaft changes based upon HP, then you have your answer.

It is far easier (at least on my engine series) to cut the offending part tab off the exiting shaft than to have to remove/replace the carb. It took me less than 5 minutes total, and that included removing the cyclonic air filter to get to the carb. If you do a nice job of carefully cutting the tab with a Dremel, and gently file it after the cut, it will look so stock that I doubt anyone could ever tell the difference anyway.

 

[NickTF]

The jets, carb, etc. are all the same between the 651 to 730 motors. I took material off the shaft until the throttle blades open nearly flat. The factory 651 shaft seems to limit the throttle blades to roughly around 3/4 of opening. I used the machine briefly in a neighbors vacant lot with thick grass and thus far the power increase/resistance to bogging seems very noticeable.

 

[Mad Mackie]

As I am the type that would do the same and have done similar mods in the past there is no doubt that if I had a Kawi that was in this category I would do the same mod on the throttle shaft stop. I used to have a Bridgeport mill and medium size South Bend engine lathe in my shop and did lots of mods over the years. both of these machines have been replaced with much smaller machines. My Scag Tiger Cub originally had a 26 Briggs ELS engine and although it had low compression in one cylinder, the only difference in power/torque that I noticed with a new 30 Briggs was less of an RPM drop with the collection blower installed. The RPM difference was so small that I could barely notice it listening and I had to confirm it with a laser tachometer. I had previously done and recorded RPM checks with the original engine. Although the new engine has more HP, it appears that the fuel consumption is slightly less that the original engine. Having replaced the intermittent hourmeter, I may be able to closely determine the per hour fuel consumption.
It will be interesting to see if you notice any power/torque changes/improvements as you operate this machine.

 

[Mad Mackie]

The jets, carb, etc. are all the same between the 651 to 730 motors. I took material off the shaft until the throttle blades open nearly flat. The factory 651 shaft seems to limit the throttle blades to roughly around 3/4 of opening. I used the machine briefly in a neighbors vacant lot with thick grass and thus far the power increase/resistance to bogging seems very noticeable.

It's great that you noticed a power increase, I had mixed feelings as to if it would be noticeable. A lot also has to do with the governor response and I think that FX Kawis and possibly other Kawi models have a quick governor response which stays there until the engine RPM increases accordingly. My 18 Briggs Vanguard horizontal engine has quick governor response, but it seems to quickly drop as there are several RPM surges before it settles in. My 30 Briggs Pro Turf engine responds and stays there, but more HP in this engine.

 

[NickTF]

The jets, carb, etc. are all the same between the 651 to 730 motors. I took material off the shaft until the throttle blades open nearly flat. The factory 651 shaft seems to limit the throttle blades to roughly around 3/4 of opening. I used the machine briefly in a neighbors vacant lot with thick grass and thus far the power increase/resistance to bogging seems very noticeable.

After extended use of the machine after this modification I would definitely recommend it as it has made a very noticeable difference in the resistance to bogging out in high load situations.

 

[Witchgrass]

Correct - we need to be specific here, because my FH series is an older one.
I typically try to be very clear in my questions and answers; hence why I listed the specific models of the engine data I looked up on the Kawpower website.

So I also found this same disucssion on another forum over at www.lawnsite.com and the same topic ended up with the same conversation, although it took them about 10 pages to come to the conclusions that it only took me an hour to discover. You can see the conversation here, but just focus on the photos on page 9; there are a few photos:
a) photo of the part used including the oil cooler set and throttle shaft
b) installed oil cooler
c) another pic of oil cooler
d) view of the 19hp shaft sitting next to the 25hp shaft (this is the most credible evidence and makes it so very simple to understand)
You can see the info and photos here:
http://www.lawnsite.com/showthread.php?t=317558&page=9


Now I am constraining my comments to my older series of FH engines; those that are all at the top of the displacement list from 601-721 series.
The ONLY thing (and I truly mean only thing) that separeates those in HP ratings is the little throttle butterfly shaft, which limits the travel of the shaft in its rotation.
Kawasaki has made a bazillion different variants of many engines, but when comparing and contrasting info within the same bloodline, this is a true statement.
You can "up-power" your FH engine (FH601V - FH721V) by simply removing that restriction. You have two choices:
1) buy the shaft for the HP you want (the 25hp shaft is 16041A-7025 is is currently about $40 give or take a bit) and install it after removing the carb, govenor, etc and put it all back together
2) get out a dremmel and cut off the offending metal on the shaft tab (I did this; took me about 60 seconds ....)

I cut off the matieral using the photo link from above as a guide. I printed off the photo (copy/paste caputred and put into Word) and then used sciscors to overlay the "new" part on the "old" part, so I could scribe a line that would represent the material to remove. If you refer to that photor link above, what I did was essentially cut off the portion of metal that has the "A" stamped upside down in the picture, and made the cut at an angle that replicates the 25hp shaft on the right.

Viola! 25hp out of my 19hp Kaw engine. The engine will now open up the butterfly shaft MUCH further, allowing for a much larger air/fuel mix under heavy loads.
Under light lights, it works just the same as any other engine would. The govenor controls the throttle shaft.
Because I didn't take anything apart, and my mower ran fine previous to this little experiment, I had no issues in having to "return" the idle speeds or govenor setting. I highly recommend that anyone doing this actually take the short cut (pun intended) and just cut off the metal material. Doing this is quicker, and there is no need to mess around with your carb and govenor settings.

I would remind those who try this to seriously consider adding the oil cooler as well. If you expect that high-loads would be rare for long periods, you can probably get away without it. But it you intend to use the new-found power for sustained periods, I really suggest you add the oil cooler; it is very inexpensive - only cost me about $25 when I added it a few years ago. (You'll need the heat sink cooler, the o-ring and the threaded extension). You can find those part numbers on the Kawpower website under the FH721 (25hp) engine parts listing. You can see my thread about this upgrade here: http://www.lawnmowerforum.com/scag-forum/8933-kawasaki-oil-cooler-upgrade.html


Yes - it truly is that simple to achive a 30% power gain.

I know this is an 8 year old post, but does anybody have a good link the info that Dnewton posted a link to? I tried it but it no longer works.
thanks,