This may answer your question:

https://physics.stackexchange.com/questions/56286/why-does-a-spring-lose-its-energy-when-compressed-for-a-long-time#:~:text=The%20repetitive%20bending%20and%20unwinding%20of%20a%20spring,of%20elastic%20potential%20energy%20as%20it%20used%20to

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PA318Guy, thanks for your input, and that does start to answer the question - but do the same principals of physics apply in an "extension" spring? In a compression configuration it makes sense - that's why car springs weaken, sag, and break.

I ground away some control panel metal and got RPM down to 3900 RPM, now I need to dis-assemble again and elongate the slots in the control panel and grind a little more.

Bill

 

Someone has been "working" on this engine before. The hook on the governor spring appears to have been slightly reshaped. Maybe the only answer is to order a new control panel and try that.

Bill

 

This is the one that I thought most closely answers your question:

 

How old is the motor?

 

Cub Cadet 3205's are 1999 - so 21 years.

Bill

 

I'm at a little over 500 hours on my 3205 and I don't have that issue yet.

 

Mines at 680 and revs to 4100ish. I just regulate it with 3/4 throttle.

 

Steve, that works for those of us who love their Cubs. But the ones my brother has are going to be for sale, so I need to try and figure this out and make it right. Otherwise these will self destruct as people just slam the throttle wide open and mow or blow snow. The fact that this issue exists on so many tractors says it is something that changes over time. I just have to find - what.

Bill

 

I figured that was the case. I hope you figure it out but if all else fails I'd fix a throttle stop up on them.

 

I have a 620d with 1100 hours on it and 23 years old and haven't noticed any changes in RPM's.Though I can honestly say I've never checked. This not in a CC but a Woods ZT. Don't think there's any difference.Might be something ill have to look forward to in the future.

 

I think this is a problem most people don't know exists. These digital tachs are only $9 and just use an impulse count from a spark plug wire. I really thought my FD620D was perfect and it idles down to a nice lope. I was really surprised when it registered 4200 RPM. People with JD Gators think it's great they go fast. Personally I like to take good care of my equipment and over revving this engine for no real purpose is just wrong. It will accomplish it's intended task just fine at 3600 RPM and last a lot longer too.

Don't get me wrong, I have no issue with working an engine to it's max. My 1976 KZ900 drag bike got spun to 12,500 RPM regularly and went through the lights in excess of 150 MPH. That was then, this now.

Bill

 

I think it's a testament to the durability of these engines that they tolerate the high rpms. Don't hear much about them breaking rods like you would expect. I knew mine was running fast before I ever put my tach on it.

I hope getting it under control helps it to live a long life.

 

PLEASE let us know what you figure out. I only have experience with 2 of the engines. My 3205 and a friends 3208. I have verified that mine revs way to high and my ears told me that his revved a lot higher than my Commands, the first time I ran it.

I tried for a long time to get the RPMs down on mine and I did get them reduced some, but it now surges while running without the PTO engaged.

I suspect that the great majority of them rev higher than 3600 RPM, but most people don't have a tach to confirm this.

I love the way the extra RPMs seem to improve the way the mower deck cuts, but I don't like to constantly over rev the Hydro Unit, at least not as much as it did when I started messing with it.

 

Joelk, will do. I ordered a couple of new springs and a complete control panel - to see if fresh parts will remedy the problem. These engines HAD to be running correctly when they left the factory. No one would take on the extra warranty issues by sending them out over revving.

Just out of curiosity I put the tach on my 3185 - 1213 hours on the Briggs - 3604 RPM. So, obviously Briggs made the system work with substantial age on it.

Bill

 

I was killing some time till my parts get here. I have one of the $9 inductive tachs among my small engine tools now and got thinking about a way to connect it a little more simply. I dug up one of my old timing lights with a clamp-on plug wire connector. I cut the clamp-on connector off (its two wire) - then I stripped off a little insulation from the end of the wire you wrap around the plug wire from the tach. And low and behold either wire from the clamp-on connector twisted on to the tach wire gives a good RPM reading.

Bill

 

Thanks for that info!. I have several old timing lights and might try using the pickup end off of one of them, or next time I see one at a sale for 1$ - 5$, buy one of those. The ends on most of mine are kind of bulky and might be a challenge to get them on a plug wire that does not have much slack and tightly hugs the engine. When I have replaced the coils on Kohler Commands I have noticed that the plug wires on the replacement coils are shorter than on the original coils. They are long enough to work, but did not leave much to spare.

 

Joelk, the cool thing about using the clip on pickup is that it is easy to reach in and hook it up. But if the engine you are working on doesn't allow for it you can still just wrap the tach wire around the plug wire. I put a spade disconnect on my tach so I can unplug the clip-on pickup.

The multi-strand wire on the tachs is kind of a pain to work with. I was using 2 small zip ties to hold the wire in place, so it was not just a reach in and hook it up situation. Another way that I tried, and it worked fine is put an alligator clip on the end of the tach wire. Then for the wire to wrap around the plug wire, use a piece of 14 gauge single strand home wire. Strip a little insulation from either end, it bends around the plug wire easily and stays in place, then clip the alligator clip on.

Bill

 

Joelk, the cool thing about using the clip on pickup is that it is easy to reach in and hook it up. But if the engine you are working on doesn't allow for it you can still just wrap the tach wire around the plug wire. I put a spade disconnect on my tach so I can unplug the clip-on pickup.

The multi-strand wire on the tach's is kind of a pain to work with. I was using 2 small zip ties to hold the wire in place, so it was not just a reach in and hook it up situation. Another way that I tried, and it worked fine is put an alligator clip on the end of the tach wire. Then for the wire to wrap around the plug wire, use a piece of 14 gauge single strand home wire. Strip a little insulation from either end, it bends around the plug wire easily and stays in place, then clip the alligator clip on.

Bill

Bill, good to have that info on using the single strand wire. I retrofit a bunch of fluorescent light fixtures to use no ballast LED tubes. I removed a lot of light gauge wire (18G?) that would be easy to wrap around plug wire and would maintain it's shape without zip ties etc. With the insulation still on, It is probably about the diameter of bare 12-14 gauge wire.

I now have several of the mini tach/hour meters. On is too bulky for me to want to mount permanently, but it should be great as a "tuning tool" if I put a quick disconnect on it. I may put the single strand wire on all of my tractors where I do not permanently install a tach, and leave it/them there, then just plug in the tach when I want to get an RPM reading.

Have you played around with how many wraps to make around the plug wire? IIRC, some instructions/comments say you can fine tune the accuracy of the tach by reducing or increasing the # of wraps.

 

Joelk, I haven't tried any different amount of wraps - I just have used the recommended 4 wraps.

Bill

 

I got an email from Scrubber City, they cancelled my order of governor parts. Claim there is a nation wide back order for them. I was hoping to compare new parts with our higher revving older ones. Maybe try to compare spring tension with a new part.

The idea of "elastic fatigue" is an interesting concept, and while compression springs will collapse under this fatigue, an extension spring "should" elongate or permanently stretch. Don't know if Kawasaki sourced a cheap spring or one made of the wrong wire size to do the job long term. I'll keep playing with it.

Bill

 

I just ordered a couple of governor springs from Parts Tree, we'll see if they show up.

Bill

 

Imma be very happy if it is something external and cheap vs internal busted plastic parts

 

The Parts Tree springs are supposed to be here today. I haven't done anything else to the 3205, because I want to compare the high revving spring with a new replacement. I will measure them both carefully to see if anything is easily distinguishable between them. Then I will install a new one and see if the RPM is any lower. I'm hoping for an easy fix.

Bill

 

Well guys, we have a real answer. And I have a 3205 with 536 hours that now runs WOT at 3600. As I worked with the spring that was on this used tractor, I tried adjusting max RPM as the service manual stated. I did grind away a small amount of the control panel where in comes up against the carb. I considered, but did NOT elongate the control panel mounting bolt holes beyond what is OEM. Sliding the control panel as far as it would go towards the carb only got me to 3900 RPM. The PO apparently had something to do with why this engine was over revving. The long end of the spring was not a smooth curve, it had been "adjusted" somewhat, but until I had a new replacement spring I wasn't sure how much. The answer is slightly more than .25". The first picture is the two springs side by side, second the new governor spring, and then a couple of pictures on a tape measure. These springs seem to be in short supply, I got two from Parts Tree at $5.00 ea. plus $7.99 shipping. I called them to verify they had them in stock and they said they had 4 total. Scrubber City has none and cancelled my order and refunded my money.

Bill

 

Well guys, we have a real answer. And I have a 3205 with 536 hours that now runs WOT at 3600. As I worked with the spring that was on this used tractor, I tried adjusting max RPM as the service manual stated. I did grind away a small amount of the control panel where in comes up against the carb. I considered, but did NOT elongate the control panel mounting bolt holes beyond what is OEM. Sliding the control panel as far as it would go towards the carb only got me to 3900 RPM. The PO apparently had something to do with why this engine was over revving. The long end of the spring was not a smooth curve, it had been "adjusted" somewhat, but until I had a new replacement spring I wasn't sure how much. The answer is slightly more than .25". The first picture is the two springs side by side, second the new governor spring, and then a couple of pictures on a tape measure. These springs seem to be in short supply, I got two from Parts Tree at $5.00 ea. plus $7.99 shipping. I called them to verify they had them in stock and they said they had 4 total. Scrubber City has none and cancelled my order and refunded my money.

Bill

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Great job Bill. I was considering picking up and 3208 and was waiting to see if the high RPM issue could be resolved without an engine tear down. Let us know if this resolves the issue on the other 3205-3208 that you have. Again great work!!!

 

Great to hear. Just got one off ebay for $9 shipped. Thanks for getting to the bottom of this for us

 

ejl6658, I will get my 3205 in the shop this next week and see what we find under it's control panel. It will also be time for the red silicone hoses and the coolant temperature gauge. It seems these liquid cooled engines are deceiving people, with the water jacket to muffle internal engine sounds, people think they are loafing. When in fact they are running perfectly, but they or their "mechanic" think they can make them run better - but they just end up beating the cr*p out of them for no good reason.

Bill

 

I want to reinforce an observation found on this Kawasaki FD620D as well as ALL the others I've worked on. The choke cable system on the Cub Cadets over extends the Kawasaki choke system. It bends the linkage if you force it to full choke on the dash mounted lever, then because it is bent it will not return to completely off choke. This tractor was over revving because of "someone" re-bent the governor spring but still at low idle it was running pig rich. After I straightened the choke linkage on this engine it gained 300 RPM at low idle. So I have installed a stop system that - stops the dash mounted choke lever at the point that the choke butterfly is completely closed. Here are a couple of pictures that show the choke completely closed but the dash mounted lever only half closed.

Bill