Increasing rpm, while maintaining governor...

oneoldjimmy

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Hello guys... The motor in question is the typical HF predator 212, non hemi, brand new, but the application is a bit different. This one is going to power a mud motor for my duck boat. I want to increase the rpm, while keeping the governor for safety precautions. I'd like to turn around 45-4600 rpm without worrying about a grenade scenario. What would be the best way to achieve this, without eliminating the gov? TIA
 

oneoldjimmy

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Read this article: https://www.diygokarts.com/community/threads/governor-removal-safety-reality-check.16518/
Down near the bottom Doc specifically mentions adjusting the governor. If all else fails, search the forum and YouTube for "predator 212 governor adjustment".
Oh, and :welcome2:
Thank you... I have watched about every video I can on YouTube, and 99% of them go to eliminating the governor. I read most of that sticky, but must have skipped the bottom! If this was a sbc it would be easy, but the simplicity of these little motors, have me scratching my melon...
 
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oneoldjimmy

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Thank you... I have watched about every video I can on YouTube, and 99% of them go to eliminating the governor. I read most of that sticky,, but must have skipped the bottom! If this was a sbc it would be easy, but tge simplicity of these little motors, have me scratching my melon...

I guess it really comes down to me removing the throttle screw, and playing with the governor spring a bit. Somethings in life just never seem to come that easily
 

vpd66

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I was in the same boat a couple years ago when I bought my Mega Moto MB212 mini bike. I wanted a little more rpm out of the engine but retain the governor. When I got the bike the governor was set at 3620 rpm. I know these engines in stock form will take 5000 rpm and still be fine. I wanted to increase the governor speed to about 4500 rpm. I first adjusted the throttle stop screw and that got me 3800 rpm. I watched several videos and the only thing they really showed was how to bypass the governor. Then I remembered a few years ago a local go kart track had a class where they were using a stock 6.5hp Harbor Freight engine. They could run an aftermarket air filter, jets, and exhaust. Other then that it had to stock. They had a 5000 rpm maximum with the stock governor still in place. I made some calls and found one of the guys the was racing that class and he told me how to achieve a higher max governed speed. you have to move the governor spring farther out on the lever. In stock form there are 3 holes. It should be in the farthest hole from the shaft. The key to getting more rpms is to drill and hole farther out on the lever.

1598894536459.png

I found this picture on the internet of exactly where to drill the hole. The key thing is to try and keep it in line with the other 3 holes. I did this to my mini bike and now I get a governed 4800rpm. Before I found this out I tried making the spring shorter and it never made much of a difference. I also tried the zip tie through the spring to keep the spring from stretching, I found that the zip tie mod did't increase the rpm but made the governor seem to react quick and it seemed to smooth out the operation.
 

oneoldjimmy

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I was in the same boat a couple years ago when I bought my Mega Moto MB212 mini bike. I wanted a little more rpm out of the engine but retain the governor. When I got the bike the governor was set at 3620 rpm. I know these engines in stock form will take 5000 rpm and still be fine. I wanted to increase the governor speed to about 4500 rpm. I first adjusted the throttle stop screw and that got me 3800 rpm. I watched several videos and the only thing they really showed was how to bypass the governor. Then I remembered a few years ago a local go kart track had a class where they were using a stock 6.5hp Harbor Freight engine. They could run an aftermarket air filter, jets, and exhaust. Other then that it had to stock. They had a 5000 rpm maximum with the stock governor still in place. I made some calls and found one of the guys the was racing that class and he told me how to achieve a higher max governed speed. you have to move the governor spring farther out on the lever. In stock form there are 3 holes. It should be in the farthest hole from the shaft. The key to getting more rpms is to drill and hole farther out on the lever.

View attachment 122532

I found this picture on the internet of exactly where to drill the hole. The key thing is to try and keep it in line with the other 3 holes. I did this to my mini bike and now I get a governed 4800rpm. Before I found this out I tried making the spring shorter and it never made much of a difference. I also tried the zip tie through the spring to keep the spring from stretching, I found that the zip tie mod did't increase the rpm but made the governor seem to react quick and it seemed to smooth out the operation.
Awesome! Thankyou very much, this is exactly what I was not having any luck trying to find!
 

oneoldjimmy

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So I finally pulled my new motor out of the box, and it has that hole already in the gov arm! Rest of my parts will be here Wednesday...
 

vpd66

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Glad to help. I too searched for quite a while to figure this out. Report back on what RPMs you get when you get it running.
 

OPmini

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Hello guys... The motor in question is the typical HF predator 212, non hemi, brand new, but the application is a bit different. This one is going to power a mud motor for my duck boat. I want to increase the rpm, while keeping the governor for safety precautions. I'd like to turn around 45-4600 rpm without worrying about a grenade scenario. What would be the best way to achieve this, without eliminating the gov? TIA

I saw the other post about drilling the hole in the governer arm this is essentially the same as removing your governer, stopping the governer from doing its job, thus allowing it to turn higher RPMs, but limited to a certain extent. overtime (1.5-2 years of medium to heavy use) YOU WILL SEND YOUR ROD THROUGH THE BLOCK OR CAUSE ENGINE DAMAGE if you do this without the proper upgrades. You will a) snap the rod and send it through the block, b) bend/ snap/ chip a valve because of valve float. This engine stock is meant for only 3600 RPM without the governer it turns about 5000-5500 RPM tops. check this video and part 2 for a better explanation:

also what will happen to your engine if you lay on the throttle with a bypassed/ disabled/ removed governor:
 

mckutzy

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If it has the stock springs.... itll retard the engine speed, before the threshold of con-rod detonation... Hence the valve float....
 

oneoldjimmy

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I am going to put a tach on it, and watch the rpms. Its going into a mud motor kit, so im not sure under load, if it will ever achieve the higher rpm. Will be a bit of a test, and will have to report back with my findings. I'm not opposed to more upgrades, but was trying to keep it as mild as possible for longevity and reliability.
 
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OPmini

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If it has the stock springs.... itll retard the engine speed, before the threshold of con-rod detonation... Hence the valve float....

To a certain extent valve float will limit RPMs but you risk bending/ chipping/ snapping a valve. Plus if you are revving higher RPMs over time you can weaken the connecting rod to the point of failure.
 

mckutzy

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In these engines... Over the last 10 years here... I haven't heard of issues described, as a fault of valve float...
 

oneoldjimmy

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If a guy keeps it under the point of floating the valves, what would be the cause of damage? (And thats a serious question, as I don't know) I honestly wonder if a slightly warmed up 212 would have the nut to hit the higher rpms under the prop load pushing a 1236 duck boat with 2 adults and gear...
 

OPmini

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If a guy keeps it under the point of floating the valves, what would be the cause of damage? (And thats a serious question, as I don't know) I honestly wonder if a slightly warmed up 212 would have the nut to hit the higher rpms under the prop load pushing a 1236 duck boat with 2 adults and gear...

Under load with a bypassed governer, over time the connecting rod will weaken (due to metal fatigue see: https://www.britannica.com/science/metal-fatigue) and get sent through the block after 1.5 to 2 years of medium to heavy use. WITH the governer, you should get a solid 5+ years of service from your engine. With proper upgrades (billet connecting rod and valve springs) and governer removed I would expect a solid 6+ years of service life.
 
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oneoldjimmy

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Governor, 5+ years, good enough for this guy! It will probably only get used 6-10 times a year (effin MN winter, slams the door on fall hunts pretty quick) Motors are cheap. If I like how it performs, perhaps I buy and build another new motor in the off season
 

OPmini

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Governor, 5+ years, good enough for this guy! It will probably only get used 6-10 times a year (effin MN winter, slams the door on fall hunts pretty quick) Motors are cheap. If I like how it performs, perhaps I buy and build another new motor in the off season

Sounds good! just make sure to put ethanol-free gasoline in the engine (see: https://axleaddict.com/misc/Pros-and-Cons-of-Ethanol-in-Gas ) and make sure you do a break-in oil change at the first 10 hours (see:
)
 

itsid

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while many things are possible, not all of them are smart.

if reliability is your main concern, I wouldn't rev the engine with the governor in place anywhere near that speed.
original Hondas (well some) can take quite some rpms I think 4400 rpms (the governor, the engine itself can take a lot more)
but it's a plastic part and if cheaply made can and will fail eventually at high revolutions

it's actually almost always the acceleration that causes a failure not the actual revolutions per minute but their sudden change,
and that's true for conrods as well.
Anyways, back to plastic penny parts.
unfortunately the 1k rpms make a huge difference already (it's about twice the load on that poor plastic gear)
And I'm unsure it'll hold in case of a hiccup.
gentle acceleration and decelleration shouldn't be much of an issue with 5k rpms even I'd say..
not exactly longest lasting setup (with the gear being ground off over time) but likely doable.
the jerk that comes from a locked drivetrain however and it's likely to be the end of the governor.

And then we're back at loose plastic shrapnel and metal bits jumping inside your crankcase locking the cam/conrod what ever it hits worst..

INSTEAD:
I'd remove the governor entirely and get a rev-limiting coil instead
(I think 4800 rpm coils are available and would be in the correct ballpark here)


'sid
 
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