Increasing rpm, while maintaining governor...

[JTSpeedDemon]

Another problem that sometimes happens is the valve retainer will slip off at high speed, dropping the valve into the combustion chamber for a spontaneous date with the piston. Evidently it only really happens on Hemi Predators since they have the one piece slip on retainers vs the non hemi's two piece automotive retainers.
So it you want to run it stock ungoverned, the best way to do that is to fully remove the governor, and change the retainers if it's a hemi.

 

[Budget GoKart]

Ive ran two engines hard for a long period of time. A 196cc coleman bypassed govenor it NEVER had an issue except two hiccups because the chain grabed and the clutch killed the engine. And my hemi 212 i ran for about 2yrs smoked really bad and had tons of blowby im sure we overheated it probably 10 times and the poor thing was over its lasting point but it kept chuggin untill i sold it. The hemi lasted the torture but was very well at the end of its life it was stock with a removed govenor and it held strong for a while. Then the person i sold it to blew it up

 

[oneoldjimmy]

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

Hmm... Now that is a new idea, I had not thought of... Who makes a rpm limited coil? That sounds like the clear ticket!

 

[JTSpeedDemon]

IIRC Honda makes them. So bonus reliability!

 

[vpd66]

Hmmm, I never stated that drilling the hole in the governor arm was disabling its function. It simply moves up the governed speed and the governor functions has normal. If these engines blow the rod threw the block at 5000 rpm then why was there a racing class that had them running stock engines at a 5000 rpm maximum??? They ran that class for over 3 years and I never remember any of them blowing a rod. I've been running my minibike for a year and a half now with my governor modded this way and the engine normally sees 4800 rpm. I guess I only have a 1/2 year left before the engine blows the rod! LOL If it does happen, I'll just go buy another engine for $99.

 

[OPmini]

Hmmm, I never stated that drilling the hole in the governor arm was disabling its function. It simply moves up the governed speed and the governor functions has normal. If these engines blow the rod threw the block at 5000 rpm then why was there a racing class that had them running stock engines at a 5000 rpm maximum??? They ran that class for over 3 years and I never remember any of them blowing a rod. I've been running my minibike for a year and a half now with my governor modded this way and the engine normally sees 4800 rpm. I guess I only have a 1/2 year left before the engine blows the rod! LOL If it does happen, I'll just go buy another engine for $99.

It's called metal fatigue: https://www.britannica.com/science/metal-fatigue
Drilling a hole partially disables the governer. They put the governer in there for a reason. Running these engines stock, under load, and at high RPMs will damage your engine over time and weaken the rod to the point of failure. 5,000-4,800=200 you're not too far from 5k pal. Plus you run the risk of bending a valve because of valve float.

 

[oneoldjimmy]

Mine has a hole factory. I'm gonna try it for the time being....

 

[OPmini]

Mine has a hole factory. I'm gonna try it for the time being....

should be fine if the factory put it there

 

[vpd66]

Obviously your not understanding anything about the modification I suggested. In fact it isn't even a modification on the original poster's engine because the hole is already there! So all he has to do is move the spring to that hole. Then you say " should be fine if the factory put it there"? but its not ok to drill the hole if your governor arm doesn't have it?? Drilling the hole does not partially disable the governor. It changes the angle of the spring so the engine revs higher before the governor kicks in. Once again, on a $99 engine I'll take my chances.

 

[OPmini]

Obviously your not understanding anything about the modification I suggested. In fact it isn't even a modification on the original poster's engine because the hole is already there! So all he has to do is move the spring to that hole. Then you say " should be fine if the factory put it there"? but its not ok to drill the hole if your governor arm doesn't have it?? Drilling the hole does not partially disable the governor. It changes the angle of the spring so the engine revs higher before the governor kicks in. Once again, on a $99 engine I'll take my chances.

No I do understand I just didn't know that OP had it from factory. So I reasoned that you would be taking a risk in modifying your engine to rev higher in doing so. No need to be a prick, i'm just trying to help. :/

 

[vpd66]

I'm not being a prick.Just stating facts. You were the one that said drilling the hole will bypass the governor, but when you found out it was there from the factory then you said it was alright. We all know the consequences of making these engine turn more then 3600 rpm, but there is also a safe range (below 5000 rpm) that you can run these engines at and still get a good service life out of them.

 

[oneoldjimmy]

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.

So I finally got it fired up today sitting in my mud motor chassis. The little tach (once I finally got it to read rpm) said my max rpm was 5200, and then the governor kicks in and chokes it back. Tomorrow I will be adding another hole, slightly back in the governor arm and see if I can dial it back some.. Anyone know approximate rpm at idle on a non hemi? TIA

 

[OPmini]

So I finally got it fired up today sitting in my mud motor chassis. The little tach (once I finally got it to read rpm) said my max rpm was 5200, and then the governor kicks in and chokes it back. Would limiting the throttle some, or adding another hole, slightly back in the governor arm seem like the best way to ween it back a hair? Anyone know approximate rpm at idle on a non hemi? TIA

idle is 3,600 RPM

 

[oneoldjimmy]

idle is 3,600 RPM

Um, idle, not working rpm... 1800 +/- 50 (when all else fails... I looked in the book)

 

[vpd66]

Yup 1800 rpm idle is correct. Glad your getting the results from your governor. Is that 5200 rpm with no load?

 

[oneoldjimmy]

Yup 1800 rpm idle is correct. Glad your getting the results from your governor. Is that 5200 rpm with no load?

Correct, no load...

 

[vpd66]

It will most likely be lower with a load. Before you drill another hole try using the throttle stop screw to lower the rpm some.

 

[JTSpeedDemon]

I wouldn’t use the throttle stop. While it will limit RPM, it will also kill power everywhere.

 

[OPmini]

Um, idle, not working rpm... 1800 +/- 50 (when all else fails... I looked in the book)

Yeah sorry my bad I was looking at the wrong thing

 

[vpd66]

Well when i started playing with my governor I backed out the throttle stop and gained 200 rpm but didn't really notice any gain in acceleration or any difference other then the 200 rpm top end gain. Wouldn't hurt to try? Its just a turn of the screw.