How do I get more RPM's

[Aaron871]

6.5 Honda Clone.
Gov. removed.
I'm looking for higher RPM's at top speed.... is this a bad idea?

[moto1fast]

Well, Higher RPM's at top speed? Do you want the engine to Have both a Higher RPM and Speed or just Higher RPM's at the same Speed it is going now?:dizzy:

[Aaron871]

Well, Higher RPM's at top speed? Do you want the engine to Have both a Higher RPM and Speed or just Higher RPM's at the same Speed it is going now?:dizzy:

More RPM - More speed

Same gear......

[moto1fast]

How fast are you going now? What size rear sprocket are you using? Do you know what your RPM is now at top speed? What is the total wieght of BSR and rider ? What size tires on rear? I other words to improve what you have I need to know what it is doing now. It depends on a number of factors involved in its performance and then calculating a way to change it to your liking!:cheers:

[Aaron871]

I "guess" I'm going 30...

I'm 220 lbs.

54 tooth sprocket (TAV2 w 10 tooth)

20" tires

rpm.... ???? I have no idea, this is my first small engine.

It will barely pull a wheelie without me helping.

[moto1fast]

Ok, Now we can go to work on this problem! # 1 the engine is probably doing all it can with the govenor removed with the setup you have! If it is running right it is starting off a little slow and gains speed slowly. Is taking a little distance to get to top speed. Is that right? The problem is the wieght, Tire size and rear sprocket but mostly the tire size and wieght. You can increase the speed by actually reducing the tire size on front and rear. You can increase the RPM's by using a larger rear sprocket say a 60 tooth but you may lose a little top end speed or maybe not, may increase it by reducing the drag on the engine letting it run up Higher RPM's. Will just have to try that to see! Do you have any cop friends that would use his radar to check your speed? The Only way to realy get it very Quick and Fast with it set up like you have it is to either put a larger engine on it or put Nitrous Oxide on it! With NOS you would have to activate it on top end and then you would go faster than you would care to!! Hope this helps some!

[Aaron871]

I've heard a myth that a smaller flywheel will have a postitve effect on RPM's

Any truth to this?

[moto1fast]

Yes that is correct! It will increase rpm's some due to the mass or wieght it reduces! It lets the crank turn at a faster rpm but also consider that the higher the rpm the shorter the engine will last! On a smaller engine it is better to over rev it than to drag it down or lug it Though! Another problem will be finding a smaller flywheel to fit the Honda Clone!!

[CritterBuddy]

** Safety considerations deleted. Be sure to wear a helmet and have your medical insurance paid up** :laughing:

Moto1fast is right on the money with his suggestions especially about whether or not your motor is actually attaining top rpm depending on total load on the motor. The major factor here is rider weight. Unfortunately, little guys can always attain slightly more top speed than even myself due to my big arse. But there are a couple of things we can do.

A friend of mine did some tuning to his Honda 6.5hp motor. He removed the governor and changed the carburator jet. I just looked for an internet link I had on how to do this but got a 404 error. :angry: Sorry I can't help you further.....

Since you are already running a 54 tooth axle sprocket (which is about the smallest you can find for speed) another item to consider is the drive sprocket in your TAV2. This sprocket is known as a type "c" sprocket and has a hub (shoulder) on both sides. You can increase your top speed some by getting an 11 tooth type "c" sprocket which is readily available. If you can do the modifications you can also run a type "b" sprocket which only has a long hub on one side. You'll have to cut off some of the hub and then redo the shims when you put it back in your TAV2. You can get additional shims at the hardware store. Regular washers are too big in diameter and I can't recall what exactly they call the smaller ones used as shims.

Below are some estimated numbers to show you what will happen with these modifications. Since you can never attain top rpms out of a motor due to load, I'll use 3000 rpms for stock motor and 5000 rpms for ungoverned motor. Even so, realize you may still not actually attain these numbers as they are estimates.

Governed Motor
33.04 mph (current setup)
36.34 mph (11 tooth TAV2 sprocket type "c")
46.25 mph (14 tooth TAV2 sprocket type "b")

Okay, let's get ridculous.....

Ungoverned Motor
55.06 mph (current setup)
60.57 mph (11 tooth TAV2 sprocket type "c")
77.09 mph (14 tooth TAV2 sprocket type "b")

I can assure you I will not be riding your BSR if you go ungoverned.....

[Aaron871]

you say "Ungoverned Motor"

Is that just unhooking all the linkage and linking directly to the carb butterfly? Cause that's what I got and I'm not close to 50.....??????

It opens the plate a full 90* but can't get to full RPM's I don't think (big tires and a fattass)

Maybe it needs a 60 tooth...


edit: maybe I should run it down a hill and see if the rpm's increase....

[moto1fast]

Ungoverned is like you have it! Just disconected and going to carb. To get that kind of speed on that setup you have to figure in the wieght, size of tires, etc... I have never been able to get a 6.5 hp STOCK engine up to 50 MPH even ungoverned. If I wieghed 60 lbs maybe!! To get it at that speed you would have to have a striaght stretch of about a mile at that! Max speed for the ungoverned 6.5 with a 54 tooth rear and a 11 tooth tav sprocket and using 11.5 X 8.00 X 6" tires is around 44 MPH with a total wieght of 275 to 300 lbs. Wieght has a lot to do with attaining High Rpm on a small single cylinder engine. It does not take a lot of wieght to pull it down!!Think of it this way if you took a V-8 350 small block chevy and put it in a 1923 T bucket roadstar and went up 20 degree incline and then put it in a Mack 18 wheeler and went up the same incline with the same gearing both at full throtle . Which would obtain the higher RPM! The lighter one of course because of the different loads on the engine!! Take two karts set up exactly the same, one with a 75 lb boy and one with a 200 lb man and go up the same incline now which engine will uptain the higher RPM? Your best bet is to change your gearing and reduce wieght to unload the engine!! Run it down a hill and the heaviest wieghted rider will have a higher RPM!! Until it Blows!! LOL It unloads the engine going down hill but going up a hill loads it!:thumb:

[CritterBuddy]

I haven't checked on a B&S motor but on Hondas to get the *full* ungoverned effect you have to remove all of the governor parts including the internal parts. The reason for this is there is a governor gear which drives off the crankshaft. Any added friction or weight on internal parts will cause some drag not allowing you to get full rpms. I know racers completely remove all the governor parts on their honda powered race karts for maximum speed.

Moto1fast is correct in that even if you do remove all the governor parts there are many more factos involved which is why I stated that those numbers are estimates. I can say that my friend who completely removed his honda governor and changed the jet size could not only start quicker from a dead stop but also outpull me on top end. We both had the same gearing and are within about 25 lbs of each other. Whether or not he was actually getting the full rpms out of the motor we don't know because he doesn't have a tach.