What's the maximum RPM you"ve reached?

[Outrunner]

I had my bike up to 38 mph the other day with a digital speedometer that was
GPS calibrated and a digital tach that showed 8310 rpm, I was very surprised
to see that, although it was only for about 4 or 5 seconds. At that rpm my
67cc engine was screaming and vibrating something fierce, and I didn't want
to grenade the thing. I'm running a 41 tooth sprocket, 18mm Mikuni carb,
and expansion chamber. Out of curiosity, what is the maximum rpm some of
you guys have seen?
shft.

[Outrunner]

Originally Posted by Outrunner

I had my bike up to 38 mph the other day with a digital speedometer that was
GPS calibrated and a digital tach that showed 8310 rpm, I was very surprised
to see that, although it was only for about 4 or 5 seconds. At that rpm my
67cc engine was screaming and vibrating something fierce, and I didn't want
to grenade the thing. I'm running a 41 tooth sprocket, 18mm Mikuni carb,
and expansion chamber. Out of curiosity, what is the maximum rpm some of
you guys have seen?
shft.

Update, I installed a 37 tooth sprocket and I can easily surpass 40 mph up
to 43 mph, at about 8400 rpm, so it is really runnin' well. I plan to rig up a
nitrous oxide system in the near future and will see what the increase in rpm and speed is.

[Cabinfever1977]

I thought that most places listed the max rpms of the 66cc engine at around 4500 rpms.
And since youre using a smaller rear sprocket that alone should lower your rpms especially at higher speeds. Im not challeging your equipment,im just stating the information i read and that some people think it would be better to have lower rpms at speed.

[Outrunner]

Originally Posted by Cabinfever1977

I thought that most places listed the max rpms of the 66cc engine at around 4500 rpms.
And since youre using a smaller rear sprocket that alone should lower your rpms especially at higher speeds. Im not challeging your equipment,im just stating the information i read and that some people think it would be better to have lower rpms at speed.

I'm using a digital tachometer that reads the spark pulses from the plug wire,
so,I'm sure that it is accurate. Riding on a flat roadway that is over 2 miles long gives me ample time and room to wind out the engine. My engine has an 18mm Mikuni carb with a #70 main jet, A tuned expansion chamber,and modified cylinder porting, combined with a modified intake manifold and a slant head.
Running 50:1 Amsoil Sabre gas mix and "tucked in", I assure you that it is accurate data. My buddy has followed close behind me and confirmed my speeds also,so I feel confident of the speed and rpm's reported. Like I first stated, "I was surprised to see that" meant that seeing that high of rpm's. Obviously,I have a well tuned and sweet running set-up. I love it!

[foureasy]

10k with a 41t sprocket and 24.5" tires

[The 26incher]

Outrunner, could we please see pic's of your bike? Thanks
I really feel like my engine spins like crazy. I would love to have a tach and speedo.

[bairdco]

i made two revolutions around the block earlier, probably took me 3 minutes.

[Outrunner]

Originally Posted by The 26incher

Outrunner, could we please see pic's of your bike? Thanks
I really feel like my engine spins like crazy. I would love to have a tach and speedo.

Here are some photo's of my bike, I have changed the air filter and added a "Thudbuster"seat post for a much smoother ride.

[Cabinfever1977]

That really is a great looking bike. I believe your speed,i was just suprised your rpms were so high.

[BarelyAWake]

That is a sweet lookin' ride - nice combo of elements for an overall effect, I likes it