how many rpm is too fast

[adb140275]

mine hits the BAD vibration point at 6000-6500. above and below that its smooth as can be

 

[Don P]

so is this why i can't get this thing to go over 25mph no matter what jet i put in it?

it hits 25 mph then kinda shuts down then at 22mph it takes off again. i was thinking fuel?

Hi all update

i got the problem fixed. i had put a lot of rubber around the the seat post and front down tube to kill vibration but it let the engine shake to much. this caused the fuel in the carb to foam up and loose power. after removing most the rubber and tighten the clamps up problem has gone.. doing 30+ mph now.. still need to tune the carb.

 

[flatblack]

I see 15,000 RPM all day long at 55mph, get 200 mpg and am 50 state legal. At least that's what most of the ads for engine kits I see say I'm doing...JNMotors can't be wrong!

 

[frozenveinz]

..... 15,000?..... Be careful there, expect it to explode.

 

[The_Aleman]

..... 15,000?..... Be careful there, expect it to explode.

You revived a 5 month dead thread to miss the last poster's sarcasm? Cmon, guy

 

[KCvale]

You revived a 5 month dead thread to miss the last poster's sarcasm? Cmon, guy

(snickers)
There are some pretty wild claims out there that's for sure, what I can't understand is why.
MB's have fantastic real life stats as it is, making wild claims just puts a bad light on all MB's just being 'too good to be true' scams.
I guess it's that old greed over integrity thing, that's a shame.

 

[MotorNut123]

my bike doesnt have noticeable vibration at all, until the last ride

i get up to just about top speed, it feels like the chain vibrating very loud, never used to before, and it feels like the motor is bogging down when i stay on the throttle

i trued the sprocket today and it doesnt look like its rubbing and its not wobbling back and forth

and i dont know why its cutting out, could it be the carb? jetting? its all stock jets, stock plug. never had this problem before, but it runs, pulls, idles, cruises perfect.

any help appreciated. thanks and happy new year everyone

 

[GearNut]

MotorNut123,
Is the engine twisting in the frame?
They tend to twist (some describe it as leaning or tilting) to the left, the mounts actually slipping on the frame tubes a teeny bit, causing chain misalignment, excessive drag on the drive line and perceived power loss.

 

[MotorNut123]

GearNut, thanks for the input.

ill have to check that out, im getting a hardware kit from SBP cause one of the exhaust studs stripped out.

that could very well be the reason cause i just did a rebuild and maybe the mount came a little loose.