vibration issue with my KZ750m1 twin

hey Guys.....I'm wondering if anyone can help me figure out why my bike vibrates when i get it up past 50mph runs reasonably smooth up to 50mph but then it vibrates a lot more as i get it up to around 60mph. this is my first time riding the 750 twin is it just the nature of the beast or is there an issue I should be looking into

Do you have a manual? Might be the counter balancer starting to fail. They do vibrate though.
Steve

thanks Steve and yes I do have a manual i will do some reading and see if i have a problem Huston ....or is it just that I am unfamiliar with the way that that the 750 twin runs.....I was told they are a bit rattly ....but have been wondering if it is more than that in my case ......I'll get back to you once I have done some more research on the issue

Engine vibrations are related to the engine's RPM rather than the bike's speed in MPH. The engine doesn't really care about what speed the bike is traveling. Try this - gradually accelerate the bike in 1st gear and see if the vibrations occur. If so, note the RPM at which they occur. Then do the same in 2nd, 3rd, etc. and see if the vibrations occur at roughly the same RPM. If so, the vibrations are engine related.

If the bike vibrates above a given MPH regardless of the engine's RPM the odds are you have a problem with the bike such as bad tires, bad swing arm bushings, bad steering stem bearings, etc. Ed

tires are good checked swing arm when I broke it down just after i got it ....will test out as you suggest today and get back to you

My old KZ750B Twin vibrated like crazy at 5000rpm and above.
Anything below that was simply fine and what a great, in and out of the city "cruiser" at 2500-3500 rpm in 5th gear.
I found that putting a 1 tooth smaller counter shaft sprocket on with my stock air cleaner, one jet up-size in the CVs and a Kerker 2:1 header, made the silly thing quite fun to drive around town on.

For open HWY one tooth more on the countershaft sprocket will lower the RPM 500. Good torque so it shouldn't slow it down much.
Steve

650ed wrote: Engine vibrations are related to the engine's RPM rather than the bike's speed in MPH. The engine doesn't really care about what speed the bike is traveling. Try this - gradually accelerate the bike in 1st gear and see if the vibrations occur. If so, note the RPM at which they occur. Then do the same in 2nd, 3rd, etc. and see if the vibrations occur at roughly the same RPM. If so, the vibrations are engine related.

If the bike vibrates above a given MPH regardless of the engine's RPM the odds are you have a problem with the bike such as bad tires, bad swing arm bushings, bad steering stem bearings, etc. Ed

Easier way: just get it cruising wherever the vibration is the most noticeable and then suddenly pull in the clutch and let off the gas. If vibration stops, it's the engine. I knew this idiot who kept rebalancing the tires because of the vibration right around 60 - 65 mph....... :lol:

And yes the twins have harmonic vibration in the 3500 - 4000 range as I recall. Gets worse with age as the balancer assembly wears and loosens up.

swest wrote: For open HWY one tooth more on the countershaft sprocket will lower the RPM 500. Good torque so it shouldn't slow it down much.
Steve

I ran my 750 twin with the rear sprocket reduced from 38T to 32T for about 20 years. Ran fine, but I only weigh 160 and don't drag race much. Lowered the RMP at 70 mph from 5k to 4200.