Forum

Login

Register

By registering at the KZrider.com community, you agree to the following terms. KZrider.com reserves the right to remove any posting it finds unsuitable. Members who refuse to play by the following rules will be excluded from the discussion board.

PRODUCT OR SERVICE ADVERTISING IS STRICTLY LIMITED
KZrider is more than a website. Its members comprise a community of KZ enthusiasts dedicated to encouraging and preserving our sport and passion for Kawasaki Z, Z1 and KZ motorcycles. We pursue our passion because we enjoy it, not to make money from it. To that end KZrider.com is not a place for you to solicit sales of any kind. No member is allowed to refer to their own business, or any business to which he/she is associated, through the discussion forum or personal messaging system (U2U). Be aware, the U2U feature has been abused in the past. If any member solicits an unwelcomed solicitation through the U2U system please report that solicitation to the Administrator or Moderators promptly.

There are four exceptions to this policy:
1. As permitted in Classifieds (consumer-to-consumer transactions).
2. An item may be offered for sale as a consumer-to-consumer transaction in any forum where there exists reasonable expectation of being welcomed by another member who has previously posted in the thread ("cold calls" and "door-to-door" solicitations are prohibited).
3. Each member is allowed a simple link (somesite.com) in their signature, which link shall include no description of any kind.
4. Paying advertisers are allowed to post in the Vendor forum.

KEEP IT CLEAN
You may not post libelous or defamatory messages or materials, or include links to such materials in your postings. You may not post messages that are obscene, violent, abusive or designed to harass or intimidate another individual. Pornography, Warez, or any other illegal transactions may not be posted or included in members profiles. No blatant nudity.

BE CIVILIZED
Don't use racial, ethnic, or gender slurs, religiously derogatory comments or any other personal discriminations even in jest. Use of slurs needlessly offends people - whether or not they're a member of the group you've insulted. Respect others' religious beliefs and culture. Recognize that others have religious and personal beliefs which may differ from yours. Stay away from political debates. Keep the language and behaviour appropriate.

USE DESCRIPTIVE THREAD TITLES
When you post a new thread, please give users some idea of what it contains in the title. Thread titles like "Help" or "Check this out!" are cheap ways of getting users to look at a thread they might not care about, and would not have clicked on had the full title "Help, I need credit card numbers!" been used. Furthermore, it helps stop multiple threads on the same subject. When starting a new thread, describe the content of your thread clearly in the 'Subject' line of your post. Don't use vague subjects. Use descriptive and specific subject lines. This helps others decide whether your particular words of wisdom relate to a topic they care about. For example: "HELP!!" is not an appropriate subject and neither is "My bike doesn't run".

PLEASE DON'T SHOUT!
That cap lock key wasn't invented to help you get your message across. Messages written in all caps are annoying, hard to read, and loud.

HAS IT BEEN POSTED ALREADY?
Please look for an existing thread on a subject before you post one about it. Chances are good that your question has already been answered. There is a search feature on these forums, use it. Starting topics that have already been answered in great detail is a waste of everyone's time. Look to see if information you're about to post has just been posted by someone else. Then go ahead and post.

WE HAVE SECTIONS FOR A REASON
The Technical Forums have different sections for a reason. If you're not sure, use your best judgment. 

DON'T CROSS-POST
Cross-posting is when you post the same message multiple times in various threads or forums. We only need to see it once guys. 

STAY ON TOPIC
Keep threads on topic. If you've got something completely unrelated to say then start a new thread. Unresponsive solicitations for consumer-to-consumer sale are prohibited as being unrelated and off topic, but solicitations for consumer-to-consumer sale may be posted in Classifieds.

CONSIDER THE IMPACT OF YOUR WORDS BEFORE POSTING
Adhere to the same high standards (or higher) of behaviour online that you follow in real life. In real life, most people are fairly polite and law abiding. The same rules of behaviour are expected on any list.

MESSAGES SHOULD CONTRIBUTE TO THE TOPIC BEING DISCUSSED
or introduce a relevant idea. If you've read enough threads, you've already learned how annoying it is to go through "Me Too" posts. A "Me Too" is a post that says "I agree with what the other guy said" and otherwise does not add to the content. If you have a comment about someone else's post, tell them via U2U or email. Generally speaking, unless it concerns the entire group and is within the group's stated purpose, you should reply only to the author. Avoid replies or responses to the whole list of yes, no, or "I agree!". This is meaningless and you too would be annoyed to open such a message.

WELCOME TO KZRIDER
If you are a new member, introduce yourself by posting to the New Member Forum. While it's nice to welcome a new member, only do so if they have posted in the New Members forum. There is no need for 50 welcome posts in a technical forum thread.

U2U IS A WONDERFUL FEATURE
Please don't start a topic that is directed at one person that could be put into a U2U to them. If you have a message for one or two posters, use U2U or email.

PICTURE PERFECT
Images & attachments may be posted as long as they are not explicive or offensive. Images are limited in size to 2mb. The Project Forum is for members' rides only and is an ideal place to document your rebuild.

FLAME-WARS
Don't even start them, they will be ended, quickly, and you'll find yourself on the short bus. Flaming: Personal attacks in cyberspace can be particularly vicious. Flaming is the rather nasty art of attacking others on a personal level.

  • Register
Welcome, Guest
Username: Password: Remember me

TOPIC: Intense high RPM vibrations

Intense high RPM vibrations 9 years 1 week ago #1886

Hey all, I have a 1980 KZ750-G1 LTD Twin, and this is only my second bike (my first one being a tiny DT80). It always has some vibration to it, definitely engine vibration, but it has really really bad vibration above 4000 RPM to the point that the mirrors are blurred and useless. Highway riding is not comfortable at all. What could cause this? I've played with carb synchronization but nothing I did made an appreciable difference.
Carbs have been rebuilt and cleaned.
Points and Condensor are new.
Ignition timing and point gap were just adjusted.
Compression is fine at 150 PSI per cylinder. What else could cause this?
THanks in advance...
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 1 week ago #1889

  • luvmykaw
  • luvmykaw's Avatar
There are guys here that own the big twins and could give you more to trouble shoot with, but... Are your frame to engine bolts to torque spec. (tightened up)? I'm pretty sure that those twins had counter ballancers in them, maybe there is a prob in that area?

Post edited by: luvmykaw, at: 2005/10/15 02:34
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 1 week ago #1894

  • steell
  • steell's Avatar
  • OFFLINE
  • Member
  • Posts: 7047
  • Thank you received: 226
I have a KZ750G1 also :)
My mirrors do get a little blurry above 4k, but not to the point of being unusable, and the vibration is certainly not enough to be uncomfortable.
I assume that sitting on the bike and revving it above 4k in neutral the vibration is the same?
If torqueing the engine mounting bolts does not reduce the vibration considerably, then do a compression test and post the results here. You also might consider checking and adjusting the valve clearance.
Getting into the balance shafts is really a last resort, as you have to remove the motor and split the cases.
How many miles on your bike?

And my standard advice to anyone with a 76-80 750 twin:
Grease the swingarm bushings, the grease fitting is below the airbox, behind the right side frame rail, on top of the swingarm. :)

Post edited by: steell, at: 2005/10/15 05:05
I just discovered that "Chemo Brain" is a real thing. Now I have an excuse for anything I do. Now that's what I call Freedom !!!!
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 1 week ago #1970

Thanx for replies - yeah, it vibrates regardless of the gear its in. I torqued the mounting bolts today and it didn't do much to help.

I have not, however, checked valve clearance. Last time I checked compression it was good, 150 psi across both cylinders, but I will test it again to be certain.

The bike has 14.7k on the odometer.

What does greasing the swingarm bushing do? Will it make the bike run like new and give me money? :)
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 1 week ago #1975

  • rstnick
  • rstnick's Avatar
  • OFFLINE
  • Member
  • Posts: 3386
  • Thank you received: 88
I'm not sure about the twins, but I find my 4's mirrors vibrate a lot at cetain rpms and get blurry, but you can still tell if someones there. I live and ride in the country, so that's not much of a problem, but in the city I can see you'd want better vision.
Rob.
Ontario, CANADA
http://www.kz650.info/
'77 KZ650 C1 newest
'78 KZ650 C2 18x18 100,000+ kms
'78 KZ650 C2 project 6 #s off
'79 KZ650 C3
KZR Ontario Chapter
Need a key for your kz/z? I can make them.
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 1 week ago #1980

  • luvmykaw
  • luvmykaw's Avatar
My 650 gets a bit too viby for my comfort at 5000 rpm on the highway. So I changed sprockets to lower the rpm. Works great, may be worth looking at if you can't find a mechanical fix for the vibes.
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 1 week ago #2025

  • steell
  • steell's Avatar
  • OFFLINE
  • Member
  • Posts: 7047
  • Thank you received: 226
Greasing the swingarm bushing will allow you to keep more money in your pocket :)
Instead of spending it on repairs, and possibly medical bills :(

Kawasaki used several rubber bushings on the twins to keep vibration from getting to the rider, the handbars are mounted in rubber bushings, as well as the foot pegs. You might check those to make sure they have not disentegrated. The handlebar bushings are located in the upper triple clamp, and the footpeg bushings in the footpeg mounting bracket. If you can move the footpeg with your hand, then they are bad, and you can look at the top and bottom of the upper triple clamp to see if the handlebar bushings are falling apart.

If I recall correctly, there are two engine mounting bolts on top of the cylinder head, one at the front of the motor, and two at the back, all of those are tight?

150 psi is good compression if the engine is cold, normally, it's 160-175 if the engine is warm.
I just discovered that "Chemo Brain" is a real thing. Now I have an excuse for anything I do. Now that's what I call Freedom !!!!
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 1 week ago #2100

steell - there's the two mounting bolts that attach the cylinder head to the bracket with the ignition coil, are those what you are referring to? Or did I miss something completely?

The footpegs are probably a little loose, then. I can definitely move them with my hand...

The vibes are definitely the most annoying at the handlebars, though. The rubber bushings look OK, from what I can see.

Rechecked compression today. ~150 PSI on both cylinders after 3 seconds, cold. I still need to check valve clearance, thats one thing I haven't even taken a peep at since i've gotten the thing.
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 1 week ago #2113

Im getting a vibration at around the same RPM, not that bad that it vibrates the mirrors to much, but it definitly sounds and feels different. Im the same way, Im not going to really be concerned about it until I adjust the valves, and check the chain adjuster. My 82 750LTD has 8400 miles on it, and I bet any money the valves were never adjusted the entire life of the bike. I also get a very small backfire through the carbs at low RPM when accellerating, Im assuming it's a valve or 2 thats a little to "tight".
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 1 week ago #2125

  • steell
  • steell's Avatar
  • OFFLINE
  • Member
  • Posts: 7047
  • Thank you received: 226
Yep. the two bolts that hold the bracket that the coil bolts to are also engine mounting bolts. The rear lower mounting bolt is a little hard to see as it is actually under the motor, under and behind the kick starter.

150 psi compression cold is good, it will increase 10-15 psi hot.

The only 750 twin that I have had with a vibration problem is my 750G when I first got it started after buying it on eBay, but it was only running on one cylinder at the time :)
I just discovered that "Chemo Brain" is a real thing. Now I have an excuse for anything I do. Now that's what I call Freedom !!!!
The administrator has disabled public write access.

Intense high RPM vibrations 9 years 5 days ago #2623

I'll definitely check that last mounting bolt, and valve lash whenever I get a break from my classes. Thanks for the reponses.

I filled the handlebars will birdshot today, it seemed to help somewhat.
The administrator has disabled public write access.
Keyword