By registering at the community, you agree to the following terms. 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.

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 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 ( in their signature, which link shall include no description of any kind.
4. Paying advertisers are allowed to post in the Vendor forum.

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.

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.

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".

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.

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.

The Technical Forums have different sections for a reason. If you're not sure, use your best judgment. 

Cross-posting is when you post the same message multiple times in various threads or forums. We only need to see it once guys. 

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.

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.

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.

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.

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.

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.

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: Repair or replace a rusted muffler? Fix a hole?

Repair or replace a rusted muffler? Fix a hole? 6 years 8 months ago #290230

I have a KZ440 that is running but not perfectly. It's starting a bit rough, but after it warms up is holding idle at around 800-1000rpm. When I rev it, there is a small lag and stutter, but not too bad. My issue right now is that there seems to be a lot of back firing and exhaust noise, which I think might be associated with the rusted muffler. The muffler body is in good shape (no exterior holes) except for the exit hole. It's a stock muffler, so has a 1"(or about that) exit hole, but has rusted out around this from exhaust moisture. I'm guessing that this is reducing the back pressure on the system and maybe leading to some of the roughness. That's my first question: do you think I'm right about this?

My second question is what to do. right now I want to get it running and use it for a bit to see if it's a bike I want to put time/$ into, so I'm not into restoring it right now. I'm wondering if I could clean up the soft rust, use a rust stabilizer to hold together the remaining muffler end and then use JB weld or epoxy putty to rebuild the rusted out portion. Any better ideas or objections?

thanks for the feedback.
The administrator has disabled public write access.

Repair or replace a rusted muffler? Fix a hole? 6 years 8 months ago #290240

  • bountyhunter
  • bountyhunter's Avatar
  • Member
  • Posts: 7113
  • Thank you received: 320
Rust usually grows from the inside out on exhaust systems. If you have holes breaking through, the chances are the metal is rusting near to through in other places.
1979 KZ-750 Twin
The administrator has disabled public write access.

Repair or replace a rusted muffler? Fix a hole? 6 years 8 months ago #290242

so, I'm inferring that what you suggest is that I should replace the muffler completely. The stock muffler is welded, so I'd need to cut it above the weld and use a slip on, right? Any good resources for a new exhaust system? there really isn't too much rust on the pipes, but I'm sure there's some corrosion inside them.
The administrator has disabled public write access.

Repair or replace a rusted muffler? Fix a hole? 6 years 8 months ago #290291

  • bountyhunter
  • bountyhunter's Avatar
  • Member
  • Posts: 7113
  • Thank you received: 320
I know MAC makes new 2-1 systems for the 750 twin that can be had new for about $220, I got a used one of ebay for about $60. MAC probably makes one for the 440 twins, you can check their website.

Places like JC Whitney used to sell an assortment of slip on mufflers if you want to hacksaw the pipes and put new mufflers onto the pipes.

Since you aren't sure if you want to keep it, you might want to sort out all the other problems before spending the money on the exhaust. It sounds like it needs carburetor cleaning.
1979 KZ-750 Twin
Last Edit: 6 years 8 months ago by bountyhunter.
The administrator has disabled public write access.

Repair or replace a rusted muffler? Fix a hole? 6 years 8 months ago #290315

  • RacerZ
  • RacerZ's Avatar
  • Member
  • Posts: 39
The administrator has disabled public write access.

Repair or replace a rusted muffler? Fix a hole? 6 years 8 months ago #290497

Well, I cleaned up the flaking rust, cleaned it with HCl acid and washed it, then put on a JB weld patch. It's working great. Hardened rock hard in about 15 minutes with the pipe warm and I've since started sanding it so it doesn't look so much like I stuck a bunch of gum on the muffler. It should work for a few months, which will be plenty of time for me to figure out if the rest of the bike is worth putting the cash into. Sorry I don't have a before picture, but you get the idea. It's definitely a lot more quiet and it really seems like the throttle response is a lot better; less lugging before revving up.

The administrator has disabled public write access.