1977 KZ650 Custom, need help with tire sizes...please!

Hey guys,

I have a 1977 kz650 Custom and I'm having a hard time finding the rear tire size online. Can anyone tell me what tires you all are using front and rear? As well as the correct tube sizes, and if I can go tubeless on the stock rims? I have no idea. THanks!!

I'm looking to go a little widder on the rear tire if possible. I have the center stand still on the bike and I want to keep it.

Any info would be greatly appreciated!!! Also, is there a way I can change the tube and tires myself, or does this need to go to bike shop? Cause a shop near by said they will only work on 1991 and newer....laaaammeooos!

77 C1
Font tire: 100/90/19
Rear tire 110/90/18 (I think)
You can go 120 or 130 on the rear.
If you go 130 you may have to loose or modify your chainguard.
I don't recall the tube size right off the top of my head. And YOU MUST HAVE TUBES for the 77 model.
You can change them yourself, but experience is the key.

Myself, I run 100/90/19 on the front and 130/90/18 on the rear.
Definitely find a different shop if you want some one to change your tires.

The stock size was 3.25H19 front and 4.00H18 rear. Yes very fewe run these. Metric sizes aren't right as a 110/90-18 is a 90 aspect tire where a 4.00-18 is 100 aspect meaning same height as width. A 110/90-18 looks rather goofball on the back because it's the right basic width but too low a profile. A 120/90-18 is better because at least being a 90 aspect tire, the additional width translates into enough height to work OK. A 100/90 vs a 3.25/19 on the front is the same story. You can still get 4.00-18 ect in quite a few tire brands and that's what I recommend. A little wider 120/90-18 is OK too. Anything larger will rub the stock chainguard although tire sizing is far from universal throughout the brands so brand "A" 130 may fit, where brand "B" does not.

I'm running a Cheng Shin Barracuda 130 on the rear of my 77 kz650 b1 and it fits everywhere except the chain guard had to go...well actually it went on its own...I didn't realize the tire was rubbing on the guard until it sucked the guard into the spokes and made one hell of a noise!!!

Hello fellow 650 rider,
I run a 120/90-18 rear,100/90-19 front,both are tubed.I recommend you do the same.Get a set for best results.A 130/90-18 rear is a little big on this bike,it'll rub on chain gaurd[see other comment].You can't run tubeless on a spoked wheel[if you have mags,run tubeless].I just bought a pair of DURO brand tires[online],they look great...[for ppl on a budget].not sure about performance yet.If you have money,find a premium tire.

120/90-18...
120 is the width,about 12 centimeters.
90 is the height,or 'aspect ratio'...90% of width i believe.
18 is the rim size.
...you can go with a lower profile if you can find'em.120/80-18 for example.
hope this helps buddy.

[if you have mags,run tubeless]

Not unless it's a tubeless mag wheel, and I think on the KZ's, that means 80 or later (with some exceptions being later).

I thought all mags could run tubeless...i stand corrected.

Quote Anarki650: "I'm running a Cheng Shin Barracuda 130 on the rear of my 77 kz650 b1 and it fits everywhere except the chain guard had to go...well actually it went on its own...I didn't realize the tire was rubbing on the guard until it sucked the guard into the spokes and made one hell of a noise!!!

This happened to me years ago when I first put on a 130. Even with the KZ650C1 mags the noise nearly gave me a heart attack! With my replacement chrome chainguard the 130 doesn't rub anything, but I have switched back to a 120. I use Michelin Macadams (120/90-18 rear,100/90-19 front) with corresponding sized Continental tubes. Don't even try going without tubes on '77 KZ rims. I have always changed my own tires, but I recommend you have someone with real practical experience show you how before you tackle it. I have never found a bike shop I would trust to do the job without pinching a tube, most of these guys think a tube is something toothpase comes in. Ed

I just went through this same exercise for my '78 KZ650. There really is no "correct" answer, and even the conversion charts can be confusing.

It appears that either a 90/90-19 or a 100/90-19 on the front will work, but the 100/90-19 seems to be the preferred size. 120/19-18 is about right for the rear. I bought Bridgestone S11 Spitfires for mine from Iron Pony. They look like a good tire, and the price was very reasonable. Iron Pony is in Ohio, so stuff I order from them arrives the next day!

anarki650 wrote:

the chain guard had to go...well actually it went on its own...I didn't realize the tire was rubbing on the guard until it sucked the guard into the spokes and made one hell of a noise!!!

Ha ha ha ha!

Glad that was all that it did was make noise.:laugh:

I just switched back to the original size from the wider tire the P.O. installed. I am happy with the stock size, although it does not look as tough.

RonKZ650 wrote:

The stock size was 3.25H19 front and 4.00H18 rear. Yes very fewe run these.

My 750 came stock with those. JC Whitney used to sell those sizes. I bought lots of them from JCW. They carry the Cheng Shin and other mediocre tires which are OK for general purpose, not for high speed (over 90) use. They carry other brands too.



www.jcwhitney.com/autoparts/Search?catal...tn.x=0&searchbtn.y=0

RonKZ650 wrote:

Metric sizes aren't right as a 110/90-18 is a 90 aspect tire where a 4.00-18 is 100 aspect meaning same height as width. A 110/90-18 looks rather goofball on the back because it's the right basic width but too low a profile.

I have been running metrics for a while. They work OK. One thing, If you go too wide in the back you'll get lousy tread life mileage because you burn the center track down faster.

Qdude wrote:

anarki650 wrote:

the chain guard had to go...well actually it went on its own...I didn't realize the tire was rubbing on the guard until it sucked the guard into the spokes and made one hell of a noise!!!

Ha ha ha ha!

Glad that was all that it did was make noise.:laugh:

I just switched back to the original size from the wider tire the P.O. installed. I am happy with the stock size, although it does not look as tough.

I got confused on the metrics and went one size too big on the front.... seemed to clear OK until I got above 50 mph and heard a squeal! The tire was "growing" in diameter just enough to skim the front fender.:laugh: