1975 KZ 900 , ZRX Swingarm, 89 GSXR front end

My motor weighs 210 lbs on my nuclear precision bathroom scale. I have a standard KZ1000A2 motor with a welded 900 crank. I'm pretty sure that I weighed it with the starter and carbs attached.

testarossa wrote:

My motor weighs 210 lbs on my nuclear precision bathroom scale.

considering the height that's chunky by any ones opinion!:dry:

leon

dutchz wrote:

Just read through the last half of your thread, great job!

Don't know if you read the reply in my thread but yes, mine weighs 450lbs with a full tank of gas, 51/49 F/R. Not bad for a steel framed bike with a lug of a motor... I forget what just the motor weighs but it's a large chunk of weight... Mark is right, it never ends... Don't get too carried away with the weight savings if you are close to your goal :whistle: You've done all the big stuff. Bike looks great!

Very good info, and advice. Thank you.
I'm not sure I can get any lighter than 450. My Ducati weighs like 425, with 120 Hp. It's just the perfect combination for riding on the street or track. More power is always fun, but how often do you really open up a bike that has say over 150 HP.

testarossa wrote:

My motor weighs 210 lbs on my nuclear precision bathroom scale. I have a standard KZ1000A2 motor with a welded 900 crank. I'm pretty sure that I weighed it with the starter and carbs attached.

More good info, man I hefted the motor onto a stand, it was a heavy beast, 210.

That leaves 240 for the rest of the bike.

The later motor with the porkchop crank, it must be lighter?
Which leads to the next question, I have heard you can breed the older Z-1 engine with the J model and have the best of two worlds...is that correct?

Which leads to the advice I keep getting (good advice) just get it done!!

Boy I sure want to, but the economy is making me careful about spending any amount.

Soon as I have 400 bucks set aside for the bike the ignition will be on, and it will be running. I work in a Machine shop, we are very busy so I think the worst of the recession is over.

I have to tell you all this forum is the greatest, i get stuck on a problem and just start surfing, there is someone always smart enough to figure it all out.

I would be in a real jam without all the help you guys are giving me..

Many thanks!!!

larrycavan wrote:

TK11b40,

I'm just going to throw this out there for you...

4 days ago a guy I know with a little repair shop was riding an old CBR Honda on a test ride.

He's going down the road about 70mph, SNAP... and the ass end of the bike hits the road. Long story short he crashed and broke his foot pretty badly.

I looked at the bike yesterday. To me it looks like somebody got carried away with the rear shock mount. It was wicked light aluminum plates and they broke...ripped right through the bolt holes :ohmy: It sure didn't look like OEM bracket.
Just be careful with your build bud.... That's all I'm saying..... be careful

Not picking anything apart on your bike.

I appreciate the advice....really. I take no offense, and certainly will be thinking about the possbility.

I actually take a great amount of care, in fact the shock mounts for instance were reverse engineered fromt the original ZRX, same size, same material (6061 Al).

The only spooky thing I think about so far is the rear brake, if it ever lets go due to a material failure, it will lock up the rear tire.

Most of the time under hard braking the rear tire is just skimming off the pavement so there is not much force involved. I rarely use it, but like to when I am not sure about surface conditions (i.e. gravel in the road).

You guys are all great, I truly appreciate the input.

tk11b40 wrote:

The later motor with the porkchop crank, it must be lighter?
Which leads to the next question, I have heard you can breed the older Z-1 engine with the J model and have the best of two worlds...is that correct?

Soon as I have 400 bucks set aside for the bike the ignition will be on, and it will be running. I work in a Machine shop, we are very busy so I think the worst of the recession is over.

Many thanks!!!

the 73 to 76 pork chop is about 8 lbs lighter than the kz,i think.the MK11 is in-between, i have a MK11 in my KZ.
the only thing desirable from the J motor would be the head. it has larger ports and valves. although it may be cheaper to convert the kz head to these specs.
the J head requires dif pistons on a kz due to the larger chamber. it also requires that u convert the cam chain tower from the J to the KZ since the chains are dif.
i think that if u were going to go to that trouble, u would be better off going right to an 84/85 gpz head. u still need to address the pistons, but in the end, u get the best head available . larger valves and ports than the J, so less money spent on those alterations.
i think the cheapest upgrade may be to put a gpz11 motor in a kz frame.

I snapped a rear brake stay on a HD I had, wasn't even going fast.

I'd use 2 heim joints and ti rod instead of that box.

I've never owned one but have seen cranks for sale that combined the lighter pork chop style crank with the 16 tooth heavy duty center pin from the '79 and '80 MKII motors. Not sure about the J crank....

79MKII wrote:

I've never owned one but have seen cranks for sale that combined the lighter pork chop style crank with the 16 tooth heavy duty center pin from the '79 and '80 MKII motors. Not sure about the J crank....

I think Falcon does that conversion.

1 finish bike....

2 license bike

3 New motor waa haaaaa haaaaha aa

Deep in the laboritory........

I want to keep the old style z motor, but the light wieght crank, porting plus one of them there humngus 1400 cc kits, and a midrange cam that will pull your arms out at 6000 rpm.

Now that would be the ultimate street motorB)

tk11b40 wrote:

1 finish bike....

2 license bike

3 New motor waa haaaaa haaaaha aa

Deep in the laboritory........

I want to keep the old style z motor, but the light wieght crank, porting plus one of them there humngus 1400 cc kits, and a midrange cam that will pull your arms out at 6000 rpm.

Now that would be the ultimate street motorB)

Response: [insert 'Tim Allen'-ish man-grunt sounds]

mark1122 wrote:

79MKII wrote:

I've never owned one but have seen cranks for sale that combined the lighter pork chop style crank with the 16 tooth heavy duty center pin from the '79 and '80 MKII motors. Not sure about the J crank....

I think Falcon does that conversion.

So does Stan Gardner Racing with a Falicon center pin