Some 903cc questions

kawsakiman wrote:

hardr0ck68 wrote:

Steve, I hate when people tell me to buy a new bike. I get it from my friends all the time.

Why hot rod a kz650? Cause I want to... If I was just looking for power I would go out and buy a zx14 and be the fastest thing on the road. Honestly there is no reason to start with ANY 30 year old machine when you want to build a performance machine. Unless that is the machine YOU want to build.

i was not trying to insult you or your bike at all.
all i was saying was the bigger bikes have more readily available parts and the motors are easier to make power out of. your kind of limited for real good performance parts. lucky for us a.p.e started a service for our cams again.
i still have the 784 kit, andrews cams, ported head and smoothbores for my 650.
i spent more on those parts then the 1260 motor.
both are 32 year old bikes and i would not trade either for a new zx-14............

I know it will not be cheap, but I don't plan on spending it all at once... small steps. I would like to build the bottom end this winter and then hit the top end hard next year.

There may be ways to make more power cheaper, but to do it you need to poke around new ideas, like running pistons designed for a 900 on a 650.

the only real problum i see is the block being to thin to support support the sleeves after it is bored to accept 900 sleeves.

now if a.p.e would like to experiment with making a big block for a 650/750, i would be first in line to buy one.

( you reading this apejay? i know there is not a big market for this kind of work but come on! help us out! )

I had my 650 built back in 1980 when the compression dropped in the #3 cylinder. There was a 740cc kit available then but I was advised to go with the 717cc kit. Back then , there were very few people who would re-sleeve a motor and some of those were questionable. After it came out using the cylinders and pistons from a KZ 750 was popular for a while.

Hi,

Hardrock PM'd me about this but I'll post the reply here so that everyone gets to see it.

I have a 903cc 750 turbo motor. It has a billet block and 73mm pistons, out of a Z1100 I think. They are domed and about 11:1. I haven't used it yet, I am going to run it on alcohol. Jeff Haines on my 750 turbo site also has a 903cc GPz750 motor, the normally aspirated version. He too fitted oversize liners but in his case he used the stock block and broke through into the finning area a little when it was bored for the liners. My 903 motor has ally rods and 17mm wrist pins (16mm is stock on the turbo - these would be good to use in an NA motor as they are nice and strong).

A while ago Mike Chestnut did an 880cc (72mm) conversion kit for the turbo using stepped sleeves to avoid boring the cases out. It didn't prove to be any faster than the readily available 810 kit and if not fitted accurately had a tendency to leak oil around the base gasket. I think it would be a good kit if you used regular sleeves though, and bored the cases. Even my 810 motor has oversized sleeves. Most 810 motors simply bore the 750 block but I wanted my motor strong for top speed running.

there you go.
an answer from the master of the middleweights.
take his word as gospel, he knows his shit.
he broke the double ton on one so i think he just might know what he's talking about.
all hail lorcan!

yep, I have been reading a lot on his forum... there are fewer people over there who think that 30 year old bikes are best left alone than there are on this board.

It seems the leading edge limit is 880cc's with 72mm pistons.

The BLEEDING edge is 904 with 73mm pistons, but there are only 2 cases of this and I don't want to o that far.... although it would be nice to be on par with the z1 in terms of displacement.

For 880 I will need custom liners and pistons. unless I shelf those Carrillo rods for another day and custom order some with a 17mm small end. I already called Carrillo, my rods cannot go any bigger on the small end... just not enough meat to be safe. If I get rods that will accept a 17mm wrist pin, then I could probably adapt a set of wiseco pistons for the 1000cc bikes. Currently all 880's are turbo bikes and the pistons are all love compression for big boost and the liners are apparently stepped to avoid boring the cases, this leads to alot of leaky blocks, it is assumed non-stepped liners would solve the leaks but also require the block be bored ...so those ready made 880 kits are out of the question

The up side is, if I go 880 and am still shy of my final goal of 100hp at the wheel...I could swap for a 880 turbo kit and start the process of adding a turbo (I will get to 100hp, it is just a question of how much I need to spend!)

nobody on here thinks that you should modify 30 year old bikes? i call bullshit look thru the gallery some time tell me how many stock bikes you will find i myself have 11 30 yr.old plus bikes and all but 2 are modified extensively engine and chassis

hey wait a minute,my project is 35 plus years old! :laugh:

Yeah and it looks it... :blink:

winters coming! :laugh:

PLUMMEN wrote:

hey wait a minute,my project is 35 plus years old! :laugh:

Looks like it hasnt been worked on in 35 years...:laugh:

oh the abuse today! :woohoo: