ZX7R Stroker (793cc)

MBP · Post by **MBP** » Tue Jul 18, 2006 10:46 pm

I have just picked up a 2001 7 motor for a song, and just so happens that i have a spare zxr750L crankshaft hanging around so its time for some serious mods so i can keep up with jpbikeboys zxr900turbo.

The plan is to drop as much weight out of my 7 and do the following mods.
knifedge the Lmodel crank and install into the P model engine (strokes it to 793cc), MBP head porting and reprofile squish area, Modify valves and seats to increase flow and a full engine blueprint.

All modifications,machining and assemble will be performed by myself.

Im estimating to get around the 145-150 rear wheel hp, and drop the weight of the bike to 175-180kg.

At least it will give me a little more of an edge against jpbikeboys 185kg(with half tank of fuel) 200+hp ZXR9.

I will be posting pics and spec of the progress of this engine build, and once finished Dyno results.

Cheers,

Matt

jpbikeboy · Post by **jpbikeboy** » Wed Jul 19, 2006 6:38 am

You can only try. Don't think i'll be helping ya'.

FrogZ · Post by **FrogZ** » Wed Jul 19, 2006 10:17 am

If the motors to pieces anyway get onto Muzzy and see if you can do some more !!!
I seem to remember they looked for more torque rather than HP....
Whereas the turbo would be mainly TALK wouldnt it jp *?

*Yeah Im jealous as shit....

MBP · Post by **MBP** » Wed Jul 19, 2006 11:41 pm

I may even looking at those JE pistons you got in your gararge jp for a big bore as well as the stroker crank that would make it 814cc. will have to do some calculations but i think a ball park figure would be at 14:1 comp around 160hp rear wheel.

Now were getting close to the power to weight.
JP 200hp @ 190 full wet weight = 1.05
MBP 160hp @ 180 full wet weight = 0.88

Man i got some work to do.

Cheers,

Matt

HemiDuty · Post by **HemiDuty** » Tue Jul 25, 2006 1:54 pm

Gas?

Seriously though sounds like a good project.

My brother just bent the frame on his 7, showing his awsome highside skills in the process.

You guys got a spare frame around...?

SocialSecurity · Post by **SocialSecurity** » Tue Jul 25, 2006 5:15 pm

has anybody ever honestly got 160hp out of a 7R motor without happy gas or forced induction? people are lucky to get any more than that out of a 9R motor stroked to 998cc with all the goodies... and 14:1 would require a permanent diet of race juice wont it?

how much do B-model 9R motors go for? im sure you would have a lot more luck getting near that figure with 899cc to begin with

MBP · Post by **MBP** » Tue Jul 25, 2006 9:56 pm

It is achievable to get 160hp out of a seven motor with the right mods naturally aspirated. Basicly i will be modifiying the whole motor including cases, head/valves/valveseats, cams to my specified grind, bottom end crankshaft, conrods, pistons, gearbox/clutch (im curently designing a dry clutch) a dry clutch can be good for 5-7hp because there is less oil drag compared to a wet clutch.
It will have to run quite a high octane fuel but i want to keep to pump fuel eg optimax, so the comp ratio isn't set in stone yet but will be quite high remember that a 7 motor runs a standard compression ratio of 11.5 - 1 and i will be either using forged pistons or CNC machined billet pistons of my design.

A B model motor is around the $1800 - $2500 mark for a stockmotor and as i have a lot of ZXR L model engine parts and a spare complete ZX7R P model engine i may as well use them. I also have machinery available to me (Lathes, mills, CNC machining centers, tig welders).
B model engines can get an easy 150hp from the right tuning with flatsides, exhaust, ignition mods etc, without pulling the motor apart.
I will be able to build a high hp blueprinted 7 motor for less than a stock B model 9 engine.

As with luck of getting the hp out of this motor, i have built quite a number of motors over the years, and have come very close to my predicted hp on each motor. With the calcs i have already done and the work im planning on doing 160hp is my predicted target.

Stay tuned.

Cheers,

Matt

MBP · Post by **MBP** » Tue Jul 25, 2006 10:02 pm

Hemiduty,

Mate could it be straightend or is it to far gone, i have a spare ZXR750 L3 frame its salvageable but needs to be straightened.

I know a guy who has a spare P model frame, will ask him on the weekend if he wants to part with it.

Cheers,

Matt

HemiDuty · Post by **HemiDuty** » Wed Jul 26, 2006 6:12 pm

Cheers man thanks for that.

Dunno if it can be straightened yet, my brother wants to mothball the whole thing for a while but I would rather sort it now instead of later.

The ZXR frame, will the P engine fit in it? And how much other stuff can be bolted over? Would be interested if a lot of existing P model gear can be thrown at it.

Thanks.

I-K · Post by **I-K** » Wed Jul 26, 2006 9:30 pm

MBP wrote:It is achievable to get 160hp out of a seven motor with the right mods naturally aspirated.

In its day, the TKA ZX-7RR superbike made that at the wheel. That was with flatslides, kit everything and no airfilter.

It can be done, but good luck getting anything more than a couple of thousand km between engine rebuilds.

SocialSecurity · Post by **SocialSecurity** » Thu Jul 27, 2006 1:00 am

sounds about right !

MBP · Post by **MBP** » Fri Oct 27, 2006 12:10 am

Well its been a bit quiet on the engine building of late due to the fact of me changing jobs so there all there ready to be pulled apart and first thing on the agenda is to knife edge the L model crank and balance it.

So many motors such little time.

Cheers,

Matt

Post by **MadKaw** » Fri Oct 27, 2006 8:08 am

Looks like fun..
I've seen a few of these done and 140 rw hp is quite achievable..

WRT_GPX · Post by **WRT_GPX** » Fri Oct 27, 2006 8:01 pm

just remember its not about straight out power to weight, its about how you get the power to the ground and if its usable.

if its a road bike, id say change your gearing and cut off a bit of top end speed for as much acceleration as possible while trying to get the bike sorted so you can get all that power to the ground without trouble.