Omega do or did some proper +1mm pistons, lighter than je and stock pistons. There the ones I'd go for.

Don't know if Omega ever did a gixer one, may be able to fit a ZXR one with a little work.

You can help the weight of the JE set by using FZR wrist pins as these are tapered on the inside to save weight where as JE pins are bored parallel and very heavy.

Lol ignore everything ive said i thought we were on about NC's

stripes1976 wrote:Biggest gains I found was swapping the crank.

to what if you dont mind me asking?

There's potential to fit the early gsxr4 crank from the 51, its longer stroke and smaller bore so would stroke the motor.

Some problems.
15 mm wrist pin.
Different taper on end - could be an easy fix due to inside out flywheel, it had Sam style.
Different clutch that may or may not swap over and could have way off primary gearing.

Theres a bloke in stoke splitting a 71b motor.

See if he gets back to me about the crank.

Are the big ends the same od as the 73a crank?

Ye sorry mate i should have said 71 not 51.

it has the same mains but you would have to find a conrod that was of the correct length with a 15mm wrist pin as it has 14mm pins.
might have enough meat to machine out but its that long since i looked at them that i cannot remember.

I think the biggest problem will be the clutch, take a look at the workshop manual to see the differences.

I will try and get you more info as i looked into it about 10 years ago.

Some reading for you...

http://forums.banditalley.net/index.php?topic=9770.0

so,

use 71b rods, with the little ends re-sized to 16mm. that's easy enough to do.

im not bothered about modifying either ends of the crank, thats piss easy.

the primary drive gear seems to be the sticking point.

i presume the centre to centre distance between the input shaft and crank on the 71b is different from the 73a.

and as the drive gears are different profiles and sizes it makes it a bit tricky.

i do enjoy a challenge.


i'm collecting a 71b bottom end on thursday so we'll see how it pans out.

Its been along time mate but on re reading I'm sure Bart had problems fitting the clutch primary in the casing or something,
Think the primary gears were bigger diameters.
Soon see if you getting a motor.

Some more info.
bearing. ( 2x shells ).


Part number 12229-43400-0G0.

83-86 GSX550

83-86 GS550 EF ES3 SE SF SG S3 (USA)

84 GSX500

87 GSXR400R