Converting a GPz750 from 630 chain to 530?

[henrys]

Hi all,

Just wondering if anybody has successfully done this mod on a 1983 model GPz, ZX750A1?

The only snag I foresee is that the stock 630 front sprocket is offset and all the 530 ones with the right spline all have no offset. I'm thinking of putting on a spacer or two to give it some offset and I think I can live with less than "perfect" chainline. That shouldn't be any problem?

Am I missing something here (I've already got the sprockets on the way from Ebay, but am holding off on the chain)? If it turns into mission impossible I'll have some nice shiny sprockets to turn into jewellery or sell on

Cheers guys

[likefry]

If it's not aligned properly it will die pretty quickly

[robwas]

Space it out if need be as alignment is critical for chain/sprocket life and performance.
If you ordered a kit specifically for the bike it should be a straight fit up.

[g0zer]

be careful when shimming drive sprockets. depending on the type of peen washer used. if the peen washer keys onto the drive shaft, if you shim too much there might not be anything for the peen washer to lock onto.

[GD Engineering (Gavin)]

They have a 15mm offset .... not enough shaft to use . Easier to use a 98-02 ZX6 front.... it will be 525 pitch but won't matter if you use a 525 rear. As it turns out, the rear for the ZX6 will fit the GpZ or a 96-03 ZX7 will fit too. If you need to, you can easily go to a 520 chain using a conversion kit for the same models. Hope this helps

[henrys]

Thanks Gavin, now why didn't I ask you before I ordered the 530 sprockets??? They arrived today (JTs)! I never even considered a 525 or 520, Doh.

I'll pull it apart and see if there's any amount of shimming I can do at the front, luckily the rear I bought has a 3mm offset so I may be able to utilise that to help too. Do you think it's a hopeless case to try the 530? How about using one of the high strength Loctite thread lockers eg. 263 or 277 instead of the peen washer, have you any experience going that route?

Cheers,
Henry

[GD Engineering (Gavin)]

I wouldn't...... they need to be within a mm either way really....... the further apart the sprockets are, the less it matters. 15/38 is std gearing...... make sure your new sprocket combo ( at approx 83% the old sprocket diameter for the same gearing ) isn't going to cause the chain to start "sawing" the swingarm pivot in half due to an under-centre output shaft. If it rubs hard on the buffer block, go to a 16/41 ( which is available for the ZX6 from memory ). If the rear spkt you have has a 3mm offset, you still need to find 12mm...... and you won't get it with a flat front sprocket. One alternative is to use the old 630 as a carrier for the 530....... involves machining and welding and may be easier to get an offset front spkt.

[henrys]

Thanks mate, but I've now done it
If anyone's interested in the details (for the record, at least)...........
It's not a 15mm offset, more like 6mm The total offset cog width is 15mm, the thickness is ~9mm, so the offset is ~6mm. I moved the rear one in by 3mm and put a ~3.5mm spacer washer behind the front one.
I used a JTF 513.18 on front and a JTR 488.38 rear. Changed the final drive gearing from 38/15 to 38/18 and it suits me better. I find 1st gear is now very usable in slow traffic.
I got a 25mm standard steel flat washer about 3.5mm thick, and this makes the front sprocket now stand out say 2-3mm max. beyond the splines, still plenty of spline engagement for strength and wear in my view. I wasn’t able to use the lock washer though (I had none on there before either) so I got a brand new shaft nut and put it on backwards for maximum thread engagement because the nut counterbore has no thread for about 2-3mm.
So it fully engages thread to the end of shaft, I did it up good and tight and used a high strength Loctite thread locker too. There are no issues with the inside of chain being too near anything, or the chainguard either as far as I can tell, so far.
The alignment looks good to my eye and runs smooth and quiet so far. I can’t really measure it any better than sighting along it, if anything I think maybe the front is out a tiny bit further than it should be.
I have the rear axle now about midway back with eccentric hole “on the top” and now have a chain that doesn’t rub/saw the front of the swing arm, or the center stand, so it feels much nicer (to me) than the old setup. Looks good, runs well so far.
If I have any problems in use I’ll be sure let you know.
Cheers