Zeal/fzx250 sprockets!

[erik]

Well, my sprockets have been pretty worn out for a while now and I've been trying to find alternatives to the expensive genuine yamaha parts. None of the shops I went to here in Auckland knew of aftermarket sprockets that would fit, but with a bit of help, I ended up finding some at Victorian motorcycle wreckers; aftermarket sprockets for about the same price (if you include postage from aussie on the aftermarket ones) as the front sprocket alone would cost if I got genuine parts.

A lot of the trouble with getting a rear sprocket was that it's dished, unlike most sprockets. Anyway, the new aftermarket sprockets arrived in the post today, and the rear sprocket is not dished! I was a bit concerned about this, wondering if there was a mistake. I thought the original sprocket was dished to keep the two sprockets in perfect alignment.
But on closer inspection, it seems this is not the case. Take a look in the attached photo, it looks to me (both in the photo and in real life) like the dishing of the rear sprocket actually makes the sprocket alignment worse.
I tried googling for posts of zeals to see if the rear sprocket on mine might have been on backwards all this time, but from what I could tell, it seems right.
So I'm guessing the dishing wasn't to put the sprockets in alignment, but was to increase the clearance between the chain and rear tyre. That's the only thing I can think of (well other than the possibility of my frame or swingarm being horribly out of alignment... but I think I'd notice that.).

Even without the dishing, I think the chain/tyre clearance is going to be ok, so the new sprockets should be fine.
The rear sprocket is only 55 tooth compared to the original 57 tooth, but hopefully it won't make much difference. The front sprocket is just a plain steel one, I think the original was a cush-drive. I'll need to use a washer as a spacer because the cush drive sprocket had a fairly thick hub and the new sprocket is thinner in the hub.
Anyway, I think it'll all be ok.
2 new aftermarket sprockets from Aussie, cost AU$50 for the sprockets and AU$16 for postage, so all up AU$66.

[Motu]

That's way out of alignment,it'd be an awfully fat tyre to hit that.I'd expect to see some evidence of misalignment on the sprockets,but they don't seem to have much side wear...what's your thoughts? The rubber ring on the original gearbox sprocket is just a noise damper,they gotta pass a drive by noise test,and chain noise is a biggy.

[Bonez]

Erik looks like you replaced the originals just in time. I'm interested in the crush drive front. Once you've finish you would'nt mind disecting it would you?

[F5 Dave]

I was going to suggest JT would probably do them & sure enough they appear to be JT

JT

They are distributed by Darbi, head office in Auckland so it shouldn’t have been too much of a prob if they had your size in stock (maybe he bike shop checked with them). Only issue is you’d have to match the sizes with that from an FZR250, but Yamaha rarely change between models. Some times it's best to do your own detective work.

Run a straight edge along the chain if there is room to be sure.

Edit: Just looked at that alignment picture & I'm scared.

[vifferman]

So which bike shops did you check with? AFAIK, Motohaus deals in JT and Charavalli sprockets, and can probably get others, so Kerry should've been able to help you out there.
By the way - I think jrandom said his rear sprocket was some funny dished thing too. If I recall correctly. Or correctly recall. Or summmatttt.

[vifferman]

Erik looks like you replaced the originals just in time. I'm interested in the crush drive front. Once you've finish you would'nt mind disecting it would you?

Like Motu said - it's not a cush drive, just rubber dampened to cut down on noise. That's common on many bikes, and consists of a rubber washer thingo (technical term) bonded to one side of the sprocket to absorb some noise. Not very sophisticated, but effective.

[erik]

I had a closer look at the original front sprocket, it does look like it's got a fair bit of side wear on the inner side, which is the side the chain would be pulling against thanks to the misaligned sprockets (see attached pic). The rear sprocket looks pretty similar on both sides to me.

I read in a usenet post someone said that the original zeal front sprocket was a cush drive, but yep, you're right Motu, it's just a rubber ring around the outside (see other pic).

Edit: Just looked at that alignment picture & I'm scared.

I'm starting to suspect the alignment isn't way too critical, I mean my bike has been running like this, possibly since it was new (1991) and hasn't thrown a chain or anything in the time I've had it (the past year). Maybe it just wears the chain and sprockets out a bit quicker?

vifferman, I tried Red Baron who originally sold the bike to the previous owner, and Mt Eden Motorcycles. Plus Frosty's friend Alex had a look through a catalogue to see if there were any listed for the Zeal. And I tried Action Bike Wreckers and Atomic Bike Wreckers.
They all seemed to think that the dishing of the sprocket was an important feature. I don't know if they were looking at JT sprockets or not. Maybe I should've tried a few more shops...
At least I know for next time (if I keep the bike that long, that is).

[erik]

I was going to suggest JT would probably do them & sure enough they appear to be JT

JT

They are distributed by Darbi, head office in Auckland so it shouldn’t have been too much of a prob if they had your size in stock (maybe he bike shop checked with them). ...

I just checked the JT website, tried typing in some of the numbers on the sprockets and lo and behold, there they are (btw, the picture of the rear sprocket doesn't look much like my rear sprocket, but the measurements match).

http://www.jtsprockets.com/61.0.html...rtnr=JTF425,17

http://www.jtsprockets.com/61.0.html...tnr=JTR1847,55

Somewhat annoyingly, it seems the rear sprocket is also available in a 57 tooth version, which is what the original Zeal rear sprocket is, but Victorian Motorcycle Wreckers gave me a 55 tooth version

The rear sprocket is still unopened, but it's probably not worth it sending it back to Australia. So I guess I either stick with the 55 tooth sprocket, or try to get a new 57 tooth one from a bikeshop here and try selling the 55 tooth one on trademe.
The thing is the 6th gear on the zeal is pretty much just like an overdrive already with the 57 tooth, so the 55 tooth is really heading in the wrong direction.

[edit] upon further perusing of the jtsprockets website, I think the front sprocket I have might actually be this one:
http://www.jtsprockets.com/61.0.html...tnr=JTF1263,17
My sprocket has E263-425 stamped on it, which doesn't match the JTF code they ask for, so I tried entering JTF425 and found the other one.
But it seems either sprocket would work on the Zeal as the zeal doesn't require the threaded holes either side of the splined center hole. Actually, perhaps my sprocket is a combination of those two sprockets, as it has both the 29mm and 34mm spaced threaded holes.

[edit#2] on second thoughts, I could just get a smaller front sprocket if it turns out the reduction in teeth of the rear sprocket is too noticable.

[RonR]

Hey Erik,

I know it's only been 2 1/2 years since your last post but i will need to change at least the front sprocket on my Zeal REALLY soon. It's quite worn, to the point that the gear is actually really sharp on the ends! Gotta love ignorant previous owners. The chain doesn't seem too bad and the rear sprocket seems OK. Just wondering if changing the sprockets is a big job. Are there any nuts or washers or anything that needs to be replaced once removed? Is realignment easy if replacing with the same sized parts? Been a while since i've thrown a spanner around but i love to get my hands dirty (as long as i don't screw anything up).
In your opinion, would it be wise to change the front and rear sprockets and also the chain in one go?

Is a significant jerk upon letting go of the throttle a telltale sign of a worn sprocket?

Thanks in advance and sorry for all the questions.

Ron.

[erik]

It's not a big job, particularly if you're only replacing the front sprocket. You'll probably need a hefty socket wrench and a piece of tube to stick over the end of the handle to give you more leverage to loosen the sprocket nut. There should be a bent lock washer on it that you'll have to flatten to remove the nut. If the washer looks like it's been reused several times before, then you should probably replace it, otherwise it should be ok to just rebend one of the unused sides when you put the new sprocket on.

The only realignment that's possible is adjusting the rear wheel, same as when you adjust the chain tension.

In my opinion, if the chain and rear sprocket look ok (make sure the chain has no tight spots, and measure the length over a certain number of links if you can find the correct info for what it should be...) then it makes sense to just replace the front sprocket, especially since they're relatively cheap.

Only problem with the Zeal is you need a front spacer washer if you want to use a JT sprocket as they're thinner than the genuine part (by about 3mm if I remember correctly. I could go measure the old sprocket if it'd help).

Here's some good reading about chains:
http://www.dansmc.com/rearchain.htm

I'd think that the jerk might be more due to a loose chain than a worn sprocket.

[RonR]

Thanks Erik,

That's some great reading. Feeling much more confident now! Thanks but don't trouble yourself measuring the front sprocket, I think to avoid any potential installation problems, i might stick with the standard sprockets. Will have a better look at the rear sprocket and chain 2moro to see if they need to go. Don't suppose you know how many links the standard chain has in case it needs replacing. The current chain says DID428 VS. Hope it's not too hard on the back pocket

Once again, many thanks.

Ron.

[erik]

Possibly 132 links, but I might be remembering that wrong. Best to count the number of links to be sure.

I don't know what prices are like in Australia, but here in NZ the aftermerket sprockets were waaay cheaper ( about $10 vs $70 for front sprocket iirc). With such high prices for genuine parts, I might start worrying the old worn chain might cause the new expensive front sprocket to wear quicker... with a cheap front sprocket it doesn't matter though.
I really don't know what sort of a difference it'd make to the life of the sprocket, so I'd be inclined to try it and see.

[RonR]

Done!

Got RK 428XSO chain, after market front and rear sprockets today. All for $180. Oh then some extra for the chain breaker and some chain lube. Oh, and a socket for the front sprocket nut. (suprising how quick you become friends with your bank manager Not a very hard job really, only time consuming cos I spent half the day cleaning up all the muck that accumulated around the frame and rear wheel. Jeez that chain breaker is a beauty! Went up and down the drive a few times and it went fine - for now Can't wait to take it for a real spin - when the flood subsides that is

Here's a shot of the front sprocket that came off the bike. And the chain definitely had a lot of play in it.

Thanks again erik for all your help!

Ron

[erik]

That sprocket looks like it's even worse than the one that came off my Zeal!

Did you have to make a spacer for the after market front sprocket? Did you get JT sprockets or some other brand?

Glad to hear it went well.

[RonR]

The previous owner had apparently taken care of the bike, oh except for the sprockets which i bet haven't ever been changed. The rear is a JT 57 tooth black sprocket. Fits and looks really nice. The front is identical to yours and yes i needed to stick a washer on before the sprocket just to line it up. Mind you the outer washer (then one with the bent edges) is only just catching on the toothed shaft, enough not to come loose. Lovely chain too. mmmmm. Gotta love new stuff

Cheers