Thumper Club Forum

Technical => Bike Problems/Questions => Topic started by: guest1130 on August 17, 2013, 11:00:22 AM

Title: XBR front sprocket question
Post by: guest1130 on August 17, 2013, 11:00:22 AM

So it was time for me to change the chain and sprockets so I ordered the required parts (all standard spec) through We-moto and begun working.

The front sprocket I got was way different from the old one:

	OLD SPROCKET	NEW SPROCKET
Spacing between the stopper plate bolts (measured from on top of outer threads)	47,2 mm	41,5 mm
Thickness from the front to the edge of teeth	6 mm	4 mm
Thickness from the rear to the edge of the teeth	3,5 mm	0 mm

(http://i12.photobucket.com/albums/a211/Jaypeesupra/XBR/XBR_sprocket_zpsd8e68f86.jpg)

I have no idea wether the old sprocket+ stopper plate are original parts, it looks like the old sprocket has been thinned a little with an angle grinder to fit the axle.

I have three problems:

• The new sprocket is way thinner than the old one and hence won't fill all the space available on the axle.
• I have no idea of how straight/off my chainline will be with the new sprocket
• The new sprockets boltholes don't line up with the old stopper plate

I could just drill and tap new threads to the new sprocket, place it on the axle and tighten it in place with the stopper plate. There will be empty space on the axle on the back of the sprocket, but I don't know if that'll be an issue.

Or is this just a case of getting wrong parts from WeMoto?

Title: Re: XBR front sprocket question
Post by: guest1130 on August 17, 2013, 11:20:57 AM

I got this sorted (sort of..)

The one I ordered is for an FG-model (-85 ... -86), which my bike is according to the frame id-plate. However, the one that fits my axle is that of an SJ-model (-87 ... -88). So now I need to order a new sprocket to fit the axle.

FG-model sprocket (http://www.jtsprockets.com/catalogue/model/379)
SJ-model sprocket (http://www.jtsprockets.com/catalogue/model/381)

Title: Re: XBR front sprocket question
Post by: Oldtimer on August 26, 2013, 08:10:21 AM

Quote from: Kaff on August 17, 2013, 11:20:57 AM

I got this sorted (sort of..)

The one I ordered is for an FG-model (-85 ... -86), which my bike is according to the frame id-plate. However, the one that fits my axle is that of an SJ-model (-87 ... -88). So now I need to order a new sprocket to fit the axle.

FG-model sprocket (http://www.jtsprockets.com/catalogue/model/379)
SJ-model sprocket (http://www.jtsprockets.com/catalogue/model/381)

Interesting,
I was thinking when I come to change my chain and sprockets of increasing the gear ratio by fitting a larger gearbox and smaller wheel sprocket.
Has anyone done this?
Basically I would like to drop the revs at 70mph not so much to try for max top end speed

Title: Re: XBR front sprocket question
Post by: blew on August 26, 2013, 10:33:21 AM

I tried a 16 tooth gearbox sprocket on my 600.The bike pulled it,and it was reasonably relaxed at 80.However,it murdered the acceleration,and it meant I couldn't engage 5th gear below 3000 rpm,about 48-50.The bike feels happier with a 15 tooth sprocket,and the acceleration is much livelier...

Title: Re: XBR front sprocket question
Post by: Oldtimer on August 28, 2013, 08:14:06 PM

Where did you obtain the sprocket and would it fit the XBR 500?

Title: Re: XBR front sprocket question
Post by: blew on August 29, 2013, 10:15:32 PM

I bought it from ebay,I forget from where.You can get 14,15 and 16 tooth sprockets.The 87-88 sprockets are slightly different to the 85-86 models.My xbr is an 87 model.

Title: Re: XBR front sprocket question
Post by: Propellor on August 30, 2013, 05:41:54 AM

If J.T. Sprockets don't make it I'll be very surprised.

B&C Express are distributors and very helpful on the phone.

J.T. Srockets main website is good for identifying what you need, part numbers, dimensions etc.

Title: Re: XBR front sprocket question
Post by: guest1247 on August 30, 2013, 07:17:17 PM

Hi Kaff, a couple of years ago I bought a Yamaha MT-03 that seemed to be somewhat low geared and very frantic in it's power delivery. Also the speedometer seemed to be very optimistic , ( reading too high ), a fact confirmed by a GPS speedo in a smart-phone. After some sums, and alot of tapping on a calculator, a new front to rear ratio was arrived at. I contacted B&C Express, telling them what I wanted. They were most helpful, and machined a new sprocket from a "blank" they stock. No links needed to be removed from the original chain, and the bike is infinitley easier to live with.... The speedo now reads so close to "spot-on accurate" as makes no odds.. B&C Express are the people to speak with, I recommend them wholeheartedly. Hope you get sorted... Regards, Tony

Title: Re: XBR front sprocket question
Post by: Propellor on August 31, 2013, 08:02:07 AM

Quote from: Calleyne on August 30, 2013, 07:17:17 PM

Hi Kaff, a couple of years ago I bought a Yamaha MT-03 that seemed to be somewhat low geared and very frantic in it's power delivery. Also the speedometer seemed to be very optimistic , ( reading too high ), a fact confirmed by a GPS speedo in a smart-phone. After some sums, and alot of tapping on a calculator, a new front to rear ratio was arrived at. I contacted B&C Express, telling them what I wanted. They were most helpful, and machined a new sprocket from a "blank" they stock. No links needed to be removed from the original chain, and the bike is infinitley easier to live with.... The speedo now reads so close to "spot-on accurate" as makes no odds.. B&C Express are the people to speak with, I recommend them wholeheartedly. Hope you get sorted... Regards, Tony

Hi

Which sprocket did they make for you, front or rear?

My old Beemer is peculiar in having the speedo drive taken off the gearbox output shaft, but I thought jap bikes tended to take it from the front wheel. I assumed as much because chain final drive ratios are so easy to carry out and therefore liable to upset the speedo reading if taken from the gearbox.

Like you, I found B&C Express very helpful on the phone. Not something you can take for granted so much these days.

Cheers.

Title: Re: XBR front sprocket question
Post by: guest1247 on September 01, 2013, 12:25:48 PM

Hi Propellor, B&C Express made a rear sprocket for me, to the number of teeth I specified. The speedo drive is a pulse generator at the gearbox output shaft..... but a test ride with another bike alongside, and a GPS speedo, confirmed a discrepancy of less than 2 mph at a true 70mph, as opposed to an discrepancy of 5mph right across the speedo, from the factory. It's a problem I have encountered before, on a car. Regards, Tony.

Title: Re: XBR front sprocket question
Post by: Propellor on September 01, 2013, 01:07:48 PM

So the japs are as crazy as the Germans after all!

Thanks for the reply. Interesting stuff.

Cheers.

Title: Re: XBR front sprocket question
Post by: guest1130 on September 04, 2013, 06:35:23 AM

Just to clarify if new to XBR's .. the XBR speedo cable runs to the front hub so the gearing doesn't effect the speedo. Also, I'm selling the wrong 15t front sprocket, check out the for sale section.

Edit: For sale an XBR front sprocket (http://www.thumperclub.com/smf/index.php?topic=7054.msg47273#msg47273)