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Main Area => General GS500 Discussion => Topic started by: dransy on March 15, 2012, 01:59:05 PM

Title: help with front piston sizes
Post by: dransy on March 15, 2012, 01:59:05 PM
hi guys I'm wondering if any of you lovely young people can shed some light and help me out to find some sizes.
My bike is made of many other GS's :D so I'm not sure what year the front caliper is from , i ordered a full rebuild kit for a 1991 model , the small piston and seals fitted perfectly but the larger one was way too big!

Ive just done some measurements to the best i can.

The outside lip measures approx 37mm where the seal sits i think?
The inside where the piston will go is approx 33mm

Now i had to use a ruler so it may be off by a few ml

Any of you experts guide me in the right direction?

Many thanks
Marc
Title: Re: help with front piston sizes
Post by: burning1 on March 16, 2012, 12:00:07 AM
What year is your bike? There's 3 different callipers that came on the GS500, and none of the pistons or seals are compatible. Later 2 models look externally identical, but pistons are slightly larger. Sounds like you have the first generation calliper.
Title: Re: help with front piston sizes
Post by: dransy on March 16, 2012, 01:02:31 AM
Hi there thanks for the reply , I've built the bike from a few bits from other Gs's, I think the caliper MAY be from a 96 model but I'm not certain , it has a small and a larger piston .

The first kit I bought was for a 91 model but that's the year of the frame only ! Duh and the larger piston from the set was too big .

Thanks marc
Title: Re: help with front piston sizes
Post by: burning1 on March 16, 2012, 08:07:28 PM
Year is very important with calipers. Unfortunately, I don't know how to easily check the difference between the last 2 models. But if you can figure out the year of what you have, you can order the correct rebuild kit.
Title: Re: help with front piston sizes
Post by: adidasguy on March 16, 2012, 09:42:31 PM
The latest ones are by AJP. 2004+ it seems.
Prior ones were TOKICO. Maybe 1997-2000?
Both of these have only one set of mounting screw holes.
The oldest ones with 2 different piston sides had 2 sets of mounting holes and don't seem to have a brand on them.
Title: Re: help with front piston sizes
Post by: burning1 on March 17, 2012, 10:18:02 PM
Awesome info, Addidasguy. The late model AJP and Tokico calipers take the same pads and are very similar in appearance. The rebuilt kits appear to be the same, but are absolutely not compatible. In one direction they wont fit, and going the other direction is a major disaster waiting to happen, because it *might* appear to work, but it'll fail in a big way once you try to use them.