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Brake piston issue, ordered from Bike Bandit???

1978GS750E

1978GS750E

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I ordered two sets of front brake pistons and seals for my 1978 GS750E thru Bike Bandit. I got one set and they cancelled the backorder??? Ordered another set and they shipped in 2 days! The problem lies in when I went to rebuild the calipers this morning. The pistons and seals that I received in both sets are 42mm diameter. The original pistons on my bike are 38mm diameter. I checked 3 websites, which I believe all use the same parts fiche, and part # 59100-45813 shows that it fits the front caliper for my bike. So.....can anyone verify what the correct diameter piston is in a 1978 GS750E? I want to make sure that someone has not changed the calipers on my bike before sending these pistons and seals back. I could just turn down the pistons but the seals are too big also. The end that holds the dust cover is the same on both the new and old pistons and the length is the same. Anyone have any ideas?
 
Alpha Sport shows these numbers...

Part# 59100-44823 Desc PISTON SET -SU USD Price 60.06 Quantity

*supersedes 59100-44820 59100-44821 59100-44822
 
Hi I looked around and I took this from Z1
Fits Front Brake Caliper - 38mm diameter Suzuki GV1200GLF/GLF2/GLG 1985-86 GS1100GZ/GD/GLZ/GLD 1982-83 GS1000GT/GLT/GX/GLX 1980-81 GS850GT/GX 1980-81 GS850GZ/GD 1982-83 GS850GLT/GLX/GLZ/GLD 1980-83 GS750ET/EX/EZ 1980-82 GS750ED/ESD 1983 GS750LT/LX 1980-81 GS700EF/ESF 1984 GV700GLF/GLF2 1985-86 GN400TX/TZ 1981-82 GN400...
i know it does not list 1978 gs750 but I cannot see the 750 be fitted with larger Pistons than the 1200, 1100 and 1000
I have not had a 750 so hopefully someone will be more helpfull

 
Thanks Hannibal! I have found a lot of confusion with these brakes. The bike that I have has the 38mm pistons and the "78" mounting bracket. The other bike that I sold had the larger pistons and the "77" mounting bracket, yet both were 1978 models and had dual disc brakes up front. It looks like Suzuki might have made a change mid-model year on these front brakes. Lots of the online parts sellers show the incorrect part numbers in their "where used" lists. It looks like I may have to actually talk to one of the "experts" at Bike Bandit, Partszilla, Z1, or Parts Outlaw to get the correct parts.

Geez......all I wanted was to stop a leaking caliper........boy this is fun! Oh well, at least it is cold here!
 
Is the bigger piston just for single disc setup. I think I can remember using a left caliper from my gs1000n on my son's gs550. The right caliper was from a twin setup and had a smaller piston.
 
I believe the larger piston is used in single brake bikes and the smaller 38mm piston is used in dual front brake bikes. none of the so-called "experts" at any of the online sellers can tell me the diameter of the pistons that they sell. May have to try the 38mm Honda pistons, at least they specify the diameter. Geez.....it's only 40 years old!
 
OK, now I'm at the end of the proverbial rope! Cannot find the Suzuki 38mm front brake pistons and seals anywhere. Or at least anyone that can verify that the pistons and seals that they sell are 38mm diameter. ANYONE know of a Suzuki brake piston and seal that is 38mm diameter and still available?
 
Upgrade to the twinpots if you don't care about originality. Part supply is still good on those...
 
59100-45833 is the part number for the 38mm pistons. I think I still have the kit. I'll take a pic tomorrow if I can find it.
 
That part number is not available on Parts Outlaw, and does not come up at all on Bike Bandit or Partzilla searches. Thanks anyway!
 
I'm looking for these myself right now. P/N for 78 piston set is 59100-44823

Unavailable on all the typical sites.

Can anyone recommend aftermarket 38mm pistons?
 
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