SMC Superceded Parts

My 2004 non ABS had a seized Secondary Master Cylinder (is now on my garage bench).

I have spent time reviewing the threads and sent pm's but have not found an answer to the following.

Current part number for a rebuild kit is '45620 MCS G04' (4th generation)
Current part number for an entire replacement SMC (including kit parts) is '06454 MCS G03'.

I am assuming the G03 is a third generation design. Has anyone compared the G03 with the original? Are there design 'improvements' or did the numbers change because of 'design changes' to reduce manufacturing costs?

Is this an improved design that would justify spending the extra money to buy the entire SMC (and be more likely to prevent future brake issues) or should I buy a rebuild kit and save the $66 difference?

I had also toyed with the idea of looking into fitment of the post 2007 '06454 MCS R02' SMC but unless someone has done that successfully and can confirm interchangeability I am more comfortable staying with the recommended part number for my '04.

Thanks
Dennis

The suffix only applies to the part described by the rest of the part number, and even a change in the packaging can cause the number to be bumped.

All prior versions of the piston set are superseded by the current version, so you should be able to install the G04 part in the housing in your '04.

If I remember correctly, there were changes to the housing that improved drainage, so it might be worth replacing the whole assembly so it's less likely to fail again.

--Mark

For now I have ordered the piston kit only as it turns out I had been quoted 'dealer cost' instead of retail. This makes the cost difference approx $110. My caliper cleaned up nicely and I am hoping that the new piston kit will last a few years (esp as I now have first hand experience). If anyone has a picture of the latest evolution of the entire assembly (drainage mods) and could post that would be great. I will post a photo of the original casting that I will continue with as soon as I get back to my desktop
Dennis

Watching this thread... Have a ST1300 in the shop right now for a faulty SMC. Currently waiting on parts to rebuild the rear caliper after is locked up and heated to a high temperature. Have not ordered the SMC yet...

2004 SMC

Nice job on the clean-up!

Looking good, keep us posted on your rebuild.

Received my much anticipated SMC rebuild kit yesterday. From John's post above it appears that there has been a substantial evolution since the G03 as pictured in his post above. The body of the piston appears to be a new alloy, hopefully non oxidizing. Here is the comparison with the original as removed (I believe it to be the G01). New circlip is included (under the boot).

jfheath said:

Brilliant - that will answer a lot of people's questions. I knew it was different - I didn't realise it was that different.

Are you sure the circlip isn't there ? I remember thinking the same when I took mine out of the packet - I had to prise it off a little for the benefit of the photo, but left it in the same location. (See post # 3).

I can see a black band below the rubber boot on your photo. Is that not it ?

View attachment 169596

Click to expand...

Yes, exactly right. I amended the original post and did not realize you had caught me out so quickly! The new kit installed beautifully into the cleaned cylinder and spring pressure alone would pop it out without any hesitation. The circlip was a bit of a pain to install as there is no room to spare. Any debris whatsoever on the seating shoulder or left in the circlip groove will make install next to impossible. Liberal application of silicon grease should assist in keeping moisture out. With the rotor reinstalled the SMC piston is actuated smoothly by any movement of the rotor and returns to resting position beautifully (hydaulic fluid has not yet been replaced).

Afterward: There were rings of deposit around the cylinder wall where the piston travel had been terminated. The corroded piston was extremely reluctant to pop out even with air pressure applied. I did not realize how effective the compressed air was and had only my finger tips over the piston to prevent parts shooting across the shop floor. When it did pop out the force was much greater than I expected. Please keep a shop rag over the open end to protect your fingers. The cylinder was cleaned out with a small buffer on a rotary tool with some fine rubbing compound. Without the buffing to clean the deposits off the cylinder wall I believe replacement would have been pointless.

Excellent - sounds like you are in business ....for the spring.

It snowed a bit this morning - even in Windsor. Dang!

Below is a picture of the SMC cup and bore for part #06454 MCS G01 as reinstalled on my 2004 ST1300. As has been mentioned elsewhere on the forum part numbers can be superceded for minor non design reasons such as packaging changes.
The current number as of Dec 2015 appears to be 06454 MCS G03. I could not find out anywhere whether the new G03 actually incorporated design changes to alleviate the documented corrosion problems in the SMC that lead to dragging rear brakes and /or seized rear calipers.
I did not upgrade to the G03 as I did not want to spend the money for what may have been an identical part.

If anyone can post a comparative picture of the G03 those rebuilding the SMC in the future can make an informed decision concerning what replacement parts to purchase.