Marko's Workshop: '73 Suzuki GT250 - Part 11 - GT550 front fork swap - 1/2

Monday 4 November 2019

'73 Suzuki GT250 - Part 11 - GT550 front fork swap - 1/2 - Rebuilding front shock absorbers

Some of you might remember me purchasing a set of Suzuki GT550 front forks quite a long time ago. At the time I wasn't sure what to do with them until I got my GT250K project going. First I was thinking of rebuilding GT250 forks for this project but the set I have was in worse condition than these ones. Good thing about these are that they are more rigid than GT250 front forks. Main difference is that stanchions have 35 mm diameter compared to 32 mm ones in GT250. Otherwise main dimensions like spindle diameter and steering bearings are the same so it's easy to swap them. I will feature triple trees and mock up more detailed on next part. This part will cover rebuild process of front shocks.

Suzuki GT550
front forks

Below is a picture of steps how to assembly Suzuki GT250 & GT550 front shocks (left to right). Same process applies also for disassembly but from right to left. I disassembled my forks long time ago I didn't unfortunately take pictures of that process.

Steps of assembling GT550 front shock absorbers

Upper parts of old stanchions were very pitted and rusty most likely due to moisture accumulating inside headlight brackets. Since I wasn't going to use original headlight brackets and wanted to leave them exposed I went ahead and bought myself a new pair of stanchions from eBay instead trying to do anything with the old ones. I cleaned sliders and circlips, which attach to bottom of the stanchions, and installed them to the new ones.

New stanchions for Suzuki GT550 front forks

Unboxed

Comparison of new and old stanchion

Sliders and circlips in order

I decided to shave off ears from outer tubes which the stock front fender attaches to since I didn't have any use off them anymore. I started by cleaning outer surfaces of them with soda blasting gun. After that I removed most of material with a saw and an angle grinder. Since there were still a lot of excess material to be removed I used a file next. I tried to be careful and not remove too much or making too deep scratches while filing so I marked a spot with a red marker pen to indicate when to stop and move on to sanding. I used normal sand paper for rough and wet sand paper for finer sanding. Last step was to polish them with buffing wheel and polishing paste. I purchased new hardware for inner tubes and axle holders and screwed them back on.

Outer surface of outer tubes cleaned with soda blasting

Ear sawed off

I marked an area which I wanted to file flat
with a red marker pen

After rough sanding...

...and finer wet sanding

Buffing wheels and Autosol polishing paste

Outer tubes and axle holders after polishing

New M8x27 hexagon socket head screws
with low head (#51147-48130) and copper washers

Rebuilding outer tubes

Non-serrated M8 flanged nyloc nuts DIN 6926 for axle holders

After getting stanchions and outer tubes back together it was time to mate them together. I started by sliding the rebuild stanchion inside the outer tube. Before installing a new oil seal I made sure that the upper slider was inside the outer tube. Otherwise it would have been a nightmare to get the oil seal out to get it back inside. For this project I chose fork seals made by Pyramid Parts (#FOS 013) just like I did with my CBR600F. After knocking oil seal in place I put on a washer on top of it and installed circlip with circlip pliers.

Pyramid Parts fork oil seals #FOS 013

Box comes with a pair of 35x48x11 mm oil seals,
seal buddy tool, lubricate and a sticker

Slider, oil seal, washer and circlip

...and order how to put them back together

Circlip installed with circlip pliers

Last step was to install new fork dust seals, slide in springs, add fork oil and screw on caps to top of stanchions. Since these forks originally had boots instead of dust seals I wasn't sure if I was able to find a suitable pair for them. I ended up ordering a set of Pyramid Parts fork dust seals (#DB10) which seemed to work decently well with them. I got myself a one liter bottle of 15W Motul fork oil and measured 2.35 deciliters for each shock. Caps were little bit pitted as well so I took a small piece of aluminum foil and brushed rusty spots with it under a running water. That's an easy trick to get rid off small rusty spots from old steel parts which are chrome plated. Off course it's not a permanent fix but a lot cheaper than new parts or chrome plating. I replaced old O-rings with new ones (#51181-31030) before screwing them back on.