'73 Suzuki GT250 - Part 7 - Betor Expert rear shocks

Last weekend it was time to brush of dust from my GT250 project bike 😀, which it had unfortunately gathered for a while 😬

Couple of weeks ago a blue box arrived from England to my local post office with a pair of Betor Expert rear shocks inside. At first I planned to order them straight from Betor (located in Spain) but unfortunately they didn't have shipping option to Finland so I had to find another supplier.

Luckily Google found me Villiers Services from England. I went and asked them by email how much the shipping would cost and after getting their answer I made my order through their website with these specifications:

Mounting bolt size: 10 mm / 3/8"
Spring weight: 50 lb
Shock length: 340 mm

Shocks have 12 mm diameter holes for mounting bolts and came with four 10x12x24 mm bushings.

I made a simple sketch in CAD to check the fitment with T250 frame, which I had modeled earlier. At first I thought about ordering longer ones than 340 mm, but after coming to conclusion that the chain would eat up my swingarm quite badly I decided otherwise. The sketch has dimensions of 21"/18" tires and GT front forks and they are just close estimations.

It's good to notice that there are differences in T250 and GT250 frames. For example head tube of GT250 is different than T250 due to different forks. Basic geometry of both frames are however pretty similar 👍

Sketch of rear suspension dimensions

Bushings (10x12x24mm)

I decided to use and modify the old GT250 rear shock mounting points to fit the new shocks. Mounting points in the 80's RM250 swingarm are not symmetrical in my setup and they are just a bit wider than the ones in the GT250 frame.

Shocks mounted very well to the swingarm and they didn't require other modifications than drilling the mounting holes from 8 mm diameter to 10 mm. After mocking up both shocks to the swingarm it was obvious that left side needed a longer spacer (14 mm).

I decided to drill through the frame mounting points to fit long bolts. I lathed two support sleeves which helped to keep the drill bits straight while drilling. I used 8 and 10 mm drills. After both sides were drilled I cut off the 10 x 12 mm sleeves which were left to the both ends and fitted the spacers in place together with shocks. I finished the job by welding the 14 mm spacer to the frame.

I used zinc plated bolts and nut for mockup and will use acid resistant DIN 931 bolts with DIN 6926 flanged Nyloc nuts for final assembly. Hopefully they will withstand the load and shear from the swingarm. Time will tell 😅

12 mm GT250 rear shock mount with 10 mm thread

Bushing helped in figuring out side offset

Swingarm didn't require other modifications than
drilling the mounting holes from 8 mm to 10 mm

Left side mockup

Dimensions for spacers

Left side spacer

Support sleeves, centre drill , 8 mm and 10 mm drill bits

Lathed sleeves helped keeping the drill bits straight while drilling

Drilled through

Cut off the 10 x 12 mm sleeve and mocked spacer in place

I used just a long bolt to keep the spacer in place while welding

Job done!

Acid resistant M10 hexagon bolts (DIN 931) and
flanged Nyloc nuts (DIN 6926) for final assembly 😀

'73 Suzuki GT250 - Part 5 - '79-80 RM/PE 250 swingarm swap

Here's first part of fitting '79 RM 250 swingarm to my '73 GT250, which at the end was a pretty easy task. Hardest part was to find all the necessary bushings for it since I didn't want to lathe them myself. I started by ordering a pair of new old stock swingarm pivot bushings (61261-40402) from eBay, which I knew I was going to need. 

Pair of Suzuki swingarm pivot bushings (61261-40402).

Next step was to find proper bushings inside the pivot bushings and bearings. After a bit of googling I came across a Kymco scooter speed up kit made by Naraku (NK800.04). Since I knew I needed bushings with 14 mm inner diameter and 20 mm outer diameter, that kit seemed like a perfect match and I ended  up ordering a pair of them. They are approximately 38 mm long (37.94 mm to be exact) so I needed a spacer which would keep them a part. I ended up lathing 113 mm long spacer out of 19 x 1.50 mm steel pipe.

Pair of Naraku Speed Up kits (14 x 20 x 38 mm) for Kymco
(NK800.04).

Lathed spacer (19 x 1.50 x 113 mm).

Once I knew how long all the bushings were I could order proper sized needle roller bearings from eBay. I decided to go with IKO TA2025Z, which are 20 x 27 x 25 mm and have open ends.

(3) Pair of IKO TA2025Z needle roller bearings with open ends
(20 x 27 x 25 mm).

Stock GT250 swingarm axle and all the new parts.

Test fitting.

I had to narrow the swingarm a bit so it would fit better with the frame and bushings. I took a bit of material out of both sides of the swingarm with a file and a sanding block. I also made the swingarm a bit narrower than the inner bushings. With a bit of clearance the swingarm swings smoothly once the swingarm axle is tightened. 

In the second part of the swingarm installation I will cover how to fit rear shock absorbers and modify their upper mounting points. But before that I have to refurbish front forks and fit them to the bike. By doing so I can check the stance and figure out how long rear shocks I need to order.

T500 swingarm swap - Suzuki T250J

I was already planning to fabricate a longer swingarm to my Suzuki until I came across a T500 project thread in dotheton.com which displayed a T500 swingarm and started to wonder if one would fit to my T250. 

I started comparing part numbers from T500 and T250 swingarm and rear wheel parts lists and realized that most of the bushings and spacers for swingarm axles were same. Part numbers for different rear wheel parts seemed to match as well.

I made a want to by add for T500 swingarm to our local Finnish veteran motorcycle website/forum and quickly came by one. Same guy who sold me the GT250 fuel tank had one for sale. He also recommended that I buy a rear brake cable as well since it's a bit longer in T500 than T250.

Suzuki T500 swingarm and axle,
rear brake cable and oil tank.

Comparison of T500 and T250 swingarms.

Overall length of T250's swingarm is approximately 385 mm and T500's 505 mm (axle to axle). Width of both axle's fastening points are same in both swingarms (182 mm for swingarm axle with bushings in place and 195 mm for rear wheel axle (inner dimension)). Fastening point in frame is 190 mm wide (inner dimension).

Comparison of T500 (upper) and T250 brake cables and swingarm axles.

T500's rear brake cable's housing is 445 mm long and T250's 310 mm. Both swingarm axles are 14 mm thick. T500's axle is 249 mm long and T250's 225 mm. Threads are 25 mm long in both axles.

Fastening points for rear shocks in T500 swingarm are a bit wider than the ones in T250 frame (224 mm vs 208 mm) so I had to turn couple of spacers to get rear shocks lined. Other than that swingarm fitted right in place.

Dimensions for spacers,...

...turned,...

... and in place.

Rear shock installed.

Closer side view.

Overall side view of my Suzuki T250 with T500 swingarm and oil tank.
Fuel tank and seat are from GT250.