'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.

'73 Suzuki GT250 - Part 4 - Removal of broken swingarm bearings/bushings

I might have teased you in my last post that I was going to show how I fitted that aluminum '79-80 Suzuki RM250 swingarm to my '73 GT250K. But before we do so I wanted to write a little post on how to easily remove old swingarm bearings/bushings with simple tools, which you can find from almost every garage. 

Here's a little backstory about the swingarm. A while ago I bought a swingarm from '80s RM/PE250 through a want to buy add, which I had written to one Finnish classic motocross forum. It didn't take long to receive an answer for my it. Seller of this swingarm was from southern Finland which meant that I had to purchase it without seen it first. He send me a few pictures of it but nothing too detailed. Once I received the shipment I noticed that it had broken bearings or some sort of bushings inside the bearing housings. For a while I had to figure out how to get them out of there. In the end the solution was pretty simple.

'79-80 Suzuki RM/PE 250 swingarm

Broken swingarm bearing/bushing.

Bearing housings in this swingarm have 27 mm diameter. This meant that I could use M8 fender washers (24 mm outer diameter) to pull both of the bearings/bushings out. I had to grind few of the washers to make them narrower. This helped to slide them through one of the bearings/bushings and set them behind one of them. After that was accomplished it was easy to pull bearings out with a long M8 bolt and 27 mm socket.

Long M8 bolt, nut and fender washers.

Narrowing few of the washers helps to slide them through 

bearings and inside the bearing housing. Use them to get the 

first bearing out of the way.

27 mm and 13 mm sockets, small ratchet and open/ring spanner.

DIY puller.

Ready to pull.

Bearing almost out.

Job done.

Broken bearings/bushings out of the way.