'73 Suzuki GT250 - Part 12 - Mock-up engine

Some time ago I bought a cheap Suzuki GT250 parts bike from an online auction site. Bike itself was in pretty bad condition but I taught I could utilize at least some parts from it. Lots of parts were missing but frame had still front forks, swingarm, fuel tank and engine attached to it. Few extra pieces, like Honda CB125 exhaust pipes, which I sold, were included to the deal as well. After disassembling parts from the frame I turned my attention to the engine. It wasn't a big surprise that it had seized pistons and plenty of rust after sitting outside and water getting in. After taking the engine a part I decided to clean it up a bit and utilize it as a mock-up engine for building exhaust pipes et cetera while I put together actual engine for this bike.

Suzuki GT250 engine out of a spare parts bike

I decided to use soda to clean upper and lower crankcase. Good thing about soda blasting is that it isn't abrasive like sand blasting so it doesn't require as much prep work since you don't have to mask as many spots. Bad thing about it is that it's rather corrosive if parts are not cleaned well afterwards.

Before blasting I used a brush and some solvent like brake cleaner to remove excess dirt and grease which would have just ended up disturbing soda blasting process. Below you can see few closeups of lower crankcase before and after soda blasting. I soaked them in warm water after blasting to get leftover soda out of them. Otherwise it would have ended up corroding the surface.

Lower crankcase before soda blasting

Soda blasting equipment: 
gun, water separator for air compressor and soda

I put both crankcases to a big bucket with warm water

after soda blasting to dissolve leftover soda out of them

Lower crankcase after soda blasting

For cleaning cylinders and cylinder heads I decided to use sand blasting. Before doing so I took rubber pieces out between cylinder head fins, removed excess dirt with a brush and some degreaser and masked surfaces which I didn't want to get blasted. I did this at my university's workshop where they have a sand blasting cabinet. I will show it in a post coming up later.

Cylinders and heads prepped for sand blasting

Closeup of sand blasted cylinders and heads

Last step was to bolt covers back on the crankcase which I bought separately. I used socket cap screws for nice aesthetic which I had in stock. I didn't see it necessary to clean up covers yet in this phase since they looked to be in OK condition.

Pieces of mock-up engine

Crankcase covers

Various M6 & M8 socket cap screws

Mock-up engine ready

I will take this engine apart and fit in necessary axles when I will start to figure out how to fabricate brake and gear levers. But before that I need footpegs which are next on my list of things to finish. If you look close at one of pics below you might find an easter egg related to them 😎

Glass blasting and boring T250J cylinders - Suzuki T250J

My T250J cylinders were in a pretty bad condition when I bought the bike. Other cylinder had deep grooves inside the cylinder sleeve which had to be removed by boring the cylinder to the next oversize. Bore was 55.00 mm (stock is 54.00 mm) before so the next step would be 55.50 mm.

Before I dropped the cylinders to my local machine shop to get bored I glass blasted them. I covered all the holes and ports in the cylinders were I didn't want the glass get into with a masking tape. I also removed rubber cushions from the cylinder heads. Both of them had 11 cushions between the cooling fins. Before blasting I used diesel fuel to get all the excess dirt out. Glass blasting is usually used for surface finishing so it might be necessary to sandblast the parts you are cleaning first. My cylinders had thick oil and dirt stains which needed to be sandblasted to get rid off. Below are some pictures of my overhauled Suzuki T250J cylinders and heads.

Suzuki T250J cylinder sleeve. Bore is 55.50 mm
(+1.50 mm/0.060" oversize).

Intake port of Suzuki T250J cylinder.

Exhaust port of Suzuki T250J cylinder.

Left side port of Suzuki T250J cylinder.

Right side port of Suzuki T250J cylinder.