WolfTechnics
Forum Apprentice
I wish to start a new thread chronicling my GS450E build, in which I’ll be using a beefed-up GS400 bottom end with a GR650 head to create a 600 cc two-valve engine. I attempted something similar in the past, as documented in a thread I started in 2014. However, I no longer have access to that username, and the old thread is full of dead photos and links, so I want to start over. This time with less naivety, more in-depth research and more realistic goals.
So what are those goals, you ask?
A 608 cc, 11:1-compression two-valve GS twin based on the GS400X bottom end, with GR650 barrels and head, custom pistons and rods. I plan to achieve this by doing the following:
- Boring out the upper crankcase to accept massive jugs (hehe...).
- Moving the cylinder studs to accept the GS500E/GR650-style cylinder block.
- Machining out the original 28 mm crankpins and replacing them with 29 mm GS1000 crankpins. We can use this opportunity to increase the stroke from 60 mm to 60.5 mm. I may skip this step if custom rods prove necessary anyway.
- Using a GR650 cylinder block, which can be bored out to 80 mm.
- Ordering custom CP-Carrillo pistons designed to match the bore and GR650 combustion chamber.
- Using stock GR650 cams at first.
- Building a custom exhaust.
- Installing a full EFI system to control and monitor the engine.
There are many—and I mean many—things to consider when building an engine like this properly. My main goal is reliability, so I won’t be chasing the absolute maximum possible horsepower. That can wait until I eventually get around to building a four-valve GS twin engine. I hope to achieve more than 60 horsepower at the rear wheel, which would be a very nice result. I have spent a lot of time thinking about this build over the past few years, and I believe this is the best route to take.
A little backstory
The GS450E that this engine will eventually go into was my very first motorcycle, bought for the grand total of €100! I never plan on getting rid of it, but I do want to turn it into something fun: a strengthened frame, lightweight wheels, a beefy USD front fork and a radical engine.
My previous attempt at building this engine, many years ago, ended when the balancing company lost my rotating assembly, including the CP-Carrillo pistons and rods. The company went bankrupt, and I never spoke to or saw the owner again. That was a lot of money down the drain, and the project has been collecting dust ever since.
I have always wanted to complete this build, but I used to work on too many projects at the same time and ended up finishing none of them. I have now done away with the other projects and am focusing solely on GS twins as a hobby. I am currently building two GS500Es to OEM+ specification, and that project takes priority over this one. On top of that, I have a baby on the way, so progress on the GS450E probably won’t be particularly fast.
So why start a thread already?
I intend to use this first post as a repository for all sorts of information I have gathered. I want to chronicle what I learn along the way and make it easier for someone else to attempt a similar build in the future.
So what are those goals, you ask?
A 608 cc, 11:1-compression two-valve GS twin based on the GS400X bottom end, with GR650 barrels and head, custom pistons and rods. I plan to achieve this by doing the following:
- Boring out the upper crankcase to accept massive jugs (hehe...).
- Moving the cylinder studs to accept the GS500E/GR650-style cylinder block.
- Machining out the original 28 mm crankpins and replacing them with 29 mm GS1000 crankpins. We can use this opportunity to increase the stroke from 60 mm to 60.5 mm. I may skip this step if custom rods prove necessary anyway.
- Using a GR650 cylinder block, which can be bored out to 80 mm.
- Ordering custom CP-Carrillo pistons designed to match the bore and GR650 combustion chamber.
- Using stock GR650 cams at first.
- Building a custom exhaust.
- Installing a full EFI system to control and monitor the engine.
There are many—and I mean many—things to consider when building an engine like this properly. My main goal is reliability, so I won’t be chasing the absolute maximum possible horsepower. That can wait until I eventually get around to building a four-valve GS twin engine. I hope to achieve more than 60 horsepower at the rear wheel, which would be a very nice result. I have spent a lot of time thinking about this build over the past few years, and I believe this is the best route to take.
A little backstory
The GS450E that this engine will eventually go into was my very first motorcycle, bought for the grand total of €100! I never plan on getting rid of it, but I do want to turn it into something fun: a strengthened frame, lightweight wheels, a beefy USD front fork and a radical engine.
My previous attempt at building this engine, many years ago, ended when the balancing company lost my rotating assembly, including the CP-Carrillo pistons and rods. The company went bankrupt, and I never spoke to or saw the owner again. That was a lot of money down the drain, and the project has been collecting dust ever since.
I have always wanted to complete this build, but I used to work on too many projects at the same time and ended up finishing none of them. I have now done away with the other projects and am focusing solely on GS twins as a hobby. I am currently building two GS500Es to OEM+ specification, and that project takes priority over this one. On top of that, I have a baby on the way, so progress on the GS450E probably won’t be particularly fast.
So why start a thread already?
I intend to use this first post as a repository for all sorts of information I have gathered. I want to chronicle what I learn along the way and make it easier for someone else to attempt a similar build in the future.
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