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RedShogun · 02-01-2024, 01:29 PM

Hello guys

So, I plan on doing some works on my 125cc Suzuki. The engine is your typical horizontal, air-cooled unit with 2 valves.

I want to refresh the engine externally, since there is a good amount of burnt oil on it, as well as a layer of mud, dust, etc. And I'd also like to improve its performance.

Two years ago I replaced the 3rd/4th gears in the gearbox, new con-rod and a new cylinder&piston set. I installed a better camshaft (handmade, an exact copy of the Takegawa S-Stage cam) and I converted from EFI to carburetor...right now I run a Keihin PD type, 20mm.

I will install new clutch discs along with tougher springs next month. Genuine Suzuki discs and Ferodo or Newfren springs. So I need some advice...

Shall I stay at the same engine capacity? Or is it better to go with a bigger piston? Keep in mind, that I'll need to get another cylinder and then get it to a workshop in order to increase its bore size, since the Suzuki one can't get any bigger (SCEM material).

And what carburetor shall I go with? I know that 22/24mm is a good size for 125-130ish cc...round slide or flat slide? Like a PWK, Mikuni TM etc. I've seen some folks here running 28mm or even 30mm on 125-130cc engines without a problem, but these sizes seem too big to me...

Also, should I just polish the intake/exhaust ports or also increase their diameter up a notch? Right now both ports are 19mm in diameter...24mm intake valve and 21mm exhaust valve.

Thanks in advance!!!

02-01-2024, 01:29 PM	#1
RedShogun Novice Join Date: Jan 2024 Location: Volos, Greece Age: 25 Posts: 3 Bike: Suzuki FL125	Engine Works Hello guys So, I plan on doing some works on my 125cc Suzuki. The engine is your typical horizontal, air-cooled unit with 2 valves. I want to refresh the engine externally, since there is a good amount of burnt oil on it, as well as a layer of mud, dust, etc. And I'd also like to improve its performance. Two years ago I replaced the 3rd/4th gears in the gearbox, new con-rod and a new cylinder&piston set. I installed a better camshaft (handmade, an exact copy of the Takegawa S-Stage cam) and I converted from EFI to carburetor...right now I run a Keihin PD type, 20mm. I will install new clutch discs along with tougher springs next month. Genuine Suzuki discs and Ferodo or Newfren springs. So I need some advice... Shall I stay at the same engine capacity? Or is it better to go with a bigger piston? Keep in mind, that I'll need to get another cylinder and then get it to a workshop in order to increase its bore size, since the Suzuki one can't get any bigger (SCEM material). And what carburetor shall I go with? I know that 22/24mm is a good size for 125-130ish cc...round slide or flat slide? Like a PWK, Mikuni TM etc. I've seen some folks here running 28mm or even 30mm on 125-130cc engines without a problem, but these sizes seem too big to me... Also, should I just polish the intake/exhaust ports or also increase their diameter up a notch? Right now both ports are 19mm in diameter...24mm intake valve and 21mm exhaust valve. Thanks in advance!!!