CR125 CR250 CR500R Aluminum Frame Conversion ①eng mounted  


This is the NEW CR500R that I built with my friends last summer. It is a single-cylinder 2-stroke 500㏄ with the current aluminum frame specification.

What you can learn from this article

It can be seen that a 1995YM HONDA CR500 engine can be mounted on a 2021~2023YM HONDA CRF450 frame without cutting the frame!

Mountability of the latest frames and 30 year old ENG


We confirmed that the 1995CR500R engine can be installed on the 2022CRF450 frame without major modifications.

It was an amazing match of frame and engine, as if the frame and engine were designed to accommodate a 30 year old 2-stroke ENG.

Swingarm pivot shaft


First of all, regarding the swingarm pivot shaft. I was impressed by the fact that the current 450 and CR500 have the same dimensions of the shaft diameter and its fastening length, and that 30 years ago, they had already found the golden ratio of the dimensions of this part of a machine of this class in terms of power performance.

Kick pedal shaft


After temporarily FIXing the ENG mounting position, I lowered the kick pedal and was impressed by how nicely it rotated without touching the frame pivot.

Mounting of exhaust to frame

If a commercially available Pro Circuit chamber is installed, it can be assembled without modification. The stock chamber can be assembled by shaving the weld ribs and rewelding them.

Two attached photos. First one. The second photo is of a 2000CR250 in stock condition for reference. The second photo is of a 2000CR250 in OEM condition for reference, with a small modification to the chamber weld ribs.

Cooling System


For the cooling system, the 2022CRF450’s mass-produced radiator was used as is for the FIX. 2 3-way joints were used and routed to maximize cooling using the 2 mass-produced radiators. Although the water hose route is slightly longer and some channel resistance may occur, the overwhelming durability and reliability of the mass-produced radiator is ensured.

Initially, in order to optimize the water hose routing, the radiator was welded and modified to optimize the direction of the JOINT and the JOINT size. However, the radiator is one of the consumable parts that are frequently replaced due to deformation and damage caused by falls of various sizes, and assuming that the vehicle will be maintained as a DIY project, we thought it would be best if the radiator could be used as it is in mass-produced products, so we did not perform any welding modification.

Handling Stability


Of course, we would like to improve the vehicle’s maneuverability, but before that, we must first ensure the power output and drivability of the ENG. During the shakedown in the summer, we addressed the initial defects and carb-setting to a certain extent. After that, I have been checking the drivability with my friends and identifying areas for future modification.

Since it seems that the engine has been lightened by about 10Kgf by changing from a 4-cycle engine + exhaust to a 2-cycle engine + chamber, it seems that the suspension needs to be re-set.



Intake area has been drastically changed from the mass-produced version. The chamber and silencer have been changed from the mass-produced version. The drivability seems to have been partially changed by these two major changes.

We are currently working to see how much we can get out of the set-up with the mass-produced carburetor.

If you want, please refer to the basic section on carb setting.

Below is a picture of the water hose and electrical harness area after the tank is removed.

It looks good, doesn’t it?

It would be nice if such a bike could be mass-produced.

Continue with (2) air cleaner area and (3) cooling area.

CR500R aluminum frame conversion ② air cleaner box production

2022CR500R aluminum frame conversion ③Cooling System Details

Once you understand the mounting characteristics, the next information you want to know is the correction value of the chainline!

Please contact me if you need information on the amount of chainline compensation I have calculated on a measured basis or the dimensions of the mounting brackets I have fabricated. I will consider it.

Also, as an option, consider purchasing a mounting bracket, which is a bit more expensive but can be purchased at BVC Offroad.