Type 2-7-1 Husqvarna CR250 1973-74
 - 35mm

1973-74 - Thin Piston Ring Stock

1972 - Thick Piston Ring Stock

These are "RT Only" installations. They require extensive machining and a modification to the top-out spring.


This piston ring is made of solid steel. This design does not fill the rebound chamber very well. Also, in stock form the top-out spring is press-fit onto a straight portion of the damping rod. It is common for these to wear and come loose.

The damping rod must be machined to accept newer style Husky Piston Rings. The machining also opens up the ID to allow less flow restriction. The machining also modifies the rod for a better top-out spring retention design.


Note - The 1972 is a bit different. The stock 1972 "piston ring" is much wider (see pic above) and has a check valve in the bottom of the chrome tube. It requires a different mod. Click here for details.



Click on the image on the left to open the .pdf for specific machining instructions. This doc explains what to do to 1973 and 1974 models. The only major difference between 1973 and 74 is the steel tube at the bottom of the damping rod on the 74.

This mod will allow the use of FPPR HQ35 piston rings that are made to fit 1975 and newer Huskys.

Be sure to bore the ID.

Drill the two existing large compression damping holes to 6mm (1/4") and add 2 more sets of holes (6 holes total) at 10mm increments above the stock holes. Each set must be at 90 degrees to the last set. See .pdf.


These are FPPR HQ35 piston rings.

 **Critical (and tricky)

The ID of one end of the top-out springs must be closed down to 17.5mm. It is essential that no more than 3/4 of the end coil is heated and it is never quenched. This is a bit tricky.


Stock on top.



Mod on bottom.


It is vital that FEGV AD3304 P Emulator Adapters are used with FEGV 3301 Emulators.

Below is the completed assembly.