Jonsered 525

[Rich Fife]

A parts designer at work found out that I work on saws... he asked if I could get his Jonsered 525 running. He purchased it new in the 80's for a little over $200. He said it hasn't ran in 2yrs. It would fire up, but once warm, it would cut out.

 

[Rich Fife]

He gave me a copy of the parts pages. I wrote down the stock numbers... and made a list of parts.

 

[Rich Fife]

The piston and cylinder have seen better days.

 

[Rich Fife]

I cleaned the cylinder as best as I could. I couldn't find a suitable drop-in piston... luckily enough, I had a Dolmar 111 piston on the shelf... the intake skirt was a little shorter than the OEM piston and it didn't have windows. The biggest 'issues' on the dolmar piston... the compression height and the gap for the small end of the rod. I machined a pop-up, trimmed the sides of the piston and I had to machine some spacers along with heat treating them.

 

[Rich Fife]

I ended up replacing the base gasket, the coil, the piston and the fuel lines. I also opened up the exhaust under the deflector. Given the condition of the cylinder as well as no port work or porting, this saw runs pretty darn good for a 49cc saw. By swapping the the piston we gained intake duration as well ad exhaust duration... without the windows I feel as if the charge is a bit more... onviously, the pop-up also helped with the gains.

 

[HuntFishMB]

Thanks for your great detail!
How did you hone the cylinder head with those deep transfers?
Im realizing a stone hone will catch on the transfers.. will a flex hone work?