String Trimmer Compression

[StarTech]

Yes compression your gauge is not design for this smaller engine. And if you are only getting 45psi on the mower it is definitely not reading right as even 4 cycle walk behind mowers with compression release needs to read at least 65-70 psi. Two cycle equipment must operate at a higher compression in order to ignite the fuel mix as it has higher ignition point than straight gasoline.

Just trash or recycle that unit as parts are no longer available for that 25cc unit. You couldn't repair it if the PNC is bad. Most of the other parts are also NLA. Now the carburetor may still be rebuilt but a new one out of the question.

What to do is try a little fuel added to the cylinder and see if the trimmer engine will try to run. If it does then it is carburetor problems; otherwise, it is compression or ignition timing which would unrepairable due the lack of replacement parts.

 

[Mad_mat222]

I think the new husqvarna 322l are not even making 90psi. Probably keep the compression low to reduce wear would be my guess. I asked the tech at local dealer and they had no idea what psi should be.

 

[slomo]

Yes compression your gauge is not design for this smaller engine.

Right, isn't there a purpose built compression tester for small 2 smoke engines?

 

[bertsmobile1]

YEs
However they are expensive because they are genuine mechanics tools
So you won't find them where cheapskates shop like ebay, amazon, Harbour Freight, Walmart or even Lowes.
hey will come as a set with a lot of different spark plug adapters and in particular different length ones because if the adapter protrudes 2 turns into a combustion chamber it can increase the effective compression ratio if you think about it it is the same as shaving a head to bump up the compression ratio .
The same goes for adapters that are too short so add volume to the combustion chamber .
Don't know where mine came from as I have had it for 50 years & I got it second hand from a 2 stoke race bike tuner .But Gunsons comes to mind .

 

[shurguywutt]

I have the same Toro but the blower version. I am not a fan of the 25cc engine at all. It has high compression and it is just hard to start in general. I have been futzing with mine for about a month already trying to repair it and it seems like it is ready to just give up the ghost. Hopefully I can get by with it until I can save up for an Echo blower.