Porting an Echo 352

[Nutball]

I mark the piston with a scribe at the port timing I want, so I can measure the distance I want to raise or lower a port. This is done having first considered how much I want off the base and piston.



There are 2 lower marks because I remembered I want .020 off the piston.

 

[Nutball]

Has anyone else here ported one of these?

I think the first one I did ended up at roughly (guessing)
EX 108-110
TR 131
IN 70-72

I'm thinking of trying
EX 106
TR 130
IN 74

 

[Nutball]

So far: 103, 125, 72 EX & IN are about 68%













Debating whether I want to mess with lowering the cylinder for compression & to get the numbers I was aiming for, or save the trouble & lower the intake a bit more and run it like that.

This time I plan on using a bigger carb. I was comparing carbs laying around, I had just finished my FT 250 at the time I started taking this apart, had a second 250 kit nearby, so I compared the carbs, and they are the same with the 250 carb having a much bigger bore. I tried ordering a 352 throttle shaft and screws to convert the 250 carb, but the shaft is not in stock at the MFG, and I assume may never be again, but it would have been a loose fit in the low precision china carb anyway.

I decided to check a 355t carb, so I grabbed the parts bag from my high performance 2511t. I found the 352 carb is basically the same as the 2511t even though the engine is much bigger. The 355t carb is the same bigger size as the ms250 carb, but with the throttle shaft I need, and a primer circuit that I need and hadn't thought about with the 250 carb. The 2511t wasn't quite big enough of an engine to run the 355t carb well, so it should do great on this engine.

 

[Wood Doctor]

Here's a simple muff mod I did for the 355t that worked rather well. The engine seemed to perk right up after I did it:
I left the spark screen in and did nothing to the P/C.

 

[Nutball]

That's all I care to do to a 355t.

 

[Nutball]

I should have a NIB 355t buried somewhere I could rob the carb off.

 

[Wood Doctor]

I've made a few more enhancements to my 355T. I replaced the chain brake strap that snapped in half, added a bearing shim to improve the loose connection to the brake handle, and then I installed a machine screw to help hold the flimsy top cover in place that kept popping off.

Now it's raring to go. Sometimes a little mechanical engineering is all that it takes to save a saw from the landfill.

 

[Nutball]

Going to test it tomorrow. Timing is 103, 125, 76, with 355t carb, no extra compression yet.

 

[Nutball]

It runs good, but I think it would greatly benefit from more compression and a lower exhaust. Tuning it by ear wasn't all that easy, so I tuned it in the cut. It's a gas guzzler with the 355t carb. I'll have to compare its performance to the stock carb.