Porting my trimmer

[Fly By Night]

I yanked the top end off my trimmer last night looking for a little more grunt. the exhaust port seems way too small. The case has some weird chanels cut in it to feed the lower transfers. It seems really restrictive. The lower transfers seem to really big compared to the uppers. The piston skirt goes all of the way around, I was thinking widen the exhaust and maybe the lower transfer feed chanels? The hole to them from lower case is teeny tiny. Thoughts?

 

[Fly By Night]

 

[Fly By Night]

Exhaust

 

[Adirondackstihl]

Enlarging those transfer tunnels might not be a good idea. Think loss of velocity.
Looks like it wouldn't hurt to slap a new set of rings in it. See a lot of blow by below the the ring lands

 

[Fly By Night]

Can I enlarge the feed to the tunnels?

The crank also looks like it's been hot as hell and there is some light scuffing on the piston on the intake side.

Here's what's odd to me, in relationship to eachother the intake is large, transfer tunnel feed is tiny, transfer tunnels are medium, lower transfers are massive, upper transfers and exhaust are small

 

[David Young]

Hmmm what's the trimmer

 

[Fly By Night]

Tanaka tbc-260pfl. The shafts is longer then a normal trimmer for us tall dudes

 

[Pud]

Is it just the photo or are they the thickest rings ive ever seen ?

 

[Thommo]

Looks like it has been running way too lean if the colour of the spark plug in the picture is accurate. I agree that the transfer setup looks restrictive and looks like someone has gone to a lot of effort to restrict flow. Maybe it was designed that way to keep the revs low to stop the trimmer head from flying apart.

 

[Fly By Night]

That is not one but 2 of the thickest rings in the world.

 

[Chris-PA]

Weird design. That small channel feeding the larger transfer volume can't be accidental - but what were they trying to do?

Be careful with the port sizes and timing, as it's a trimmer not a saw and will spend much more time at lower rpm.

 

[Chris-PA]

How old is it?

I'm going to guess that it's an attempt to reduce scavenging losses by allowing exhaust gases to fill the upper transfers and delay the arrival of the fresh charge. Thick rings for better thermal transfer on a hot running engine?

 

[Fly By Night]

It's a few years old, it has (had) a cat on it so emissions are definatly in play.

I don't plan to change port timing minus loosing the base gasket. other then that I'm thinking widen the exhaust, maybe intake some, and the holes that feed the lower transfer ducts from the crankcase, those feel wayyh too small and I don't see a need for it.

I'm really afraid to go blindly cutting into the thing.

The way the lower ducts go from narrow to wide looks to me like it's designed to keep the charge from going back into the duct, kinda a check valve if you will. I don't know however see why that would be important.

I agree it's been running lean, which is weird for me at 6,500' everything is always rich out of the box. Stupid non adjustable rotary valve carb. I need to get a bigger jet for it or order a carb that has an adjustable highspeed.

 

[1Alpha1]

Maybe I missed it or something, but what brand and model is it?

 

[Fly By Night]

Tanaka Tbc-260pfl

 

[Chris_In_VT]

I don't think I'd get too in depth with it.
If you port it, will you really notice it trim grass faster? I don't think it will be like a saw, and cut X% faster. Likely it will just make more noise and use more fuel, that's all you'll notice. Grass isn't that tough

IMO just give it a real healthy muffler mod, maybe enlarge + match the exhaust.

 

[1Alpha1]

Unless you have experience and know what to do, I'd pass on the porting. As the above forum member, just maybe do a MM and call it a day.

You want more power? Buy ya a Stihl FS-250R. The weeds start shaking just hearing me start mine up.

 

[Chris-PA]

The weeds start shaking just hearing me start mine up.

They're laughing - they know you'll never run it outside of the garage!

 

[Chris-PA]

Only an idiot would port a trimmer: http://www.arboristsite.com/community/threads/ported-poulan-pro-pole-pruner.276194/

 

[1Alpha1]

They're laughing - they know you'll never run it outside of the garage!

He who laughs last, usually dies a painful death.

Just when they (weeds) thought they were safe and I'd never leave my garage, the facts were stacked against them. I mowed them down and didn't even bother to rake um up.