Porting my trimmer

[Fly By Night]

Well it looks like I'm in good company then!

My shaft is 14" longer then yours which means I can get the head to the ground without having to hunch over, which certainly makes that chore less fatiguing.

I don't NEED more power, especially for weekly trimming but it would be nice for knocking over stuff that gets long.

 

[1Alpha1]

Well it looks like I'm in good company then!

My shaft is 14" longer then yours which means I can get the head to the ground without having to hunch over, which certainly makes that chore less fatiguing.

I don't NEED more power, especially for weekly trimming but it would be nice for knocking over stuff that gets long.

The shaft on my FS-250R is pretty damn long.

I know my wife was impressed by it.

 

[ANewSawyer]

Sadly, Stihl no longer makes the fs 250. Pity.

 

[1Alpha1]

Mine is 58" long, and, it's solid!

 

[Fly By Night]

Mines 71" and solid for smoother power transfer

 

[AUSSIE1]

I wouldn't bother with your inlet. Do the exhaust and muffler. The trans area in the cases is ugly. Work them and match trans in both the cyl and cases. Leave the base gasket out.

 

[Landmark]

Been running a Robin NB321 for 10+years with no problems. Never thought of porting but might do a MM after reading this. Hope it lasts for ever as I dont think they make robins anymore.

 

[Fly By Night]

My trimmer difinatly woke up with a mm, that muffler had all sorts of baffles and restrictions in it, the hole to the deflector was the size of a pea. I just opened up everything, I didn't bypass any baffles and it's just ad quiet as ever.

What do you suggest I do to the lower ducts aussie? Just make them larger?

 

[AUSSIE1]

My trimmer difinatly woke up with a mm, that muffler had all sorts of baffles and restrictions in it, the hole to the deflector was the size of a pea. I just opened up everything, I didn't bypass any baffles and it's just ad quiet as ever.

What do you suggest I do to the lower ducts aussie? Just make them larger?

When they build/design these things they aren't too fussed about good flow etc.

Have a good look at the relationship between the barrel and case trans.

Where the passage way in the case comes around to meet the barrel trans it opens up quickly. you would get turbulence here. I would open it up to reduce the possibility of turbulence matching your barrel.

 

[jughead500]

Took the cat out of my tanaka tbc340 pf and it really really made a difference. Going to pull the base gasket soon.
Hey fly by night.could you get me a measurement on your shaft length? Having back problems and im 6'5" and would like to compare to my 340 and stihl fs 250

 

[Fly By Night]

In 6'4, this is the only trimmer I've held that I can get to the ground without hunching over. I wonder if a taller front handle like the older echo trimmers had would help compensate? The shaft is 71" per Tanaka, when I was selling them my rep told the shaft was 14" longer then and average strait shaft. It definatly is way the heck out there and takes a little time go get use to, it's also a little harder to whip around as fast being so far out but I won't got back to a normal trimmer.

If you'd like I can measure whatever you'd like and take a pic next to a normal trimmer tomorrow If you'd like.


Aussie, do you mean taper it to the larger diameter instead of having it abruptly open up?

 

[AUSSIE1]

In 6'4, this is the only trimmer I've held that I can get to the ground without hunching over. I wonder if a taller front handle like the older echo trimmers had would help compensate? The shaft is 71" per Tanaka, when I was selling them my rep told the shaft was 14" longer then and average strait shaft. It definatly is way the heck out there and takes a little time go get use to, it's also a little harder to whip around as fast being so far out but I won't got back to a normal trimmer.

If you'd like I can measure whatever you'd like and take a pic next to a normal trimmer tomorrow If you'd like.


Aussie, do you mean taper it to the larger diameter instead of having it abruptly open up?

Yeah I don't like the abrupt change in size. I'd flair it like a funnel if you get my drift. That inner radius could be worked further around. Make sure you do the barrel so it matches. What ever you do to the base/case, cut the base gasket so you can transfer what you've done to the barrel using it as a template. I wouldn't be concerned about a loss of velocity here. It help with turning up into the transfer.

 

[1Alpha1]

Mines 71" and solid for smoother power transfer

Damn, that is long.

No way I'm going to mention that to my wife. She thinks mine is as long as they come.

 

[Fly By Night]

Makes sense to me, Thanks aussie. Does any one see a reason the feed from the case to the lower ducts shouldn't be enlarged? It's obviously teeny right now

 

[LegDeLimber]

I'd love to see (well lighted) view down into the crankcase.
be interesting to see how that transfer tunnel begins?
Was someone at Tanaka thinking that the crank spinning could sort of sweep/push
the charge into the tunnel??
how tight are the cases and how does everything blend from one area to the next?

after seeing that, then it could help to decide IF you want to alter anything.
almost wondering about epoxying that tunnle right at the top of the crankcaes.
Then go grind out the sides and let the transfers feed directly out of the cases
(on either side of the crankweight areas) like we usually see in these things.

If need be, I'll copy a couple pics and make a few marks, then ropost them.
Afet my stops hurting.
==
And ive got a migraine comming on, so sorry guys, if i'm not making much sense.

 

[splitpost]

I'd love to see (well lighted) view down into the crankcase.
be interesting to see how that transfer tunnel begins?
Was someone at Tanaka thinking that the crank spinning could sort of sweep/push
the charge into the tunnel??
how tight are the cases and how does everything blend from one area to the next?

after seeing that, then it could help to decide IF you want to alter anything.
almost wondering about epoxying that tunnle right at the top of the crankcaes.
Then go grind out the sides and let the transfers feed directly out of the cases
(on either side of the crankweight areas) like we usually see in these things.

If need be, I'll copy a couple pics and make a few marks, then ropost them.
Afet my stops hurting.
==
And ive got a migraine comming on, so sorry guys, if i'm not making much sense.

thats what i would do if it were mine ,+ open the muffler up and look for an adjustable carb

Sent from my GT-S7500T using Tapatalk 2

 

[AUSSIE1]

Keep it simple, it's only a trimmer

 

[LegDeLimber]

AUSSIE1 does have valid point.
But that "I have tools and I wanna see what I can learn and do" urge just runs
so dadgummed tenaciously amongst us.

So whatever Fly by night does, i hope there are more good photos.

 

[jughead500]

I found the specs on it from the tanaka website.figured all of the old models had been taken off since the hitachi take over.im in the process of hunting one now.looks like its discontinued and everyone has sold out.

 

[AKDoug]

I wouldn't go any farther until you figured out an adjustable carb. In fact, the MM might just be the reason it's currently running lean.