found 30min of time... 361 muffler mod

[tatra805]

Due to all the inspiration found here in all the related threads i took the jump...

I modded my FS250 some time ago and was cutting today after long time in dead/overgrown thick grass.... amazed so much again that the 3 blade seems unstoppable.

So came home and took off the muffler of the 361...

Being tired not finding a brazing solution for this 1 time job i decided to follow the internal mod.

Opened up the muffler, cut out the exit pipe and opened the exit hole to a more square form.

Closed the muffler (this opening and closing is much easier than expected)

Muffler looks stock but....

1st impression without retuning, so i was carefull, no WOT just a short play with the trigger. First thing monday is a trip to the dealer for a re-tune.

Starts easier, almost as half of the compression is gone.
The burble at pulling now really comes straight from the engine and not from the muffler.

Way louder although the sound is still directed away from the operator.

Of course idle way too high but the trigger response in combination with the sound..... BIG

the 361 for sure is no lazy revving saw stock, but this.... :jawdrop:


If this first impression is going to be confirmed after the tuning i am going to smile way too much.


Thanks to all of you at AS !!!

 

[tatra805]

Follow up and some help needed.

Follow up.... :deadhorse:

Could not resist
Please all of you experienced, give me your thoughts on my method. This is the first time i dare putting a screwdriver in these 3 sacred holes.

Took out the limiter caps.
FYI, you have to turn them completely anticlockwise for the tabs inside to align so you can pull them out. if not the tabs will break and stay inside. ( on the 361 you have to remove the rubber guiding cover as the caps are a fraction bigger in diameter than the holes for the screwdriver)

First of all, after the muffler mod it is clear the 361 has more visual smoke (without changing any carb setting)

Took RPM measurement with inductive clamp on spark plug lead.

Idle set at 90hz or 2700rpm. That was easy.

High set at 460Hz what should be 13800 RPM. (reading was not stable enough to risk going higher)

Played with the LA setting which resulted in:
- Blue cloud
- Almost no smoke but not as revvy
- setting in between that i considered safe although not knowing what i am doing.

After that Idle was at 100Hz or 3000rpm and the chain started moving, so reset that to 90Hz.


Now, Related to the Hz to RPM conversion. Am I right with my calculations:

100Hz is 100 cycles per second or 6000 per minute
This devided by 2 gives RPM. Because Hz measurement is looking at a pos-neg peak cycle as 1 and RPM is 1 sparkpulse per revolution.

If i have this wrong the 361 would now be doing 27600RPM. Tell me i am right, please:help:

I made 2 testcuts in an old oak beam (9x9) not timing anything but the roostertail was impressive. As was the fact that bogging it down was simply not possible, while stock this was possible on this same beam.


IF the 361 is near a good setting now (visiting the dealer anyway tomorrow) it became a frightening tool.


1 Note: I did not measure any difference when clamped around the plug wire as when just holding the clamp NEAR the saw. Even laying 25cm from the saw, the frequency was the same. Tip for those with inductive multimeters??? If so :

 

[Wirenut2266]

Follow up.... :deadhorse:

Could not resist
Please all of you experienced, give me your thoughts on my method. This is the first time i dare putting a screwdriver in these 3 sacred holes.

Took out the limiter caps.
FYI, you have to turn them completely anticlockwise for the tabs inside to align so you can pull them out. if not the tabs will break and stay inside. ( on the 361 you have to remove the rubber guiding cover as the caps are a fraction bigger in diameter than the holes for the screwdriver)

First of all, after the muffler mod it is clear the 361 has more visual smoke (without changing any carb setting)

Took RPM measurement with inductive clamp on spark plug lead.

Idle set at 90hz or 2700rpm. That was easy.

High set at 460Hz what should be 13800 RPM. (reading was not stable enough to risk going higher)

Played with the LA setting which resulted in:
- Blue cloud
- Almost no smoke but not as revvy
- setting in between that i considered safe although not knowing what i am doing.

After that Idle was at 100Hz or 3000rpm and the chain started moving, so reset that to 90Hz.


Now, Related to the Hz to RPM conversion. Am I right with my calculations:

100Hz is 100 cycles per second or 6000 per minute
This devided by 2 gives RPM. Because Hz measurement is looking at a pos-neg peak cycle as 1 and RPM is 1 sparkpulse per revolution.

If i have this wrong the 361 would now be doing 27600RPM. Tell me i am right, please:help:

I made 2 testcuts in an old oak beam (9x9) not timing anything but the roostertail was impressive. As was the fact that bogging it down was simply not possible, while stock this was possible on this same beam.


IF the 361 is near a good setting now (visiting the dealer anyway tomorrow) it became a frightening tool.


1 Note: I did not measure any difference when clamped around the plug wire as when just holding the clamp NEAR the saw. Even laying 25cm from the saw, the frequency was the same. Tip for those with inductive multimeters??? If so :

I'm a tad confused......But;

Fluke inductive pickup on Fluke meter reads:

230 hz (example)

230hz x 60 cycles per second = 13,800 actual RPM

Remember: Your Fluke is measuring frequency, it has no clue about rpm's....If you have the 88, it should do conversion for you.

Now were idling and fluke readout says 90hz..........90hzx60 cycles per sec.= 5400 rpm's........

If I understand what you wrote, never devide anything, multiply HZx60=RPM

I don't believe your saw can be idiling at 5400 rev's and chain not moving.

You pushed freq. button on Fluke, but what setting is your rotary dial turned to????

I just emailed Fluke and went to there forum about this same thing, but I beleive this is the correct Formula