Tuning?

[Ricko]

Hi, could anyone signpost me to a simple online explanation of setting a carb up. I've reassembled a Partner 550 and although it's now running, the carb settings need adjusting as its a bit reluctant to start without some throttle.

Cheers

[Stubby]

Hi, could anyone signpost me to a simple online explanation of

 

Spud is your man if you want it done . Plenty off stuff on you tube .

[peatff]

Hi, could anyone signpost me to a simple online explanation of setting a carb up. I've reassembled a Partner 550 and although it's now running, the carb settings need adjusting as its a bit reluctant to start without some throttle.

Cheers

 

It's normal for there to be a fast idle setting for the start after choke is shut off, is there a latch on the throttle or do you have to wedge the trigger with your foot I had to give the L screw a tweak to richen it up but I still have to use fast idle sometimes when the saw is warm.

Check youtube to get the hang of what they sound like running rich and weak.

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[Ricko]

Thanks, I forgot about the educational aspect of YouTube.

[Ricko]

peatff, I had to keep one hand on the throttle slightly to get it to start. I'll watch the video and give it another go. I can do most repairs to small engines but carbs still give me trouble. I let it warm up then set the tickover screw (T), I then adjust the low speed screw (L) until it ran smooth then I adjusted the high speed screw (H) to get it running smooth at the top end. Is this the right sort of approach?

[Stubby]

Actually at the top end it needs to be " 4 stroking " slightly ( in fresh air ) if not it will be too lean and possibly over heat and nip up .

[adw]

The old Partner 550 will have a button to lock the throttle part open, as i recall the carb has a govenor in it to stop the engine over revving, carb settings will not be too far away at 1 and 1 on H and L screw maybe a slight richen on the L screw if it does not pick up clean.

[spudulike]

Usual poor starting, if carb related, is down to the starting fast idle setting not holding the throttle open enough or the L screw being set a bit lean. Get these right and if there are no other major issues, it should go and then be tuned.

 

The fast idle start lock looks to be a push button on the side of the rear handle just above the throttle trigger - common on older saws as is the thumb latch type -

Edited February 14, 2017 by spudulike

[bmp01]

I let it warm up then set the tickover screw (T), I then adjust the low speed screw (L) until it ran smooth then I adjusted the high speed screw (H) to get it running smooth at the top end. Is this the right sort of approach?

 

Here's what i do, generally works for me, probably more definitive guides available elsewhere . ..

Low speeds first, I generally start meddling shortly after the saw has started and assume fine tuning might be necessary at later date.

-Idle speed set a little below where chain rotates.

-Adjust low speed screw to give highest idle (steps of 1/8 turn initially, pause at each step for a few seconds for speed to stabilise). Then richen up by 1/8 - 1/4 turn, speed drops a little and often not quite as smooth but the saw will be more responsive here.

-Reset idle speed.

 

You can check saw response at this stage, may need to go slightly richer if the saw doesn't pick up cleanly.

 

Make sure the saw is reasonably warmed up before giving it too much grief with the high speed adjustment.

High speed, no load, chain fitted and tension adjusted correctly, the saw should be 4 stroking and sound pretty rough, you do NOT want it to run smooth and scream, that is asking for trouble. The previous Youtube video is a good one to learn what 4 stroking sounds like.

-I start deliberately rich, hold the throttle open for a second or so but no more, determine the 4 stroking, adjust leaner 1/8 turn and retest. Continue until the 4 stroking is only just there.

 

Repeat the low speed settings, they won't be far out, stick with a slightly rich setting.

Repeat check of saw response.

Repeat the high speed if you made changes to the low speed - confirm its 4 stroking.

 

Test cut in wood, you're looking for the 4 stroking to disappear as the cutting load brings the saws speed down slightly. Easiest way to listen for this - during the cut, continue to hold the throttle open but just lift the saw away from the cut. Speed will go up and the 4 stoking should come back, sounds horrible ! If in doubt richen it up a little.

 

Saws with speed limiting coils must not be tuned in this way, safest is to use a fast response tachometer. Saws with the strato engines are also less easy to tune by ear in my limited experience.

 

HTH,

 

bmp01

Edited February 14, 2017 by bmp01
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