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Post by stancejontland on Sept 15, 2017 14:42:23 GMT -5
whats up guys i have an older stihl fs36 weedwhacker and everytime i try to cold start it just wont fire. pull and pull and pull. mess with choke in between pulls and nothing. take the plug out dip it in gas and bam 1 pull right up. it even does this with new plugs. granted.. it will fire up a few times on new plug but maybe after 5 starts its back at it. really like to figure this out because i know the plug threads cant be happy... please reply with any good places to start thanks.. p.s. it never used to do this just came out of no where about 2 months ago.. oh p p.s. when its warm it will fire right back up.
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Post by AtariGuy on Sept 16, 2017 21:15:51 GMT -5
Could be the pickup/coil module. Check your gap with the business card. Mine may start and run for a moment on near full choked first couple pulls, then it floods the crankcase. Replaced the carb, burned the exhaust clear, gaskets, and plug. Got a new flywheel (its keyed thank god) and ignition module coming. Also got one of them silly carb tuning keys - tillotson style cv diaphragm carb. Hey 190mech - quick question about adjusting them style carbs - if the new iggy/fly don't get it to run, how should i adjust the low mix for a "factory starting point" - clockwise til it stops, then 2 turns out? And is cw richer, ccw leaner? Still new to till carbs |
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Post by ryan_ott on Sept 16, 2017 21:33:40 GMT -5
Could be the pickup/coil module. Check your gap with the business card. Mine may start and run for a moment on near full choked first couple pulls, then it floods the crankcase. Replaced the carb, burned the exhaust clear, gaskets, and plug. Got a new flywheel (its keyed thank god) and ignition module coming. Also got one of them silly carb tuning keys - tillotson style cv diaphragm carb. Hey 190mech - quick question about adjusting them style carbs - if the new iggy/fly don't get it to run, how should i adjust the low mix for a "factory starting point" - clockwise til it stops, then 2 turns out? And is cw richer, ccw leaner? Still new to till carbs I think mine are in the neighborhood of 1.5 - 1.75 out on both needles. I can check tomorrow. |
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Post by Cincikid on Sept 17, 2017 8:22:18 GMT -5
It sounds like a vacuum problem. I would start with an adjustment.
This Guy is pretty good.
If that doesn't solve it, rebuild the carb and replace lines, gaskets and primer bulb if you've got one. (watch multiple youtube vids)
I do this every few years in winter. It's relatively inexpensive (around $25) and with it being a Stihl your likely to get a long life of service by taking care of the little things.
An air leak will lean out the air to fuel ratio causing the engine to run hotter and could damage your motor. My advice would be not to run it much till this is solved.
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Post by ryan_ott on Sept 17, 2017 20:26:38 GMT -5
AtariGuyI checked mine today and mine is set at 1.6 out on low speed needle, 1.25 out on high speed. +/- 1/8 turn.
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Post by AtariGuy on Sept 17, 2017 22:22:18 GMT -5
Cincikid i agree, just found his videos earlier today before i popped in here and saw you linked a vid of his. "Takes about a half a beer to do this job." Or "For this job you will need... a can of beer. Today i've got labatt blue, but any can of beer will work for this job."
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Post by Cincikid on Sept 18, 2017 7:15:42 GMT -5
AtariGuy In one of his vids, he shows how to open a beer with a chainsaw! 
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Post by stancejontland on Sept 21, 2017 11:34:38 GMT -5
anyone have a link for a new spark plug wire??
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Post by AtariGuy on Sept 21, 2017 19:04:10 GMT -5
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Post by AtariGuy on Sept 27, 2017 13:33:51 GMT -5
Still stuck on my whip, i got a weed eater sst25 - new carb, new ignition coil, new spark plug, and new flywheel. Still cant get it to start/run. It loads itself with premix everywhere. Air filter's soaked, about 25-30ml pooling in the crankcase, and the exhaust is completely saturated. When its drained out, it tries to run (stumbles) for about 5-10 seconds, but within a few more pulls, its soaked again. I got the carb adjustment tool and have tried multiple carb settings from closed to 2 turns out on the low and high and still the same result. What am i missing?
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Post by AtariGuy on Sept 27, 2017 13:38:28 GMT -5
It has fresh 40:1 fuel, 91 octane and amsoil synthetic. Might be 4-6 days old...
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Post by AtariGuy on Sept 27, 2017 17:02:17 GMT -5
Ok so i got it running, but... tell me if this seems strange... my carb low and high, i closed them, and degrees (not quarter turns) from closed is where it runs...
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Post by Cincikid on Sept 29, 2017 12:38:52 GMT -5
Doesn't sound right in my experience.
A few things come to mind.
How well is it running? Sounds like the MJ needle isn't seating. OEM carb or aftermarket? New as in brand new or new to the trimmer? Was the carb disassembled? If so the H and L side ADJ may have been swapped by accident, they may have diff tapper and same threading.
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Post by AtariGuy on Oct 1, 2017 2:53:14 GMT -5
Oem new carb straight outta china. Never disassembled. Runs well enough, hard as granite to start it, occasionally works its way out of tune, have to adjust them by a couple degrees of a turn. Both adjuster screws will mess up high and/or low, if i adjust the idle, i have to check wot to be sure it didnt go rich/lean. More than 10 degrees of a turn will stall the engine
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Post by ThaiGyro on Oct 1, 2017 4:14:48 GMT -5
Is that a diaphragm carb? My late experiences with them are good, but the clone versions have poor tolerances. We have been testing a 16mm venturi clone on our 49cc Hondas. The venturi on mine measures bigger, while the 19.8mm throttle bore measures 19.5mm. It is just tuning for us, since we are playing.
For your need, you must find a replacement that has the correct specifications. My business partner/friend has a clone that measure near perfect, but the low and high screw bores are not good tolerances. The low end bore can suck a bit of air, causing freaky issues. Starting or sudden OMG! The high end one became loose after about 8,000km.
We corrected the issue on both using a tiny, undersized O-ring and thin washer under the spring....and Loktite 222 on the threads. The new purple Loktite seems to be good in poorly cast aluminum. We are not sure that the o-ring has any effect, except to create more spring load. The washer by itself might do.
My diaphragm carb is 16mm and works fantastic on my highly tuned 49cc engine.(Though it measures 16.4) It was designed for a chainsaw with a 55cc engine. It is a $12 clone. NOTE: diaphragm carbs need smaller venturi/throttle bore to supply proper air on a 2T. Higher differential pressure creates more airflow...so, please do not compare to slide/float carbs. (We use 19mm PHBG carbs on many 49cc tuned engines)
I guess my point is...the cost of a clone is FEED...front end engineering design. (Time...cheaper than parts) In our case, we measure and record EVERYTHING before mounting and testing. Most chainsaws are already high performance tuned to some degree. You have less room for playing than a street engine. As an additional note: We have made Hybrids...old carb bodies that have proper measurements, with newer parts and sealed to perfection.
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