Author Topic: 038 diagnosis help. See video  (Read 290 times)

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Offline Mark71gtx

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038 diagnosis help. See video
« on: September 29, 2015, 06:46:04 am »
https://youtu.be/-2clMPd4OBY

The saw runs like crap at high rpm.  The carb has been rebuilt and I put a new coil and new seals on the crankcase.  It still runs the same.  Any ideas?  Thanks!

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Offline jmester

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Re: 038 diagnosis help. See video
« Reply #1 on: September 29, 2015, 06:56:51 am »
Sounds like an over rich high speed adjustment. Or the metering lever is set to high. Just a thought.
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Offline Mark71gtx

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Re: 038 diagnosis help. See video
« Reply #2 on: September 29, 2015, 07:01:36 am »
I started it with the high adjustment at 7/8ths out  and turned in and out it does not ever clear up.  I have rebuilt many carbs for many saws and have never had this kind of trouble before.  Maybe I need to check the metering lever though.  Thank you for your input.  Do you know the proper setting for the lever?  It is a Magnum if it matters.

Offline jmester

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Re: 038 diagnosis help. See video
« Reply #3 on: September 29, 2015, 07:12:45 am »
Let me check. I will get back with you. I am pretty sure the low speed helps to feed the high speed on that saw. So there maybe a need for some low speed adjustment.
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Offline jmester

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Re: 038 diagnosis help. See video
« Reply #4 on: September 29, 2015, 07:34:52 am »
I did some looking around. The low speed does help to feed the high speed. 028 are the same way. So that means if you mess with one screw you are going to have to adjust the other. I am thinking that your low speed needs the adjustment now. The basic setting should be 1 turn out from a lightly seated postion on both the L and H screws. I think you are going to want to back the low speed screw out ( richen ) I may have it backwards it has been a while since a messed with a carb like that. I think if you take the low speed in and out you will see a big difference in how it runs.
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Offline Mark71gtx

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Re: 038 diagnosis help. See video
« Reply #5 on: September 29, 2015, 08:04:17 am »
Thanks. I started it at 1 1/4 turns out on the low and 7/8 out on the high.  I messed with both, but I didn't mess with the low much.  I will check it out hopefully this evening.  If that don't work where should I check next?  Would a bad intake boot cause my problem?  I wouldn't think so - seems to me it would run lean if it was bad.  I can't think of anything else that could be my problem since I have replaced so much already.  Someone actually threw this saw away.  There was a lot wrong with it when I got it.  It is the largest Stihl I have ever had and I wanted to see how it would perform in comparison to my Husqvarna 288XP (which is by far my favorite saw that I have ever owned).  I thought it would be cool to have a big saw from each of the big two.

Offline aclarke

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Re: 038 diagnosis help. See video
« Reply #6 on: September 29, 2015, 01:23:21 pm »
Make sure the fork in the metering needle isn't bent if it's a captivated arm. If you have a pop of gage you can check the sealing ability of the needle

Offline jmester

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Re: 038 diagnosis help. See video
« Reply #7 on: September 29, 2015, 03:25:52 pm »
If the boot was torn or leaking the saw would be way lean and screaming. I think it is in the carb adjustments. Start there and then go back through the carb. I have a feeling your low speed is the problem.
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Offline Mark71gtx

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Re: 038 diagnosis help. See video
« Reply #8 on: September 29, 2015, 03:37:24 pm »
Thanks, I'll check it.  I got a new plug for it today.  I'll put it in and adjust the carb while it is running.  If I can't adjust it out I will pull the carb and check it out again.

Offline Cut4fun .

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Re: 038 diagnosis help. See video
« Reply #9 on: September 29, 2015, 05:46:01 pm »
@Al Smith  I know he is into these. So just in case he has info too.
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