038 magnum High speed changes by 3000rpm

[WearTheChaps]

No matter how hard I pulled I couldn't get the old girl going on the weekend. Today I checked the basics but the plug was still dry. Tipped fuel in the plug hole and off it went. Stopped and started without to much problem from then. See what happens tomorrow on a cold start.

Once going I put the tacho on and was reading 13,000+ rpms. I adjusted the H screw so it was 10,000 rpm and stopped and restarted. On restart the revs were 10,000 but in 30 - 40 seconds started to climb back up to the 13,000+ rpm. Stopped and started a few times but the result was the same.

With my limited knowledge I guess something is leaning the mixture but I can't think what it might be. At 10,000 revs could it start to push past or suck in a seal? Do the rubber carby boots collapse at high speed?

I have been trying to work out which is the right test flange. My book says 11288504200 which I cant find. Ebay says 11188504200 is the correct one. Is ebay right?

 

[ballisticdoughnut]

Has it been sitting with fuel in the tank? If so how long? Most likely needs a carb rebuild, fuel hose, fuel filter, etc. Inspect and/or replace the pulse hose as well. I don’t have a paper repair manual for the 038 handy so can’t look up the number for the test flange.

 

[ballisticdoughnut]

This is the current test flange for the 038, as well as the part history.

 

[WearTheChaps]

Thank you [SIZE=4]ballisticdoughnut[/SIZE] for the detailed info on the flange number. Is that info available to everyone or is it only on a dealers system?

This 038M had a hard life when I bought it about 5 years ago, It was a cow to start and would die at full revs. In my "fixes" that didn't work, included replacing the ignition, carby, filter, pipes and intake manifold. After pulling my hair out I realized the choke flap spring was to weak causing the choke to close and killing the saw.

Ever since it has mainly been a shelf queen and only used when I have broken my husky.

The fuel is new, I will check the pulse line and double check the previous work. I am now thinking I didn't spend enough $$$ on the carby.

 

[ballisticdoughnut]

That’s dealer level in the pictures, not available to the public that I’m aware of. Could certainly be a carb problem, was it replaced at some point or still original? Bing or Tillotson? Would be a good idea to do pressure/vac test regardless. Could block off muffler and carb, do the test through spark plug hole. Just make sure piston is at BDC.

 

[Dennisthemenace]

I wouldn't be doing the wide open throttle thing again before having a good look around the saw. Something is wrong. Maybe fuel /carb side or maybe a leak. The test flange is 1118 850 4200. It is the same as for the 660. Stihl often updates tool and part numbers with little or no change to the item just to confuse us I suppose. So 1128 850 4200 is probably also correct

This is the current test flange for the 038, as well as the part history.
View attachment 1127667View attachment 1127668

That doesn't fit on my 38 Mag. There is no impulse line to block off with the pin. That on is for 046 and 660 series.

 

[Dennisthemenace]

I wouldn't be doing the wide open throttle thing again before having a good look around the saw. Something is wrong. Maybe fuel /carb side or maybe a leak. The test flange is 1118 850 4200. It is the same as for the 660. Stihl often updates tool and part numbers with little or no change to the item just to confuse us I suppose. So 1128 850 4200 is probably also correct

That doesn't fit on my 38 Mag. There is no impulse line to block off with the pin. That on is for 046 and 660 series.

Edit, I got confused and mixed up posts. The correct flange is 1111 850 4200.This does not fit 660s. Note there is no pin for the impulse because the impulse comes THRU the carb. (see first pic).

 

[ballisticdoughnut]

I wouldn't be doing the wide open throttle thing again before having a good look around the saw. Something is wrong. Maybe fuel /carb side or maybe a leak. The test flange is 1118 850 4200. It is the same as for the 660. Stihl often updates tool and part numbers with little or no change to the item just to confuse us I suppose. So 1128 850 4200 is probably also correct

That doesn't fit on my 38 Mag. There is no impulse line to block off with the pin. That on is for 046 and 660 series.

I thought there was something a little off about that flange. I’m wondering if the gasket (part #3 in first picture) is used to block the pulse hole in the flange on the 038?

 

[ballisticdoughnut]

When I looked it up on the IPL under special tools the “flange” is listed as 5910 850 4207. Must be a mistake? I didn’t have the paper repair manual on hand at the time.

 

[WearTheChaps]

Would you need the flange gasket on a 038M? Wouldn't the flange face torque down on the inlet manifold and block the pulse at the same time?

 

[WearTheChaps]

I forgot the picture

 

[ballisticdoughnut]

I’ll have to compare the two flanges on Wednesday when I’m back at work. Wondering if either one will work, or if Stihl made a mistake listing a tool that isn’t compatible with the 038.

 

[singinwoodwackr]

Sounds like air leak to me.

 

[tripleSrepairs]

https://www.manualslib.com/manual/979301/Stihl-38.html
This site is awsome not just saws they have manuals for just about everything and they are free if your looking for owners manuals be specific if your looking for dealer level manuals type service manual

 

[stihltech]

Did you check the complete fuel system, including the vent?

 

[Dennisthemenace]

I’ll have to compare the two flanges on Wednesday when I’m back at work. Wondering if either one will work, or if Stihl made a mistake listing a tool that isn’t compatible with the 038.

It wouldn't be the first time. There are 2 or 3 mistakes in the 084 Service Manual

 

[WearTheChaps]

I got the Mityvac today so I did some testing.
The tank vent was able to hold at least 20 psi. Out came the grub screws and I cleaned the threads. It can't hold 5 psi now.
The carby held 7 psi. It is a Chinese copy. I found the original Bing carby 48A101a in my chainsaw parts box.
However at high speed it still settles at 10,00 rpm for 30 - 60 seconds before climbing back to the 13,000 rpm.

I rang the local Stihl dealer who said the 11198504200 isn't available but the 59108504207 is.

 

[spuldup]

Hey @WearTheChaps if you dont have the service and parts manuals you can get them in this thread.

 

[ballisticdoughnut]

So I’ve got one of the flanges, the other is currently MIA but I think it’s at home. Anyway I believe this flange will work on the 038, got one here at the shop so I will confirm.

 

[ballisticdoughnut]

So flange 5910 850 4200 will work with plug screw removed. Needs a little “encouragement” to slide onto the studs but nothing major.