bogging 038 super

[ZIM]

I just purchased a 038 super with it bogging when I first hit the gas, but would rev out close to what it should be. It would not idle either. I bought it thinking it was a quick fix. I replaced the fuel line, fuel filter, intake boot, carb kit, head gasket,impulse line, gas tank vent. After all of this it runs better on the top but still will not take the fuel properly on the low. The best I can get it running is 3 turns on the low, and 3/4 turn on the high. It has 150lbs compression, and had the local stihl dealer do a leak test on the motor(that's why I had to replace the head gasket) and they said it was good. Seems to have good spark. The only thing is, unless the low is adjusted 3 turns it will not start. The plug is new and always comes out black. I run 25:1 with high octane fresh fuel. One thing is weird with it is that the more you turn the idle out the higher it revs. Any help will be great!
Thanks

 

[Lawn Masters]

Run it with 40:1 or 50:1 STIHL oil, and adjust the carb properly, those 25:1 mixes are pretty much ANCIENT things for the REALLY old oils that no longer exist. try this, and if you havent already, rebuild the carb, and it might just go great.

 

[ZIM]

I tried leaner mixture tonight and I also installed a carb kit, but still no better.I also own a 38mag, pulled the carb off of it, same thing. The carb is a bing if that helps anyone.
Thanks for the reply

 

[Lawn Masters]

well, I dont know then. could be a number of things, but I really dont know now. I'm stumped.

 

[Fish]

I had a customer bring me a saw that he could not get running right. He had bought
a new Bing carb kit, @ $48, from the local Stihl dealer. After taking it apart a few times and scratching my head, I examined the circuit plate gasket, it didn't loook
like it lined up right with a couple of the passages well. I called the customer
and asked him to bring in his old kit, if he could find it, he did, and I used the old
gasket, and it worked fine.

 

[Lawn Masters]

Thats likely to be it right there. always the simple stuff we forget about.

 

[Simonizer]

Do a pressure/vacuum test on the saw to see if you have an air leak, could be crank seal(s)

 

[lostone]

Do a pressure/vacuum test on the saw to see if you have an air leak, could be crank seal(s)

and had the local stihl dealer do a leak test on the motor(that's why I had to replace the head gasket) and they said it was good

He says he did Simonizer, Or are you meaning that he should have it checked again after the new cylinder gasket was installed to test to see if it mated to the surfaces and is sealed? and that the seals could be the next link in the chain that is leaking.

 

[HiOctane]

Did you check if the gasket behind the carb match with the pulse hole ?Remove the carb ,put a bit of oil in the the pulse hole ,pull the cord slowly and check if the air is sucked in and out when you pull.Your elbow in the case where the hose is connected could be blocked at least partially.Assuming that pressure test was OK and you changed the carb,not much left to look for.

 

[ZIM]

Thanks everyone for all the great info!!!!!
I noticed the new circuit gasket was the same as the old one, but thats the funny thing, I didn't think both of them looked right, covering up what I thought was a little too much area on the jets. I just thought that if both of them are l like that it must be right, but maybe not...thanks a million for the heads up on it. I am heading out this morning to play with it some more. I am also going to try the great idea with the pulse line.
Thanks again guys!!!!

 

[Fish]

Keep looking at the circuit plate gasket, punch out a little material where you think
it needs to be on the old gasket, and I bet you will have it whipped. Especially where
it covers 80% of that one jet/opening. Sounds like the same scenario.

 

[ZIM]

I took the carb off my 38 magnum again, (last time I tried this was before I had the head gasket replaced)and I put the one from the super ran like a top. The super ran no better with the magnums carb. I checked the pulse line with some oil and it looks good. I blew it out again anyways. I swapped plugs also. The saw will not start unless you have the low out 3+ turns and then it will barely move the chain untill you lean it out a little, then it will not idle.
I started to take the clutch side apart to look around . When I took off the sprocket under neath it was like grass wrapped around the shaft, but it wasn't it was like metal but easily to pull apart, the colour was off green.
Just reading up in my shop manual how to get to the oil seal.
I am wondering if the oil seal is leaking, but shouldn't it lean it out??
Thanks fish for repling back!!

 

[HiOctane]

I took the carb off my 38 magnum again, (last time I tried this was before I had the head gasket replaced)and I put the one from the super ran like a top. The super ran no better with the magnums carb. I checked the pulse line with some oil and it looks good. I blew it out again anyways. I swapped plugs also. The saw will not start unless you have the low out 3+ turns and then it will barely move the chain untill you lean it out a little, then it will not idle.
I started to take the clutch side apart to look around . When I took off the sprocket under neath it was like grass wrapped around the shaft, but it wasn't it was like metal but easily to pull apart, the colour was off green.
Just reading up in my shop manual how to get to the oil seal.
I am wondering if the oil seal is leaking, but shouldn't it lean it out??
Thanks fish for repling back!!

If the seal is leaking,its leaning out for sure.But you said they take a leak test and she was Ok ???
To reach the seal,you remove sprocket,unscrew clutch(L.H.thread),remove the oil pump and you are there.

 

[ZIM]

The stihl dealer did leak test it . But they also said the saw was running great. ( I did not buy it from them)
I am kind of doubting them at this point about the leak test. I do not have a leak tester but I might try to fab up something. There seemed to be alote of black oil when I took of the side cover to get to the clutch, not sure if it is just old chain oil or what.
Its been a great learning experience if anything!!!
Thanks

 

[ZIM]

I did some what of a leak test and the clutch side seal is leaking.
Now it is just to get to it. I have the handle, clutch,gas tank ,oil pump all the bolts I can see, the cylinder head off, but still cannot get the crank to spit. Am I doing this correct? Any help would be great.
Thanks

 

[Fish]

Well the parts will sell ok on e-bay..........
A small seal leak will not mimic the problems you describe, I think your trouble is in
the carb.

 

[HiOctane]

I did some what of a leak test and the clutch side seal is leaking.
Now it is just to get to it. I have the handle, clutch,gas tank ,oil pump all the bolts I can see, the cylinder head off, but still cannot get the crank to spit. Am I doing this correct? Any help would be great.
Thanks[/QUOT
You remove it from the OUTSIDE,dont open the case.Just use something to lift off the seal like an old screwdriver sharpened to go tru the seal.Be careful to not damage the case around.

 

[ZIM]

Thanks HIOCTANE for the info. When I did the leak test it was leaking really bad.
I still am alittle puzzled, so I take a screwdriver in by the crankshaft and try to pry the seal out. Looks like there is a ring around the seal that I have to get out first, but I could be wrong. My shop manual reallly doesn't explain things too well in this area.
Any more info would be greatly appreciated
Thanks

 

[lostone]

ZIM get a good close up photo of it and post it, that will help alot.

 

[Lawn Masters]

Part of what you might be looking at is probably the outer race of the crank bearing. while looking at this, I'd check my bearings for play and see if there is any. if there is, REPLACE THEM.