Stihl 028 idle problems

[69Pony]

I am working on an 028 that has been sitting. I have been through the carb hoses etc. replaced most gaskets and hoses but not impulse hose as it seemed OK. Runs good when cutting but when going to idle it is very inconsistent. Either wont idle or wont slow down. Adjusting low jet or idle speed does not get expected response. Anyone have thoughts?

 

[HarleyT]

Hell....
Go through the carb/kit after replacing the fuel filter would be first....

 

[Ax-man]

Most likely a bad carb. This question has popped up before and a different carb solved the problem . It even happened to me with a 28 somebody brought in a box of parts. I got the thing back together . It ran but was all over the place . I swore that thing had an air leak but it didn't . Took that carb off numerous times still the same problem. I finally got P O 'ed at the thing and took a carb off one of my 28's and it ran great. Got a different used carb and the saw ran great but only after I cleaned all the fine saw dust out from under the metering cover and it was packed to say the least. . That little episode turned me off to buying used parts from these saw salvage parts dealers. This wasn't the first time I had gotten a used part that was in one way or another worse than the part your trying to fix from these salvage guys.

Anyway the guy was happy with the saw and I was glad to get rid of it. I just can't help but think if I had a US cleaner at the time that it might have saved that bad carb.

 

[69Pony]

Replaced all carb gaskets diaphragms. It is a Tillotson HU-40B. Not available. Suspected air/vacuum leak too. New carbs on ebay for 10 bucks but I don't trust. New Tillotson HU-40D available. Is there a setting on metering height as with the Walbro carb?

 

[69Pony]

Fuel filter is new too

 

[Ax-man]

You must have an early model 028. That HU is too small a carb for a 28 but will still work ok. Get a Walbro whatever they are , if you can, should interchange . Been awhile since I messed with one. Metering lever is set the same height as the carb body by putting a straight edge across the body of the carb, unless that lever is sitting in it's own little well then the lever is set to he height of the well. I am probably confusing you.

 

[HarleyT]

Did you check the passages after you cleaned them?

 

[69Pony]

I think so. carb cleaner and air. All seemed Ok. Maybe am missing something though but not obvious.

 

[Ax-man]

Try soaking the body of the carb in some Seafoam for about 10 to 15 minutes ,then spray it down and into all those little holes with carb cleaner or brake cleaner. You don't need to really hit the carb with compressed air. If you changed that screen or strainer on the pump side that is good . If not make sure that little screen is letting fuel get to the other side . Some times those darn things seem to take forever to let fuel pass , other times it drains through very quickly which is a good thing verses slow. Using 2 cycle mix is better than carb cleaner to do this little test. That is what I have found anyway, but it really doesn't matter that much.

028's are pretty rock solid as far as air leaks on the bottom end. But anything is possible.

 

[HarleyT]

If you changed that screen or strainer on the pump side that is good . If not make sure that little screen is letting fuel get to the other side . Some times those darn things seem to take forever to let fuel pass , other times it drains through very quickly which is a good thing verses slow.

If the passage underneath is choked up with debris!!!!

 

[HarleyT]

Did you remove the needle and clean that passage properly?

 

[69Pony]

Thanks. Did not try the seafoam thing and will. Screen is good although not new. Ax is right carb cleaner will go where fuel mix will not but fuel mix travels through screen OK. I will look into a Walbro carb. Can anyone comment on the difference between the Tillotson HU-40 B vs Hu-40D? Try again tomorrow after hangover is gone.

 

[Jasonrkba]

A lot of people are afraid of remove the welch plug to clean the three holes under it but it is necessary to do a proper rebuild. Did you remove the welch plug? Also I bet yours has points, I don't know much about them but if you haven't yet I would change out the coil with a 290.

 

[69Pony]

A lot of people are afraid of remove the welch plug to clean the three holes under it but it is necessary to do a proper rebuild. Did you remove the welch plug? Also I bet yours has points, I don't know much about them but if you haven't yet I would change out the coil with a 290.

Is that the aluminum plug on the metering side. If so I did not remove as was not sure If I could get it back to remain tight. It is an AV electronic though so no point problem and runs good when cutting so don't suspect ignition.

 

[Jasonrkba]

It would have to be replaced. Should be in the rebuild kit.

 

[Poleman]

Have seen both the HU and WT have this issue and be bad. Have never had the chance to change out the Nozzle with a known good one to see if that correct the problem and if that’s what is bad on the ones that act like this.
Ultrasonic or soaking may sure help and can cure a lot of issue before trying to source another good carb.

The Walbro carb or a WT-16.

 

[Good ole’ boy]

My 028 super did the same thing. I ended up putting a new piston/cylinder and crank seals in it. If the carburetor doesn’t work look into replacing the crank seals. Be careful with compressed air also, I blew the welsh plug out of my fs80 carburetor.

 

[Old2stroke]

Can't be sure a carb is really clean unless you remove all the welch plugs and make sure the passages under them are clean. A sticky nozzle check valve can really screw up the idle and is never included in a carb repair kit. Also you have to be careful using compressed air on them as it is easy to blow the little rubber disc right out of the valve.

 

[69Pony]

Went back through the carb recleaning everything. Adjusted the metering lever attached to the needle as it seemed a little high. I did not have welch plug because the kit I got from my local dealer did not include a new one but was able to get cleaner to flow freely through both low speed holes. Saw seems to run and idle fine now. Not sure but suspect the fix was actually metering lever being .02 or .03 high. Thanks for all the help

 

[Poleman]

Metering level can play a big part on those carbs and a recleaning never hurts with suspect carb...
Good job!!!!!!