Stihl 088 carb problem

[Raj]

My 088 was acting up. kicking back when cold. Then it would loose power and die in a cut. It would idle no problem. When reving no load it would sound great, no sputter or hesitation. Spark plug is a nice brown ashy colour with some light black oil around the threads, I do run 40:1 oil.

I put in a carb kit but there was one small brass plug I didn't change and a screw in nozzle that I didn't touch.
Ran good for a few heavy cuts.

Now today it seems to over rev, the speed doesn't match the throttle and when you release the throttle it will drop RPMs to a higher idle, then within seconds rev down to idle. Saw will idle and rev no problem, no cutting.

Whole carb is not available in my area.

Any idea what I missed when i put the carb kit?

 

[pete mctree]

Almost sounds like an air leak or split impulse pipe. I presume you have pressure tested the machine?
The 200t carbs used to develop a similar problem - welch plug was often the cause (that and the accelerator pump, which I don't think the 088 has). It may be the issue allowing air in. Simple way is to use something like nail varnish to seal it & then test again.

 

[Raj]

No pressure test yet.

I did discover the new diaphragm was bent up. Hope that's the issue. Dealer has a new kit coming tomorrow, otherwise I'll try to bend it back.

 

[SkwerI]

Check your fuel and impulse lines for cracks. Sounds like it is sucking air.

 

[Nutball]

Does it make a pulsing sound too after you let off the throttle? We have saw like that. I keep forgetting to richen it. It doesn't kick, but can be hard to start and keep going at times as it leans out and dies at idle.

 

[Raj]

No, just a smooth engine bog. Idles fine and throttles great no load.

Thanks all. Going to make plates for pressure testing tomorrow. Dealer has some replacement parts for me. Hope I solve this. Damn milling is backlogged.

 

[Raj]

Pressure test. Held 6psi for more than 5 minutes. Pressurized through impulse line.

Metering diaphragm was bent up bad in the carb kit. It didn't push the meter arm down far enough?

Edit. Saw held a vacuum no problem.

 

[pete mctree]

The damaged diaphragm is not going to help at all - has to be the next thing to do, even if it just eliminates it.

 

[Raj]

Dealer got a whole new kit for me, sold at cost because of the other new kit had the bent diaphragm.


Edit: cylinder compression easily reached 150psi.

 

[Raj]

A Facebook page mentioned that cracks tend to develope in the plastic angle fuel inlet, sucking air. Seems it's not a separate part. Mine has a small crack. What can be done? Rubber extension?

 

[SkwerI]

Can you paint the crack with some type of sealant? Silicone?

 

[Magnus]

I use epoxy.
Common problem on most with plastic extensions.

 

[Raj]

Thanks! Any specific epoxy?

 

[Magnus]

No, I have some generic two component glues.

 

[Raj]

I'll put a dap on, wrap some metal around it.

New fuel filter just came in, hope it's all solved. Did a couple passes, one on some white oak and a spruce board for a custy.

 

[Raj]

I have not epoxyed the crack yet. I hate to say I think my fuel filter was a big issue that I over looked. Carb did have some crud in it, and damaged carb kit didn't help, nor the long delivery time for parts. I hope I have it fixed. Milled a 9ft long white oak no problems today, RPMs matched the throttle.

Going to look into a tach to mount on the saw when milling.

I tend to stay away from cheap filters, any good sources for decent aftermarket fuel filters?

 

[squisher]

I never had any problems with the stihl ones myself. Glad it seems you've got it sorted.

 

[Raj]

Now it seems my second 088 has carb problems. Took the carb apart to find little plastic like pieces. Looks like someone used epoxy on a welch plug! Hope to fix it Monday.

 

[Raj]

Some epoxy over the large welch plug?? Carb is easier to tune now, with it removed and cleaned up.

 

[Magnus]

I use nail polish to Welshplugs. If set correct its not needed..

 

[Raj]

Bump.

New issue, my second 088 broke the crank somehow, finally got a new to me one, put the saw back together, new gasket, seals and bearings, cleaned up and lightly oiled (with 2 stroke oil) cylinder, rings and piston. Started up great then died. Now it floods, I was hoping thoughts and prayers will work, so I'll ask for them. Try again tomorrow, both arms and shoulders are sore, the saw has a lot of compression now, for some reason.

If the thoughts and prayers don't work I guess it's going to need the carb taken apart.

 

[Frankie]

I’d just get rid of it ... send it to me and I’ll use it as a boat anchor ... Besides according to @Nutball STIHL is “lacking” in the torque department 😂

 

[Raj]

I'll throw it in the lake for you. Which one is better? Erie or Ontario?

 

[pete mctree]

Check the gap on the coil - can mess with things for sure

 

[Raj]

I did set it to spec, I hope.

Thoughts and prayers didn't work, so carb work tomorrow I guess. Still floods.

I'm thinking of taking and old bar, beefing it up and make a mount to a bench, may be a little easier to pull start and trouble shoot the 088s.