Cleaning a 290 carb?

[bobdog]

I see alot here that folks clean their carbs. How do you go about it? I have a new ms290 and don't expect to have to do it anytime soon, but am curious as to how it is done. Thanks.

[jteneyck]

If you are lucky enough to still be able to buy gasoline w/o ethanol it may be many years before you ever have to open that carb if you use fresh fuel mix in it.  But if like most of us your fuel has ethanol then it may come a lot quicker.  There's mixed opinion, but I like to run my saw dry after I'm done using it.  I drain the tank, start the saw and run it slowly until it dies.  I do this mostly to that the rubber fuel lines don't get eaten by the ethanol, which is especially problematic with my Shindaiwas.  Some of the internals of the carb., however, also are effected by ethanol so running them dry seems like it should increase their usable life as well.  I'm not sure the carb. actually is dry, however, so this may or may not be helpful. 
So once you start having running problems, and changing the fuel line, filter, etc. doesn't help then you can be pretty sure it's time to clean the carb. and change the diaphrams.  There are several replaceable components in most carbs.  Generally, there are one or two diaphrams, one or two gaskets, a replaceable screen, and a fuel metering needle.  There also might be one or two replaceable Welsh plugs, but it's rare that they actually have to be taken out.  The carb. comes apart with a few screws on one side and typically one or a few on the other.  Essentially, you take it apart, keeping track of the orientation of everything as you do so.  Take out the high and low speed jets as well.  Soak the body of the carb. in carb. cleaner then blow out all the passages.  Put it back together in reverse order, replacing the diaphrams and gaskets, screen and needle valve, which you can buy as a complete kit for around $12, as you go.  Tighten everything snuggly, put the hi and lo speed jets back in and set them to the factory settings.  Put the saw back together and tune the saw.  Once you've done it a few times it takes all of 30 minutes on a typical saw.  The MS-290 is a bit more of a challange to get the carb. out of the saw than some of my other saws, but not overly so.  Hopefully, you'll have forgotten this thread before you need to work on the carb.  When you do finally need to work on it, do a search here or other forums and you'll find complete descriptions and photos of the process. 

[Al_Smith]

Whatever model of carb it is just click on their web site and you can get detailed info on just about any question you might have .

As for rebuild kits you are better off with OEM kits most of the time meaning for example Walbro ,Tillotson .If it comes with Stihl named on it any place expect to pay about double . Generic kits work too but here of late the OEM kits are using a more ethanal resistant materials than most  generics and should last longer .

It's a shame really ,the old gasoline would allow a carb to go for decades before it needed attention but alas not so any more . Couple three years if you are lucky .Thank you very much EPA .

[John Mc]

It's a shame really ,the old gasoline would allow a carb to go for decades before it needed attention but alas not so any more . Couple three years if you are lucky .Thank you very much EPA .

The EPA and various organizations are also making noises about doing away with 100LL aviation gas. It is the last leaded fuel in the world. The search is on for an unleaded replacement, but it's probably several years away. I'm hopeful that whatever they come up with will also be something I'm not afraid to run in my chainsaw... I'm not nuts about breathing the exhaust of anything burning fuel with tetra-ethyl lead in it, so I've avoided using 100LL so far (but, up until tomorrow anyway, I've still been able to get non-ethanol fuel around here).

John Mc

[Al_Smith]

That tetra ethyl lead killed off a lot of them alright ,most of them were around 90 though at the time .  ;)