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  #21  
Old 01-06-2014, 05:58 PM
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Jeff in AL Jeff in AL is offline
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Quote:
Originally Posted by BigFish View Post
Good to know on the valve adj!
Yeah, it's been awhile since I worked for a Stihl dealer, so have not heard much in the way of tech info. The last 4-mix info I got concerned the valve change,( Sept. 09 or so) but no mention of the clearance increase. Thanks again for sharin'.
No problem!

It is not "published" to double up on the exhaust valve clearance in the Service Manual.

But in some tech info it states the following:

The adjustment setting for all Stihl 4-Mix engines is 0.1 mm (.004) when engine is cold.
This is the minimum gap to use for setting valves, but a gap as wide as 0.3 mm (.012) is acceptable.

It has only been an issue on the BR's as opposed to shafted product, and only on the exhaust valve.
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  #22  
Old 01-06-2014, 10:53 PM
rlitman rlitman is online now
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Quote:
Originally Posted by Jeff in AL View Post
BigFish,

I'm not sure why the double on exhaust, I saw it on Youtube...


Actually, the real reason is that there was an issue with excessive carbon build up on the exhaust valve years ago. Then they changed the exhaust valve to a "bi-metal" valve. This helped with the excessive carbon build up for the most part. Even with the changes, there is still a unit from time to time with carbon deposit issues. However, today it is mostly due to their fuel or running with a broken tube and not getting the RPM's/engine temp up to burn off the deposits.

The thought process or reason to double up on the exhaust valve on the BR units is to allow a longer seat time to help keep the valve cooler. Even though it is only nano-seconds that it is closed longer, it has made a big difference, combined with other changes to help minimize carbon deposits forming on the valve face and seat. There has been no issue with the trade off of doing so which will cause a slightly lower lift height to the valve when open!
This is not just for Stihl or 4 mix. When adjusting the valves on my car, the procedure is to tighten the intake to minimum spec and adjust the exhaust to maximum spec. This is SOP for all 4 stroke engines.
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  #23  
Old 01-12-2014, 06:16 PM
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bare spot bare spot is offline
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read this last night, interesting on the adjustment numbers. gotta remember this and re-read, thanks. with my machine getting up in the yrs and countless hrs. it's been a great machine btw, seams it never gets a rest, in use all 4 seasons here. anyway me being not the most experienced in working on these machines and learning as i go. do see at some point me having to possibly going and replace some internal engine parts (for lack of a better way of putting it, tearing it down). so atm trying to learn what i could without them but gotta ask, without any diagrams or something to reference, is they a way to get such. is there a way to get these? can i get these from a dealer, are they for sale?
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  #24  
Old 01-13-2014, 04:35 PM
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Quote:
Originally Posted by rlitman View Post
This is not just for Stihl or 4 mix. When adjusting the valves on my car, the procedure is to tighten the intake to minimum spec and adjust the exhaust to maximum spec. This is SOP for all 4 stroke engines.
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To each is own...

Just to keep on track here, this discussion is not about automobile engines or their specs. This discussion IS on Stihl 4-Mix engines and the specs. that pertain to them.

In my opinion, the SOP is to follow the manufacturers specs. unless other wise noted, such as in this case, which is to double the exhaust valve on the BR engines only!

But what do I know...
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  #25  
Old 01-13-2014, 04:47 PM
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Quote:
Originally Posted by bare spot View Post
read this last night, interesting on the adjustment numbers. gotta remember this and re-read, thanks. with my machine getting up in the yrs and countless hrs. it's been a great machine btw, seams it never gets a rest, in use all 4 seasons here. anyway me being not the most experienced in working on these machines and learning as i go. do see at some point me having to possibly going and replace some internal engine parts (for lack of a better way of putting it, tearing it down). so atm trying to learn what i could without them but gotta ask, without any diagrams or something to reference, is they a way to get such. is there a way to get these? can i get these from a dealer, are they for sale?
Any Stihl Dealer should give you an IPL of your machine or they can order one for you, same with a service manual!

If they won't, PM me with your Model(s) and the DOM or Serial numbers to know which versions you have and I'll see what I can do!

Jeff
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  #26  
Old 01-13-2014, 07:58 PM
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thanks jeff much appreciated. hope the op doesn't mind posting on this, was thinking of starting a new thread but for now will keep short, hopefully could add to it something of use. where i at is used the bp blower (only own one) the other day after some light snow for clean up and at one point had the machine die out on me. fuel issues, idk but do want to go in and give it a going over at some point. like mentioned before it's been used constant since 07 and not sure what the norm is on the compression or really remember what it was like new but it seams when the machine warms up and i restart there is hardly any at all. recheck of the valves seams in orders later this wk but have been thinking with its age and use of looking into the de-carbonizer procedure mention earlier. never really explored getting into the machine past getting to the point of adjusting the valves getting it back together but now curious about how to go about it, see what the internal looks like (cam etc.).
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  #27  
Old 01-14-2014, 10:49 AM
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Quote:
Originally Posted by bare spot View Post
thanks jeff much appreciated. hope the op doesn't mind posting on this, was thinking of starting a new thread but for now will keep short, hopefully could add to it something of use. where i at is used the bp blower (only own one) the other day after some light snow for clean up and at one point had the machine die out on me. fuel issues, idk but do want to go in and give it a going over at some point. like mentioned before it's been used constant since 07 and not sure what the norm is on the compression or really remember what it was like new but it seams when the machine warms up and i restart there is hardly any at all. recheck of the valves seams in orders later this wk but have been thinking with its age and use of looking into the de-carbonizer procedure mention earlier. never really explored getting into the machine past getting to the point of adjusting the valves getting it back together but now curious about how to go about it, see what the internal looks like (cam etc.).
Being that you said you were using it to blow snow...
Did you switch the deflector inside the a/f housing from "summer mode" to winter mode"? If not, it is very likely that the carburetor is "icing" from the cold air.

There really is no reason to tear into a unit unless there is a problem that cannot be repaired prior. So unless you have a "dead" unit that you just want to take apart and see what makes it tick, I would advise not to do so on a running unit.

A dead give away that the valves are in need of adjustment on the 4-Mix units is that the unit is harder to pull over, "more compression". When the valves are set correctly, the unit is very easy to pull over when cold and hot.

As mentioned prior, on units with high hours, not being opperated correctly or having an issue with excess carbon buildup, I would recommend using EDTA (Ethylenediamine Tetraacetic Acid). It's sole purpose is to break up carbon deposits!

Jeff
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  #28  
Old 01-14-2014, 10:52 PM
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bare spot bare spot is offline
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jeff. thanks for that. be interesting to see how the stuff works. on the compression, not hard to pull.
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  #29  
Old 01-15-2014, 10:35 AM
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Quote:
Originally Posted by bare spot View Post
jeff. thanks for that. be interesting to see how the stuff works. on the compression, not hard to pull.
It works great!

The primary unit I use it on is the BR 4-Mix. For some reason, my commercial guys are bad about running their units with no nozzle, or a worn nozzle. With that being the case, it slows the engine speed down and combined with the few that can't even adjust their throttle cable to make sure it opens to WOT, these units tend to see carbon issues more often. Not to mention the fuel and off brand oil they use that contribute to this problem.

It's not a matter of if, but when the exhaust valve will see a chunk of carbon stuck between the valve and the seat on these units that are run as described above! When this happens, there is no compression.

When I get one of these units, I increase the valve setting more than normal to open the valves more, set the piston to TDC on end of exhaust stroke (both valves are slightly open), fill the cylinder through the spark plug hole until full with the EDTA and let sit over night.
The pour out the EDTA, pull the unit over a few times, reset valves to spec., install new plug, fire the unit up and send it on it's way!

In some cases, it may have to be done a couple/few times to get the majority of the carbon buildup free and greatly reduce the chance of further issues. The buildup comes back over time again!
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  #30  
Old 01-17-2014, 09:43 PM
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got a little busy over the last couple of days but been thinking about the decarbon procedure and was curious about something. before that though i wanted to check out the valves so i got the back cover off but i had to take care of something so i ran out of time and decided i'd put it on the side till today. today rolls around and never got a chance to check it out and now didn't feel like messing with it this evening and seeing snow in the forecast, decided to get it back together just in case i might need. so i got it back together, was tighting up the last hex screw on the back cover and it didn't want to tighten it. figure it good for now and will check it out sunday but in the meantime i wondering now if it is stripped out and what's gonna be the fix if it is. should of took it back apart to see and where it tourqe's into, thinking incerts. maybe could replace and pop new one back in if that's the case. anyway, was wondering on the decarbon procedure, should i keep a spare plug handy, after a few use's after decarbonizer will the plug get effected? anybody?
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