# Small Engine guru's I need some help



## Kevin (Aug 11, 2012)

yesterday both my 50cc saws went down within 2 minutes of each other. Iwas using my new favorite saw the 346XP (Heidi) and the throttle trigger broke at the base of the plase where it pivots. Just snapped i n two. Have a replacement ordered. So I pick up Hannah - the Dolmar - and went back to limbing and within 30 seconds she started hunting really bad. I'm fixing to check the fuel filter that's inside the tank, but I'm pretty sure it's a carb problem. I have rebuilt a few 2 - cycle carbs but I hate it. The last one I did I ended up having to take it to my chainsaw guy. It was a weed eater but same as a chainsaw. 

Any ideas? I'm pretty handy around small engines but far from a guru. 


:dunno:


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## brown down (Aug 11, 2012)

my buddy is the head of a large township around me and uses anything that uses oil mixed with fuel and he claims that the ethanol in the fuel is horrible for the engines and really trashes them quick. he uses this stuff called BLUE STAR GAS TREATMENT FOR ETHANOL
i run that with everything i mix and it goes a long way
maybe that might help he has noticed a difference maybe you will too!


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## Kevin (Aug 11, 2012)

brown down said:


> my buddy is the head of a large township around me and uses anything that uses oil mixed with fuel and he claims that the ethanol in the fuel is horrible for the engines and really trashes them quick. he uses this stuff called BLUE STAR GAS TREATMENT FOR ETHANOL
> i run that with everything i mix and it goes a long way
> maybe that might help he has noticed a difference maybe you will too!



:exactly:

I run it too Jeff.


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## Ancient Arborist (Aug 11, 2012)

Kevin,
The broken throttle can be bypassed by attaching a ring of some sort to the cable end. It takes a little fiddling, but you can limp her along till the part comes in. The other one may just need a good cleanup of all carb, filters and such. While cleaning you may spot a gasket or boot that is not in shape. Sometimes that cleaning helps me get things running for awhile.


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## Brink (Aug 11, 2012)

Kevin said:


> yesterday both my 50cc saws went down within 2 minutes of each other. Iwas using my new favorite saw the 346XP (Heidi) and the throttle trigger broke at the base of the plase where it pivots. Just snapped i n two. Have a replacement ordered. So I pick up Hannah - the Dolmar - and went back to limbing and within 30 seconds she started hunting really bad. I'm fixing to check the fuel filter that's inside the tank, but I'm pretty sure it's a carb problem. I have rebuilt a few 2 - cycle carbs but I hate it. The last one I did I ended up having to take it to my chainsaw guy. It was a weed eater but same as a chainsaw.
> 
> Any ideas? I'm pretty handy around small engines but far from a guru.
> 
> :dunno:



Broken triggers on huskies. Happens, and for no apparent reason.

Hunting. Two things I go after. First, check the connections from the carb to the cylinder. Air leaks can cause hunting, and engine damage. Next, remove the muffler. Make sure there's no carbon blocking the spark arrestor, or the exhaust port. While in there, slowly turn the crank and check for scoring on the piston skirt.


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## woodtickgreg (Aug 11, 2012)

Kevin I think you know I am a small engine mechanic and work ( up untill the injury ) at a power equipment shop. Brown down is correct on the ethanol thing and it's only 10% right now and I hear it's supposed to go to 15%. At the shop I work at I have never seen so many 2 cycle machines in for repair as I have this year. We don't even mess around with rebuilding the carbs now as it's about 50/50 that you can save one, the alcohol seems to be coroding the small passages in the carbs too. Brink is also correct in making sure you don't have an air leak and are sucking air, which could cause a lean burn condition and a seizure. An easy check for an air leak is to spray a little wd 40 around the base gasket at the cylinder and intake manifold mounts while the motor is running at idle, I also spray around the crank seals and case center gasket, any changes in rpm or a engine stall indicate an air leak. The simplest way to determin whats going on in a 2 cycle engine is to just pull the muffler and look in the exhaust port at the piston and rings, any vertical scratches or scoring, or stuck rings and you have a problem. Making sure the internal engine parts are sound is the first thing you do before any work at all, if the piston and rings are bad why start throwing parts at it untill you figure out what caused the failure. It is very important that you make sure you don't have an air leak before doing any carb work or you can end up damageing the piston, rings, and cylinder. I wish I was in your back yard as I am a wiz with 2 cycle, every shop I have worked at has always given me the tough ones to repair. It is a hard thing to diagnose without seeing it myself. But this might give you some insight and things to look for.


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## Kevin (Aug 11, 2012)

Greg I totally forgot you were the small engine guru. And I can tell you are from your suggestions. Great info thank you very much! You may have saved my saw from serious damage. I'll follow your prescription and report back once I've checked out the piston and wall and valves.


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## woodtickgreg (Aug 11, 2012)

Kevin said:


> Greg I totally forgot you were the small engine guru. And I can tell you are from your suggestions. Great info thank you very much! You may have saved my saw from serious damage. I'll follow your prescription and report back once I've checked out the piston and wall and valves.


Um, no valves in a 2 cycle, LOL. Except old tecumseh snow blower engines, and you don't have those in texas! it could be something very simple like a pin hole in a fuel line, a gas cap that's not venting, or the carb. But a good small engine mechanic will make sure the piston, rings, and cylinder are sound before doing anything! It's a process of elimination.


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## shadetree_1 (Aug 11, 2012)

I'm not a guru by any means but don't forget that little pencil eraser size screen under the top plate of that Walbro carb on the Huskys they do like to plug up, I have pulled my hair out several times on my Huskys until I remembered that little bugger!! I may be wrong but I think the Dolmar is the same?


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## Kevin (Aug 12, 2012)

shadetree_1 said:


> I'm not a guru by any means but don't forget that little pencil eraser size screen under the top plate of that Walbro carb on the Huskys they do like to plug up, I have pulled my hair out several times on my Huskys until I remembered that little bugger!! I may be wrong but I think the Dolmar is the same?



That's exactly what happened to my Dolmar weedeater. Don't lay it down on the bench because if a fly farts anywhere in the vicinity it will blow away. Fortunately my small engine guy stocks them. It was for a Stihl but he knew it crossed for this model Dolmar. I'll check that also good idea, that's not a carb takedown pretty easy actually. .


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## Kevin (Aug 12, 2012)

woodtickgreg said:


> ...
> Um, no valves in a 2 cycle, LOL.



Does that mean my chainsaw does not have a cam or push rods either? What about a timing chain? 

:rotflmao3:

I knew that but old habits die hard I'm a 4 stroker at heart. 

:lolol:


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## woodtickgreg (Aug 12, 2012)

Kevin said:


> shadetree_1 said:
> 
> 
> > I'm not a guru by any means but don't forget that little pencil eraser size screen under the top plate of that Walbro carb on the Huskys they do like to plug up, I have pulled my hair out several times on my Huskys until I remembered that little bugger!! I may be wrong but I think the Dolmar is the same?
> ...


Theres really only a few manufacturers of small engine carbs and a lot of the parts are interchangable. walbro, zama, tillitson, might be another but it evades me right now.


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## Kevin (Aug 12, 2012)

Greg I pulled the muffler a few minutes ago, but I can only see a small portion of the piston and only a small portion of the the cylinder wall whenever I move the piston down. My inspection mirror is too big to fit into the exhaust port. From what little I can se it all looks great - I mean like new with no lines of any kind, but I can see probably less than 25% of the piston and wall. 

I can pop the top if you think I should it's not big deal. 

Awaiting your instructions . . . . .


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## woodtickgreg (Aug 12, 2012)

Kevin said:


> Greg I pulled the muffler a few minutes ago, but I can only see a small portion of the piston and only a small portion of the the cylinder wall whenever I move the piston down. My inspection mirror is too big to fit into the exhaust port. From what little I can se it all looks great - I mean like new with no lines of any kind, but I can see probably less than 25% of the piston and wall.
> 
> I can pop the top if you think I should it's not big deal.
> 
> Awaiting your instructions . . . . .


If you move the piston up and down and don't see any scratches your good to go! The exhaust side of the piston gets the hottest and will be the first to fry, intake side is cooled by the fresh charge of fuel entering the cylinder. Good job Kevin, now you can reinstall the muffler and procede to diagnose the fuel issue with short runs until you find the issue. With the alcohol issue today it's probably just the carb, but I would replace the fuel lines and filter. Also try this, fill the tank to the top and see if it runs, that will eliminate a hole in the fuel line in the tank, if it runs it's just a fuel line-cheaper than a carb. Also check that the air vent screen on the carb diaphragm is clear or the diaphragm wont work properly. If all these things do not work, cut your loses and just replace the carb. I am assuming you know how to adjust a carb in, if not take it to your repair guy. a carb that's not tuned right can fry a motor. any questions please ask my friend!
The good thing is you now know the motor is sound!


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## Kevin (Aug 12, 2012)

Okay sounds good so far. 

If I fill the tank plumb full and it runs why will that tell me if there's an air leak? Because the vented cap can't vent and if it runs that means it's venting through a leak somewhere?


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## woodtickgreg (Aug 12, 2012)

Kevin said:


> Okay sounds good so far.
> 
> If I fill the tank plumb full and it runs why will that tell me if there's an air leak? Because the vented cap can't vent and if it runs that means it's venting through a leak somewhere?


It will tell you if the fuel line has a hole in it inside the tank, it may run ok till the fuel level gets down to where the hole is. I have had this happen not only on customers machines but my own. Also remember to do the wd40 test, that will eliminate the possibility of an air leak and then just let you concentrate on the fuel issue. So button up the muff, top off the fuel and see if it runs ok, if not break out the wd40 and spray around the intake manifold and cylinder base and both sides of the crank at idle. I don't think you have an air leak but it's a good thing to check. If all these things check out it's your carb.


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## DKMD (Aug 13, 2012)

I hate to state the obvious, but have you checked the black box thingy? :i_dunno:


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## Kevin (Aug 13, 2012)

Greg,

It idles fine with a full tank, but before I put it back together I used a mirror to reflect sunlight to look inside the cylinder and on the piston wall, and I do see one really fine line on the piston wall. Of course I cannot see if it's on the inside of the cylinder wall also because my inspection mirror will not fit inside the port. 

I can't see how this one line could cause any appreciable blow-by/compressions loss if that's your concern. I'm ready to do the WD40 test but i don't really understand it. Am I looking for bubbles? By "leak" you mean a compression leak not a suction leak right? :dunno:


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## shadetree_1 (Aug 13, 2012)

Kevin said:


> Greg,
> 
> It idles fine with a full tank, but before I put it back together I used a mirror to reflect sunlight to look inside the cylinder and on the piston wall, and I do see one really fine line on the piston wall. Of course I cannot see if it's on the inside of the cylinder wall also because my inspection mirror will not fit inside the port.
> 
> I can't see how this one line could cause any appreciable blow-by/compressions loss if that's your concern. I'm ready to do the WD40 test but i don't really understand it. Am I looking for bubbles? By "leak" you mean a compression leak not a suction leak right? :dunno:



Kevin,

I'm sure Greg means a suction leak, because if rpms and idle increase when you spray the WD it means the leak has been temp plugged by the WD and as soon as the WD is sucked in through the leak rpms and idle would go back down or be rough. I have used the WD on motors for years as Greg says and it will show a suction leak in a heartbeat.


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## woodtickgreg (Aug 13, 2012)

Kevin said:


> Greg,
> 
> It idles fine with a full tank, but before I put it back together I used a mirror to reflect sunlight to look inside the cylinder and on the piston wall, and I do see one really fine line on the piston wall. Of course I cannot see if it's on the inside of the cylinder wall also because my inspection mirror will not fit inside the port.
> 
> I can't see how this one line could cause any appreciable blow-by/compressions loss if that's your concern. I'm ready to do the WD40 test but i don't really understand it. Am I looking for bubbles? By "leak" you mean a compression leak not a suction leak right? :dunno:


Kevin you really don't have to look inside the cylinder just look at the piston exposed in the exhaust port. Very fine scratches are considered normal wear, and the one you see could just be from the ring gap. The purpose of the wd40 test is to see if the motor is suckin air in from anywhere it will either change the rpm or stall. Based on what you found in your inspection of the piston I think your ok, the test is just a precaution. The reason I use wd40 instead of starting fluid or carb cleaner is because it is a lubricant, anything else will cause a lean burn and could cause damage.
Now lets get back to the fuel thing. With a full tank does it accelerate normally? When you had your running issue was it after running for awhile and then started to run poorly after some of the fuel was used? The reason I asked to see how it ran with a full tank was to see if there might be a pin hole in the fuel line, it would run normal untill the fuel level came down to the level of the hole. Keep askin questions Kev, I will try to explain the best I can.


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## Kevin (Aug 13, 2012)

woodtickgreg said:


> Kevin said:
> 
> 
> > Greg,
> ...



I'm fixing to go log a few more FBE's I need a couple more trees so I'll take it along with the 372. This really stinks not having a limbing/bucking saw. I used to use the 372 for all of it before I got old last year. :dash2:

I'm not sure with my right elbow the way it is now that I can even freehand the 395 monster anymore. 
[attachment=9147]

The way I feel today I know I couldn't  :cray:

Will report back my experiences with Hannah in a few hours. . . . . .


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## woodtickgreg (Aug 14, 2012)

Kevin. did you get a chance to run the saw yesterday? What did it do?


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## Kevin (Aug 14, 2012)

Yes I ran it. I never made it out of the log yard though, got involved cleaning and milling, but I ran about a 1/3rd of a tank through it bucking and it never missed a beat. I'm waiting on a delivery right now but after it arrives I'm heading out to the log patch and will run a tank or two through it. 

I'll let you know how it runs.


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## woodtickgreg (Aug 14, 2012)

Kevin said:


> Yes I ran it. I never made it out of the log yard though, got involved cleaning and milling, but I ran about a 1/3rd of a tank through it bucking and it never missed a beat. I'm waiting on a delivery right now but after it arrives I'm heading out to the log patch and will run a tank or two through it.
> 
> I'll let you know how it runs.


You know it could have been something as simple as a partially fouled spark plug? Duh! I just assumed you would have checked that first. LOL I carry a box of them with me in my saw tackle box. Run it with a full tank untill it's empty though to make sure there's not a hole in the fuel line. An intermitent problem can be difficult to diagnose. Coils can break down when they heat up, I have replaced mine on the 365.


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