# Saw cuts out full throttle???



## Wildman1024 (Aug 31, 2009)

OK here it goes. I have a saw that runs basically perfect. Starts right up, Idles nicely and revs easily and nicely until just before full throttle. Once you hold it full throttle for about 3 seconds it cuts out and almost stalls but if you let off the throttle it will recover and go back to idle just fine and run great again.

It just had the carb rebuilt, new fuel line from the tank to the carb and new reeds installed. All work was done by someone who knows what they are doing. i got a tip that maybe it was the filter in the tank because that line wasn't replaced and when I pulled the tank it was so dirty and nasty I don't know how the saw ran at all. I took a new piece of line and ran it from a bottle to the carb (simulating a clean tank) and it still does the same thing

Anyone have any ideas as to what is going on? Could the tank have been so dirty that it needs the carb cleaned again???


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## spudulike (Aug 31, 2009)

Sounds like fuel starvation at high revs, is your "H" carb adjuster around 1 turn out from fully screwed in? is your tank breather functioning ok - may be causing a vacuum within the tank! Possibly muck in your carb - the dirty filter in theory should filter more effectively to the point it will cause fuel starvation but worth checking your carbs internal filters if they havent been done - am assuming your air filter is in good condition.

Sounds like the carb has enough fuel for a short high speed run and then runs out of fuel and can only support idle speed.

Check petrol and impulse lines.

Worth checking your coil and HT leads - check the coil to flywheel distance - I use two layer strips of A4 paper. Would think spark/HT probs would cause rough running though - favourite is fuel starvation - check the carb/inlet manifold for leaks - ending with crank seals if all else fails:-(

Spud


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## Fish (Aug 31, 2009)

Your first post seems kind of contradictary.

Did the guy that rebuilt the carb know what he was doing?

Sounds like the passage under the needle is partially clogged.


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## Wildman1024 (Aug 31, 2009)

I'm leaning tward the fuel starvation to. I ran a fresh line from the carb to a bottle of fuel and it was still doing it. So all I can think of is maybe the carb is getting plugged again from the crap that was in the tank.

I did notice some bubbles in the fuel line. I blew threw the vent on the cap and it was clear and easy to do so i think thats ok. I really do not think it is an ignition issue because it starts right up everytime and runs great except WOT.


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## Wildman1024 (Aug 31, 2009)

Fish said:


> Your first post seems kind of contradictary.
> 
> Did the guy that rebuilt the carb know what he was doing?
> 
> Sounds like the passage under the needle is partially clogged.



Yes this person defiantly know what they are doing. Maybe it got clogged again from the crap that was in the tank


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## SawTroll (Aug 31, 2009)

It doesn't sound as a typical tank vent issue, but I would take a look at it anyway.......opcorn:


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## Fish (Aug 31, 2009)

Wildman1024 said:


> Yes this person defiantly know what they are doing. Maybe it got clogged again from the crap that was in the tank



Well, that is kind of what I mean..........

So someone put old crappy fuel and a fouled fuel filter on/in the saw after this
guy worked on it?

When rebuilding a carb, you definitely take care of those areas as well.


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## Wildman1024 (Aug 31, 2009)

I understand what you mean and I know the person meant well and knew what they were doing. I don't think they realized the tank was that bad


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## Fish (Aug 31, 2009)

Not trying to bust your balls, but I think your problem is still in the carb.

And don't keep running the saw until you get it fixed.....


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## Wildman1024 (Sep 2, 2009)

A little ball busting is ok! I'll admit I'm still young and learning. I pulled the carb today and it was pretty clean. There was some stuff in the filter but no wear near enough to cause any kind of issue. I pulled the entire carb apart and sprayed it down with carb cleaner and made sure everything was good to go and reassembled.

I gotta grab a new piece of fuel line and filter for the tank before I put that back together and attempt to get it running again. If that does not solve the problem I'm stumped.


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## Scooterbum (Sep 2, 2009)

I had a Mac610 that did exactly that.Turned out it wasn't fuel related at all.
The spark plug wire was shorting out under the cover.

Just something to check........


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## Wildman1024 (Sep 3, 2009)

Scooterbum said:


> I had a Mac610 that did exactly that.Turned out it wasn't fuel related at all.
> The spark plug wire was shorting out under the cover.
> 
> Just something to check........



I'll have to give that a try. If it isn't fuel or that then I'm really lost.


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## pgg (Sep 3, 2009)

If it was a grunged fuel filter, there'll be debris clogged on the small round mesh filter in the carb. Also the saw won't run properly without a filter on the fuelhose end


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## Fish (Sep 3, 2009)

You need to tear the carb down again and remove the needle/spring
and hold the carb up to a light, look through the hole up to the screen on the other side, that passage is likely choked up with gunk, it lets the saw get enough fuel until you get to high rpms, then starves the saw.
Blow out that passage and hold up to a light again. Visually verify that it is clear.


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## Wildman1024 (Sep 11, 2009)

I put the new fuel line and filter on it today and ran it for a few minutes. Still a no go. It still runs great until you hold WOT for 2-3 seconds then it still cuts out. 

I was watching the fuel line going to the carb while I was running it today though. The line was nice and solid/full of fuel until I held it WOT. Once I did that I got alot of bubbles in the line then it started to stall. once it goes to stall and you let off the throttle it will recover and idle but if you try and rev it again it will bog out and stall. Once it stalls its very very hard to get running again

I did take the carb apart again and the filter was clean and the rest of the carb was clean. Fish do you still think I gotta check the needle?


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## Trigger Man (Sep 11, 2009)

I had a maruyama trimmer that was doing the samething you describe and the carb was very dirty, pump diaphram and metering diaphram where shot make sure there's no dirt under the little tab that pushes on the metering lever. you may have another problem not sure. Like fish suggested check for dirt arond the H needle.


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## KRP (Sep 11, 2009)

SawTroll said:


> It doesn't sound as a typical tank vent issue, but I would take a look at it anyway.......opcorn:



Fuel demand at WOT is asking for more, but getting air. A fuel system vacuum is being created at WOT. The vacuum is released after fuel demand drops. It's most likely in the carb, check the needle. Are your fuel lines tight?, where is the air coming from?


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## Wildman1024 (Sep 11, 2009)

KRP said:


> Fuel demand at WOT is asking for more, but getting air. A fuel system vacuum is being created at WOT. The vacuum is released after fuel demand drops. It's most likely in the carb, check the needle. Are your fuel lines tight?, where is the air coming from?




It looks like the air comes from the carb and goes back to the tank but usually gets trapped in the line between carb and tank. It looks like groups of very small bubbles.


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## Fish (Sep 11, 2009)

Fish said:


> You need to tear the carb down again and remove the needle/spring
> and hold the carb up to a light, look through the hole up to the screen on the other side, that passage is likely choked up with gunk, it lets the saw get enough fuel until you get to high rpms, then starves the saw.
> Blow out that passage and hold up to a light again. Visually verify that it is clear.



Yes, you need to do this. At this point, you might want to take another look at the piston through the exhaust.


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## edisto (Sep 11, 2009)

Fish said:


> Yes, you need to do this. At this point, you might want to take another look at the piston through the exhaust.



I'm starting to feel your pain Fish.


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## Fish (Sep 11, 2009)

edisto said:


> I'm starting to feel your pain Fish.



OOO, A little lower, and to the left...... Big guy..........


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## Wildman1024 (Sep 11, 2009)

*Pics*

Are you saying I should be able to see light from under the needle?


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## Trigger Man (Sep 12, 2009)

Is the muffler pluged?


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## Trigger Man (Sep 12, 2009)

Those exahust ports look choked off , I would check the muffler too


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## Trigger Man (Sep 12, 2009)

I'm not saying this is problem but I would still check


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## stipes (Sep 12, 2009)

*Yikes!!!*

That alot of carbon build up!!!! I'm thinkin,,and this might be a shot in the dark,,and I been wrong before,,but if you gotta friend that knows how to check the coil,,I'd do that too.....


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## Brushwacker (Sep 12, 2009)

Another possibility, if the saw has points ( I see you have some older saws ), sometimes the spring in the points weakens enough that at high rpm's the points will not return fully closed. 
I didn't see if you post what model saw this is on.


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## Wildman1024 (Sep 12, 2009)

Brushwacker said:


> Another possibility, if the saw has points ( I see you have some older saws ), sometimes the spring in the points weakens enough that at high rpm's the points will not return fully closed.
> I didn't see if you post what model saw this is on.



Homelite C-9


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## Brushwacker (Sep 12, 2009)

I had a homelite c-5 and c-52 in the mid 1980's. c-9 must be huge.
I remember buying points for 1 of them and they were a Tecumseh part.
That thing does'nt have a governor does it ?
I reread the first post and to me it sounds more like ignition then fuel delivery.


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## Wildman1024 (Sep 12, 2009)

Brushwacker said:


> I had a homelite c-5 and c-52 in the mid 1980's. c-9 must be huge.
> I remember buying points for 1 of them and they were a Tecumseh part.
> That thing does'nt have a governor does it ?
> I reread the first post and to me it sounds more like ignition then fuel delivery.



85cc's and no governor.


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## spudulike (Sep 12, 2009)

That exhaust port is well choked up, pull the jug off and clean it up, also check that the muffler isn't full of carbon and oil as the port looks blocked - this would normally stop the motor reaching high revs but may cause the motor to have the fault you have.

Had a Husky pole hedge trimmer with a blocked muffler - just wouldn't rev at all and no power.

One thing to check is the correct assembly of the carb gaskets - I have had two saws off the bay with the gaskets back to front - just check the servicing guide from the manufacturer - your diaphragm spacer gasket may be under the diaphragm rather than above it thus cutting back the carbs fuel capacity - if the diaphragm has a location dimple on its metal disk with a groove around it then this locates on the yoke on the needle arm - found this out on one of my Jonsereds.

Good luck

Spud


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## Wildman1024 (Sep 12, 2009)

Finally broke down and bought a decent air compressor today. I'll finish going threw the carb tomorrow now and make sure you can eat outta it. 

The tank is all spic and span and the sealer is drying now so tomorrow i'll be able to throw some fuel in it. All new fuel line and brand new filter to. Everything is nice and tight. I'll deal with the carbon build up the best I can from out here. I do not want to pull that jug just yet. Anything I should look out for? If when it all gets back together and still does it then I have 1 last hope. Found a used carb so when that gets here this week i'll swap that out and try that.


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## Brushwacker (Sep 13, 2009)

If you havent, I would pull the flywheel, check the fly wheel key, if the points and condenser are old,replace. If it didn't fix it , you have a tune up when you do get the problem fixed.


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## spudulike (Sep 13, 2009)

Be careful in cleaning out that carbon - if it gets in to the combustion chamber, it may just work itself around the piston and do some damage to your cylinder lining.

Dont forget to check the positioning of all your carb gaskets, it is a common mistake to get them the wrong way round, the saw will still run but not too good.

Also make sure the needle arm is set correctly - the maintenance support pages from most carb manufacturers are usually very good.

Spud


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## AKDriveSprocket (Sep 13, 2009)

Looks like your running to rich. Too much fuel even at the right carb adjustment. Look at the trigger and see if it is hanging lower than your other saws. The linkage to the carb my need to be bent alittle more. I was working on a TS 400 that the linkage needed to be bent to bring it down on fuel. Not sure if this is the right way to fix it but it did fix the TS 400.


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## Wildman1024 (Sep 26, 2009)

*Got it running!!!!!!*

OK it took a little time but I did it. After I pulled the saw apart to the crank case I noticed the plug wire was all cracked and frayed up under the cylinder shroud where you could see. At high rpm's it must have been enough for the spark to jump to ground and cause the stall to want to stall. I was able to get the wire out of the coil and a great member here (matt9923) sent me a new wire ASAP. I epoxied it back in the coil and all is well. Thanks matt for helping me out when I had no real support from the small engine repair shops locally.

Anyways saw runs 100% now and has tons of power with that 24" bar. Don't mind the no recoil cause of course the rope broke after i got the saw back together. Luckily she starts easy since I had to wrap rope and a handle around the crank to start it for the video. Anyone have a new recoil since the one on it wasn't the correct one anyways???? Here is a quick run video. Check the noodling thread if you care to see that. 

Thanks to everyone who was here to give me a hand and get this sorted out and matt once again for the wire 

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/hSr3m4k_Wmg&hl=en&fs=1&rel=0&color1=0xe1600f&color2=0xfebd01"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/hSr3m4k_Wmg&hl=en&fs=1&rel=0&color1=0xe1600f&color2=0xfebd01" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


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## wigglesworth (Sep 26, 2009)

Wildman1024 said:


> Don't mind the no recoil cause of course the rope broke after i got the saw back together. Luckily she starts easy since I had to wrap rope and a handle around the crank to start it for the video. Anyone have a new recoil since the one on it wasn't the correct one anyways????



Real men don't need a recoil......just use your teeth.


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## andrethegiant70 (Sep 26, 2009)

Hey, it doubles as a mosquito fogger!!

Nice saw... I see C-5s, C-51s, C-52s, and C-72s a lot, but I've never seen a C-9. Sounds good and looks good. That's a cool piece of magnesium.


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## Wildman1024 (Sep 26, 2009)

wigglesworth said:


> Real men don't need a recoil......just use your teeth.




LOL yea its really not hard to start with the rope just gets irritating if you gotta pull it more then 2 times.


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## Terry Penman (Oct 12, 2015)

Probably not the carburetor. I had the same problem with the chainsaw running fine until it got to high revs/ high power cuts. Took the ( two stroke ) carbie apart and , sure enough (after 5 years!), discovered that the metering diaphragm was warped and slightly distorted (not surprising I suppose, seeing as the average chainsaw runs between 9,000 & 12,000 RPM, that tiny little piece of plastic must move that often as well!)

Went on the internet to find a replacement kit: two gaskets, metering diaphragm and flap valve, for $15 delivered.

For $21 delivered, I could get a brand new carburetor complete! "No Disassemble Stephanie!" Guess what I got. (within 5 days) 

New carbie,(ie new needles/jets, ergo no junk inside), already had new filter, emptied tank and new fuel, vent cap clear, runs 90% better, needed slight adjustment for idle but still has the occasional high rev cutout. Must either be high speed mixture (stock standard carbie from manufacturer quite possible) which I haven't tried yet , as I only received it 3 days ago, or the magneto. ( I had to replace one three years ago as the retaining bolts had come loose and it overheated and warped but that is fine now. I do, however, have a $12 replacement on it's way, just in case. (At that price, I cannot lose!)

Once I fit that, I will keep you informed as to whether I've determined the "real" problem.

Good luck to all. Hope this post has been helpful.


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