Engine Trouble

[Radar67]

I need some help determining what is wrong with my sawmill engine. It is a Briggs 8 HP Intek OHV.
The problem is fuel coming back through the air filter and loss of power. I changed the filter and the spark plug with no change. Checked the oil for possibility of gas in the oil, it did not look or smell like gas had got in the oil. The engine runs with some vibration. Any ideas?

Stew

[Tom]

Check for a stuck float in the bowl.

[Captain]

I'm with Tom.  As I recall, the Intek has a remote fuel tank, with a fuel line to the carb.  With the engine running, grab the fuel line with a pair of pliers, like needle nose pliers, and pinch it off until the engine just about runs out of fuel, then release.  sometimes this action will flush a contaminant from the needle/seat.  If the carb is spilling over, the engine my actually begin to run better as the fuel runs out in the carb bowl.

Let us know!!

Captain

[swampy]

any smoke coming out of the exhaust? If so what color is it?  Black smoke will usually mean it is getting too much gas and you will smell the raw gas coming from the exhaust. Could also be something stuck in the valve seat like a chunk of carbon. Ed

[sawguy21]

I am with Tom and Captain. Remove the air filter, start the engine and you will probably see fuel coming out of a small hole in the carb throat. That is the bowl vent and the fuel indicates a stuck float/inlet needle.

[Radar67]

Thanks guys, I've been doing some research on the net and everything is pointing to the float or seat as everyone has suggested. The only other possibility may be an adjustment of the valve clearances. I'll check the float first thing in the morning.

Stew

[Radar67]

any smoke coming out of the exhaust? If so what color is it?  Black smoke will usually mean it is getting too much gas and you will smell the raw gas coming from the exhaust. Could also be something stuck in the valve seat like a chunk of carbon. Ed

Ed, there is a little black smoke coming from the exhaust on start up.

Stew

[swampy]

Stew,  If the black smoke goes away after startup I don't think it would be a carb problem. If the intake valve is open just a hair when the exhaust valve opens to release the used vapors out of the cylinder it will cause some of the air flow or exhaust back into the carb. If there is any gas left in the carb at that time it will blow it back on the filter. This is just a worse case deal. I would do as Tom suggested first and if that is not the problem I would do a compression check on each cylinder. That will tell you if the problem is internal or not. Ed

[edsaws]

Stew heres a link that may help http://m-and-d.com/helpfaq.html?id=QNQvxmPJ
Also get the model numbers off the engine and go to their online parts finder ( on the left of page in yellow) if you need to get parts for the carb or motor. I've used them recently for a carb rebuild fast service.

[jack]

I had a similar problem with a Old Kohler and i was advised to run the engine get it to operating temp.  Then carefully pour a smidge of water down the carb.  The combustion and the heat of the water/gas mixture cleared the buildup of carbon.  That cleared up the bad running problem.........ALSO CHECK the Muffler......clogged mufflers will mess up the running also.

take care
Jack
  Dirtdoctorjak@aol.com

[Tom]

You've been real lucky so far.  I remember, as a kid, some of the remarks I would get when I had a problem with my plymouth.  Somebody would study it real hard and say something like, "what you need to do is take that gas cap off and put a chevrolet under it.". ;)

[leweee]

Tom's comment reminded me of a u-fa-misum for Briggs & Staton from an oldtimmer.

Stew....Give that "Bolts & Scrapiron "a kick for me too ;)

[Murf]

Tom, my Grand-dad used ta' like ta' say the problem was "the loose nut behind the wheel"...... :D

[Radar67]

Stew....Give that "Bolts & Scrapiron "a kick for me too ;)

The problem was not the float or the seats. The fuel is coming from the overhead valve body. The valve clearance seems to be the problem. In the process of adjusting, I broke a bolt. And guess what, of the five shops I called, no one kept the rocker arm bolt in stock. The last place I checked, I ordered the bolt. The owner told me that he has never had my particular size engine come in and has not heard any bad info on it. The local Briggs salesman happened to be in the store and had good things to say about my 8 horse. (he could have just been saying that) Considering no one carries parts for it, you have to figure not too many problems with it.

As for scrapiron, just as Tom's Plymouth, all brands will have problems. Each of us has a personal preference, so brand doesn't matter. If I had my way, I'd put a 350 Chevy on it.  :D

Stew

[highpockets]

radar,
How was the fuel coming from the overhead valve body? I am lost here

[Radar67]

The fuel was coming from the overhead valve cover via the breather tube that connects to the back of the air filter plate.

Stew

[sawguy21]

How is fuel getting in there if the crankcase is not flooded?

[Radar67]

How is fuel getting in there if the crankcase is not flooded?

That's a good question, one I can't answer. I'm not a small engine mechanic. From what I know about car engines, I would figure the valve clearance was allowing the gas to come through. The engine was running, so I would think the intake valve was at least opening partially and the exhaust valve was pretty close to clearance. My thought is the gas was building up behine the intake valve (allowing enough through to fire and run) and spilling over in the valve cover. With the breather tube disconnected, no gas in the air filter chamber or carb throat, connected, gas in the chamber. Why the gas didn't run down into the block (oil) is beyond me. The oil level was the same when I noticed the problem as when I did my pre-run checks. I see a small engine course in my future though.

Anybody else got any theories?

Stew

[highpockets]

Radar,
I don't mean to be a pest but that doesn't sound right. I am not a specialist but have been working on and building engines for 45 years and I am concerned. Now having said that, I have had a 20 H.P. Honda on a mill that has eaten on me lately. 

In two cases in the past couple of years, I have experienced some strange delution of oil by gasoline.  When I got this mill back in my shop after some years, the oil looked like water.  I also have two 18 H.P. Kohlers.  Last year I brought one of them in to clean the carb. I happened to check the oil level and found the engine full of gasoline.  I am talking full.  What had happened was the fuel tank was above the carb.  While sitting some months, the gasoline had bypassed the card float and flooded the engine. 

If you are getting gas into the overhead covers and it is being sucked in from the carb, I'd think filter restriction of some sort.  What about crankcase ventilation?

[GF]

My brother had a new Honda 5.5 on a power washer that the crankcase filled with gas also, since it was under warranty he took it in they said the fuel pump was bad and put a new one on it and that took care of the problem. 

[Radar67]

Radar,
I don't mean to be a pest but that doesn't sound right. I am not a specialist but have been working on and building engines for 45 years and I am concerned. Now having said that, I have had a 20 H.P. Honda on a mill that has eaten on me lately.

If you are getting gas into the overhead covers and it is being sucked in from the carb, I'd think filter restriction of some sort.  What about crankcase ventilation?

This is my theory, someone correct me if I'm wrong, please!!!   ;D

My tank sits above as well, it is fitted with a fuel cut off switch. During normal operation, the fuel should be gravity fed into the carb bowl, allowing the seat to deliver fuel to the carb. Air intake from the filter (which is created by vacum from the piston) delivers gas to the intake valve, which is sucked into the cylinder on the downstroke of the piston (while the intake valve is open). On the up stroke, the fuel air mix is compressed and the plug fires, creating the combustion. The piston travels down, then on upstroke, the exhaust valve opens allowing the excess out. (on a four stroke, the piston makes 4 revolutions to get one firing cycle)

What I think is going on with my engine is when the intake valve opens, it is not opening far enough because the clearance is off (over .010, the specs call for .005). The gas that does not make it into the cylinder is traveling back up the valve guide to the rocker arm area. The breather tube connecting the valve cover to the air filter is sucking that excess back into the air filter (visually verified) and the carb. There is enough fuel getting into the cylinder to combust on firing, but it is not enough to generate the power needed to operate at prescribed RPM. The breather tube is picking up enough of the fuel to keep it from draining into the crankcase. That's what I think is going on. I'll have to wait for my rocker arm bolt to come in before I can test my theory. If the clearance is the problem, once the bolt is replaced and the clearances adjusted to specs, the engine should run normal, if not, I will have to rethink things.

The only crankcase ventilation I find is the breather tube from the valve cover back to the air filter plate.

I'm basing my theory on what I know about how V-8 Chevy and Ford engines work. Small engines are new to me and I have done only a small amount of research on them.

Stew

[GF]

FYI
   I purchased and engine from this site in the past and was very pleased, sometime their special section has some pretty good prices.  http://www.smallenginewarehouse.com/

[D._Frederick]

Radar,

I don't think that your valve clearance being 0.005 inches out of spec is causing your problem. You may have a leaking head gasket, I would check the engines compression and see what it is.

I hate to tell you your engine theory is off, a 4 cycle engine makes 2 revolutions not 4.

You said that your engine has a lot of vibration, could you have an ignition problem that is causing the engine to miss? If it isn't this, you may have something broken in the crankcase.

[Radar67]

Radar,

I hate to tell you your engine theory is off, a 4 cycle engine makes 2 revolutions not 4.

could you have an ignition problem that is causing the engine to miss? If it isn't this, you may have something broken in the crankcase.

Thanks for correcting me, I was adding the two upstrokes and downstrokes to come up with the four.

Could I have an ignition problem? yes, the fuel flowing back into the air filter is re-entering the carb and causing the plug to foul. ( dry black, sooty residue) As for the valve clearance, I know .005 over is not a lot, but the specs call for .005, that makes the the valve not open enough (almost none at all) to intake all the fuel/air the engine is needing. If you have a valve stick closed in a one cylinder engine, the engine won't crank.

I would think I would hear some type of knocking or other odd sound if something in the crankcase was broken. At least that is the case when something internal breaks on a big engine.  ;D If the valve clearance doesn't solve the problem, I will check the engine compression, although it is cranking on first pull.

Stew

[Paul_H]

the fuel flowing back into the air filter is re-entering the carb and causing the plug to foul. ( dry black, sooty residue)
Stew

The 20 hp Honda on my resaw started over fuelling due to a haywire needle and seat in the carb.I have the tank suspended over the engine and run gravity and it filled the crankcase with gas because I didn't shut the fuel off at night .I drained and changed the oil but the engine still wouldn't run right because the needle and seat was allowing too much gas into the engine and it ran rich,which sooted up the plugs.

I'm sorry if I missed it in your posts but what have you done to rule out the needle and seat causing your problems?

[leweee]

The 20 hp Honda on my resaw started over fuelling due to a haywire needle and seat in the carb.I have the tank suspended over the engine and run gravity and it filled the crankcase with gas because I didn't shut the fuel off at night .I drained and changed the oil but the engine still wouldn't run right because the needle and seat was allowing too much gas into the engine and it ran rich,which sooted up the plugs.

Same thing happened to my Honda 20 hp motor. Seems the bean counters at
Keien carbs decided that a brass seat was not needed....they use the carb casting as the seat smiley_dunce smiley_dunce smiley_dizzy....to make a long story short I lapped the seat area and it worked again

[Radar67]

I'm sorry if I missed it in your posts but what have you done to rule out the needle and seat causing your problems?

I took the float bowl off and removed the float and needle. Then, I sprayed carb clearner through any hole I could find. I also made sure the float did not have gas in it. The float bowl was clean as a whistle when I removed it, no sign of trash or gumming. I have left the fuel valve on a couple of times, but did not notice a rise in my oil level. My engine's oil level is fill to overflowing. No spillage when I take the cover off to check oil before running.

Stew

[Fla._Deadheader]

How did you check the float level ???

   That is one of the most precise things about an engine.  Also, the .005-.010 clearance on the valve is not that great a deal. That is the clearance between the tappet and valve stem, so when the engine heats up, the valve doesn't swell enough to eliminate all clearance and burn the valve head-seat. I wouldn't worry too much about that clearance. Still sounds like a carb problem to me.

[Radar67]

How did you check the float level ???

The float is plastic. I looked at the amount of fuel in the float bowl and checked to make sure the float wasn't stuck by pushing on it and making sure it lifted up and down smoothly. There wasn't any type of adjustment that I saw. Some of the older floats where made of metal and had a metal bar you could bend. I could only estimate the float's level by the amount of gas in the bowl (about 2/3 full) The float should "float" level in the bowl, is that correct? What is the correct way to check the float level?

Stew

[Fla._Deadheader]

These newer engines are getting beyond my knowledge. If the float is hung on a pin so it swings up and down, and is attached to the top of the carb, you hold the top of the carb upside down and eyeball the level of the float against the level of the carb top. It should be just a hair higher than level with the carb top. That way, it gets to slowly adjust itself as the engine wears out along with the needle.  There almost HAS to be a way to adjust it  ??? ???

  If it's not made like I have described, ignore my input, as most here already do.  : : ;D ;D ;D  Good Luck  ;) ;D :D :D

[Radar67]

If the float is hung on a pin so it swings up and down, and is attached to the top of the carb, you hold the top of the carb upside down and eyeball the level of the float against the level of the carb top. It should be just a hair higher than level with the carb top. That way, it gets to slowly adjust itself as the engine wears out along with the needle.  There almost HAS to be a way to adjust it  ???

Okay, I have not removed the carb, that is something I can do while waiting on my bolt. The float does hang by a plastic bracket that comes from the carb body and a steel pin goes through the bracket and the float. I'll have to study a little harder on the float to see if I can find an adjustment. Who knows, they may have it designed where the length of the needle regulated the float.  :-\

Stew

[Paul_H]

Same thing happened to my Honda 20 hp motor. Seems the bean counters at
Keien carbs decided that a brass seat was not needed....they use the carb casting as the seat smiley_dunce smiley_dunce smiley_dizzy....to make a long story short I lapped the seat area and it worked again

I think you will either have to replace the needle and seat or do what Lewee did and I'll bet the problem goes away.

[Radar67]

I hate to say it, but we were all wrong. Turns out, the exhaust lobe on the cam shaft was worn off, and I mean really worn. And the tappet/lifter was cupped. I've ordered the parts to repair it. Thanks for all your help.

Stew

[Fla._Deadheader]

That sure is discouraging news ???  How many hours, approximately on that engine ???

[Radar67]

My best estimate on hours is 50. I purchased the saw used. The original owner said he only cut 2 or 3 cherry logs, but I don't know that for sure. As for me, I've cut about 500 BF with it.

Stew

[Fla._Deadheader]

Man, and the cam lobe is worn off ???   NOT GOOD.  : : : ??? ???

[Minnesota_boy]

Make some phone calls.  Let the manufacturer know what happened.  That cam didn't get the proper heat treatment.  That happens and it usually gets replaced under warranty.  With calls to the right place that may happen for you too.

[Fla._Deadheader]

I agree. That's some BAD publicity, especially on the number one Forum on the 'net.  : : ;)

[Radar67]

I wanted to pass on my experience with customer service for http://www.m-and-d.com/

Due to Briggs and Stratton being closed for the holiday season, I had to find other means to get the parts to repair my saw. I'm in the middle of my first paying job.  :

Wednesday evening I went to M and D Mower's website and found the parts I needed and ordered them (about 4:00 pm) They had closed for the day. First thing Thursday morning, I called customer service to verify their shipping method. I have different addresses for US Postal and the delivery services. They told me my order would ship via UPS, FedEx, or DHL. I made sure they had the correct address to ship to. I made no mention that I needed the parts ASAP.

I was expecting the parts to arrive Monday or Tuesday due to the holidays and the parts coming from Ohio. Much to my surprise, the parts were delivered today (Friday) before noon via Airborne Express. Needless to say, I was very impressed.  ;D And what did shipping cost me you ask???? A mere $6.95 for STANDARD SHIPPING. I will direct all my business to this company in the future.

Thanks for all the help everyone gave me. I should be back in business tomorrow evening after work.

Stew