Is it running on BOTH cylinders?

Walt Conner

Yes, Walt. It will run just fine on either cyclinder and has 90 lbs of compression on both cylinders. To check the compression, I started it on the remaining cylinder and it had 90 at idle and went to 150 with throttle. Just turning it over without starting it, the compression was also 90.

Thanks

This engine requires periodic valve adjustment. I do not see where you have checked that and valve adjustment may not even be the problem but should be checked anyway.

I have pages from the B&S Manual that I can send IF you like. Address below, put in proper format.

Walt Conner
wconner5 at verizon dot net

Motokid,i don't think 90 psi is enough to sustain a load. I have a briggs 21 hp that reads 150 on both cylinders by just cranking it over e few times. I may be wrong,it just doesn't seem right to me and this could explain your condition.

Walt, I've checked the valves three different times both hot and cold. I've seen very little change since the first reset. This did make a difference in the way it was running though.
Swamadcat, I have no idea what the compression should be running, so your input was important. This engine only has 160 hours on it, but its previous owner did very little in the way of care, so I'm not surprised if the compression is down. I'll try checking it again wet (three squirts of oil in the cylinders) and see if it comes up. If anyone else has any input on what their compression is running, I know I'd like to hear from you.
Thanks again for your input. My next efforts will be to see if the compression will come up with wet cylinders. I'm still perplexed about having to choke it to keep it running. I would have thought that 90 lbs would have been enough to create the vacuum necessary to run without the richer mixture. I have checked around the intake manifold to see if I could find any leaks using engine cleaner (basic disillate or diesel) but I never got any smoke from the exhaust when I did that. So, I'm going to assume (bad assumption probably) that the intakes are sealed for now and go with Swamadcat's input on low compression.

Thanks Everyone!

Good Morning Everyone- I'm retired so I have plenty of time to work on the little tractor. I just ran my compression checks and after finding that my 'O' ring on my compression gauge wasn't sealing properly I found the little engine to be in real good shape. "Dry" the compression on both cylinders was 160 psi. After adding oil to the cylinders the compression went to 185 psi "wet". This was with both plugs removed and turning it over with the starter, so this confirms what you were saying, Swamadcat. I believe we can move on to any other thoughts you might have now.

Thanks again for your help!

I have an old B&S 16 HP tractor that with starter cranking only yields about 85 lbs compression per cylinder. That said it's got lots of power & doesn't bog down at all.
I also went through a similar problem with a small Tecumseh powered rider & found a problem eventually in a partially obstructed main jet plus poor gas flow out of the tank itself. It would surge & stall out under load, needed choke to idle.
Finally I have a question regarding battery charging on that B&S. The diode on the DC side of the connector was blown so I replaced it with one off another old Briggs but all I get is 9.5 V DC. What should the AC volts be off this stator on the coil side of the diode? Could I solder this diode onto the AC (headlight) side & be able to charge the battery -never used headlights -just wait till tomorrow!
Thanks, BC in BC

A better way to check for "vacuum leaks" at the intake or other suspicious places is to use spray carb cleaner. While the engine is idling, spray a small amount of carb cleaner around the gasket seam or other suspicious place. If a vacuum leak exists, you will notice an immediate change in the engine RPM (usually more RPM).

Can you observe the operation of the governor linkage and whether it is functioning correctly? The governor should allow the throttle plate to be wide open with the engine not running if the "throttle control" (this is whatever you would set, pull a knob, or move a lever, to increase engine RPM during use) is moved to the fast position.

Most issues where the engine fails to produce power, or rev up under a load, but otherwise idles ok, can be linked to a blockage or obstruction in the main jet circuit.
Because you have replaced the carb, one would believe that the carb is not an issue, but the fact that partial application of choke improves RPM somewhat......sort of disputes that. Check the operation of the governor to make sure it is permitting the throttle plate to open fully when the engine is off but the throttle control is moved to the high speed fuel position. Do this with the operator controls, not with the linkage on the carburetor.

I have read articles of people having issues with the governor gear coming off inside the engine. They would running fine one moment and not the next. I hope thats not your issue, but its not to bad to fix. I am glad to see you have good compression. 160lbs sound much better. If your governor is working fine.I agree that you could have some kind of restriction in the main jet circut

Hi Again Everyone! Just finished running my vacuum leak tests again using both starter fluid and carburetor cleaner. Used a generous amount without blowing the tractor up but it never did come off idle. Used the 'swizzle' stick and put it in every seam where the manifold attaches to the block and where it attaches to the carburetor without one change. Also ran it around that "wonderful plastic manifold" without any change as well. Am going to try my "auxillary" gas tank again that I use to tune my motorcycles with. That way I can bypass anything from the gas tank up to the carburetor. I'll be able to use gravity flow with it.

Thanks again for your inputs. I'll keep you posted on any successes. Would appreciate any inputs that you might have.

Thanks, Motokid

Sorry, forgot to add on my last follow-up that I checked out the governor and its working just as you said, Mownie. Dead still it opened the throttle plate up wide open. Also observed it opening it wide open when I tried to transition from idle to half throttle and it was struggling without the choke on. It acts like when this transition is ocurring that it wants more fuel to gain RPM but the gas isn't there to mix with the air properly. This says main jet BIGTIME, but you'd think a new fuel filter and carburetor would at least afford you the luxury of operating properly for some amount of time. After the fuel supply check with the auxillary tank, if that doesn't work, I'll go into that new carburetor......man, I hate to do that!

Thanks, Everyone!

That really sounds like a fuel pump , but since you changed it ,i would have to rule that out. How about the tube that drives the pump? Have you checked your flywheel key? Just a few more options
Is that carb the non-adjustable one?If it is pay close attention to the tubes that drop down into the bowl

Swamadcat, I replaced the fuel pump with a known good one and it didn't seem to change a thing. I checked the tube today and it appeared to be in good shape, although, I think those things should fit a little tighter than they do. I pulled the flywheel and checked the key several days ago and it was in really good shape. Yes, its the non-adjustable carb that's just a hunk of aluminum. I assume you're referring to the two brass tubes that go inside the plastic tube that the main jets fit into. I haven't had this new carb apart yet, but, if and when I do, I'll be sure to clean those. I had used a needle and compressed air on my old carb, but it didn't make any difference.

I used my auxillary fuel tank today and bypassed everything in front of the carb.....gas tank, fuel line & fuel pump and let it gravity flow. I had no success whatsoever.

Thanks for your input!

thinking "outside the box" for a minnit.. be patient :)
any possibility that there is a restriction in the exhaust end of things ?

With a gravity fed MC auxiliary tank feeding the carb, you are pretty much looking at fuel starvation due to blocked mainjet circuit. When you get into the carb, be sure to remove the main jet and clean the bore it threads into. I've seen a few cases where a carb was "cleaned" by someone and when I took out the main jet, there was all kinds of junk in the cavity the main jet threads into.
Just to confirm that it is getting insufficient fuel volume, see if you can get it to rev higher by spraying a few short bursts of spray carb cleaner into the throat of carb while you open the throttle. If all that's wrong is the amount of fuel being fed to the engine, it should rev hingher when you spray the carb cleaner into the induction stream, provided you are also opening the throttle when you spray.

Mownie, today while I had the engine running full throttle, I sprayed some carburetor cleaner AND starting fluid into the intake and it choked it down rather than speeding it up. Not for sure what that's about, but that's what happened. Spent most of today readjusting the valves in accordance with Walt's instructions, took off the exhaust pipes and inspected them and the exhaust ports and found all to be clean. And last but not least I broke into the NEW carburetor and found........NOTHING. It was clean as a whistle, but I used a good portion of a can of carburetor cleaner and some compressed air just to make sure. I did confirm that the intake manifold was indeed sealing and that was good news. I have now buttoned it up and set it aside. There comes a time when you must say enough is enough. I've spent the better part of two weeks and over $200 trying to fix the problem to no avail. I'll let a swap jockey see if he can switch out enough parts to locate the problem. Thanks go out to all of you who have done your darnest to help me out. If and when I get a solution, I'll get back in here and let you all know what they found.

Thanks again!

Motokid

I feel your pain. I too have 21 hp briggs that won't stop popping thru the carb at idle.I have a small leak at the throttle shaft,but i just don't think its enough to cause my issue. I have cleaned my carb 3 times to no avail.I have heard stories of good mechanics unable to save these unadjustable carbs. My last step in my trouble shooting is to break out the wallet and buy a new one against my better judgment. Its the only way of knowing.
Back to your issue,i'll add a few more thoughts.
The flywheel key, did you check it? Are all your rocker arms moving the same amount. Partialy wiped cam lobes on the intake side would make a motor weak. Mine had a lobe wiped almost completely off on the #2 cylinder. Here is a quik test: Pull a plug wire off while its running, there should be almost no change in the way the engine runs.

"Are all your rocker arms moving the same amount. Partialy wiped cam lobes on the intake side would make a motor weak. Mine had a lobe wiped almost completely off on the #2 cylinder"

Now there is a good idea, checking the amount of rocker arm/valve movement.

Walt Conner

Thanks for the come back, Swamadcat. I think you have hit the nail on the head and that is the reason that I pulled out on it today. I have checked the flywheel key and it is fine. Now, to what I think the real problem is. This morning while setting the valves once again, I noticed that neither of the intake rockers were moving much. So I drug out my trusty measuring stick and measured the movement of the intake rocker arms.......less than 1/8th of an inch. Since I had nothing to compare it against, but the exhaust rockers, I decided that it either had to be due to the decompression system they use or the cam was rock solid BAD. Since I knew that this would entail pulling the engine and tearing it apart on the bench I decided to just set it aside. Is there any way to confirm what the movement would be with a known good cam?

Thanks, Motokid - in Texas too

The valves should depress the same amount. My cam has the decomression built into the cam on the intake lobe. It doesn't have anything to do with the amount it opens but when it closes. My intake valves stays open .002 up until the piston get almost to the top. Sounds funny i know, but the engine won't crank all the way over with out it. I am guessing when it comes up to speed it doesn't have any effect on performance. After doing some reading, i am not alone with wiped cam lobes. It is more common than i expected. Its an easy change by the way.you can damn near leave the whole engine complete to do it. You do have to remove the valve covers and remove the push rods. Other than that it just case bolts. A new cam is about 70 bucks

Yah, sounds like bad cam. B&S has furnished new ones free even though the warranty period has past BUT they generally require the work be done by authorized dealer which wipes out the savings of free cam.

Walt Conner

The Tractors Forum does it again. Ordered the new cam this morning and we'll get it in when it gets here. I don't have a service manual, but it appears that I will be able to put it in from the top without removing the engine from the tractor. Would appreciate any comments regarding its installation.

Thanks to everyone who contributed to the discussion while we were trying to figure out the problem. Especially, Swamadcat, Walt and Mownie. You hung in there after I gave up the ghost. I will post again after I get the new cam in and let you know how the little tractor runs.

Thanks again!

Motokid

"it appears that I will be able to put it in from the top without removing the engine from the tractor. Would appreciate any comments regarding its installation."

Hmmm, I thought you had gotten a response on this yesterday. NO you can not do that.

Suggest you go to the B&S site, put in your model and type number and look at the exploded view of your engine.

Walt Conner

Thanks, Walt. I could have sworn that I saw where you could get in from the top when I removed the flywheel to check the key the other day. Oh boy, its the hard way or no way it looks like. Oh well, just as long as we get it repaired. Got the cam on the way, so won't be long now.

Thanks again, Walt!

Motokid

Motokid check your other post. I made some comments on changing your camshaft
http://forums2.gardenweb.com/forums/load/tractor/msg0814022713925.html?1

I have a similiar issue to this. does anyone know if it was the cam?

I seriously doubt it.....

Online, there is much info/details that go ignored.....

That is the danger posting here.

Fish