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BF30A Mystery :'(

S

Samav

Contributing Member
Hello guys, its finally time for me to post on here again after going through every trick I could pull out of my hat to figure out yet another problem with my 30+ year old engine. I hope you wizards are more perceptive than me, because I am beyond frustrated and defeated.

Here's the problem: BF30A idles rough, cuts out at low rpm, and sometimes is hard to start after dying at idle. Keep in mind, I have experienced no power loss whatsoever at low, medium, or high throttle. Just problems at idle.

Easy, right? Carbs, obviously. Time to clean them. Did that, no change. Must have missed something, let me do it again. No change. Ok, fine, I'll rebuild them. New o-rings, new jets, new fuel/air mixture screws, new float pins, completely and thoroughly cleaned this time, no orifice was left clogged. Check throttle plates, check choke, all good. Engine isn't hard to start anymore, but still dying at idle. Progress?

Next thought was fuel, tried replacing my fuel in case it was tainted, fuel can was clean, new fuel-water separator, cleaned and replaced all fuel lines, new fuel filter, fuel pump working well, everything fuel wise I double and triple checked. No change.

I noticed my fuel filter was dropping well below half-full the longer my engine idled, but the hesitation at idle and eventual dying will happen well before the fuel filter reaches this point. I tried continuously priming the priming bulb to maintain constant high fuel pressure, and there was no change.

Compression test time. Perfect readings across the board (120 psi if anyone wondered. And before anyone comments that that reading is low, 120 psi has been the steady compression reading across all cylinders for me since I bought this engine. And it has run perfectly for years at 120 psi).

Spark check, all good. New spark plugs anyway. No change

Drop coil test, no apparent issues, Replace coils anyway, no change.

Valves?? Went through the each cylinder at TDC and did valve clearances. All were good, except one, which I fixed. No change.

Vacuum leak? Tuned my carbs and didn't notice any signs of a vacuum leak, still sprayed carb cleaner around intake etc.. couldn't find one to speak of.

TIMING?! Yes, checked the timing, was good, but I still decided to take the belt off and go through the timing procedure again just to be thorough. No change.

Finally decided to do a leak-down test. Yes, I checked each cylinder at TDC of compression stroke. I have a cheap Amazon special leak-down tester, so I don't know if I trust the readings, but after calibrating it I got about 35% loss across all cylinders. Not terrible for an old engine. This is where it gets weird. For each cylinder, when I plugged the leak-down tester and compressed air shot in the cylinder, I could hear air blowing out inside my head. I took the valve cover off, and sure enough, I could FEEL air escaping from my intake valve on cylinder 3. Mind you, my tester was plugged into cylinder 1. Plugged it into cylinder 2, same story. Air seemingly leaking past the intake valve on cylinder 3. Plugged into cylinder 3, same story, BUT I got the same 35% loss in cylinder 3 that I did for cylinder 1 and 2.

So here's my question to all of you. How is it possible that I could have a leaking intake valve in cylinder 3, seemingly connected to cylinders 1 and 2, while still maintaining perfect compression across the board and having even and good leak-down test numbers? My first thought was a blown head gasket, but I would think if cylinders 1 and 2 were leaking into cylinder 3 to that extent, I would have massive power loss and misfiring, which I don't. Also, I would think that the compression readings would be significantly lower across the board, and especially in cylinder 3 where it seems I have a leaky valve. If I can HEAR air leaking past a valve, even when it is closed, compression should be wayyyy lower in that cylinder, and leak-down should show massive loss. And yet, compression is good across the board, leak-down is even and good across the board. How is this possible? Am I just stupid? Please someone help me. I'm out of ideas.

Also of note: I know water and steam coming out of the exhaust is normal, but sometimes it seems like an excessive amount of water and steam are coming out. Nothing crazy just...maybe slighly more than normal? Honesly I can't even tell, but maybe this also points to a head gasket leak. I would think if that were the case, though, I would have water in my oil.
 
Samav,
Sorry you're having such troubles. I know it's very frustrating.

The truth is though, it is pretty obvious this engine has alot of wear. When it was new, the compression was close to 200 psi so 120 IS low. But....it makes power enough to satisfy your needs, so OK. Fair enough. They will sometimes run fairly well with under 100psi compression so I get what you're saying.

The leak down numbers: 35% IS very low and considered excessive. Below 20% is considered "viable" but 15% and under is typically considered "good".

I think you know all this already.

You did this test to gain information and now you have it. This engine seems to be pretty worn but is worn evenly.

The leaking between cylinders seems to indicate head gasket failure or maybe something worse. But I don't really know.

I assume that the leaking you're hearing from the valves is at the valve stems. Could it be that the valve is leaking so badly, that air is charging the intake manifold and is coming up past the other cylinder's open valve?

Try doing the test with the throttle held wide open and see if the "cross cylinder leakage" goes away. If so, it's entirely possible that you might be able to get the valves sealed well enough to make many more wakes with your outboard.
 
Agree with Jimmy, comp should be 180 to 200. Did you do the test with wide open throttle?.130psi will most certainly cause idle issue. You don't mention carb sync, did you check it?
 
Thanks for the responses guys. Jgmo, thanks for clarifying basically my position on this engine. I know that the readings are low, I've posted enough on this forum and heard it a million times, but those readings have been consistent for years without any change, and the engine has always run well enough for my liking (puts out plenty of power, very fuel efficient, has always started first crank, and always idled quietly without any hesitation). This is with 120 psi compression. And yes, iang, I always do the test with the engine at operating temperature and WOT, and I always sync my carbs after I clean them and adjust the pilot screws to their favorite positions. Trust me, I want it to be a carb problem as much as anyone, but I have been pretty thorough in my efforts here, especially fuel side.

Jgmo, interesting idea with cross cylinder leakage. I will perform the test you mentioned and get back to you with the results. Also, I think I'm just gonna spray some soapy water in the general area of my cylinder 3 intake valve and see if I can isolate where exactly the air is coming from. I guess it's entirely possible that there is some hole or crack in the head that I am missing. I'll let you guys know the results. In the mean time, if anyone else has any ideas, please chime in.
 
Hi Samav,
Just fyi....
If you're going to spray soap solution on and around the valve train, using water, a good dish soap like dawn treated with a small amount of glycerin makes better, more easily seen, hearty bubbles.
To protect the metals, spray WD-40 on everything afterwards when cleaning up. WD-40 was developed for N.A.S.A. in my adopted hometown....San Diego... to help prep metals for painting prior to going into space.

The WD actually stands for Water Displacing and 40 is the number of the "batch" that they deemed worked the best.
GOOD STUFF!
 
Jgmo, thanks for the tip with the WD-40, did exactly as you said. Also, I did your cross cylinder leakage test and it made no difference. Anyway, I have determined the source of the air leaving my cylinders to be from the oil drain hole at the bottom of the head, not from my cylinder 3 intake valve. Not sure how I missed that, but to me that indicates a head gasket leak into one or multiple of the oil galleries. It must be quite small as I'm pumping almost 100 psi into those cylinders and only getting a tiny whistle. This would also explain why I'm not seeing any differences in compression readings and why my leak-down test results were the same across the board. Let me know if you guys agree with me or maybe I'm just making stuff up in my head lol. Honestly, at this point I'll probably just tear the engine down to the block and do a head gasket replacement. Probably should do piston rings as well if anyone has a good place to source those. And I'll hopefully reuse the whole valve train as long as the valves and seats aren't pitted to hell. Once again, if anyone has a good lead on where to source parts for such a job for a 97 Honda 30, please let me know. Boats.net has some stuff, but not everything.
 
Well,
I wonder if that leakage is simply piston ring "blow by" into the oil sump?

I agree with you that you will probably need to open it up to try and fix it and that will neccesitate a new head gasket.

But, because this engine seems to be so evenly worn, you might just be able to put in some new piston rings and get some more miles out of her if the cylinder walls will clean up some with a ball hone. I don't know. I'm just trying to "speculate positive" here.

boats.net only lists standard size piston rings available and yumbo-jp said "contact us" when I put in the 0.25mm oversize number.

Make sure to check the crankshaft end play before tearing down. New thrust bearings are available.


I hope you can get it back up and running.
 
35% Is very borderline. If you motor is in good condition corrosion wise I would probably be inclined to do a rebuild. The best priced parts are from Yumbo Parts in Japan, look them up. They have full catalogues same as boats.net only way cheaper.
 
Blow by seems to be a more reasonable explanation honestly. I wonder if it has gotten just bad enough for my engine to finally realize some performance issues such as the idle problem that started all of this. Anyway, thanks for the parts website guys. I'll start looking into doing a semi-rebuild. Just enough stuff to get a little more life out of the engine. I'm moving soon anyway and will be selling the boat. Thanks for all the responses jgmo and iang.
 
Hey guys. Finally finished a rebuild on this engine. Couldn't source new pistons or valves, so I was forced to reuse them :( pistons were in perfect shape but valves were pretty pitted. Old rings were way out, so new rings, lapped the old valves and worked to get them to seat perfect, all new seals, bearings, gaskets, pretty much everything I still could get I replaced. She's all put back together and I was doing the wiring and ran into some issues. I'm hoping someone can lend some insight. I'm good with mechanics, electronics not so much. I only disconnected a few wires from the CDI (charging coil, exciter coil, pulser coil, regulator, and starter) and left everything else attached. I marked everything so I know it went back exactly where it belongs, so I'm not sure what's going on.

My issues are these: the starter is continuously firing when hooked up to the battery. I took the fuse out so I could connect the battery, and if I touch the fuse to the fuse box, the starter fires. The whole wiring harness is hooked up to my controls, and I suspect an issue at the controls since the starter circuit is so simple. It seems like the key switch might be stuck constantly signaling the starter to fire or something, but I honestly have no idea. Also, I'm not getting any spark. To me it seems like also possibly an issue at the controls. Emergency stop switch or, again, possibly at the key switch, since it needs to be in the on position for the engine to send spark. Anyway, I need help isolating this issue. Can anyone give me a run down on what to check and how to check it to get to the bottom of this issue?
 
Hi Samav,

I'll try to help but I don't have a good wiring diagram to work with.

But here goes....

Ignition switch OFF

Disconnect the battery negative cable.

Remove the black with white stripe wire from the starter magnetic switch. Make sure that it can't touch ground.

Touch the battery cable end to the ground post briefly.

Does the engine crank over?
It should not. If it does, the magnetic switch internal contacts are fused together. The magnetic switch is faulty.

If the engine does not turn over when you connect the cable to the battery then check the black/white wire for voltage. It should be 0.00 volts with the ignition off and battery connected.

If you read battery voltage on the black/white wire with ignition switch off, you need to find out why it's getting voltage.

To keep the starter from spinning while you troubleshoot, disconnect the battery ground again and remove the battery cable and other wires from the starter magnetic switch.

Use an appropriate sized bolt and nut to connect all those wires and cable back together and then wrap in electrical tape to insulate them.

This keeps everything supplied with power EXCEPT the magnetic switch and starter motor so that you can safely check for volts at various places.

If you disconnected the bullet style connectors at the top of the engine, make sure that you didn't accidentally plug the black/white wire to the white wire at that location. All those wires are color coded so just make sure all the colors match at those plugs.

If that's all good then you will probably need to next unplug the ignition switch and probe the black/white wire terminal for power.

If there is power at the black/white wire terminal then there is a short to power somewhere in the harness powering up that wire.

If you get 0.00v at the black/white wire then check the corresponding terminal on the ignition switch. It should also be 0.00v.

If there is voltage on the switch side terminal for the black/white wire, then it is likely that the ignition switch is internally shorted and needs to be replaced.

A lot of words, I know!
But I tried to be as clear as possible.

Hopefully this helps you and doesn't just confuse you even more.

Good luck.
 
Good job Jimmy, probably as far as you can advise from a distance. I was just going to mention that the problem has to be on the motor given that it was working fine before. As Jimmy said, recheck all your bullet connectors, it's easy to make a mistake.
 
Thanks Ian! And great point about it working well before. My tunnel vision let that buzz right on by....as usual. ;>)
 
iang6766 said:
Good job Jimmy, probably as far as you can advise from a distance. I was just going to mention that the problem has to be on the motor given that it was working fine before. As Jimmy said, recheck all your bullet connectors, it's easy to make a mistake.
Click to expand...
jgmo said:
Thanks Ian! And great point about it working well before. My tunnel vision let that buzz right on by....as usual. ;>)
Click to expand...
Yes, as it turns out I am an idiot and switched two bullet connectors. No spark was a bad kill switch. Anyway, compression is back to what it should be after my overhaul. I'm happy with everything and it's running well, but it seems I still have the same pesky problem. Must be the carbs hahahaha after all that work.

Jgmo and iang, thanks so much for all your help. I was wondering if either of you could give me a detailed run down on how you would go about cleaning, inspecting, and/or rebuilding carbs, because I am clearly missing something. To reiterate, problem is poor performance at low rpm/idle. Mid to high throttle runs perfectly, absolutely no issues. After poor performance engine bogs if given throttle, then appears to find the fuel it needs and runs great again until you let it idle again and then further fuel starvation occurs and it returns to running poorly. If I don't give throttle after bogging starts, it will eventually die. Pulled spark plugs and cylinder 1 running rich, which I expected, the other two look fine. All the mixture screws are very uneven, but the engine runs best at those positions. Cylinder 1 is, of course, positioned to run the richest, and cylinder 3 running the leanest. That's the settings at which the engine performs best. Let me know what to look at guys.

Fuel pump good, fuel good, no vacuum leaks that I could find.
 
First thing I always double check when there's a problem after cleaning one of these is the little oring at the top of the slow jet tube. It's very easy to pinch or roll it when reinstalling.

If you didn't use new orings there, it's likely that you have a leaker.

If you didn't use lube to install the orings then one or more could be damaged/leaking.
----------------------

Next guess....

This almost sounds like you might have a low float causing minor flooding in one carb. Try shaking them at disassembly to see if you can hear anything inside.

If you have a small scale that you could weigh each one with you might find one heavier than the others.

I don't know how your's are constructed but I've seen the composite floats absorb gas and water before. That makes them weigh too much and partially sink.
--------------------

Other than that, you may have a restriction in the slow air jet. If you haven't spent some effort blowing out the main and slow air jets, do so.

Those are the two holes on the front mount flange closest to carb throat entrance. The slow air jet passages is the one closest to the carb throat and the main is just above it and off to one side a bit.

With these symptoms, I would concentrate on the slow air jet the most.
You will want to LIGHTLY seat the idle mixture screw, prop the throttle wide open and then spray cleaner into the passage while observing to see that fluid comes out ALL the transition orifices at the top of carb throat above the throttle plate.

Once you know that's properly clear get back to me and I will explain how to clear and check the main air jet....if you don't already know that is.
 
jgmo said:
First thing I always double check when there's a problem after cleaning one of these is the little oring at the top of the slow jet tube. It's very easy to pinch or roll it when reinstalling.

If you didn't use new orings there, it's likely that you have a leaker.

If you didn't use lube to install the orings then one or more could be damaged/leaking.
----------------------

Next guess....

This almost sounds like you might have a low float causing minor flooding in one carb. Try shaking them at disassembly to see if you can hear anything inside.

If you have a small scale that you could weigh each one with you might find one heavier than the others.

I don't know how your's are constructed but I've seen the composite floats absorb gas and water before. That makes them weigh too much and partially sink.
--------------------

Other than that, you may have a restriction in the slow air jet. If you haven't spent some effort blowing out the main and slow air jets, do so.

Those are the two holes on the front mount flange closest to carb throat entrance. The slow air jet passages is the one closest to the carb throat and the main is just above it and off to one side a bit.

With these symptoms, I would concentrate on the slow air jet the most.
You will want to LIGHTLY seat the idle mixture screw, prop the throttle wide open and then spray cleaner into the passage while observing to see that fluid comes out ALL the transition orifices at the top of carb throat above the throttle plate.

Once you know that's properly clear get back to me and I will explain how to clear and check the main air jet....if you don't already know that is.
Click to expand...
Thanks for the info. All the orings are good and haven't been damaged. Floats are not filled with any gas or water, and needles are in perfect condition. I have all the carbs apart right now, so I would love to hear your process of clearing and checking the main jet. After playing around a bit, I discovered that one of my carbs had a bad slow jet tube. It was weird because I could see through it like nothing was clogging it, which is why I dismissed it previously, but I couldn't blow any air through it no matter how hard I tried. Anyway, I replaced that with a good one. Slow air jet was definitely clogged in one of my carbs. Got it flowing decent, but just to clarify, I should see carb cleaner coming out of ALL 4 of those little holes above the throttle plate? It's hard to tell, but it seems like it's only coming out of one really strong and the rest kinda weak. If something is REALLY clogging the passages, is there anything I can use other than compressed air and carb cleaner? I know you're not supposed to use wire, but it seems like something is not loosening up in there. I'm debating throwing them in an ultrasonic cleaner. The main jets seem to be clear, but please give me your recommendations.
 
Are you sure that the one orifice that most of the flow you see is coming from isn't the idle port?

Did you lightly seat the mixture screw first?

With the slow jet tube removed, place the tip of your finger into the slow speed hole to block fluid from coming out into carb throat there then spray cleaner into the slow air jet passage.

Leaving your finger in place, cover each delivery orifice (idle, transition and high speed) one at a time with the tip of the spray straw and give them each a blast. Then spray into the air jet passage again and then spray each orifice again. Back and forth, back and forth....in a backflushing exercise.

I also wouldn't hesitate to put it in an ultrasonic cleaner. Those can be very effective. Although
I have found spray carb cleaner usually gets the results I want, I would try anything on a carb that was badly plugged.....including wire.

I mean....it's got to get clean...right?

I don't like using wire primarily because it can break off inside and then you're screwed. So, you need to be careful trying that.


I have not had one that I couldn't bring back from the dead using carb spray and the back and forth method (backflushing) I outlined above. But, then, I certainly haven't seen everything.
 
jgmo said:
Are you sure that the one orifice that most of the flow you see is coming from isn't the idle port?

Did you lightly seat the mixture screw first?

With the slow jet tube removed, place the tip of your finger into the slow speed hole to block fluid from coming out into carb throat there then spray cleaner into the slow air jet passage.

Leaving your finger in place, cover each delivery orifice (idle, transition and high speed) one at a time with the tip of the spray straw and give them each a blast. Then spray into the air jet passage again and then spray each orifice again. Back and forth, back and forth....in a backflushing exercise.

I also wouldn't hesitate to put it in an ultrasonic cleaner. Those can be very effective. Although
I have found spray carb cleaner usually gets the results I want, I would try anything on a carb that was badly plugged.....including wire.

I mean....it's got to get clean...right?

I don't like using wire primarily because it can break off inside and then you're screwed. So, you need to be careful trying that.


I have not had one that I couldn't bring back from the dead using carb spray and the back and forth method (backflushing) I outlined above. But, then, I certainly haven't seen everything.
Click to expand...
Well I spent hours backflushing until I was confident everything was clear. Covering the orifices with my finger to direct the carb cleaner was the trick. It seems either the slow air jet or the slow jet tube was the issue. Man, I hate carbs. Engine is finally running as it should. With the rebuild and finally working carbs, maybe she'll run for another 10+ years. Thank you for everything, Jgmo. You saved my engine once again.
 
Hey! That's really good news!
Glad you got it Samav.

You sound HAPPY!

Yes, I kinda hate carbs too but they were my "bread n butter" when I was young.

I was really intimidated when electronic fuel injection came out big in the 80's but I learned that, at least most of the time, it's much easier than carburetion.

So happy now though that I'm out of the auto repair biz

With the multiplexing and networking complexities of modern cars (think: brake lamp fails...transmission won't shift) you have to be a fairly good programmer if you want to solve problems consistently.
I would starve now!

And
...it's already showing up on outboards!

Cheers sir!
 
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