1999 F50TLRX Noise

[ChuckB1954]

Bore-scope just to rule out the pistons hitting something inside the cylinders.

you have to wonder why those carbs were sold
someone parted out a motor due to some bad thing happening to it.

Did you go thru the carbs before installing on your motor?
was this the 1st time the motor was started with these carbs?

I found out My C40 closed up the gap on #2 spark plug last week.
not all of the way, but it started an erratic miss firing .

I will run it out on the water today after cleaning and regapping the plugs.
I may need to find a bore scope and inspect my cylinders also

I'd pull one plug wire at a time (ground to engine) and see if the noise lessens...

That noise is too regular and sounds as if it's being amplified thru the air box..

And nothing would last that long bouncing around the combustion chamber..

The carbs were from a blown engine according to the ebay seller. I think he said it threw a rod.

I don't think you could find a better set of used carbs if you tried, although I only removed the bowl from the #4. I have little doubt that the others are just as nice. I know the effect of this engine running with bad carbs. That is what started my adventure in the first place

My plan of attack..

Look at the plugs and check for something I might have overlooked externally. I will also do the plug wire test.


I will recheck the valve adjustments. I picked up some new gages tonight. If I see something wrong with the valve adjustments, I will correct it and run the engine.

Just to verify if a screw is in the cylinder, for my piece of mind, I will loosen the carb assembly and peer into the throat to verify the screws are all there. I well also account for the other two screws from the other #4. Very doubtful though, The noise does not indicate that, It is coming from front, at the intake box. I would think if something was in the cylinder it would ping and be coming from the rear of the engine, where the cylinders are

I will let you know my results.

[99yam40]

what I would worry about on the carbs from a blown motor is what caused that other motor to chunk a rod? .

would not a lean running cylinder cause piston damage and possibly a rod to come out of the block?

[panasonic]

Assuming you changed the oil / filter when you got the engine and still have the old filter, you could cut it open and see if the engine is making metal.

[zenoahphobic]

That noise sounds to me going at half speed, ie cam shaft speed.
I would have said you loosened the tappers, and somehow when you pushed it lessened. I would check all that again and check the torque on the cam blocks and cover.
The popping is of concern and may very well indicate a tight exhaust tappett (not fully closing).
There is a proper position or crank angle that checks and adjustments should be done. I don't know at what angle this is but suspect this a possibility that you did this wrong.

[ChuckB1954]

Yes an engine running too lean for a long. time can definitely do some internal damage. I will look at the plugs. That will tell me a lot.

I checked the oil when I first changed it and saw no evidence of metal. I never took the filter apart but I think it's around somewhere maybe I will do that.

That noise sounds to me going at half speed, ie cam shaft speed.
I would have said you loosened the tappers, and somehow when you pushed it lessened. I would check all that again and check the torque on the cam blocks and cover.
The popping is of concern and may very well indicate a tight exhaust tappett (not fully closing).
There is a proper position or crank angle that checks and adjustments should be done. I don't know at what angle this is but suspect this a possibility that you did this wrong.

Yes I think everything points to the valve adjustment. I used the specs that were on the valve cover decal, and used the midpoint tolerance.. I performed the procedure by the book.. point the casting Arrow to number two on the flywheel and then adjust the two pertaining intake valves Along with the two pertaining exhaust valves. Then you turn the flywheel around until number 4 is pointing to the casting, and adjust those pertaining valves. I would be very surprised if they were out of adjustment though. but then again it was the only thing I touched besides the carburetors.

I checked the cam blocks and they were nice and tight.

I did notice something that I thought was strange. I could push down on one of the valve stems with my thumb and make it move easier then I thought it should be. You would think that would be very hard to do. Never thought about it again until right now.

[99yam40]

I guess a weak, collapsed, or broken spring could not close the valve as it should, but I have not heard of that happening much

[TownsendsFJR1300]

I did notice something that I thought was strange. I could push down on one of the valve stems with my thumb and make it move easier then I thought it should be. You would think that would be very hard to do. Never thought about it again until right now.

How hard is it to push the other valve stems?

IE, compare them but I wouldn't think it'd be that easy. With a possible broken / weak spring that valve would float and make a racket.

Was that valve an INTAKE spring? That would likely resonate back thru the intake (more so then an exhaust valve)

[ChuckB1954]

Thanks everyone for your input.


I've been working long days, so I have been getting home late. I haven't had a chance To do any further investigation but plan to do so in the next couple of days. I will keep y'all posted.

[zenoahphobic]

I think you have your answer and suggest you look at those valves again. I don't know anyone with strong enough hands that can push down a valve!
As suggested rare for spring to break, but we are all aware of the possibility . Could also have something to do with the collet and washer; maybe your pushing dislocated them.

[ChuckB1954]

When I was outside tonight, adjusting my valves I realized that I made an error when I was describing how I did the adjustment. The correction is shown below in red. And no, I didn't make a mistake adjusting my valves, only a mistake when I earlier posted the procedure.

"I performed the procedure by the book.. point the casting Arrow to number ONE on the flywheel and then adjust the two pertaining intake valves Along with the two pertaining exhaust valves. Then you turn the flywheel around until number 4 is pointing to the casting, and adjust those pertaining valves."

Anyway, I checked the valves and they were all within these specs: intake .008 (specs: .008 +/- .002) and the exhaust to .012 (specs: .012 +/- .002) I will readjust them on the loose side though.

The springs appear normal with all of them the same tension. I guess that is how this engine is. They are not easy to compress, just easier that I thought they should be.

Then it started raining and I had to quit.

I was going to post my results later, but I wanted to bring attention to my error. Maybe a moderator can correct it.

[ChuckB1954]

I worked on the motor again today between the rains. Before I tell you what I discovered about the noise, let me show you some maintenance I did. I checked the valve adjustments and they were fine, but I readjusted them again anyway. I surrendered to the fact that the spring tension is normal and me being able to press them down with my thumb is also normal. All of them are like that and all appear to be in good shape.

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I have always wanted to check the timing. To do so, you have to remove the flywheel, stator and the magneto base. I went for it. I was hoping the timing was off a tooth for going to all this trouble, but it was as it should be. After looking at things, I realized that all you have to do to check the timing on this engine, is to point the #1 on the cam sprocket (not shown) to the arrow on the casting and look at the timing mark on the flywheel. It should point to zero, which is TDC. No need taking everything apart\, as I did. The book never mentions that. The second picture shows the proper position for the crankshaft sprocket. The hole lines up with the casting arrow below.



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Not a waste of time though. Not only did I have to use the puller to break the flywheel loose, I had to use it to get it completely off. It was very rusted up. A little sandblasting and paint and it was new again. This was probably the rustiest area on the engine so I was glad I removed the flywheel after all. I also de-rusted all the related parts in that area.

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[ChuckB1954]

The stator had a few broken isolator tabs, so I used some epoxy.



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[ChuckB1954]

Now, about the noise. I put everything back and the noise was still there. I pulled the plug wires one at a time as suggested. When I pulled the wire from the #2 cylinder, the noise went away. Also there was no noticeable affect on the running engine. The RPM's never changed, nor did the sound of the running engine. I then put the plug wire back and went to the other side of the engine. I turned the air mixture screw on the #2 carb all the way in and the noise went away. Again, no affect on the running engine. For the heck of it I switched the dual coils with one another.. no change. To me, this points to the carb, as this noise never happened with the old cabs. If not that then it could be the cylinder. One way to find out is to pull the carbs (again) and look at them, especially the # 2 carb. What do you think?

Could the diaphragm, #1 shown below cause this problem? I have a spare.

EDIT: In the service manual, they call it an accelerator pump, so I am probably barking up the wrong tree.

dia.JPG

[TownsendsFJR1300]

Sounds like #2 is the issue with no RPM change. (or at least a running / power issue)

Can the old carb for #2 be cleaned up and installed?


It certainly can't hurt to swap the diaphram, easy enough. Dunno if that's issue with the noise.


BTW, just for S & G's, check the #2 cam that the lobes are "there", and not gone... Just compare the amount of lift to the valve compared to another cylinder. Probably not going to be..

[99yam40]

it would be interesting to know what cylinder chunked a rod on the motor that those carbs came from.

I would go thru all of the carbs, but that is just the way I roll.

hope cleaning the carbs solves you problems.

have to wonder what chewed on that stater , and where /why all of the rust up on top. water should not get to that under normal situations.