Surging Idle on a new Moyer Exchange A4

[Sloopdogg]

Hello all,

I'm still tinkering with the idle on my Moyer A4. This will be my 3rd season with it. I've probably ran it less that 50 hours as I have only burned up 2 tanks of gas. I have never been able to get this thing to idle reliably with out the impending threat of a stall...

I usually run seafoam fuel treatment in almost everything I own. It really seems to keep things running smooth and in the case on my lawn equipment it has helped thing run even better. It is also a fuel stabilizer. I read a review in a boating mag and they were pretty happy with it too.

Anyway, I can only get the engine to idle between 900 and 1000 RPMs, Measured with a contact meter on the shaft at the front of the engine. However, the engine has a bit of a surge and fluctuate beteen about 930 to 1050 rpms and has a tendency to stall. Especially if I bring it down to idle too quickly. It is really a PIA especially for docking and catching the mooring. I was able to shift into reverse and into forward while idling and it didn't stall. So, this is an improvement over last year. I could get it into reverse but not forward without giving it more throttle to prevent stalling last year.

Can anyone give some advise on a way to make idling less worrisome and maybe get even lower reliably?

Here are a couple of links to videos of it running so you can hear it surging.

http://1drv.ms/1o5fL7E

http://1drv.ms/1o5gsOb

As for the stalling coming down from idle, I feel like it needs a dashpot or something that would dampen the throttle...

Anyway thanks for any and all inout

[ndutton]

As a test, have you tried running the engine with an outboard gas tank with fresh gas and no additives? I'd probably disassemble and clean the carb as part of this test.

I can't help but think although you have a fresh rebuild it's fuel comes from the old fuel system, same goes for the exhaust.

[Sloopdogg]

As a test, have you tried running the engine with an outboard gas tank with fresh gas and no additives? I'd probably disassemble and clean the carb as part of this test.

I can't help but think although you have a fresh rebuild it's fuel comes from the old fuel system, same goes for the exhaust.

Well, the old fuel tank, yes. It is definitely not the original fuel tank as it is plastic. So, at least we know we didn't get any scale from a metalic tank falling in, right? I did pump it dry of all old liquid and then fill with treated new fuel. I also replaced all the fuel lines and separator filter so, not completely old system.

[sastanley]

Sloop, I would do a thorough carb cleaning first..You need to find a nice skinny piece of wire to get the idle jets cleared...there is one on each side of the main butterfly valve in the carb. They are notorious for collecting gunk and causing idle problems.

[Sloopdogg]

Sloop, I would do a thorough carb cleaning first..You need to find a nice skinny piece of wire to get the idle jets cleared...there is one on each side of the main butterfly valve in the carb. They are notorious for collecting gunk and causing idle problems.

I have a freshly rebuilt carb on board. Maybe I should swap that out?

[romantic comedy]

Can you hook up a vacuum gauge. See if you have a leak. Check the timing also.

[ndutton]

Be that as it may, I still recommend a test with a clean carb and fresh unadulterated fuel. Even if there's no improvement it's still good information, we'll know that isn't the cause.

I attended a Perkins marine diesel seminar decades ago and the instructor discussed fuel additives. He said depending on the amount of fuel you use, you put a little additive last season, a little this season and a little more next season. At some point you have more additive than fuel and your engine runs like shi-shi.

I was pretty impressed with this instructor. He was the only one of several professionals I asked who could answer why the head bolt torque on the Perkins 4-107 was roughly twice that of the Perkins 4-108 (same engine, later version).

edit:
There was no mention of a PCV system, correct? (Hey, no groans, at least not yet)

[sastanley]

Sloop..yes...Neil & I have different suggestions..recommend you do one at a time. Since I am lazy, I'd pick which ever one is easiest and do that one first...if there is no change, try the other.

I also like Seafoam, although I do not run any in the boat. I use it in all of my small yard engines.

I found a local source for ethanol free gas, so I am running only a bit of Sta-bil in that..one ounce per 5 gallons.

[Sloopdogg]

Okay, I'll try the suggestions and see how it goes.

I did have the PCV system on there but, have since removed it with no improvement. I did not re install the PCV kit.

[ndutton]

I did have the PCV system on there but, have since removed it with no improvement. I did not re install the PCV kit.

Also good information.

[Dave Neptune]

Adjustment

Do you have points or an E/I ign? If points try advancing the timing a tiny bit. I'd also make sure that the c-advance is working. Timing can often cause poor idle quality.

Surging is usually an over-rich indicator. Take a look at the plugs and if they're black or sooty open the idle mixture screw to lean a bit, start with a 1/4 turn at a time. If you have tried adjusting with no joy the idle passages may have an issue.

If your carb is correct the PCV will have no influence on idle quality.

Dave Neptune

[Sloopdogg]

Do you have points or an E/I ign? If points try advancing the timing a tiny bit. I'd also make sure that the c-advance is working. Timing can often cause poor idle quality.

Surging is usually an over-rich indicator. Take a look at the plugs and if they're black or sooty open the idle mixture screw to lean a bit, start with a 1/4 turn at a time. If you have tried adjusting with no joy the idle passages may have an issue.

If your carb is correct the PCV will have no influence on idle quality.

Dave Neptune

I have the updated moyer engine with Electronic Ignition and electric fuel pump

[Dave Neptune]

Info

Danny, have you ever moved the distributor to set the timing?

Check to see that the C-advance is operational.

Have you tried to lean the idle at all by "opening" the adjustment screw?

Dave Neptune

[Loki9]

I was pretty impressed with this instructor. He was the only one of several professionals I asked who could answer why the head bolt torque on the Perkins 4-107 was roughly twice that of the Perkins 4-108 (same engine, later version).

Different head gaskets?

[Sloopdogg]

Danny, have you ever moved the distributor to set the timing?

Check to see that the C-advance is operational.

Have you tried to lean the idle at all by "opening" the adjustment screw?

Dave Neptune

I have not played with the timing at all.

What is the C-advance?

I have played with the adjustment screw and it did help. maybe I should open it a bit more and see if it continues to help. Basically it seemed to raise the idle a bit when I "leaned" the screw out (or Open) and then I was able to bring the throttle down a bit more and this is how I was able to get it down to under 1000 rpms. I was concerned about leaning it out too much. What are the effects of too lean or should I open it until it falters and then bring it back in?