Screaming high RPM's

[NorfolkRagbagger]

Been reworking a frozen engine (reference http://www.moyermarine.com//forums/s...ead.php?t=4369) and have made starter turns after a week of oil and prybar, got compression, and now, starting (after a lot of rotations to finally get it started.) Started for the first time today on full choke, then choke off and after a brief time raw water inlet opened, the engine idles at about 5,000 RPM. This is no exaggeration. Scares the hell out of you, and no way to slow it down. Cable adjustment from throttle is full forward (accelerates even faster if throttle move to higher speed - ooooohhhh no) , even checked with cable disconnected and throttle lever full forward, as in idle position. Idle is not high, it's seriously around 4 or 5 thousand RPM (no tach). I shut the engine down after a second or 2. It's not the throttle cable position.

Yesterday a friend and I (more him, he knows what he's doing) disassembled the carb (late model Zenith) and cleaned everything as the bowl was full of oil after filling the cylinders for a week trying to unfreeze the engine. All was cleaned out with CRC Carb and Choke cleaner including removing jets and blowing cleaner through them, then reassembled and assembled to engine. (Got a serious feeling the root of the problem is there some where)

As the cable is not the culprit, all I can think that is making this thing scream is the innards of the carb. Any idea what we did wrong, and more importantly,what to fix? I'm on my own for the fix for the next few days - I'm not an Atomic 4 expert but am learning the ropes REAL quick. As always, you guys (and girls) are a wealth of information - I'd appreciate your input.

[ndutton]

Nfrb,
Except for no control and possible detonation, it sounds like it's running pretty well, yes?
The only way I can think for runaway revs to occur is uncontrolled air and fuel, and strangely, in the right proportion.

This tells me you've got a wide open throttle butterfly or a huge air leak between the butterfly and the jet. It seems the carb is metering the fuel properly for the massive volume of air. Remember, the throttle only controls the air flow (since we don't have accelerator pumps), then the carb meters the proper amount of fuel for that volume of air. To get the right amount of fuel for the air volume it has to be coming in before the jet as the jet does the metering.

So, when you think the throttle is closed, is it? For sure? Butterfly closed? Regardless of where the cable might be? I think a nekid eyeball looking down the throat of the carb might be in order. Use a mirror if necessary. Take a picture. Please post it.

[Al Schober]

Hey NR,
There's no spring pulling the throttle arm closed - The only thing closing the throttle is the throttle cable. With the engine off, disconnect the throttle cable and make sure the throttle is closing. If your throttle are comes up from the shaft, fwd is the closed position. Perhaps the throttle plate fell off the shaft?? You'll have to drop the carb from the manifold to check this, as all you can see through the air inlet is the choke - even with a mirror. Then, reconnect the cable (both ends secure on both wire and jacket?), making sure the cable pushes (pulls?) the throttle shut (and then some).

Al

[tenders]

Put a really big prop on it with adjustable pitch and don't worry about the throttle.

[ndutton]

Perhaps the throttle plate fell off the shaft?? You'll have to drop the carb from the manifold to check this, as all you can see through the air inlet is the choke - even with a mirror.

It's been a while since I had my carb off and I completely forgot that the butterfly was where it mounted to the intake. Sorry for that bad bit of information.

[NorfolkRagbagger]

Thanks!

Neil - be sorry for NOTHING and thanks for the comments. The problem and solution should have been obvious to me. Too much air = too much fuel = runaway RPM's. Don't know why I didn't grasp that. Disassembling now. I do like the big prop idea - then I can take the mast down and get under lower bridges. SHORT memo only to follow when all is solved. THANKS ALL.

[ndutton]

Hey, a man's gotta do what a man's gotta do. When I'm wrong, I'll fess up. Been wrong before, will be wrong again. Hell, I'm married, wrong all the time!!

I'm sure you'll find the issue at the butterfly. It's about the only place that'll let that amount of air in and it has to be going through the carb to get the proportionate amount of fuel.

[roadnsky]

Wait! This might start a revolution...

I'm thinking we should take Tenders' big variable prop idea and run with it a bit further...

Think about it...
You're sailing along minding your own business.
Along comes a big over-powerd boat with a knucklehead paying no attention at the helm.
Crosses ur bow and makes you frantically change tack.
Hmm, what to do?

Well, fire up the higher rpm A4 and set the prop to max.
Head after him (and with sails still up) go do donuts around 'em!

Might even be able to get Tom at Indigo to design the new prop?
Just food for thought...

[hanleyclifford]

Is this the time to start talking about adding a few items to the Wish List ,like bolt on turbocharger for the A4 or maybe electronic fuel injection?

[ndutton]

Along comes a big over-powerd boat with a knucklehead paying no attention at the helm.
Crosses ur bow and makes you frantically change tack.
Hmm, what to do?

Well, fire up the higher rpm A4 and set the prop to max.
Head after him (and with sails still up) go do donuts around 'em!

Good friend of mine has a Cadillac CTS-V that's a hobby car for him. He's swapped the engine for a bigger block, swapped the Magnusen blower twice goin' for bigger, had the drive line (to handle the power) and brakes (to stop the beast) replaced. It currently dyno's right at 1000 HP yet is a total sleeper, completely stock appearance.

He can blow the doors off just about anything on the street and not by a little. These guys with the big bucks cars as well as the ones with all the hot looking goodies and do-dads plastered all over are in disbelief when grandpa's Caddy blows by.

I talked him into putting a child car seat in the back and one of those yellow diamond shaped window signs that says, "Baby on Board" just to demoralize the competition further.

[NorfolkRagbagger]

90% there!

Took the carb off, tightened the two halves, studied the OEM engine manual (!!! - I have one!) and followed the beginners menu. Manual says "If the adjustments have been altered, start with the standard settings which are": 1) throttle stop screw (1.5 turns IN from closed), 2) idle needle valve (one turn out from seated) and 3) main jet adjustment (2.5 turns out, mine was all the way in). Reinstalled carb and cables, started the little bugger, and she runs fine. "Idle" is now about 1,000 + but I can handle that by the conventional advice found here. Started repeatedly at this speed, accelerated normally, needs tune to get to lower out-of-gear idle. THANKS ALL!! Now I have a 28" x 30" 4-blade prop for sale! (Didn't get to do the donuts - dang!) (last week it was frozen up!! Viva la A4 community and the Moyer Forum Group!)

[hanleyclifford]

[QUOTE]
He can blow the doors off just about anything on the street and not by a little. Neil - Not too many recognize this expression from the "good old days". Regards, Hanley

[ndutton]

Yeah, really dates me. Here's another one - went for a ride and when he stepped on it, it put me in the trunk!