Carb/Governor/Throttle Issue on Nissan 36HP CG13 Engine

[nblumberjack94]

Hello,
I've run into an issue with the engine on my LT40.
It was spitting and sputtering, not wanting to start. My brother in law who's a mechanic came over and with some manual operation of the throttle/carb linkage, he got it to start.
However, it wanted to run away from us, at max RPM.
It also seemed to not run smoothly, so we went over the spark plugs and wires. Nothing seemed obviously out of line.
One thing that we could see that WAS broken was a like white plastic cog/gear like part, connected to the throttle/carb linkage. It was missing some teeth.

Unfortunately, since the Nissan engine was only put on mills from '00-'05 there's very little help I've been able to find. My local Woodmizer rep is doing some digging, and I'm trying to find anything I can to help get this resolved and get back to milling.

Had anyone ever had this issue?

Another option; maybe it's the governor?
I'm not mechanically inclined, so I am entirely out of my depth.
Any information, or wisdom is greatly appreciated.

Cheers

[rusticretreater]

What engine do you have?  Also, can you post a pic of the linkage and the broken part?  Thanks.

[nblumberjack94]

The engine is a Nissan CG13, Twin Cam 16 Valve, 36HP, family 1NSXB01.3340.

I took a bunch of photos, however they will not upload for me, so they are at this Google drive link: LT40 Nissan Engine photos

[Ben Cut-wright]

There are a few posts relating to this engine.

https://forestryforum.com/board/index.php?action=search2

Was the intake pipe removed to inspect choke operation?  The mechanism may be holding the throttle open. Does the governor attempt to control the throttle lever? 

[rusticretreater]

I'm kinda amazed that they used a plastic gear in the throttle assembly like that.  Certain to break down the line.

If the gear is missing some teeth it certainly isn't going to do its job well.  Also from above it looks like the gear and the pawl that moves it are misaligned.

Unless I'm mistaken, the carburetor is a what is called a variable venturi design.  A venturi goes from a wide opening to a narrower one.  At a rate of constant air flow, the air must move faster through the venturi to keep up with the wider opening.  This creates a vacuum and is what pulls the fuel out of the carb jets into the air.   This carb appears to have a smaller secondary venturi that comes into play when the engine is accelerated.  Basically, the carb gets bigger when you need more power.  Remember that this is actually a car engine that is put onto a sawmill.

When your engine is revved up, the pawl pulled by the accelerator cable opens the throttle plate.  But that white gear driven by the pawl opens up the smaller secondary venturi.  This provides more air/gas to the engine when accelerating. 

If this gear has jumped teeth, it may be holding the second butterfly open when it should be closed.  So when the engine starts to run, it is not regulated as expected and too much air/fuel gets into the engine so it accelerates.  Another scenario is that the vacuum from the engine tries to pull the secondary venturi butterfly open.  The white gear is meshed with the pawl holding it steady.  If the gear is missing teeth, then the butterfly can be pulled open and the engine put into acceleration.

Put another way, when you try to idle the carb says no, we're going 50mph.

As the engine is pulling too much air/fuel when you try to start it, it doesn't want to start because things aren't right.

At any rate, you need to replace that gear and tighten up the linkage for a start. 

[nblumberjack94]

Copy that.
Thank you!


Has anyone had to source any parts for a Nissan Engine similar to this? If so, where at?

[KenMac]

I don't know about your local auto parts stores, but here we have a couple that will go above and beyond to find parts for a customer. One is a NAPA and the other is O'reilly. That's where i'd try if google was no help. Good luck in your search!t