vanguard 18 surging

[Patrick62]

It has been a busy time, otherwise I would have gotten on here more often in the last few months...

The homemade splitter that ended up with a 18hp vanguard is finally getting some attention.
The idle circuit got me into the carb the other day, and I got that cleaned out nicely.
Next thing was it really wanted to RUN after that. played with tension on springs, until I finally decided that the governor was just "out of adjustment"
Ok, let's get that shaft to where it will actually adjust the carb... That is working correctly now, next was to get the tension up to where it would hold something around 3000 or a little more rpm. Which revealed the next conundrum. I get a surge... it will settle down to a steady speed, but a load sends it to surging for awhile.

from a almost closed throttle, cracked open a bit, it should go a bit lean? no?
When the throttle finally gets opened up enough the rpm comes up, causing the governor to close the throttle...

I am trying to figure out what I need to change just a little, and I mean a "little" to get this thing to run nice smooth and steady.
It is that close... Plastic float, but I might shim the needle and lower the float a touch, see if that helps. it would answer questions...

It seems that it has to be rich tho, because adding some choke makes things worse.
ok, if I were lean the main jet just a tiny bit.... maybe just try a small wire in it...

The 18 runs very smoothly, and should not even notice the 22 gpm pump on it. I know I could run it a touch faster than 3100 or so, but there is a reason I run it a little slower.

 

[Patrick62]

Well, I will go try a experiment...
IT has to be going lean... so I am gonna work the main jet over with a acetylene cleaner tip, and see if getting it just a fuzz larger helps.

maybe see if I can do something with the idle, which actually seems pretty close.

 

[Aknutter]

Try running it without air filter. Fuel tank/filter clean, lines not collapsed.
Fresh fuel, new plugs correct oil viscosity? Try putting some seafoam in the fuel.

 

[Patrick62]

Well... I stuffed the wire tip cleaner down every hole I could find.
Did not really "enlarge" anything, atleast not more than a scooch.
Still surged. The short answer, for now, is to just leave the idle screw up kind of high.
Don't let the throttle drop all the way down. That improved things to where it didn't surge much.
I can atleast run it now. WIth a the governor actually doing speed corrections the splitter is working a lot better. what I had before was essentially just a set throttle position...

I ran it until it ran out of fuel, and in that time... I had another idea.

propane conversion??

 

[biggerstaff94]

This might sound dumb but have you sprayed carb cleaner around the intake to check for vacuum leaks? The intake split at the seam on my 16hp in my Bolens and it surged pretty good.

 

[dave_dj1]

tune the carb with a load on it
\

 

[Patrick62]

Well, I have been running it for several cords now, since the twiddling.

Essentially, the situation is the 18hp vanguard is complete overkill on this machine.
After the china diesel gave up the ghost, I said "we ain't gonna run short on power now".

So, once the linkage and springs are set up and the governor is actually willing to adjust the speed of the engine, this is the result.
Drop a block in there, or hit reverse, whatever. a light load... The governor senses that the rpm has decreased, and it cracks open the throttle. Which causes the 470cc worth of pistons to go nuts...
It over speeds a little, which causes the governor to drop the throttle out. which is too slow...
which causes the governor to open throttle...
I thought about it, a dashpot would do it nicely. I might see if I have one laying around.

Leave the idle set a little "high" and it is workable. throttle can't drop below the minumum, and then it can settle down nicely, after a "surge".

what would be a fun upgrade would be to switch the cylinder out to one with a 4 1/2 bore instead of the 5 inch I have on it now, and get larger than the 1/2" ports, which restricts the oil flow somewhat.

But it works...