422 Robin eng...problems AGAIN.

ldabe · Jul 30, 2009

Went to fire up the PT and would not start. Just kept cranking over and over. Had to get ready to go somewhere so I left it till the next day.
Fired right up!
But, started sputtering and also had greyish white smoke come out of the muffler.
It wanted to die if I throttled full, then it would do better as I moved throttle back down, almost to idle.
I took the cover and filter off of the carb, and it was spitting fuel (lightly, off and on, not a steady thing) out of the port to the side of the carb as you look directly at it from the top.
It always has seem to run rich, but I think, for some reason it is really rich now. So much so that it is spitting excess.
Before I search the forum for others that have had similar problems, or go to the Robin site, can anyone help with this?
Do I need to try and adjust something? And where would that adjustment be?

Thanks in advance.

Gator6x4 · Jul 30, 2009

Do a engine compression check, you could have either a bad or leaking valve.

ldabe · Jul 30, 2009

Gator6x4 said:
Do a engine compression check, you could have either a bad or leaking valve.

Is that with 2 breaths to every 15 compressions? ;~)

Just kidding. But I have no idea of how to do that, much less if I even have the tool (if tool needed) to do it.

Not very mechanical.

But thanks for the suggestion.

Gator6x4 · Jul 31, 2009

My next suggestion would be to have someone with mechanical skills determine if the problem is internal or with Carburetion. Given the cost of parts today, it can get very expensive quickly if one starts turning screws or making adjustments without knowing what the consequences of their actions or the outcome of adjustments or modifications made is going to be.

Marks481 · Jul 31, 2009

Stuck float or sticking intake valve. My vote is stuck float valve, which is much easier to fix then the sticking intake valve.

Engine compression test is easy. You need a compression gauge, which you can buy at any auto parts store for $25 or so. It must have an adaptor that fits 14 mm spark plugs (almost all do). Search Amazon for "JABETC compression tester" will show you one for $30.

You take out a spark plug and thread it in the hole, then turn over the engine with the starter. The compression gauge will put a pointer on the highest pressure it sees. You should see something like 110-120#. Repeat for the other cylinder.

westcliffe01 · Jul 31, 2009

And hold the throttle on the carb fully open while cranking to get the cylinder compressiion. Else you are building up a high vacuum in the intake and will get low compression readings even if the compression is good.

Not doing this is a neat trick for getting un - savy consumers to spend money on rebuilds that they don't need.

ldabe · Jul 31, 2009

Thanks guys! I will try and get me one of those testers soon. First, I think I will ask a couple neighbors if they have one to borrow.

Also, Tim, should I check the "float" first, or do the test first?

ldabe · Aug 1, 2009

Was in the barn doing some work, took a break, went over to the PT to see what it would do today.
Throttle - full
Choke - off

Turned the key, had a small pop, and immediately fired right up!
Ran great at full throttle, no choke, for about 45 seconds.
Then, began to sputter. Got worse over next 20 seconds.
Throttled to half-throttle, seem to even out...until about another 20 seconds.
Trottled all the way down, and engine died!

First, a question for "MossRoad" (and others that never seem to have a problem with their eng).
- Do you have a gas cock shut off valve under your gas tank, and do you use it?

Second, now that I think about it.....this seems to be what was going on when I had a piece of junk (object) in the bottom of the gas tank a couple months back! I think I will try to look at that possibility today if I can work in into the schedule.

Thanks again guys for all your knowledge and advice, especially for a "mechanically challenged" fellow like myself ;~)

westcliffe01 · Aug 1, 2009

If you can start the engine cold with no choke I suggest it is flooded. In fact, the procedure you describe is exactly what to do with a flooded engine. But once you burn off the accumulated fuel it will go lean and rough and probably quit. You sould try adding some choke and if it smooths out, the first paragraph is confirmed. Once it is warm, open the choke (it should start "hunting" which indicates the misture is too rich).

Could well be that the needle is not sealing on the seat. Could be due to dirt or plain wear and sometimes they just never work out of the box (had this on an outboard after installing a carb rebuild kit). The priming bulb would never get firm and fuel would overflow into the intake.

I have a generator with a robin engine and it starts first pull every time.