550 choke question

RC78

Member
I have an early 550 gas. To get it to run, I have to keep the choke pulled all the way out. Correct me if I am wrong, but I think that means I have either a cracked intake manifold or leaking intake gaskets.

Any thoughts?

Thanks folks!
 
You're either getting too much air, or not enough gas. Usually, its the latter, and its a partially plugged tank outlet, more often than not.

Take off sediment bulb, and see if you get a steady stream from the tank. A fast drip is not enough.
 

She runs a pretty steady stream out with the line off. She has 1/4" fuel line on her, is that normal? My 88 has 5/16" line.

I have checked the jet settings several times, they are still set right. She fires right up every time, just cannot push the choke off.

Thanks guys!
 
Any history to this? Often much easier to diagnose if we know
whether it was OK yesterday and not today or whether the fuel
system has been interfered with recently, etc, etc.

A vacuum gauge may help you diagnose the problem. Simple
gasket failure can often be found by spraying with oil.

You say it fires, but does it run on all cylinders?

RAB
 
90,

Sorry, not much history. I bought it a year and a half ago, it has been like this the whole time.

It hits on all 4 cylinders, at least it sounds like it.

I have been working hard to get my 88 back up for the last 10 days. Now that it is up, I am going to take the 550 out of service and pull the manifolds for a look see. I am going to replace the exhaust manifold with a header, since I cannot find a new one, and mine is broke big time. I'll post what I find.

Of course, if someone has any other ideas, please post 'em! <grins>

Cheers!
 
Not aware of what carb you have, but I once had a marvel
shebler on an 80 which had a boring blocked on the slow speed
side, which stopped it running slow. I think it was all OK if you
could get it onto the power jet side (revs up), but gave up as
soon as back to tick-over. A bit of a job to find as the blockage
was well up the boring. I am lucky enough to have a known
working replacement, so I soon knew it was that carb that was
the problem

RAB.
 
(quoted from post at 20:44:23 11/15/13) 90,

Sorry, not much history. I bought it a year and a half ago, it has been like this the whole time.

It hits on all 4 cylinders, at least it sounds like it.

I have been working hard to get my 88 back up for the last 10 days. Now that it is up, I am going to take the 550 out of service and pull the manifolds for a look see. I am going to replace the exhaust manifold with a header, since I cannot find a new one, and mine is broke big time. I'll post what I find.

Of course, if someone has any other ideas, please post 'em! <grins> there is a nice looking one on ebay right now, chuck

Cheers!
 

Yep, I know that trick, it would be difficult on the 550, there just ain't alot of room in there...(has a loader to make things worse. I have to pull that cracked exhaust manifold anyway, I will just pull the intake to check it out while I am at it.
 
Back in the mid-1980's when I bought my 550, was going through it and rung off the jet by over-tightening. Ordered a new one. It came, marked or stamped with the correct part #; put it in. It would crank up fine, but pulling the throttle also required pulling the choke to keep it running. Got is home, kept looking for trash or something in the carb. Sub-soiled, disked, and sowed 10 acres of fescue for pasture. Looked at that new jet one more time; didn't seem like the hole in it was as big as in the old one. Measured; it wasn't; drilled it out. Didn't have to pull the choke anymore!
 

Dave,

Hmmmmm... I will have to check that.

The carb is the Marvel Schebler. I bought a Zenith to replace the MS on my 88....I am beginning to really dislike the MS carbs after using the Zenith.

Grins!
 

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