Running Rich ?

[stsmith]

1978 55 Johnson <br /><br />I just rebuilt the carbs, checked timing and sync. replaced the prop. and I still can not get over 4000 rpms. The idle is lousey. Spark plugs are always wet when I pull them out and check them. Unfortuneatly the slow speed and high speed jets are fixed no adjustment possible. Compression is equal and 105 psi. New fuel pump. Do they sell smaller jets? Can adjustments be put on these carbs. Type IV? Can the reed valves/plates cause a rich acting problem? <br />As you can see I am at a lost for new ideas. The reason I believe it is rich is because the always wet plugs,large fuel consumption and when I ran out of gas a while ago, before it died it ran great for about 15 seconds. It also will not idle less than 1000 rpms. <br /><br />Any and all help or ideas woulld be greatly appreciated!<br /><br />Thanks Smitty

 

[R.Johnson]

Re: Running Rich ?

On that twin cylinder 55, I would pull the cylinder head regardless of what the compression reading was. It's very easy to be fooled by the compression reading on a two cycle engine.

 

[stsmith]

Re: Running Rich ?

I forgot to mention that I put a new head gasket on when I changed the stats. The cylinders didn't look bad.<br /><br />Thanks Smitty

 

[stsmith]

Re: Running Rich ?

I pulled the head and replaced the gasket, cylinders did not look bad. How would it fool a compression gauge?<br /><br />Thanks Smitty

 

[JB]

Re: Running Rich ?

Recheck your carbs, Smitty.<br /><br />Float setting, needle valve seating.<br /><br />It is not unusual for the plugs to be wet with fuel pumped into the cylinders after ignition was off and when the engine is still turning, but you do sound like it's running much too rich and 4 stroking.<br /><br />Other possibilities include fuel being sucked directly into the crankcase through a leaky diaphram in the fuel pump and restricted air flow to/through the carbs. That could be caused by a loose choke assembly.<br /><br />Good luck.

 

[Dhadley]

Re: Running Rich ?

When was the last time it ran right and what was done between then and when it started running bad?

 

[stsmith]

Re: Running Rich ?

I bought it the first of June and have never had it right. Before I bought it I checked the compression, it was good, and equal. and it started right up. it still does. Doesn't really idle bad for a 2 stroke. I have had 2 strokes since the early 70's even had a few 2 stroke cars. (Saab) I took it out again about 4 hours ago to check timing with a load and to decarb it as suggested. 1 can Sea Foam 3/4 gallon gasoline and 2.6 oz oil. run for 15 minutes let it sit for 15 minutes then do it again. Well it went though that gallon mixture in the first 15 minutes. The funny thing is, it ran good with that mixture. but as soon as I put the normal 50:1 back on it started running like dodo again. 1 gallon in 15 minutes thats got to be a record for fuel consumption. It has a new fuel pump on it, put on in June. But I'll pull it again just to be sure its not defective. The reason I changed it was I thought it might be the problem.<br />I have changed gas tanks, fuel lines, plugs, wires, rebuilt carbs, fuel pump, and inline filters. The only othedr thing I can think of is the reed valve/plate, will that cause this type of behavior. And why would it run good on the sea form mixture??<br /><br />Thanks for all the help<br />Any thoughts greatly appreciated.<br /><br />Smitty

 

[Dhadley]

Re: Running Rich ?

A couple of things. Now this is a real silly question so dont take it the wrong way -- are the high speed jets in place? 1 in each bowl, not two in one and none in the other? Trust me, it happens.<br /><br />Although the compression is even it seems a bit low. That could be the gauge or anything.<br /><br />Are you saying it went thru a gallon of fuel at idle in 15 minutes?

 

[stsmith]

Re: Running Rich ?

At this point nothing is a silly question. I wish the high speed jets were not in place then I would know what the problem is, but they are in place. Yes it went through 1 gallon of seafoam mix in 15 minutes.<br /><br />Getting ready to pull the fuel pump this morning, I hope it is defective. (Then I found the problem)<br /><br />Smitty

 

[jim dozier]

Re: Running Rich ?

The only 4 ways I can think of to get more fuel than desired into the cylinder are:<br />1. Leaking fuel pump diagphragm injecting into the intake port.<br />2. Stuck open float valve in carb with fuel running into the venturi.<br />3. Something amiss with the main jet/emulsion tube in the carb causing rich mixture. Check that the engine has the correct jets and that they are in correctly<br />4. Stuck closed choke (or stuck open primer system).

 

[stsmith]

Re: Running Rich ?

Well I pulled the fuel pump from the engine, leaving the lines and the rest in tack. Pumped the bulb till it was rock hard and then pumped some more and did not even get a drop of fuel from the vacumm <br />hole on the pump. However the hole in the block where it connects has a small damp area around it, damp to touch and smells like fuel.<br /><br />Any thoughts<br /><br />Smitty

 

[jim dozier]

Re: Running Rich ?

The hole the pump is connected to is connected to the intake port of one of the cylinders and as a result is exposed to the fuel/air mixutre during operation and would be expected to be damp with fuel. What you don't want (and apparently you don't have) is a leak in the diaphragm injecting unmetered raw fuel into the intake port. Apparently your problems lie in the carbs. Or perhaps you have a non-firing cylinder which would put the motor down on power but continue to suck fuel, may explain the high consumption.

 

[stsmith]

Re: Running Rich ?

Getting ready to pull the carbs back off, but what I don't understand is why it ran so well on the seafoam mix. ??<br /><br />Any thoughts<br /><br />Smitty

 

[stsmith]

Re: Running Rich ?

Pulled the carbs off and the floats are the same as I left them. Hold carb upside down they are level with the body of the carb, float drop is 1 3/8 of an inch.<br />This gasket came in the carb kit OMC 396701 but I have no idea where it goes. Any ideas?<br /><br />

<br /><br />Thanks for all the help guys<br />Smitty

 

[moderator1]

Re: Running Rich ?

Topic: I may have found the problem!! Carb Jets <br />stsmith <br />Seaman <br />Member # 45144 <br /><br /> posted October 21, 2004 03:12 PM <br />--------------------------------------------------------------------------------<br />55 Johnson 55EL78S<br /><br />Talke to an old boy who had a listing on carb jet sizes. He said the listing on mine showed to be .054<br />So I pulled mine and found it to be .062.<br /><br />Does any body know where I can buy carb jets?<br /><br />Thanks Smitty <br />--------------------------------------------------------------------------------<br />Posts: 69 | From: Tampa Florida | Registered: Jul 2004 | IP: Logged | <br /> <br />jimd <br />Lieutenant Commander <br />Member # 18514 <br /><br /> posted October 21, 2004 03:39 PM <br />--------------------------------------------------------------------------------<br />Hope thats it. You should be able to get them from a dealer I would think. <br /><br />PS don't start a new post keep the old one going, people won't know whats going on. <br />--------------------------------------------------------------------------------