Question about 1955 restoration

[parshman]

I have been restoring a 1955 cd-12 5.5 hp and have replaced about everything inside. I have followed the instructions on converting to the mikumi pump, have thoroughly rebuilt everything but one problem remains; I can't get it to keep running. I have started it and run it, but when I give it some throttle it immediately dies. I rechecked the point gaps, plugs, (whole magneto is new) new wires, fuel hose (installed new connectors and no leaks) so I am thinking that the conversion is not resulting in the correct vacuum necessary, or that the fuel/oil mixture is too heavy on the oil. Any suggestions? Like I said, everything...EVERYTHING is new on this thing, and it has run, and I have tried to adjust the high and low speed needles starting them out as directed, but no dice. I have seen fuel/oil mixtures suggested at 16:1 and 24:1. I am at 16:1. HELP! I love this little motor and want to get it on the back of my new 14' Tracker Topper (First new boat )

 

[1946Zephyr]

Re: Question about 1955 restoration

I happen to own a couple of those CD-12's myself. Nice little motors. Mine need restoring, but they run.

I'm thinking that your fuel pump is not keeping up with demand. Where do you have the pulsator line hooked in at? I have seen the Duckworks trick, but I still believe in the method of using the intake port or bypass cover. What I would do, is disconnect the line to the carb and put the end in a jar. Get it started and see if it pumps fuel into the jar. If not, then you might need to re-locate your pulsator line.
16:1 is the best mix ratio on that, so you're doing fine there.

 

[parshman]

Re: Question about 1955 restoration

Thnk you for your response. This motor is a 1955 CD-12 so it does not have the removable cover that I have seen used to drill and tap for the connection nipple. I currently have the vacuum line connected to the barb under the fuel intake manifold. Today I purchased a vacuum pump tester at Auto Zone for $25 and I am going to test it tonight. If there is sufficient pressure, then I will know the problem is elsewhere. If not, I wonder why. I know there are two ways to get the suction; one is the vacuum cap inserted, and the other is to fill one of the air channels from the cyclinders. I think my next step will be to try a different blockage method if this doesn't work. It is frustrating becuase I know the engine is right, and the only funky thing is the conversion. I suspect the conversion is the culprit. I will post my findings tomorrow. Thanks again for your comment!
(Sometimes I think working on these old motors is like hitting yourself on the head with a hammer; It feels so good when you stop! :facepalm

 

[HighTrim]

Re: Question about 1955 restoration

Nah, youll miss it.

Cant tap the bypass covers on the 5.5 as you know, they are not removable, you have to use the intake modification route. Which method did you use, the vac cap or the sealer in a channel? Which pump did you use?

While the conversion may be to blame, Im not convinced it is. The fuel bowl will hold enough fuel to run at least 30 seconds. If it dies when throttling at first startup, there may be another issue.

What are your needles set at? How did you set your float?

 

[parshman]

Re: Question about 1955 restoration

Again, thank you for your assistance. The needles are set with the low speed one turn out, and the high speed 1.5 turns out. The float was set to be level. I used the method where a vacuum line plug is used to block one of the holes behind the fuel manifold cover to create the vacuum. Tonight I am going to:
1. Check the vacuum pressure between the Briggs and Stratton pump and the vacuum barb on the manifold.
2. Remove the carb (again) to be sure no stray bits or debris has clogged a jet.
3. If these two things fail to make a difference, I am going to take another look at the plug wires to be sure all the connections are (still) sound.
4. If it starts and runs good I'm going to dance in my driveway like an idiot. I don't care who sees me.

 

[HighTrim]

Re: Question about 1955 restoration

You removed the check valves right?

 

[HighTrim]

Re: Question about 1955 restoration

4. If it starts and runs good I'm going to dance in my driveway like an idiot. I don't care who sees me.

Reminds me of a Saturday afternoon a couple years ago. I had been struggling to get a stubborn AC35 to run. When it finally did (at 10pm) I proceeded to fist pump in the driveway yelling "Im the greatest boat mechanic in the world!"

My wife was so ashamed.

 

[bbstacker1]

Re: Question about 1955 restoration

Again, thank you for your assistance. The needles are set with the low speed one turn out, and the high speed 1.5 turns out. The float was set to be level. I used the method where a vacuum line plug is used to block one of the holes behind the fuel manifold cover to create the vacuum. Tonight I am going to:
1. Check the vacuum pressure between the Briggs and Stratton pump and the vacuum barb on the manifold.
2. Remove the carb (again) to be sure no stray bits or debris has clogged a jet.
3. If these two things fail to make a difference, I am going to take another look at the plug wires to be sure all the connections are (still) sound.
4. If it starts and runs good I'm going to dance in my driveway like an idiot. I don't care who sees me.

I think I would try reversing your needle settings and see what it does. Most of mine want to have the low speed open more than the high speed.

 

[HighTrim]

Re: Question about 1955 restoration

I think I would try reversing your needle settings and see what it does. Most of mine want to have the low speed open more than the high speed.

True was going to mention that when I got laughing at my old story.

Low speed 1.5 turns out from lightly seated, high 3/4

 

[nwcove]

Re: Question about 1955 restoration

id also try a gravity feed straight to the carb. very simple to do.....and it will tend to point you in the right direction for trouble shooting the conversion.

 

[1946Zephyr]

Re: Question about 1955 restoration

Yes, the old 5.5's don't typically lean sneeze like the bigger motors. If the needles are too lean, they just loose power or die. Low speed is 1 1/2 turns out and 3/4 turn out for the high speed. After you get it running right, these will tend to set leaner to offer a smother operation.

The only good way to install an air nipple for the actuator line in a 5.5, is to do it, while it's disassembled. Otherwise like HighTrim says, you'll need to use the one on the intake manifold. According to duckworks magazine, I believe you remove the rubber piece inside, so it won't push the air only one way. A fuel pump needs to push and pull, in order to work the diaphram.

 

[parshman]

Re: Question about 1955 restoration

You removed the check valves right?

Yes, the check valves have been removed. I put in a vacuum line plug on the left side as you look at it, and put some sealant around the edges to prevent air leakage. Now correct me if I'm wrong, as mentioned above, if I disconnect the hose going from the fuel pump to the carb and crank the engine, fuel should spurt out of the line, right? If it doesn't, then I have an air leak somewhere that is affecting the vacuum pressure. I bought a vacuum line tester yesterday, and that should tell me what's going on in the line definitively. Last night I pickled 4 quarts of cucumbers, so I didn't work on it. Tonight I will tackle it. By the way, all you guys rock for being so helpful. Thank you so much for your support.

 

[parshman]

Re: Question about 1955 restoration

id also try a gravity feed straight to the carb. very simple to do.....and it will tend to point you in the right direction for trouble shooting the conversion.

That sounds like a good idea on a couple of levels..it will point me in the right direction as you mentioned, and it will do my spirits good to hear it run. I had actually taken it to be worked on, but it just sat on the ground for two weeks so I picked it up. Mechanics, I am learning, do not want to work on these old engines. I have heard every excuse. "Parts are hard to find, (untrue) We just don't work on anything before ____ , I wouldn't know where to start, I just don't know anything about these little motors." etc. I guess I see their point...we really are the pros on these motors because we have researched them and tinkered with them so much.

I will try the gravity feed this evening, and thanks for the suggestion.

 

[parshman]

Re: Question about 1955 restoration

One other thing I was wondering about. If I put on a new head gasket, tighten it down, and remove it again, do I have to change out the gasket again? Is there some sort of gasket sealant that should be used on the gasket itself? What about the holes on the cover, do they also need some sort of sealant?

 

[parshman]

Re: Question about 1955 restoration

One other thing I was wondering about. If I put on a new head gasket, tighten it down, and remove it again, do I have to change out the gasket again? Is there some sort of gasket sealant that should be used on the gasket itself? What about the holes on the cover, do they also need some sort of sealant?

I thought of something else. When I adjust the needles, do i need to tighten the packing screw back down to create an airtight seal or does it matter. (Aren't I the bundle of questions today? :redface

 

[HighTrim]

Re: Question about 1955 restoration

Ok let me see if I can remember all the questions.

I really hate trying to reuse head gaskets. The work best the first time only. I guess if you must you could add gasket sealer the second time, I know a couple cheap fellers that do it often, but I personally try not to.

Always keep the packing nut tight. If not, you will get an air leak like you mentioned, OR the needle will be vibrating all over the place, possibly to the lean side, which could be bad WOT.

If you remove the fuel line from the carb, yes you should see fuel spurting out while cranking.

By the way, did you ever run it on a pressure tank or did you get it and start modifying immediately?

 

[parshman]

Re: Question about 1955 restoration

Ok let me see if I can remember all the questions.

I really hate trying to reuse head gaskets. The work best the first time only. I guess if you must you could add gasket sealer the second time, I know a couple cheap fellers that do it often, but I personally try not to.

Always keep the packing nut tight. If not, you will get an air leak like you mentioned, OR the needle will be vibrating all over the place, possibly to the lean side, which could be bad WOT.

If you remove the fuel line from the carb, yes you should see fuel spurting out while cranking.

By the way, did you ever run it on a pressure tank or did you get it and start modifying immediately?

I immediately did the modification and got it to run a little. I think that packing nut is a problem, if not THE problem. Tonight I'll know. I'm going to really check it out this evening. Thanks!

 

[parshman]

Re: Question about 1955 restoration

Update: It seems that every time I worked on it, I found something else that needed tweaking. This time, I went back and made sure the vacuum plug was in securely and being held in place by the manifold cover. I used gasket sealant on the undersides of the screws to seal things up. I tightened up all the connections, and got the cowl to go on just right. I applied protective gel to the plugs, rechecked the float on the carb to make sure it is level, checked the needles and blew out all passges with air. Everything is right now. Unfortunately, the tweaking also included my back this week, so I have not been able to pull the cord to see if everything works. Oh, I also zip-tied everything in place to prevent any movement. Everything fits nicely under the cowl. So, my next post will either be a victorious rant, or a rant of another sort. Either way, I will be dancing in my driveway. I just hope its for joy!