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Oil Field Engines & Related Equipment

Ajax 7 1/4 x 8 will not start


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  #1  
Old 08-19-2013, 10:11:52 PM
Allan Wright Allan Wright is offline
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Default Ajax 7 1/4 x 8 will not start

Ladies and Gents, I need a little help in trying to get my 7 1/4 x 8 Ajax running. I know very little about these 2 cycle engines. I have definitely got my cardio-pulmonary excercise by kicking on this thing time after time after time.
The piston was originally stuck. I got it loose and removed the piston. Cleaned out all of the old carbon I could get to. When I went to put the piston back in, I tried to line up the packing gland up the best I could before I put the piston back in. Tried to be very careful and put the piston in easily. The first tap I gave to the piston, the dang thing went all the way into the packing. I don't know if I tore up the packing or not.

I had an old American Bosh mag MRF 4 1B 308 laying around so I put it on the engine. It appears to have good spark and trips about 3 degrees past TDC. Does this mag work on an Ajax? 3 posts are grounded and only one firing.

I took the reed valves out and cleaned all of them up. They appeared to be in pretty good shape after getting all of the carbon out.

It has an Impco 200 carburetor and I know nothing about these either. I took it apart, cleaned the sealing surfaces and put back together. The diaphram appears to be OK (no holes in it). After kicking the engine numerous times to try to start it, I was not sure if the propane was getting past the carburetor, so I took the diaphram and seat out and let the propane go directly to the reed valves. Still no luck in starting. Tried all sorts of settings with the gas valve and the butterfly valve.
Still can't get it to fire.
Any kind of help at all is greatly appreciated. Anyone needing a little excercise can come and kick start this thing with me.
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Old 08-20-2013, 01:55:56 AM
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Jack Innes Jack Innes is offline
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Default Re: Ajax 7 1/4 x 8 will not start

Allan,
I am certainly no expert on these engines but your story sounds very familiar. I went through most of the same procedures & finally found that the reed valves in the charge cylinder were gummed up. Once they were cleaned & set the Clark engine fired right up. If your Ajax has a similar charge system I would look there next.
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Old 08-20-2013, 08:10:08 AM
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Default Re: Ajax 7 1/4 x 8 will not start

Try squirting gasoline into the cylinder, a few pumps from a squirt can into the compression release or straight down the spark plug hole. Then, after it hits a few times try the propane.
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Old 08-20-2013, 09:20:28 AM
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Default Re: Ajax 7 1/4 x 8 will not start

Allan,
Wish I was a little closer, I owe you some exercise! I have never worked on an Ajax so you gotta temper my post with that bit of info, but as you know I have twisted the flywheels on a few of the oilfield two strokes. It seems the bigger they are the more "thinkin" and less "sweatin" is needed.
It sounds like you almost have the ignition figured out, but a final check is pretty easy if no other engine guys are around. Propane has a very narrow explosive limit, you gotta get between 2.1 and 9.5% fuel to air or there will be no fire. Gasoline is even worse, at 1.1 to 7.8%. The guys at Coolspring have it figured out, Hydrogen works all the way from 4% to 75%, but unfortunately most of us don't have access to Hydrogen. That leaves starting fluid, with explosive limits between about 1.8% to 48% depending on the actual blend. Yeah I know people are dead set against using it, it will "blow up" motors, etc. The best thing you can do there if there are other engine guys around is to let them crank on the big un a while, then they will start thinking maybe it would be ok to try once. Get it at bottom dead center more or less, take the spark plug out, give it a squirt, put the plug in and give it a kick. If you can't kick it over unless you are just past tdc then I would get it past the point that the mag fires, then give it a little bigger squirt of starting fluid since some of it will be exhausted. If you have fire then you can go on to other things.
Now at this point you will be tempted to give it a squirt in the mixer to see if you can get fuel through the whole system. I will caution you about that, I have done it "several times" with my cantankerous two strokes and have had occasional detonation on the back side of the piston. Since this will be your crank case this could be destructive. The chances that you will do damage to an Ajax are pretty slim (let any doubters crank on it a few times) but I don't know about the reed valves and think you probably should test that another way. You have a pretty good assortment of other oilfield engines, is there any chance you can belt it up to one of your other engines?
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Old 08-21-2013, 11:06:00 PM
Allan Wright Allan Wright is offline
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Default Re: Ajax 7 1/4 x 8 will not start

Eddie, I have tried gasoline a few times, but no fire. I think I will try it some more and lay off the propane a while.
If the rod packing is messed up, will this affect the firing? Like loss of compression if it did fire.

Ray, I may give the ether a shot as well.

Thanks for the replies.
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Old 08-22-2013, 08:27:38 AM
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Default Re: Ajax 7 1/4 x 8 will not start

The packing has a lot to do with the intake of fuel into the cylinder. It's blown in under pressure on BDC. That's the purpose of the bottom piston ring on the piston too. If all is working well you will notice almost compression on BDC as you have on TDC. That's why an Ajax is so hard to crank.

I'd lean toward its flooded. Take the spark plug out and roll it through and let it breath. Then give it 4 shots of gasoline in the spark plug hole, install the plug and go for it. Don't give it any more fuel till it hits a couple of times. It will. If the mag is hot enough to fire under compression, is the spark big and blue?
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Old 11-25-2013, 12:04:59 AM
Allan Wright Allan Wright is offline
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Ok, here we go again. I replaced the rod packing, removed the piston rings and really cleaned the ring grooves. Each ring had TOP stamped on them and I placed them on facing the top of the piston.
I took the reed valves out and cleaned them again. On the valve plate there is a little wear where a couple of the reeds sit. Do the reeds have to have a perfect seal?
With the reed valve assembly off, I rolled the flywheel over several times and you can hear the compression leaking by the piston rings? Can this affect the fuel/ air mixture and cause it not to fire?
Still trying to get it to crank and thanks for any and all suggestions!!
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Old 11-25-2013, 08:41:22 AM
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Default Re: Ajax 7 1/4 x 8 will not start

Allan:

Have you swapped spark plugs? I can't tell you how much grief is caused by a good looking plug that fires fine in free air but won't fire under compression.

As far as getting fuel is concerned, I've held a small flame up to the exhaust while cranking a balky engine. If the exhaust burns easily, you are getting fuel through the engine. Now, wether the mixture is right is still a question.

Remember that this advice comes from zero experience with big two-cycle engines.
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Old 11-25-2013, 10:24:54 AM
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Default Re: Ajax 7 1/4 x 8 will not start

According to my book, the 7 1/4 x 8 takes a Bosch XBM-109661-1 mag.

---------- Post added at 10:24 AM ---------- Previous post was at 10:19 AM ----------

Axaj start a lot better on gasoline. About 3 shots in the spark plug hole should be enough. Also there should be a petcock on the cylinder to shoot gas into. Leave it open while you crank it and after it fires, keep shooting in gas until it gets up speed then switch to propane. Always make sure you prime the lubricator a couple of shots. This will lube the cylinder and help with compression.
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Old 11-25-2013, 06:40:44 PM
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Default Re: Ajax 7 1/4 x 8 will not start

Fuel gas pressure should be 4-6 oz pressure. If you have a fuel cock on the gas line open and close it while cranking as wide open it likely to much pressure. It may start with the valve pinched. Good Luck.
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Old 11-26-2013, 12:10:02 PM
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Default Re: Ajax 7 1/4 x 8 will not start

Allen, you are beginning to understand why so many old Ajax engines have been scrapped.

I have had good luck coating the reed valves and mixer face with gun grease to get them to seal on start up.

Will it backfire? If so, it will run. Mag may be to cold to fire under compression. Which mag do you have, Bosch MRD 4/1 or a Bosch MRF 4/1?Champion W18 is a very common spark plug.

Compression may be too low. I've seen people pull the oil check and install a grease cert in it's place and then take a grease gun to fill the void around the piston to give it some extra compression to get it to start. Just be sure to put the oil check back.
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Old 11-28-2013, 11:29:58 AM
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Default Re: Ajax 7 1/4 x 8 will not start

Allen, I'll describe the method I saw a man use once to start his 6 1/2 X 8 Ajax. This engine had the Dodge type clutch. (They look a lot like a FM J clutch with a sheeve in the middle and a hand lever outside) This was before camera phones so I have no pictures to show it.

This is the God's truth.

The engine was inside of a little building that had rafters about 5" 3" so every time you stood up you'd hit your head and there was just enough room inside to walk around the engine, about 3 feet on a side.

He disengaged the clutch and rolled the drive belts off and took a long (50-60') heavy rope and rolled it around the sheeve. He engaged the clutch. He then backed his pickup up to the door and took the end of the rope and hooked it on his trailer hitch ball.

(at this point I got out of the building and watched through the window)

He takes a squirt can and shoots several squirts in the compression relief pit-cock and several in the carburetor. He gets in the pickup and tears out throwing dirt and rocks back at the building. When the rope flew off the sheeve he jammed it in park and ran fast back to the building. The engine was spinning pretty fast and trying to fire. He kept giving it gas until it was running. He shut the compression release and got it running on natural gas.

(about now I remember the drive belts are off?)

He goes out to his pickup and grabs a 5' rock bar and goes into the building. (I'm still looking in the window but from a greater distance now) He disengaged the clutch had a board in there he used to stop the sheeve. He then took the rock bar and put it through the spokes and wedged it into the pump jack frame to hold the sheeve while he started rolling the drive belts back on. After he got all three on he kicked in the clutch and off it went.

Allen feel free to use this method but if you do please have someone video it.
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Old 01-04-2014, 11:48:51 PM
Allan Wright Allan Wright is offline
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Default Re: Ajax 7 1/4 x 8 will not start

Mr Reed I am going to pass on using the pickup to start the Ajax with. Definitely would like to see that in person.
I finally got the Ajax to run this afternoon. Ran it for about 40 minutes. I had to use an electric starter to start it with. It finally started firing after I got it rolling pretty fast.
I took the Reed plate in and had it ground flat. I could tell a difference on the air sucking in on the carburetor.
It still has low / leaking compression. I am thinking about putting new rings in it.
Thanks for all of the input you guys have offered. This has definitely been a challenge for me. Gotta get back on them Fairbanks engines.
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Old 01-05-2014, 09:25:25 AM
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Default Re: Ajax 7 1/4 x 8 will not start

Congrats Mr. Wright!
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Old 01-19-2014, 01:50:24 PM
Allan Wright Allan Wright is offline
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Default Re: Ajax 7 1/4 x 8 will not start

Here is a video of the 7 1/4 x 8 Ajax if I can get it to upload. Try this and see if it works.
http://www.youtube.com/watch?v=32Oa6ABmFbg
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