1975, 25 HP , Johnson, Hard starting

I need some input on this engine. I rebuilt this engine for my own use fishing our local river. The power head is a total rebuild. Pistons, rings, gaskets, seals. The problem is the engine is hard to start when cold, once started, the engine runs fine, and will start with little effort for the rest of the day. I have two spare carb's that have been rebuilt, along with the carb on the engine. Changing them makes no difference. The magneto has been redone with all new components, and put's out the proper spark. This engine has the 22 cubic inch block with the 1-3/8" bore carb. The sync, and link is right where it belongs, along with ignition timing. I have worked with choke spring tension, and did'nt make any difference. I have worked with a lot of these engines, but this one has me on the ropes. I have two older 18 HP engines that have the same 22 in. block with 1" bore carb that start, and run as they should.

Re: 1975, 25 HP , Johnson, Hard starting

R.Johnson, may I make a suggestion. I am completly sold on using Boyesen Reeds. They make the engine start more easy, and idle more smoother. I dont know if they make any for this engine or not.<br />What about the thermostat, maybe its stuck open?

Re: 1975, 25 HP , Johnson, Hard starting

This is stricly a cold start problem, the engine is fine in other respects. If I use a squeeze bottle with a squirt down the carb throat, it will start instantly. It simply is'nt pulling in enough fuel with the choke.

Re: 1975, 25 HP , Johnson, Hard starting

Did you by chance put any new parts on it ?? The newer intake manifold is a little higher causing choke butterfly not to close properly. Assume it has the manual choke. They have to close choke butterfly hermetically. Otherwise, maybe leaking lower cranckshaft seal. Didnt know the 22 cid block still came out in 75, I thought they ended in 74.

Re: 1975, 25 HP , Johnson, Hard starting

This is stricly a cold start problem, the engine is fine in other respects. If I use a squeeze bottle with a squirt down the carb throat, it will start instantly. It simply is'nt pulling in enough fuel with the choke.

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I understand that perfectly. However the question is, do you understand the concept I was suggesting? If its not pulling in enough fuel with the choke, then that is where the dual stage reeds help during startup. The lighter the reed, the easier it to start. Again, just a suggestion.<br />I assume the choke is closing fully.

Re: 1975, 25 HP , Johnson, Hard starting

Basscat 1<br />It is a good suggestion and might help, but those motors usually starts fine with stock reeds, and this one is even freshly rebuild. The higher intake manifold moves the carb just a tad longer foreward, and the standard choke pull knob wont close choke all the way, I tried that.

Re: 1975, 25 HP , Johnson, Hard starting

The problem can also be a faulty choke pull knob somehow.

Re: 1975, 25 HP , Johnson, Hard starting

The choke is closing fully, I have worked with the choke spring tension to insure that is does. I am aware of the Boyesen reed's, I have them in my V-4 engine. Generally! these small 2 cylinder engine's are quite straight forward to work on, and I have worked on many. The cold start on this one has me stumped. If they don't start in 3, or 4 pulls of the cord, something is wrong. As I said earlier, this engine has new seals, gaskets, pistons, and rings. I have looked thru prior service bulletins, and can find nothing there either, other then improving idle quality.

Re: 1975, 25 HP , Johnson, Hard starting

Please don't think I'm getting above my station here. I know that you have more knowledge than I do, but here's just a little suggestion.<br /><br />I don't know if this applies to that particular engine, but is the linkage on the choke pulling the throttle butterfly open just a touch when the choke butterfly is fully closed?<br /><br />I've done an old 18hp and a newer 20hp, and on those engines there is a link between the choke and throttle. When the choke is fully closed, the throttle butterfly should be just a little bit open.

Re: 1975, 25 HP , Johnson, Hard starting

Well let us know what you find. I am curious.

Re: 1975, 25 HP , Johnson, Hard starting

The choke on this engine is a little different! When you pull the choke out, there is a mouse trap spring wound around the choke linkage shaft. This spring has a long tail that bears on the choke link. This spring is .025, and lighter than the other link springs. The choke link follows the the choke link lever, and held closed under slight spring tension. When the engine starts, the choke is pulled slightly open, keeping the engine from flooding out. The choke, and throttle shaft on this carb show normal fit as to tolerance, and choke is going fully closed as it was designed to do. If I but the engine in gear, as to give more advance on the throttle, it will start when cold. This is not correct for this engine, and that is what I am trying to find the cause of. I have seen these small engines beat to death, and start better than this. I wonder how big a splash it would make from the Cedar River bridge, about a 25-30 Ft. drop.

Re: 1975, 25 HP , Johnson, Hard starting

Could sound like Steviecops got something. If throttle butterfly isnt slightly open, too little vacuum will reach reverse side of throttle butterfly to draw gas from main and intermediate orifices, where it gets its gas from in choke operation. Better recheck trottle butterfly. Choke sounds like it is on all manual 22 cid's to mee. Did you ever check iddle timing with a timing light ??

Re: 1975, 25 HP , Johnson, Hard starting

On this carb, there is a link shaft that connects the choke linkage to the throttle linkage. The throttle link has a split nylon bushing that lets the link shaft slide back, and forth. When you pull the choke on, this shaft pulls the throttle plate slightly open. The timing is set right on. When adjusting the throttle pick-up point on this carb, it can be quite touchy. That's what has me stumped, everything check's right on.If this engine was electric start, you probably would'nt be aware of the problem, but trying to rope start it will leave you wore out.