Home › Forum › Ask A Member › 1972 Johnson 2hp – low speed and idle problem
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stan-k.
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July 19, 2015 at 12:40 pm #20378
Will do my best not to "muddy the waters" here. Stan, I think you mention replacing upper and lower crankshaft bearings, do I have this info right? If so, you had the powerhead completely apart, did you hone the cylinder/replace the rings? Why is it that you pulled the powerhead apart and replaced those bearing?
Did you run the engine before doing all this work? If so, how did it idle then?July 19, 2015 at 12:48 pm #20379Stan, that looks like the carb bowl I was thinking about. If so, there is no way to run a wire through the idle circuit on that carb and there is a great chance it is plugged up. The circuit takes a 90 degree turn in the fuel bowl.
The only way to clean that circuit is to either let the bowl sit in cleaner for ??? until it is clean or drill the lead shot out of the other side with a 1/16" bit and let the bit cross the nozzle well and clean out the passageway on the other side.
Pull your bowl again and see if it is plugged there. Won’t take long on a 2hp.
Also interested in the answer to Fleetwin’s question.July 19, 2015 at 2:37 pm #20384quote fleetwin:Will do my best not to “muddy the waters” here. Stan, I think you mention replacing upper and lower crankshaft bearings, do I have this info right? If so, you had the powerhead completely apart, did you hone the cylinder/replace the rings? Why is it that you pulled the powerhead apart and replaced those bearing?
Did you run the engine before doing all this work? If so, how did it idle then?Actually I only replaced the two oil seals, which I was able to do without taking the complete power head apart. The one on the lower bearing assembly was it bit more difficult. Hard to push the seal out without damaging the needle bearing. So one new needle bearing too. My local bearing supplier was very helpful in finding the correct replacement parts (at very reasonable prices). The reason for replacing those seals is because this motor had been sitting for a while and I suspected that the rubber seals may have dried out. Now I’m starting to think it was all for not.
The engine was running before I started the work on it, but I could get it to run on low speed or have it idle. I even ran a complete tank of gas through it while testing it on the lake. After the work I mentioned, I tested it again at home, with typically the same results.
So I haven’t taken the power head apart, but the compression tested at 85 PSI.
Thanks.
July 19, 2015 at 2:57 pm #20388quote Pappy:Stan, that looks like the carb bowl I was thinking about. If so, there is no way to run a wire through the idle circuit on that carb and there is a great chance it is plugged up. The circuit takes a 90 degree turn in the fuel bowl.
The only way to clean that circuit is to either let the bowl sit in cleaner for ??? until it is clean or drill the lead shot out of the other side with a 1/16″ bit and let the bit cross the nozzle well and clean out the passageway on the other side.
Pull your bowl again and see if it is plugged there. Won’t take long on a 2hp.
Also interested in the answer to Fleetwin’s question.Yes, you’re right about not being able to trace that 90 deg. path, but I had the carb well cleaned (ultrasonic) and I also tested it with air pressure and it seems unobstructed. I also removed the top core plug for access (all clear). I have the carb all apart now and did a thorough examination…very clean.
Would the level of fuel in the bowl effect the flow to the low speed fuel supply? The reason I ask is because I noticed the float did need some adjustment, so now it is sitting level with the face of the bowl casting. If you think it may have some effect, then I’ll put it back together and test it again. Doesn’t take long…I’m almost able to assemble this motor blind folded by now.
Thanks.
July 19, 2015 at 4:46 pm #20390While the carb is off you may want to check the reeds and see if they are completely closing and not slightly held open by a critter or whatever.
Sure you got the upper and lower seals oriented correctly? Lip facing the center of the crankshaft?
The fuel level will give very minor changes unless it is drastically off one way or another. I take it the nozzle well gasket is in place?
Float not on upside down? Tab pointing down at the seat?
What happens if you take the needle out another turn or more for testing purposes?July 19, 2015 at 4:51 pm #20391Check the throttle shaft for wear where it goes thru the carb casting. Any excessive up/down forwards/back play here indicates a worn casting or shaft which will allow a vacuum leak at idle. The amount of leakage here seems to be more critical on the smaller motors.
July 19, 2015 at 5:19 pm #20392Just want to make sure I understand. You ran the engine before replacing the seals, and it did not idle correctly then either. Am I correct?
I have never done a compression test on one of these 2hps, but others have reported much higher compression readings, like 115PSI. Any signs of overheating? Have you had the cylinder head/exhaust cover off? Please don’t rip it apart based on my questioning though, hopefully the problem is a much simpler one like others have described.
I will just emphasize what others have said so far. Make sure the carb butterfly is closing fully, and the throttle shaft is not jammed/corroded. The only way to do this is to remove the carb and look at the butterfly while manually opening the butterfly slightly, then releasing it. The butterfly should snap closed on its own, without having to "help it". Have a look at the throttle plate as well, does it look like someone has been at the screw/removed it before?July 19, 2015 at 10:24 pm #20416quote fleetwin:Just want to make sure I understand. You ran the engine before replacing the seals, and it did not idle correctly then either. Am I correct?
I have never done a compression test on one of these 2hps, but others have reported much higher compression readings, like 115PSI. Any signs of overheating? Have you had the cylinder head/exhaust cover off? Please don’t rip it apart based on my questioning though, hopefully the problem is a much simpler one like others have described.
I will just emphasize what others have said so far. Make sure the carb butterfly is closing fully, and the throttle shaft is not jammed/corroded. The only way to do this is to remove the carb and look at the butterfly while manually opening the butterfly slightly, then releasing it. The butterfly should snap closed on its own, without having to “help it”. Have a look at the throttle plate as well, does it look like someone has been at the screw/removed it before?Yes, it ran before and after seal replacement, but still only at high speed.
No signs of overheating.
I’ve gone over every detail of the carb…all components appear to be in good shape and operating well. Good suggestion about the throttle plate… it doesn’t look like it’s ever been removed, but I’ll check it out the alignment mark.
You got me thinking about the compression. Before I take the cylinder head off I’m going to try another compression test. But I won’t be able to do it for a couple of days now.Thanks again…stay tuned.
July 19, 2015 at 11:10 pm #20421quote Mumbles:Check the throttle shaft for wear where it goes thru the carb casting. Any excessive up/down forwards/back play here indicates a worn casting or shaft which will allow a vacuum leak at idle. The amount of leakage here seems to be more critical on the smaller motors.I checked, and the throttle shaft has no play at all. Actually the carb is in good shape…that’s what’s so puzzling.
In the next couple of days I’m going to re-assemble the motor and do a compression test before doing anything else.Thanks.
July 19, 2015 at 11:30 pm #20424quote Pappy:While the carb is off you may want to check the reeds and see if they are completely closing and not slightly held open by a critter or whatever.
Sure you got the upper and lower seals oriented correctly? Lip facing the center of the crankshaft?
The fuel level will give very minor changes unless it is drastically off one way or another. I take it the nozzle well gasket is in place?
Float not on upside down? Tab pointing down at the seat?
What happens if you take the needle out another turn or more for testing purposes?Thanks Pappy. All good suggestions and advice. Yes the reeds are closing well. Actually, now that I’ve had a good look at most the engine components (except for cylinder head), I don’t think this motor has seen that many hours. Just been sitting around in conditions unknown.
In the next couple of days I’ll re-assemble the motor, going over all the points that you’ve suggested. Although the carb is the key suspect in this problem, I’m still leaning towards low compression, so I’ll do another compression test before trying to run the motor again.
I’ll not be able to get back at this for a few days, but I will update you with results.
Thanks again for all your help.
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