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Timing 70 hp 2 cycle 1996 Johnson

N

Neil Friesen

New member
Have a rebuilt power head but the timing at idle fluctuates and the motor keeps stalling after a few minutes at idle. What could be the cause. Runs fine at high speeds.
 
Huh....are you saying that WITH A TIMING LIGHT, that you see the timing jumping around? Like all over and around 4* ATDC? If so, look at the timer base under the flywheel and try to see if it too is moving around. It should be set solid and not moveable at idle. It should be against a stop. If not, do a proper link and sync. If the timer base is solid, fixed in place, then you have a bad timer base, or loose magnets under flywheel (if your model has such). EDIT: Possibly a bad PP also, but that is the last place I would look.
 
daselbee said:
Huh....are you saying that WITH A TIMING LIGHT, that you see the timing jumping around? Like all over and around 4* ATDC? If so, look at the timer base under the flywheel and try to see if it too is moving around. It should be set solid and not moveable at idle. It should be against a stop. If not, do a proper link and sync. If the timer base is solid, fixed in place, then you have a bad timer base, or loose magnets under flywheel (if your model has such). EDIT: Possibly a bad PP also, but that is the last place I would look.
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"That's exactly what I'm saying. We pulled the flywheel and bingo, the magnet was loose. The glue used to attach it had let go. Can we clean it up and JB Weld it back in place?
 
Thanks. We pulled the flywheel and "bingo" the magnet was loose. The glue used had let go. Can we clean it up and glue it back using JB Weld? What is PP? You obviously know your stuff. Can't say the same for my mechanic.
 
Yes, you can JB it back, but it has to be in the exact correct position. This is the center magnet ring around the hub of the flywheel, correct? If so, we are on the same page. It has to be very precise. Do you have any witness marks, or will it place itself correctly by using the old glue as a locating method? Sometimes they will "lock in" place where the old glue is. Remember, the hub is a much, much smaller diameter than the outside of the flywheel. That is why the need for such a precise location of the magnet. I have done many V6 looper flywheels, and it takes mucho aligning and adjustment before final gluing. You gotta re-time the engine after the repair, if you are successful.
 
You will see a thin slot in the magnet. If it is re-glued and off by maybe 2-3 widths of that slot, the timing will be way off. You may need to do a timing pointer adjustment also, after the repair, just to be sure of what you are seeing. Most mechanics will not even try this repair, but I figure "What the heck? Try it." So, I have been successful on these V6s that I have done. I have the position discovered/located/known and I do it by counting teeth on the outer rim of the flywheel, putting a straightedge from that point across the wheel to the exact other side (180* out ), and aligning the groove with the straightedge. It is meticulous.
 
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daselbee said:
Yes, you can JB it back, but it has to be in the exact correct position. This is the center magnet ring around the hub of the flywheel, correct? If so, we are on the same page. It has to be very precise. Do you have any witness marks, or will it place itself correctly by using the old glue as a locating method? Sometimes they will "lock in" place where the old glue is. Remember, the hub is a much, much smaller diameter than the outside of the flywheel. That is why the need for such a precise location of the magnet. I have done many V6 looper flywheels, and it takes mucho aligning and adjustment before final gluing. You gotta re-time the engine after the repair, if you are successful.
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"Thanks, we will give this a go. There is a mark we can us to position the magnet. Will let you know how it turns out."
 
We glued the magnet, installed the flywheel, timed the idle and wot. The timing no longer fluctuates and the engine continues to idle when under load. The only concern I have now is that the engine isn't smooth at idle. My mechanic made small adjustments to the carbs but couldn't smooth out the engine. If you have any ideas about this they would be greatly appreciated. I installed new plugs just prior to the break-in period of 10 hours. The new power head now has about 20 hours on it. Would new plugs make a difference?

I am most appreciative of all your excellent advice. I feel like I owe you something besides a thank you.
 
I am talking in general rules of thumb here. Some of the things I say next might not apply to your motor, but most likely will be very close. These engines are very, very much alike. OK, just make sure your mechanic knows that the throttle butterflies absolutely MUST be closed at idle. You cannot "prop the butterflies open" with the idle stop screw, and hope to adjust idle speed that way. Don't know if that is what he is doing or not. I generally loosen the screw that adjusts the throttle cam roller position, and move it completely away from the throttle cam. That way I know the butterflies are completely closed. You absolutely have to physically verify it though. Adjust mixture screws, and idle timing to obtain correct idle, then re-position the throttle cam roller. Another thing that will cause rough idle is if all three butterflies are not in complete synchronization. They all must be closed. You cannot have even one that is slightly open, and the others closed. Double check that. Lastly, if all that fails, then you will probably need to clean the carbs, paying extra close attention to the idle circuits that are mostly located in and below that top plate on each carb. The idle circuits have very tiny holes and passages that clog easily, especially with the poor gas we have now. I use a welding tip cleaner wire set to get in those holes. There might be a brass tube that extends down into the carb bowl. That tube must be clean. It tapers to a smaller size up at the top where it goes into the carb body, so it can be deceiving. You may not have that, though. I keep thinking of other stuff....on the center plastic tube that runs down into the float bowl, there is a round gasket. That cannot be leaking, or split. Proper fuel draw depends on that gasket making a seal. Fishing? No, thank you very much, but I doubt I will ever get to Canada.....I appreciate the thought, very much, and I am glad you are closing in on the troubles with the motor.
 
Thanks again. I'm printing this page and giving it to my mechanic tomorrow. I can get by the the way it is right now, but it would be so much better if the motor purred smoothly.
 
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