07-21-2004, 07:00 PM
I have the exact same problem with an old johnson and murcury moters I have, I have yet to remidy the problem,
I am sure the problem is in the jet valves.
I need to go down and pick up from the auto shop some valve files. (teeny tiny wire hone) with this I need to run it though the jet pin hole. to do this you need to take the valve screws all the way out. find the smallest soft wire circle brush to run in there and clean the race of the jet valve and the wire hone you will need to start with the smallest probeing in gently in and out untill it feels smooth then move to the next larger one.
to gage how big the biggest wire hone needed simply pull out the valve screw and measure the diamiter of the ring imprint on the pin with your callipers.
I cleaned my motors in this area and it did make a big differance in how it ran but I need to do a through job as I mentioned above.
you may want to even throw in a little "gunk" fuel additive in the mix to disolve any residue in the carb. just because it looks dry and clear dosnt mean there isnt a build up of varnish in your fuel port valves.
you may even find it benificial if you pull the carb right off the motor and set it in a bowl of "gunk" compleatly submerged for a day. (with gaskets and any rings removed) blow out with air hose compleatly dried and replace back on the motor.
sounds like a lot of work, it is and it isnt. it is just a matter of getting my self motivated to doing the job.
there is only other one other thing that can cause this that I am aware of and that is the water pump (if water cooled) but you mentioned that the motor is not over heating so that is most likely not your problem. but do make sure that you have pleanty of gear lube in the lower end.
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I am sure the problem is in the jet valves.
I need to go down and pick up from the auto shop some valve files. (teeny tiny wire hone) with this I need to run it though the jet pin hole. to do this you need to take the valve screws all the way out. find the smallest soft wire circle brush to run in there and clean the race of the jet valve and the wire hone you will need to start with the smallest probeing in gently in and out untill it feels smooth then move to the next larger one.
to gage how big the biggest wire hone needed simply pull out the valve screw and measure the diamiter of the ring imprint on the pin with your callipers.
I cleaned my motors in this area and it did make a big differance in how it ran but I need to do a through job as I mentioned above.
you may want to even throw in a little "gunk" fuel additive in the mix to disolve any residue in the carb. just because it looks dry and clear dosnt mean there isnt a build up of varnish in your fuel port valves.
you may even find it benificial if you pull the carb right off the motor and set it in a bowl of "gunk" compleatly submerged for a day. (with gaskets and any rings removed) blow out with air hose compleatly dried and replace back on the motor.
sounds like a lot of work, it is and it isnt. it is just a matter of getting my self motivated to doing the job.
there is only other one other thing that can cause this that I am aware of and that is the water pump (if water cooled) but you mentioned that the motor is not over heating so that is most likely not your problem. but do make sure that you have pleanty of gear lube in the lower end.
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