Starting 25 H.P. Johnson problems

[piggy]

Posted yesterday and screwed it up trying again. 25 H.P. Johnson Model J25RCIM (not sure of the I) S/N E5435464 1984 model (I think) With both plugs out motor turns over great. With plugs in it will come up on compression then stop or sometimes will go over and stop on second compression. Both manual and Elc. starter the same. Compression is 130 # both cylinders. Started one time on a manual pull and ran great. Is there a way to check starter or is this motor just hard to turn over. Thanks for any help or suggestions.

 

[tashasdaddy]

Re: Starting 25 H.P. Johnson problems

90% of starter problems are bad connections. remove and clean both ends of the battery cables, so that they are shiney, also the cable from the solenoid to starter. check for nicks in the cables. and make sure the connectors are on the wire good. the cable tend to corrode from the inside out, if nicked, corroded wires, and connections, heat up and cause resistance to the follow of electricity, thus the starter doesn't get enough. you can also take jumper cable pos battery post to large post on starter. with a good connection, the engine should spin. then if the starter is good clean everything and retest. then trouble shoot solenoid. starters can be rebuit at a starter/alternator shop, much cheaper than a new one.

also have the battery load tested at the auto parts store, free, i've had new batteries go bad

 

[asdasc]

Re: Starting 25 H.P. Johnson problems

He says he has the same problem with pull starting it also, so it may be something more sinister. What plugs do you have in it? Any chance they are too long and JUST touching the pistons?

 

[freddyray21]

Re: Starting 25 H.P. Johnson problems

possibly the plugs, but if the had it running with those plug and it is the plugs the pistons may be damaged now.

 

[piggy]

Re: Starting 25 H.P. Johnson problems

Spark plugs are champion L77JC4. If plugs were hiting piston would it not bend the end of the plugs. Also ran great that one time.

 

[tashasdaddy]

Re: Starting 25 H.P. Johnson problems

these are recommended plugs and gaps,
20, 25, 28, 30 1978 - 2001 QL77JC4 or L78V or QL82C .030

the difference is L77JC4 is not a resistor plug. but should run on it. check your gap.

 

[piggy]

Re: Starting 25 H.P. Johnson problems

Is it possible that the fuel pump has a leaking diaphragm leting gas being pumped into motor loading it. I did pump the bulb up hard before trying to start motor. Plugs were gaped.