25hp Johnson won't start

[sinkhole]

I previously posted this issue some time ago without success, I'm at a loss & once again ask for advice to try and get motor running. Since I received this motor not running I checked out the part numbers of flywheel points cam etc. (all good). I should mention that I have installed a new carb kit, champion JC4 spark plugs, fuel pump, driver coil, points etc. put starting fluid down plug holes, set points to open on the cam set mark turn the key and motor doesn't attempt to fire, very occasionally backfires thru leg relief ports. When I check the position of #1 piston when points wear band is at the cam set position, piston is well past when points presumably fire which would suggest timing is way off. Not being as knowledgeable as I boat contributors any suggestions would be appreciated. Thank you.

 

[Crosbyman]

some points .. bad ones.... have appeared in recent years whereby the pivot arm rubbing on the cam lobe is not the proper length.

There is no reason to have an off-set from the highest point of the lobe and TDC....reverify your points to ensure you are using the proper ones.

 

[racerone]

Switch plug wires ?

 

[sinkhole]

Switch plug wires

 

[sinkhole]

Tried that. No luck.

 

[sinkhole]

some points .. bad ones.... have appeared in recent years whereby the pivot arm rubbing on the cam lobe is not the proper length.

There is no reason to have an off-set from the highest point of the lobe and TDC....reverify your points to ensure you are using the proper ones.

View attachment 381941

 

[brodmann]

If timing marks don't line up with actual piston position, you need to remove the flywheel and you'll probably find a broken key where the flywheel fits onto the crankshaft. The key will be a half-moon shaped piece that fits into slots on crankshaft and into flywheel. I'd bet that's your problem.

 

[sinkhole]

The thought that the point arm in contact with cam might be too long, did occur to me I checked old points with new & they were identical.

 

[Crosbyman]

If timing marks don't line up with actual piston position, you need to remove the flywheel and you'll probably find a broken key where the flywheel fits onto the crankshaft. The key will be a half-moon shaped piece that fits into slots on crankshaft and into flywheel. I'd bet that's your problem.

he replaced points and coils I am certain a missing or broken key would habe been noticed no ?

 

[sinkhole]

If timing marks don't line up with actual piston position, you need to remove the flywheel and you'll probably find a broken key where the flywheel fits onto the crankshaft. The key will be a half-moon shaped piece that fits into slots on crankshaft and into flywheel. I'd bet that's your problem.

 

[sinkhole]

One of the first things I checked. Unfortunately no such luck.

 

[Crosbyman]

point must open at TDC ..something mecanical is needs a deep look into.
did you change the condenser ..yes no ?

 

[sinkhole]

point must open at TDC ..something mecanical is needs a deep look into.
did you change the condenser ..yes no ?

No I didn't change the condensers. The only way I can think of to change point opening is to relocate the cam keyway.

 

[racerone]

Does spark jump a gap of at least 5/16" ( 8 cm ) on a test device, yes or no ?

 

[sinkhole]

Does spark jump a gap of at least 5/16" ( 8 cm ) on a test device, yes or no ?

I only have the spark testers with the light and you attach plug to end of wire, spark looks fine. Would strength of spark help if piston is in the wrong position?

 

[racerone]

In my opinion the flashing light testers are best thrown out.-----Make something.----Cardboard / glue / wires to do a real spark test.----Glue wires onto carboard with 5/16" between ends.