80s honda bf100, spark but wont fire.

[Mopar440ci]

hello, i just picked up a bf100 that wont fire for 100 $ and im trying to get it to fire up.

it seems to be getting spark on new plugs , the carbs have been recently cleaned and needle reset to 1 7/8 turn outs , i checked the float and needles.
it has good compression.
i adjusted the throttle cable so that it sits at proper idle / start positions, cleaned out the fuel filter.

but it just wont fire up. the most i have been able to get are these little puffs every now and then but nothing significant,


where would you guys go from here?

this is the 80s CDI ignition 4 stroke 10hp

thanks
-Justin

 

[Sea Rider]

Welcome to Iboats.

Having spark is no indication it's sufficiently strong as to properly ignite the fuel air mixture in combustion chamber. Check with an electrical spark plug tester how far does the spark jumps, will indicate its condition. Will need the factory tech parameters to rule that out.

Happy Boating

 

[Mopar440ci]

alrite , i will see if i can track one down. could it be determined with a multi meter?

spark would be my first guess as i was told it had a spark issue. but it was intermitant spark, like first pull it would spark next few it wouldent.
i couldent replicate this problem , for me it would spark every time.

 

[Sea Rider]

Prior checking erratic electrical issues, remove the ground contact of each electrical copmponent and sand it to a shiny state, including the powerhead spot it connects to. Use a piece of medium grade sanding paper for metal.

Nope with a multimeter, it's a visual thing. Try a spark plug tester, the one that have a light bulb placed inside a glass container, or one where the tip groove rests on top of spark plug cable, check spark in a dark room while pulling cord hard several times. Will be able to check the spark intensity. Plug must be kept screwed to cylinder head. .A strong spark should briefly illuminate adjacent bulb area.

Have seen cases where the grounds were bypassed and boater was driven to insanity trying to figure out which electrical component was the culprit. Report your findings..

Happy Boating

 

[Alumarine]

It's very difficult to see the spark on those motors unless you are in a totally dark environment.
It's possible the timing is incorrect. Do you know the history?
Was the belt recently changed?

 

[Mopar440ci]

no i have no idea what its been through. i will pick up one of those testers and let you know what i find.

 

[Sea Rider]

The spark has a very short visual life. If the test is not done at a dark environment, put a large dark cover over powerhead and yourself to check spark intensity. Have someone pull cord at front while checking spark from behind. Post results.

Happy Boating

 

[Faztbullet]

Spark need to jump a minimum 3/8 air gap to fire under compression..,..

 

[raczekp1]

my advice is to check timing. on cam shaft is a smole hole and on cam under flywheel is a mark.
both marks should be in line with marks on cylinder pinting marks.
second is to set proper gap on valves.
remember that both pistons reach Top Dead Center at the same time