Johnson 9.5 gouged pistons, swapping parts.

[nabiul]

Aaand it's not working again. Today it warmed up to t-shirt weather, but the motor didn't want to start and when it got started it wouldn't stay running anymore.
Played around with the choke and the low speed, nothing keeps it running. Compression reads 60/60 like before, spark is 1/4" top cylinder and 1/8" bottom. Even with a weak spark it should work on a single cylinder.

 

[racerone]

If spark will only jump 1/8" you have ignition problems.--Time to get some help as these motors are ultra simple !

 

[nabiul]

Simple is part of the problem, these things will keep chugging along long past the time they should've died. With faulty ignition, low compression, water leaks and clogged carburetors they will keep unreliably working and give you a false sense of security that can be pulled out from under you at any time. And when you try to fix them you will never know just how close to the threshold of barely operational the motor is unless you restore it completely to factory condition.

 

[nabiul]

Ok I don't know what's up. I looked at the points, I found some grease embedded in pits on the bottom cylinder points, cleaned them and now the spark jumps 1/4". BUT the sparks don't fire reliably on every pull on either cylinder. It's like every 3 or 4 pulls I'm getting one spark strong enough to clear the gap. Could this be caused by a loose timing plate somehow? I noticed that without the plastic ratcheting plunger the plate wobbles alot.

 

[racerone]

On a magneto like yours you get the strongest spark when points are timed using the 2 marks on the flywheel and magneto plate.--But when the plate wobbles it does throw this timing all over the place..-And yes there are timing marks !

 

[nabiul]

Ok I keep seeing two conflicting ways to set the points. Some line up the flywheel and the marks and then gap the points to 0.02 while other guys line up the marks and set it to just break continuity. Which one is it?

 

[racerone]

Some will argue , but the best way is to use the marks and a meter to set them to open at the correct time.--That way you get the strongest possible spark at 180 degrees apart.

 

[HighTrim]

^^^ What Racerone says.

I don't believe there is an argument, personally, that you can set the spark timing with a feeler gauge as accurately as you can using the timing marks. period. No way, no how. Of course using a feeler gauge at 020 when the rubbing block is at the widest part of the cam is used by many with success, is true, but that idle CAN be improved upon.

If you want, bring the motor over, and I can show you how to do this if you like. I feel bad for the trouble you are having.

Your issue is definitely dirty points, and possibly incorrectly set as well. Other contributing factors could be coil heel gap, magnet strength (very rare), continuity throughout the plug wire from coil to spark plug, etc...

 

[nabiul]

The sparks are so erratic I don't even know what to think anymore. When I try cranking with the spark plugs installed, the sparks end up very weak or not there at all. With the plugs out so that cranking becomes easier the sparks are sometimes strong and sometimes not there.

My new theory is that maybe the timing cam is slipping from the home made key that I am using which is slightly undersized. I remember some one mentioning that it isn't a regular key that you can buy from the hardware store?

 

[Chinewalker]

If your points have pits in them, replace them!! I suspect new points will alleviate much of your problem.

 

[HighTrim]

Throw that key in the garbage! PM me with your contact info, I can help with parts and aid setting it up.

 

[racerone]

????---You are using " home made parts " and doing what you " think " is right.-----You are no doubt having some problems here.

 

[nabiul]

The timing cam is fine, the key is fine.

Today I:
-trimmed the corroded ends of the plug wires
-installed almost new points and set them
-wrapped electrical tape around the primary wires
-put on another flywheel with an undamaged keyway

Whatever was wrong is fixed for now; I am getting sparks hot enough to jump the 1/4" air gap plus the spark plug inline.

And it still wont start. I've tried every needle setting I can think of, choke in choke out. The plugs are gapped at 0.03. Still reading 60psi.
What's left to try? Longer gap? Shorter gap? New gas? Another carb?

 

[HighTrim]

If you spray pre mixed fuel directly into cylinder, will it pop and fire for a second?

 

[nabiul]

Well this is interesting, spraying fuel into the cylinders or carb throat wasn't working so I got new gas to add to the mix.

When I went to drain the carb it was bone dry. To see if the fuel pump was bad I connected the gas line and started priming, the pressure built up and leaked around the fuel filter bowl but nothing went into the carb. Next I took off the fuel line to the carb and started priming and fuel just squirted out of the pump.

EDIT: The float setting is messed up, I fiddled with it and got it to open enough for the primer to push fuel through but not the fuel pump. And the motor started.

Anyone have a guide on how to set the float, the one from leeroy's page isn't very clear.

 

[racerone]

Float upside down ???

 

[nabiul]

No it's right side up. I messed it up before when I tried to set it, I thought I was doing it right according to the instructions on leeroy's website.

http://www.leeroysramblings.com/OMC_9.5.htm

The site says to make the float slightly off level, but doesn't say if it should be up or down.

 

[HighTrim]

I do the same thing he does. By slightly off level, he means to have the float more in line with your green line, then your red line.

This is while the carb is upside down, as in your pic.

What this does, is ensure that the float will seat, when the fuel bowl fills, and you do not get flooding. Just slightly though. When you look at it from the other angle, should be square, and not cocked.

Some other measurements to check.

When the carb is upside down, as in your diagram, measure from the gasket surface to float, should be 13/16"

Now flip the carb right side up. Measure now from the gasket surface to the farthest edge of the float. Should be 1 7/16" gap.

To adjust the open position, bend the stop tab with needle nose pliers.

To adjust the closed position, bend the float arm with your needle nose pliers.

 

[HighTrim]

A very important adjustment on these 9.5s is the linc n sync. I have had many come over, that were lean sneezing at idle, and the owner could not solve it. Ended up being the throttle plate was slightly open too early.

To adjust this, throttle up until the center of the cam follower is aligned with the hash mark on the armature plate brass cam. At this point, the cam, follower, and nylon roller on throttle lever should all be in contact and the throttle plate needs to be completely CLOSED! NOT cracked open at all.

If it is open, loosen the adjustment screw, and move the throttle lever until that slack is gone and the plate is closed. Hold it like that, then retighten the screw.

After set, move the tiller grip to FAST, in gear, and ensure that the plate is fully open.

 

[HighTrim]

I re read your post here. Are you saying, that if you remove the fuel line from the carb, and pump the primer bulb, fuel does not spray out the hose, but instead sprays out of the fuel pump?? Pull your fuel lines, and check for blockage. Also, rebuild the pump.