1993 70hp stumped!

[ct1762@gmail.com]

hi guys. friends motor i'm working on.This motor is a tricky one! It wasnt sparking on all 3 cyl... #2 only very weakly. I tested stator (250v charge coil cranking, ohm test good), timer base (again, voltage and ohm good as per manual with DVA). took off the flywheel and it was rusty.. both stator and timer base so replaced them brand new . Pack cranks out 190v with the load adapter, and again 190v when connected to coil terminal extenders cranking DVA. I replaced 2 coils that were suspect... bam hot spark on all 3 cyl now. BUT... top cyl not firing. Has great 1/2'' spark, took carb off and cleaned it thoroughly (done 100 of these). still not firing. Squirted fuel mix into top carb... no change. compression 130-135psi on all 3. Primer bulb stays hard and no change when squeezing. replaced the flywheel (lapped on to taper of course) from a known good sparking motor since this was was so rusted, especially the timer base ring magnet.
Now heres the odd part: #1 cyl, when all other plug wires are disconnected, fires! its trying to run on 1 cyl so dies out of course, but confirms its got spark and fuel... but when you reconnect all 3 plug leads and pull #1, no change in RPM at all like the others. plug on #1 looks wet like all the rest. I will do a running voltage test next to see if its the pack, but how could this be? i tried another pack and same result. is it possible its running on all 3 cyl? how is that possible when the drop test shows no RPM drop when only the #1 plug wire disconnected? it sounds like 2 cyl as well... very lumpy idle and slow to rev up.

 

[flyingscott]

What is the model # of the motor?

 

[ct1762@gmail.com]

J70TLETS. Really strange why it pops with just #1 connected, but RPM wont drop during running drop test with all cyl connected. Nor will it change if fuel is manually introduced. never had this, but could the reeds be stuck closed or maybe water getting into #1? no signs of water on the plug/s though.

 

[jakedaawg]

I would start by insuring al the pins in the amphenol connectors are seated to the correct depth. Then I would do a check for shorts to ground of stator, trigger and coils.

 

[oldboat1]

Might be a case where testing #1 plug on the block might be a proper test. Maybe a bad plug.

 

[racerone]

Reeds do not stick closed !----Doubt that rust on the flywheel does any harm either.

 

[ct1762@gmail.com]

Well found out some interesting info. Block is a 1986 non-ovalport matched to 1993 linkages/quickstart electronics and carbs. Got it to fire on all 3 now... was a bad ground on the top coil. Idles like all hell though. The needle settings and low speed jets, since they are for a different block, could be all out of whack causing the terrible idle. I really do not enjoy blocks that are a mix n' match... rarely does that work out well in my experience. should i replace the carbs with ones from an 89' motor? might be a better match i'm guessing? thanks for all your help thus far great input.

 

[oldboat1]

Might initially try setting the needles 1/4 turn out, 1/2 out... until it pops. I'm doing some trial and error settings with a Rochester quadrajet to get the secondaries blowing my grey hair back. So far it appears to require a very lean setting.

 

[ct1762@gmail.com]

thanks oldboat. 2 turns seems to be the sweetest spot for this motor... not as sooth as i like but should do ok.

 

[flyingscott]

That makes sense you have an 1986 block because those compression #s would be high for a 93 block. Somebody replaced the block at one time or another no big deal. The carbs and ignition will work fine on it. Those motors were not the smoothest idling motors so dont expect a lot..

 

[ct1762@gmail.com]

thanks Scott appreciate the words. yes, the old freeze plug revealed itself to be an 86'. gonna plop it in the drink and do the link n synch and see what she can do.