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55 HP with strange problem

U

usafvet

Member
"It has a dead number 1 hole.

"It has a dead number 1 hole. Both holes have 123lbs compression, both have fire at the plugs. The motor has trouble starting, it has gas and oil thats not buring in the top hole that is being sprayed out the exaust hub on the prop. The carbs have been gone thru, even swaped number one carb with a nother one from a running motor still nothing. Will run across the water at top speeds just fine. Can hold my hand over the top carburator when the motor is idleing and it sucks my hand in but will not shut off the motor, I tried this on bottom carburator and motor shuts off rightaway. Please any help?"
 
"A few questions. Do both car

"A few questions. Do both carbs suck your hand with the same force? Is the dead cylinder's plug wet? And, are you saying that at top end the dead cylinder kicks in?"
 
"I cant leave my hand over the

"I cant leave my hand over the bottom carb as this kills the motor, but when I put my hand over the top carb it does not efect the motor at all. You can also pull the top plug wire off while its running and still no change. You can hear the top plug wire firing while the plug wire is away from the sparkplug, so I know its firing it has gas and it has good compresion. Top plug is wet when pulled. When you put a load on it the top cylinder starts working."
 
Does the spark jump a gap of 7

Does the spark jump a gap of 7/16" on the bad cylinder?????
 
"Wet plugs are normally a sign

"Wet plugs are normally a sign of a lean condition, providing You have sufficient spark.
If blocking the throat of upper spark, fuel should 'flow'. If not no fuel!
Try spraying fogging oil, (NOT start assist) or 2% fuel mix into upper carb when engine is idling."
 
"Yes it jumps 7/16". When

"Yes it jumps 7/16". When you block off the top carb with your hand gas is left on your hand. We have tried running the motor while spraying gas oil mixture thru the throat of the carb, it does nothing. Also add some gas in spark plug hole before start up and still nothing."
 
"In that case I would have pul

"In that case I would have pulled the head and checked for piston/head/gasket damage.
Do the thermostat when You have the head down, quite a bit easier."
 
You have had the reed valves o

You have had the reed valves out to inspect them??? You remove the spark plugs and then bring #1 slightly past TDC. Now push quickly on the piston with a screwdriver and take it down till the intake ports open.You should hear a " poooff " from crankcase compression.Compare it with #2.
 
"Forgive me, but I have to ask

"Forgive me, but I have to ask. You have changed the top plug, haven't you? The reason I ask is your comment that when you pull the wire away from the plug, you can hear the spark firing. If the plug is shorted, your coil wire will arc to the top of the plug all day long, but you won't have spark inside the cylinder, where it counts."
 
"As far as pulling the head of

"As far as pulling the head off to check for damage on the head or piston, and head gasket. I thought that doing the compression test would let me know what kind of shape those were in? Or am I missing something during the test?"
 
cylinder compression and crank

cylinder compression and crankcase compression are a totally seperate thing.You need to check and trouble shoot this stuff.
 
"Ikia what is the difference

"Ikia what is the difference between the cylinder compression and crankcase compression, cant locate it in my book, help"
 
"Does the cyl's fire at co

"Does the cyl's fire at correct time or do #1 and #2 fire at the same time?
Compression test is an indication, no guarantee that cylinder and piston rings might be in ok shape at least from top of inlet ports and up. I would expect Your engine to read slightly lower at bottom cylinder, they normally do, and that might be an indication that upper is not quite up to it as You have equal comp reading.
Crank case 'compression' is the pressure built up below the piston as it goes down, but before the intake port opens. (what drives the fuel pump). Opposite You have the vacuum created when piston goes up. There are no values set."
 
Have not solved the problem ye

Have not solved the problem yet. Going to try to use a timing light to see if the top plug is firing at the correct time. Dont know if this will show me anything?
 
"Being it's the #1 cylinde

"Being it's the #1 cylinder, I'd pull the flywheel and check for leaks around the top seal and bearing carrier. You'd probably see oil seeping from any leaks. This would substantially diminish the vacuum/pressure pulses in the crankcase so the intake charge would not be drawn into the crankcase and pumped to the cylinder. Another thing to check would be the recirculation valves on the front half of the crankcase under each carb. If these are stuck open, the effect will be the same."
 
Another thing to check would b

Another thing to check would be the recirculation valves? Are these the same as the reed valves? Still no luck on fixing this problem.
 
I do not believe it has "

I do not believe it has " recirculation valves ". Have you checked the " REED VALVES " ???? Put the timing light on #1 and put the motor thru its paces ---report what the flashing light shows you when you look at the flashing.No need to check actual timing.
 
Anything new to report about t

Anything new to report about this Todd? Does this motor have 2 magnets? Could one be loose and cause bad timing at slow rpm's and shift into the right place at higher rpm's.
Just a thought.
 
"Please keep us posted. You h

"Please keep us posted. You have a lot of us stumped on this one. We all thought that intake, compression, fire (at the right time)= running. Yours defies logic."
 
"Still stumped on this end. Wi

"Still stumped on this end. Will pull the flywheel today, I been sick since last post, stupid VA Hospital."
 
"I do not believe that motor c

"I do not believe that motor could have loose magnets , they are cast in place."
 
"We think we have found the pr

"We think we have found the problem. The fuel pump runs off the #1 cylinder, and the #1 cylinder was the one that was not working at slow speeds but was working at upper speeds. The fuel pump had two small pin holes in the diphram, which was causing it to leak into the #1 cylinder thru the suction port wear the fuel pump attaches to the engine, which was flooding out at slow speeds and was able to burn the excess gas at higher speeds. Wont know for sure untill the new fuel pump arrives. We started the motor with out the fuel pump on, by using to old gravity feed gas tank method, the motor runs perfect at slow speeds that way. Will provide a update soon."
 
"Took the bass boat out yester

"Took the bass boat out yesterday and she is fixed. Want to thank all those that helped. Man was this a learning lesson. Thanks again, and happy boating.
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