deason

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Hello all. Recently got my old 5.8 off the shelf after about 4 years and converted to electronic ignition. Removed all mechanical advance and Set the timing at 30 degrees and new carb (WJ-71). With low needle at .75 out and high the same. Checked the timing again to make sure.

Ive attempted to start this thing for 2 weeks now, with same results every time. Eventually each time i try to start, the plug is soaked. I have fire, I have gas, but not even a hint of it trying to hit.

Anyone know about these engines or ever had this problem? At first, i was sure it was a timing issue. ive probably checked it a dozen times and its right on the money. even with the spark plug out and watching, it fires where its supposed to - just past the sensor on 30 exactly.


im stumped.

speedracerntrixie

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deason

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The ignition is powered through an IBEC set at 6v. I am getting 6 v to the ignition. This is all fed by 2x 6.6v LIFE thru a smart fly power expander.

I am timing by basically finding top dead center and then inserting piston stop and turning crank slightly clockwise to screw stop in. Turn crank both ways to find where its stopping making sure to find exact medium between both sides. with piston turned count clockwise against stop, adjust piston stop out until the degree wheel is at 30 degrees. Magnet sensor is turned past sensor till beep stops on timing sensor tool. This is the firing point. At this point, i make sure that the piston stop and piston are touching as the unit fires. Check with spark plug as well. Ring locked down thak houses sensor. NGK BPMY8Y plug

Redline oil mixed 40:1. regular gas. CH ignition

tedsander

Hmmm - "the plug is soaked"...might that be the issue? Too much fuel?

deason

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larry@coyotenet

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You are setting the timing right if you set it at ~30% before top dead center. Newer electronic ignitions like RCExcel have auto advance which will advance the timing as the rpms increase. If you are using an older ignition like a C&H they may not have auto advance because they were meant to be used with an advance linkage, like original Brysons. To make sure you are actually firing the plug remove the plug and turn the engine over by hand and see if the plug sparks when the magnet goes over the sensor. If the plug sparks and you have fuel and air it should try to fire. I usually set my 5.8 carb at one and a half open on the high and one and a quarter on the low and tune from there. You may have to rebuild the carb with a kit and check the screen inside to see if it is clogged. Mostly the rubber diaphragm will lose it's resilience after setting dry for awhile.
Larry

Truckracer

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Regarding how the ignition retards for start up, as you flip the prop briskly during start, the ignition senses the speed of rotation as the magnet passes under the sensor. If turned fast enough, the ignition will retard the spark. If turned very slowly, the spark will not retard. Some people get a kick back when using a limp wristed flip because there is not enough rotation speed to create the retard. These ignitions should be called auto retard rather than auto advance as they can never advance the timing beyond the preset static timing. Some time in the past they were called auto advance and it stuck with them.

Some years ago, I bought a used Brison 2.4 that would pop and run a bit but not well. I could never find a definite problem why that engine would not run right until I disassembled it. I found that both of the main crank bearings had the seals blown out causing a severe leak that suppressed the crankcase compression / bypass. No trace of this could be seen w/o removing the crank. When you rotate the engine, do you hear the normal bypass airflow through the cylinder intake ports? Do you have a muffler in place? Some of these old chainsaw based engines won't run well at all w/o some form of muffler or pipe in place.

speedracerntrixie

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deason

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Yes, i have the muffler in place. Now that you say it, no. I don't hear the bypass. When the piston passes top dead center, i don't hear anything but it FEELS like it has good compression. please describe what seals you are talking about? Are you talking about the seals on the bearing itself? Actually, that makes sense. if the seals aren't there, the compression can pass right thru the bearing.

speedracerntrixie
Still don't have enough information to make an educated guess. What brand of ignition? What brand of IBEC? What is your starting procedure? To really help you we need as much detail as possible.

Tech Aero IBEC, CH-ignitions ignition, flip to start.

speedracerntrixie

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deason

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Yes, its the correct ignition. I spoke to Adrian at CH when i ordered it and we discussed what it was going in ETC.

I really dont know what you don't understand when i say flip to start. Was it because i didnt say flip "briskly" to start?

So to start, I flip it Briskly to start.

Truckracer

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deason, yes the seals on the main bearings. They use integral rubber seals on each side of both bearings to seal the crankcase and this is common to most engines today. The rear seal on the back bearing was missing so I assume it had been removed before assembly. This was also common with some engines assemblers. These days, most leave all (4) seals in place. No separate seal in this case.On a related topic, if the bypass action is weak you may also want to inspect the backplate gasket and make sure the cylinder base gasket is good and the base bolts tight. Weak or no bypass = no run.

Speedracer, deason and I have had several PM conversations regarding this engine so I have had more info than what appears in this thread.

deason, Speedracer knows his stuff so trust his opinions and suggestions.

speedracerntrixie

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deason

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Trying to start this engine, i have attempted the same was i do all others - The way I start an engine cold is to turn the choke on and open the throttle 30-40% and with ignition on, "briskly" flip until the engine pops. Then turn choke off and lower throttle high idle and "briskly" flip until ignition.

deason

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Understood sir. I am positive he does and not questioning that. Just seemed like the questioning was a little redundant.

Looks like ill be tearing down an engine.

Thank you Speedracer and Truckracer..... I'll let you know how it turns out once engine is apart and inspected

Truckracer

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If you do pull the engine apart, start with the cylinder. Carefully inspect the ring to make sure it is free on the piston. These rings are fit very close in the ring groove and are prone to stick which could cause your problem. These engines should have a very strong compression feel when the prop is pulled through. Quite a bit more than most more modern engines. If stuck, freeing up the ring might resolve your problem. These engines are getting some age on them now so any number of problems might be found with a good teardown and reassembly but no need to go much further than necessary if it is a simple problem.

deason

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Gotcha... will definitely be pulling it apart. Will probably order a Bowman for re-assembly.

Truckracer

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Those are great rings but I've rarely had to replace a stock Sachs based ring. Unless the engine has extremely high time, has been abused or the ring breaks during disassembly which it can if stuck, I try to reuse the original ring if possible. They are pinned and remain mated to the cylinder even after disassembly. If the ring is free on the piston, I don't normally remove it unless necessary. I do check ring gap by sliding the piston back in the cylinder where the gap is visible through the exhaust port. Replacing both rod bearings is usually good practice on these engines any time they are apart unless the engine is low time.

deason

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Understood sir. Im very anxious to get it apart and see whats going on inside.

51-D GUY

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do you want to sell the mechanical advance stuff ? im interested if so .