Outdoor Power Equipment and Small Engines - k301 backfires
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scp1180
10-06-08, 03:31 PM
I have a problem I hope you can help me with. I rebuilt a 1971- k301 electronic ignition, w/electric start/generator and kill switch and had it bored out to .030,new piston,rod,crank .010, timing is right on, checked w/ timing light. It starts easy and idles with a little miss but when I give it gas it backfires hard thru the exhaust. I have rebuilt and adj. the carb, new plug, lashed the valves to spec,replaced bad wiring, set the trigger to .005, replaced all gas hoses, fuel pump seems to pump good manually and has a decent flow when I checked it while cranking it over. Also is there a way to check the pump pressure? Any help would be appreciated
Airman
10-06-08, 07:58 PM
To test the fuel pump the manual says nothing more than “crank engine several times and observe fuel flow”.
With everything you say you have done, I am at a loss. When I am confronted with a problem such as this, I check and double check. Typically, your problem is carburetor or ignition timing related.
I hope that someone else can give better insight.
With everything you say you have done, I am at a loss. When I am confronted with a problem such as this, I check and double check. Typically, your problem is carburetor or ignition timing related.
I hope that someone else can give better insight.
30yearTech
10-06-08, 08:21 PM
Can you post the spec number off your engine??
shelbyscott
10-07-08, 01:35 AM
check your points and condensor
shelbyscott
10-07-08, 01:38 AM
my bad sorry i had the same problem on a JD 214 i didn't
read the elctronic ign part sorry
read the elctronic ign part sorry
scp1180
10-07-08, 03:30 PM
Hi 30 year tech-- The #'s are ser. 3105029 - spec. 47407c - Tractor model 1-400 - I hope you can help, I can't figure it out Thanks
30yearTech
10-07-08, 04:44 PM
Well I can't say that I have ever run across this issue before.
Since the engine is firing out the exhaust, things I would suggest to look at are:
Valve timing, make sure camshaft is timed properly to crankshaft.
ACR, check and adjust compression release as per service manual, and check ACR operation to make sure it moves freely and is not sticking in the engaged position. ACR should release above 600 rpm's.
Exhaust valve, make sure it's not bent and valve face seats all the way around.
Keep us posted and Best of Luck...
Since the engine is firing out the exhaust, things I would suggest to look at are:
Valve timing, make sure camshaft is timed properly to crankshaft.
ACR, check and adjust compression release as per service manual, and check ACR operation to make sure it moves freely and is not sticking in the engaged position. ACR should release above 600 rpm's.
Exhaust valve, make sure it's not bent and valve face seats all the way around.
Keep us posted and Best of Luck...
scp1180
10-07-08, 04:52 PM
Hi Thanks for your reply I check it out and let you know if I figure it out thanks again
cheese
10-08-08, 02:51 AM
I agree with 30yearTech... on all 3 points mentioned.
scp1180
10-08-08, 04:19 PM
Hello, I checked the acr and it works the way it's supposed too- the timing is perfect and valves are adjusted - One thing I did notice is that the spark on plug is kind of yellow instead of blue, could this cause the backfire? Is there a way to check a coil they are $80, so I want to make sure before I buy one Thank you for responding, I appreciate it
30yearTech
10-08-08, 04:22 PM
The color of the spark means little, the hottest spark is ultraviolet and invisible to the eye. There are test procedures for the coil in the service manual, I am assuming you have one, but if not they are available for download from www.kohlerplus.com
cheese
10-08-08, 04:23 PM
The spark should be a crisp blue one. Yellow would indicate weak spark and if the coil is breaking down, it could cause the problems you have. I have no method of testing the coil on that setup.
scp1180
10-08-08, 04:48 PM
Thanks- I check the coil out and let you know
30yearTech
10-08-08, 04:51 PM
Here is an excerpt from a column with general information about ignition systems, not specific to your engine but overall just general misinformation that has been passed around through the ages.
"Now, how about some of those old wives tales that just aren't true.
* Rust on the flywheel magnets causes a loss of spark. Not true. A magnetic field does not care about rust. It has no effect on it.
* A bright blue spark is best. A yellow/orange spark signifies weak ignition. Not true. Spark color determines virtually nothing. The hottest spark is ultraviolet which we can't see. Blue spark is cold in comparison to ultra-violet. Orange and yellow come from particles of sodium in the air ionizing in the high energy of the spark gap.
* Laying the spark plug against the block and pulling the engine over can adequately test ignition coil output. Not true. The ignition coil will only generate enough output to jump the gap of the plug. When under compression, the plug requires twice the voltage to fire. This check is not an accurate test of the coil and can be misleading.
* An armature air gap that is too wide will prevent spark. Not true. Well, sort of not true. Briggs & Stratton air gaps cannot be made too wide to prevent spark providing the coil is healthy and the engine is spun over fast enough. A wide air gap, say .030" will ever so slightly retard the ignition timing as the magnetic field takes longer to build within the coil windings."
"Now, how about some of those old wives tales that just aren't true.
* Rust on the flywheel magnets causes a loss of spark. Not true. A magnetic field does not care about rust. It has no effect on it.
* A bright blue spark is best. A yellow/orange spark signifies weak ignition. Not true. Spark color determines virtually nothing. The hottest spark is ultraviolet which we can't see. Blue spark is cold in comparison to ultra-violet. Orange and yellow come from particles of sodium in the air ionizing in the high energy of the spark gap.
* Laying the spark plug against the block and pulling the engine over can adequately test ignition coil output. Not true. The ignition coil will only generate enough output to jump the gap of the plug. When under compression, the plug requires twice the voltage to fire. This check is not an accurate test of the coil and can be misleading.
* An armature air gap that is too wide will prevent spark. Not true. Well, sort of not true. Briggs & Stratton air gaps cannot be made too wide to prevent spark providing the coil is healthy and the engine is spun over fast enough. A wide air gap, say .030" will ever so slightly retard the ignition timing as the magnetic field takes longer to build within the coil windings."