bobj Posted May 16, 2006 Posted May 16, 2006 Been working on this problem all winter. Engine runs but timing is ahead. 3314H Simplicity, 14 hp Briggs, engine model 320421, type 0134-01. Points were not hooked up when I got the machine. At first it would just kick back and not start. Checked flywheel key - it was worn. Replaced it, engine now ran but but starts like timing ahead - still some kick back - all this without points. Got new points condensor, hooked up wires according to manual - wow back fire woke the neighbors. Checked manual for timing and found that flywheel arrow on my machine was at 3 o'clock position instead of 12 o'clock. Figured the points pushrod or plunger was worn which would change timing arrow mark orientation. Bought a new one, part # 298125. Now my arrow is at 6o'clock. My question: Is it common to have to file or grind plunger shaft to time these things correctly. I'am guessing /040-.060 needs to come off the plunger shaft. I did that to a new valve to correct that tolerance. See pic Thanks Bob J.
firefoxz1 Posted May 16, 2006 Posted May 16, 2006 I don't know if I understand you completely. The points plunger would not change the orientation of the TDC marks of the flywheel or the timing they would only move where you adusted your points at ( I don't have that gap figure) because the gap is adjusted against the plunger, so as long as it's long enough to open the points to get the correct gap it should be fine. To find TDC(top dead center) put a straw in the spark plug hole and when it's as far up as it gets thats TDC. http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=62384
maxtorman1234 Posted May 16, 2006 Posted May 16, 2006 I agree, as long as your flywheel key is good, armature gap is good, points & plug are set right, nothing else can effect timing. As long as you have the right points gap , your timing should be ok. I dont know how these alignment arrows can be in the wrong place, unless theres something drastically wrong with your crank or flywheel, as they are set by the flywheel key, and its fixed. you must not be at TDC
D-17_Dave Posted May 16, 2006 Posted May 16, 2006 Your working under the assumption that no one else has altered the cam position from the crank. There is no way as mentioned above that the timeing would be floating around as there is only one place on the cam lobe that should stroke the plunger enough to fire the points. However if someone assembled the engine a tooth or 2 off it may still run just not very well. This may cause the timeing to be way off but it would still show up in the same spot each time it's checked. A cheaters way of checking the cam to crank timeing without pulling the whole engine and doing a dissasebly is to remove the head, bring the piston to TDC on the dead stroke. This will place each valve in the partially open position when the piston hits TDC. The exhaust and intake valve should both be open the same amount as the piston tops out. You should notice that the flywheel can rotate quite a bit just before and just after TDC and the valves will quickly go from one open to the other open so you'll see the equal amount easily. If the valves don't show both open at TDC the cam is off time and going into the engine is the only way to correct this. Then reset the ignition timeing.
maxtorman1234 Posted May 16, 2006 Posted May 16, 2006 I meant to mention that dave, that could easily be the problem, i hate it when people work on stuff and dont know what theyre doing,
PatRarick Posted May 16, 2006 Posted May 16, 2006 When it backfired, it most likely sheared the flywheel key. The points run off of the camshaft on the cast iron engines. With the exception of a sheared flywheel key, the only other reason the points could be that far out of time is if the camshaft timing was off. Pat
bobj Posted May 17, 2006 Author Posted May 17, 2006 I had pulled the front cover and looked at gear alignment marks a few months ago, looked ok. The plunger seal retainer, # 221873, is missing. It appears that this part sits under the points. Going to try that today. Thanks for your help. Bob J.
MrSteele Posted May 17, 2006 Posted May 17, 2006 Grinding the plunger is unnecessary, as the points should have plenty of adjustment on the adjuster screw. The seal retainer is missing on most engines I have ever torn down, and is missing when I put them back together, as well, with no ill effect on the engines. For your flywheel to have moved as much as you say, from 3 o'clock to 6 o'clock, the key is likely sheared completely. Something I have found to be a necessity in the old Briggs engines, it to be certain that your flywheel is tight, beyond hand tight. I give the wrench a few good strokes with a hammer to be certain. Far less sheared keys that way. A loose flywheel will shear the key as soon as the engine fires. You say you checked the timing marks with the front cover off. Were you at TDC when checking the marks? If not, your problem is that the cam is in the wrong position. Be certain of that before going to any extremes.
bobj Posted May 17, 2006 Author Posted May 17, 2006 This is Bob J. I took the head off and the front cover & pto gears. The rear was already apart, flywheel off. With the piston at absolute tdc the exhaust valve was 1/2 open. With the piston within 1/4" of top, which aligns timing marks, the valves are closed or nearly closed and behave as mentioned in a previous post by D-17 Dave. Looked at the front gear marks while crank and cam in the above mentioned position. Gear marks look just like the book, that is circle mark on cam gear perfectly aligned with chisel mark on crank gear. Also points seem to be fully opened, rather than just starting to open as the manual states. This is not looking good so I decided to take it to a long time Simplicity dealer/engine rebuilder who knows these things like I do with old Corvettes. I am restoring this thing for my son who indends to use it for his landscaping business which is 1100 miles from me. I have designed a bucket system for it so he can make a living using this machine. It will probably be used more for building stone walls and lugging logs and plowing snow more than cutting grass. It needs to be dependable and I think long lasting because of the way it was built. I told Bob Merrow to bring the entire engine up to spec. We'll find out what's been altered next week. Will post it here for you all to see. Thanks for all the helpful comments. Bob J.
maxtorman1234 Posted May 17, 2006 Posted May 17, 2006 Your points and valves indicate Your crank and cam cannot be set right, maybe your looking at the wrong mark? at tdc the valves have to be closed, all that could be doing that is the cam/crank off a few teeth.
MrSteele Posted May 17, 2006 Posted May 17, 2006 It would seem, that your engine was not on TDC when you looked at the timing marks, most likely on the exhaust stroke. The valves should be closed, not one or the other open, even half way. Whoever put the engine together this way was a brainchild, it would seem, as sliding the cam into the proper position with a valve spring loaded in such a manner may be close to impossible. What is most likely, is that the "rebuilder" simply put the engine back together.
UCD Posted May 18, 2006 Posted May 18, 2006 For timing purposes the piston has to be top dead center on compression stroke. With the head off, the piston would be at the top of its stroke with both intake and exhaust valves CLOSED. The cam shaft turns one revolution for every two revolutions of the crank shaft. Combustion stroke = plug fires, Both valves closed, piston on down stroke. exhaust stroke = piston on upstroke, exhaust valve opens, exhaust pushed out. intake stroke = piston on down stroke, exhaust valve closes, intake valve opens, fuel sucked in. compression stroke = piston on upstroke, both intake & exhaust valves closed, fuel compressed. Plug fires just before TDC on compression stroke, process starts over. Combustion stroke + exhaust stroke = 1 revolution of crank shaft = ½ revolution of cam shaft. Intake stroke + compression stroke = 1 revolution of crank shaft = ½ revolution of cam shaft.
bobj Posted May 19, 2006 Author Posted May 19, 2006 I think best clue came from UCD: "The cam shaft turns one revolution for every two revolutions of the crank shaft." This would account for why alignment marks on cam and crank gears looked proper. Cam was probably installed on wrong stroke of crank. If cam was removed and the crank was turned 1 revolution and then reinstall the cam I think the problem would be solved. The question is what else got overlooked or messed up? The plot thickens: The engine has a new piston, .020 oversize. The engine had to be bored. This would lead me to believe that some shop had assembled the engine improperly. Some poor Joe probably was not able to get the rebuilder to correct the error and sold the non-running machine cheap. Bob J.
firefoxz1 Posted May 19, 2006 Posted May 19, 2006 With the cam out turning the crank would do nothing, if the marks align they align. If memory serves me correct the points stay open most of the time on these engines, close for a short amount of time before TDC. If this ran without the points hooked up are you sure someone didn't put a magnatron(?) coil on with-out repolarizing the flywheel? this may be your whole problem? Easy to distinquish the two coils: if the field coil is in the middle of the two legs only, you have a points coil, if your field coil has a lump on the one side between the leg and the coil that is the trigger and a magnetron, also I found regular coils had the lead permenantly fixed to it and the mag. had a tab to attach a lead to (this may or may not be the case in all situations, just what I've observed so far).
Doll Posted May 20, 2006 Posted May 20, 2006 On the cam, you have a circle with a flat spot in it.. When the plunger wears the circle, The flat spot goes away. This not only changes the lift of the points, It changes the timing of the engine because the points close late and open early. Also, It the plunger is bent, The timing will be off. I ran into a problem like this last fall. A friend bought a 7014 that ran rough. In fact, it quit as we were loading it on the trailer. Once I got it here, I started finding that it was an engine that had been rebuilt and pieced together. CHanged from an S/G to a newer starter and no provision for a charging system. Ring gear flywheel and a magnatron. I didn't have the tool to check the polarity on the flywheel so I changed it back to an old coil and points.. Still wouldn't run. Checked the points for continuity and nothing.. FOund that the points had to be set at something like 10 to close. I guess that a person could have taken a dial indicater and a flat file and recut the flat on the cam. ( THe plunger had been bent when the engine was built and the wide base on the plunger had cut a groove in the cam ) But figuring how much lift to leave out to make up for lost diameter gave me a headache and I just installed a new cam..LOL I'll leave the higher math to some of you smarter guys.. I'd really like to know if this turns out to be something like your trouble.. Please let us know.
bobj Posted May 21, 2006 Author Posted May 21, 2006 In support of the previous comments by Doll, the timing mark on the flywheel was at the 3 o'clock position when I first tried to set the timing, (off by 90 degrees). That's when it was suggested that the points plunger might be worn. When I installed the new plunger I noticed very noticable wear on the cam side of the old plunger, maybe .020"-.030". With the new plunger installed the timing mark is now at the 6 o'clock position, or 180 degrees from where it should be. In other words the timing retards the spark as the plunger wears. Bob J.
Al Posted May 21, 2006 Posted May 21, 2006 Hi, One thing to remember is that the points don't open at top dead center, but about 20 degrees before TDC. This is where these fire. Same for Kohlers. Firing at TDC they will barely run and have little power and generate a lot of heat. The plunger on the points should never have to be ground off. If they fire at TDC, by the time the flame front crosses the combustion chamber the piston is well down on the stroke and and the compresssion has diminished when the combustion occurs. This results in low power and as a result of this the engine runs hot. In normal operation the spark occurs when the crank is 20 degress Before Top Dead Center. The piston travel is minimal because the arc of the rod is almost flat. The plug fires and by the time the fuel is ignited and the flame front travels across the chamber, the crank has gone past TDC and started to move the piston downward. The compression is at max and the maximum amount of energy is used to move the pistom downward. Due to the angle of the crank throw, the movement of the piston turns the crank significantly. Once the crank throw gets past the 1 oclock position, the piston travel accelerates rapidly. At this point the effect of the combustion has little effect, or provides little added energy as the piston travel it becoming very rapid and the expansion of burned gases is slowing. This is why spark timing has so much effect on output power. We used to rework the advance curve of the distributor on the Chevys when we raced them. We started with 12 degrees initial and changed the springs on the advance weights and ground the weights to change the curve of advance. We had about 32 degrees at 3000 and 42 degrees at 4000 rpm where we stopped it and we ran these engines to 9000 rpm. We won the World Series of Drag Racing at Cordova Ill. in 1960 both class (B Competition Coupe) and Middle Eliminator (all gas powered cars except Rail dragsters) with a fuel injected 58 Corvette engine with an Iskenderian 5 cycle cam 300 degree duration and basically stock 10.25 compression ratio pistons and reworked heads. We used this curve in the igniton. This was in a 1600 lb coupe with the engine in the back. We crawled through the windshield opening to get in and the engine was in the back. We ran in the 9s and about 130 mph in the quarter mile. With 1960s tires and 283 cu inches. My 348 1958 and 1960 Super stockers liked a similar curve, but the 348s didn't like more than 39 degrees total advance at 3400 rpm. They would go 7000 but went faster at a 6200 shift point. If any of you were at the 1960 World Series of Drag Racing, We won with a car called POKIE. My best friend that I ran the car with was killed the next Spring as a passenger in a car accident. Sorry about getting off course. Tractor pullers here is a place for you to look for the edge. Put them on a dyno and put a degree wheel on the engine and then power time it. Then figure a way to build an ignition curve . Al Eden
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