KF82 Flathead Nightmare

Deceptive

Hi there

I am having a problem after a rebuild

Engine cranks ccw and will occasionally fire and when it does, it almost stops rotation of the engine instead of adding to the ccw momentum.
I get a puff out the intake/carb as though it is a backfire. The engine flodds/ dumps gas in to the cylinder and out the exhaust, but might be due to not firing.
Pulled plug and soaked, tried plug out of cylinder and great consistent spark...


I am /was positive timing was lined up properly
I am sure the balancer is correct... as per this pic (timing Balancer)
I am also hoping I have the correct timing mark on the Cam timing picture...
I used that and I get a short puff out the intake just before the TDC and magnet/magneto pass each other for the spark. I am assuming it is something to create a vacuum or back pressure into the carb for gas intake, but unsure. I did measure the cylinder pressure and was just over 100 so it would fall just into spec..

There also is another mark on the camshaft in the second cam picture (outer) where the two wholes align and the inner whole seems to have a dimple in it.I am sure this is not the timing mark , but want a verification on that asw I am going to try that alignment mark as well in an attempt that i am perhaps i am using the wrong mark .

Can anyone shed some light on this... I have ripped the engine apart 5 times already and and at whits end... Checked valves , clearances, tappets, lifters ... All are correct and the same size when measured..

I am thinking timing , but I did have it back together and running before an under tightened bolt let go on the piston arm and caused another mess.. that is all fixed but this attempt at rebuild has left me with this issue now. I used the original mark in the first and second picture in that first rebuild and things seemed fine then .

HELP.....

Attached Images

	Timing Blancer.jpg (90.3 KB, 0 views)
	Timing Cam.jpg (183.5 KB, 0 views)
	Timing Cam Outer.jpg (190.1 KB, 0 views)

BGW

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Doc's BoneCracker

sure sounds like your 180 degrees out.

Deceptive

I have downloaded a manual and read the complete section on dis-assembly and it clearly states
6. Turn crankshaft to bottom of stroke (crankpin down) .

Then on step 12
Align timing mark on cam shaft gear with timing mark on crankshaft gear... the initial picture I had where the timing mark and the small indent is correct then... BUT ON BOTTOM OF STROKE and not TDC..... BDC i guess it would be.

So i will go with this and update...

Doc's BoneCracker

Good luck keep us informed and also I know on my ezgo you have to turn two revolution's for it to be in time for each stroke so basicly turn twice for exhuast and twice for intake

Deceptive

Okay so i took it all apart again and looking at it , with the crank and cam timing marks matching, the only possible spot for it to be is TDC.... ARRRRG **** manual is obviously wrong, or implies ...rotate crankshaft to line up timing marks...

Okay will assemble again and test, but I am sure I was already here before

Deceptive

Put it back together... doesn't really seem to much different.

I am thinking I have an electrical issue though now.

I ripped apart the carb , seeing as though it was already off and gave a good cleaning.. I had done that last rebuild but what the heck.. new gas and bypassed existing tank as well .

Was troubleshooting and bound the neutral lockout switch is broken and loos according to my wiring diagram to be miswired...

At any rate, have to order a switch as now with me tinkering , wont even pass power to the starter...


Question about engine kill hookup... to me it looks at though it shorts to ground ... If I unplug at the engine plug, that would bypass completely the kill if it were shorting ??

I didn't check spark this time but will once again ... I did get a few good fires , but for the most part same difference and I am 100 positive timing is right...

I will update when I trace some more wires and get the micro switch in... I will post a video as well so perhaps someone can shed some light on seeing what it is doing...

toadady

where did you find the manual to download?

fastercarter

100 percent sure that everything is correctly aligned and timed ? You have to have something out of whack here. At piston TDC on the firing stroke, both valves will be closed and the flywheel magnet will be right on the coil. The exhaust valve will then be actuated and remain open approx to 3/4 before TDC is again achieved at which point the intake will begin to open on the downward cycle of the piston. Look here if it helps; This just a simple digitised operational tutorial. http://en.wikipedia.org/wiki/Four-stroke_engine Also remember these engines have a lost spark so the motor also sparks on the exhaust stroke.

FC

Deceptive

I have the manual for the 86... I can post the complete PDF manual if that is allowed..?? MODS?????

toadady

just E-Mail it, that's how the yamahauler's do it

jdckdc@centurylink.net