1986 Kawasaki ke100

Well I got this thing a while back. Traded a 20 ho Kohler garden tractor for it (never actually knew the brand). Got it and bought a new cylinder and piston, new Kickstarter, new paint, new tires, new fuel line, new petcock, new steering stem bearings, and new rear rim. Probably more I'm forgetting, but I'm trying to figure out why it runs rough at high rpms. I can rev it no problem, but when running high rpms while riding it will kind of stutter and jerk. Pulled the plug today hoping it would give a hint maybe. Not really sure where to look. Never dealt with 2 strokes.










Just some pictures throughout the build. Have more if anyone cares to see anything specific. Might add some more details and pictures later.

Looks a lot better after the rebuild. Ever get it to run right?

mr.modified wrote:

Looks a lot better after the rebuild. Ever get it to run right?

thanks, took a long tim to get it all where it is. It will start everytime, but won't run right. Not sure what the issue is, I haven't dealt with two strokes much. It will run and get up to 50 mph, but at high speeds it will kinda stutter and it will slow down and speed up. It seems like it's running lean, but the spark plug is oily so that says it's running rich. I'm not sure where to go.

Did you ever clean the carb out? Might have missed something I guess. How much oil do you mix in or is it oil injection? Even if you had way too much oil mixed, wide open running should keep things cleared out I would think. Kinda weird if it runs good otherwise. I wonder if you have good enough fuel flow from the tank and through the inlet on the carb. If it was partially restricted, maybe it starts to run out of fuel at high speed.

mr.modified wrote:

Did you ever clean the carb out? Might have missed something I guess. How much oil do you mix in or is it oil injection? Even if you had way too much oil mixed, wide open running should keep things cleared out I would think. Kinda weird if it runs good otherwise. I wonder if you have good enough fuel flow from the tank and through the inlet on the carb. If it was partially restricted, maybe it starts to run out of fuel at high speed.

cleaned the carb out probably 5 times. Cleaned and soaked in carb cleaner, jets are perfectly clear, blew out the carb inlet with compressed air. Run 50:1, still spits oil out the tail pipe. Even after running wide open then shutting it off and pulling the plug, the plug looked pretty oily. I have 3/16 fuel line on it now, I was thinking of trying 1/4 and see if that's restricting it maybe. Might clean the carb again because I guess it can't hurt. Just not sure where to start. Oh and it's only fouled out one plug, and that was after trying to Kickstart it with the choke on and the run switch off (don't act like we don't all make stupid mistakes). Not really sure what I should be looking for. Might help to know that the muffler no longer has a baffle or spark arrestor. Someone in its 30 year life decided it didn't need one I guess.

Put on 1/4 fuel line and a new spark, seemed to clear up a little, but definitely still there. We'll see if it gets worse, the same, or better. Maybe the spark plug is slowly fouling causing more and more stutter.

Unless the muffler being gutted out makes it run lean up high, no idea. I don't know what kind of carb it has but if you could try picking the needle up one notch in whatever throttle slide it has. Usually about 5 notches in the needle with a small clip on it. Take the clip off (careful not to lose it) and move it down one notch so the needle will be slightly higher. That would make it slightly richer throughout the range. If it helps at least your heading in the right direction. 50:1 sounds a tad on the scary side of the oil mixture spectrum, but that wouldn't effect the running issue. I mix pretty much everything at least 32:1, even the new chainsaws and stuff that are marked 40:1 or 50:1. I read in a 2 stroke performance book that the author even picked up a couple hp on a dyno by mixing heavier than recommended. I can't remember how much heavier, but I think it was quite a bit. I think it was something nuts like 14:1. I think then of course you'd run into plug fouling all the time at lower speeds and probably carbon build up would be horrible.

I second mr.modified. I bet gutting the exhaust makes it run lean up high. Two strokes need backpressure to keep the air/fuel mixture from just blowing straight through the cylinder and out the exhaust. Restrict it too much, and you wont have any power anywhere in the rpm range. maybe try an old mower muffler just for S&G to see if that helps it?

mr.modified wrote:

Unless the muffler being gutted out makes it run lean up high, no idea. I don't know what kind of carb it has but if you could try picking the needle up one notch in whatever throttle slide it has. Usually about 5 notches in the needle with a small clip on it. Take the clip off (careful not to lose it) and move it down one notch so the needle will be slightly higher. That would make it slightly richer throughout the range. If it helps at least your heading in the right direction. 50:1 sounds a tad on the scary side of the oil mixture spectrum, but that wouldn't effect the running issue. I mix pretty much everything at least 32:1, even the new chainsaws and stuff that are marked 40:1 or 50:1. I read in a 2 stroke performance book that the author even picked up a couple hp on a dyno by mixing heavier than recommended. I can't remember how much heavier, but I think it was quite a bit. I think it was something nuts like 14:1. I think then of course you'd run into plug fouling all the time at lower speeds and probably carbon build up would be horrible.

it still fouls plugs with oil so I'm not too worried about the mix. It's the premix bottles that are 2.6 ounces for a gallon. I think I'm going to either make or buy a baffle to put in it and try that. Oh and I don't think the carb has needle adjustments.

CraftsmanQuad19 wrote:

I second mr.modified. I bet gutting the exhaust makes it run lean up high. Two strokes need backpressure to keep the air/fuel mixture from just blowing straight through the cylinder and out the exhaust. Restrict it too much, and you wont have any power anywhere in the rpm range. maybe try an old mower muffler just for S&G to see if that helps it?

I'd like whatever I make to be on the inside like the baffle used to be so it won't look weird and out of place. I'll have to come up with something.

I only meant the mower muffler as a quick test to see if it helped (S&G = ***** 'n giggles)

CraftsmanQuad19 wrote:

I only meant the mower muffler as a quick test to see if it helped (S&G = ***** 'n giggles)

I guess I could try it. I'll have to see if I can make a decent baffle. Definitely would be nice to quiet it some.

Made a baffle for it. Now it runs better higher up but it dies idling out of no where sometimes. Maybe just adjust the idle screw.

SatiricalHen wrote:

Made a baffle for it. Now it runs better higher up but it dies idling out of no where sometimes. Maybe just adjust the idle screw.

How's she sound? Yeah, two strokes really don't like to idle very well. That's just the nature of the beast I suppose

CraftsmanQuad19 wrote:

SatiricalHen wrote:

Made a baffle for it. Now it runs better higher up but it dies idling out of no where sometimes. Maybe just adjust the idle screw.

How's she sound? Yeah, two strokes really don't like to idle very well. That's just the nature of the beast I suppose

it's definitely quieter. It's not perfect still but a lot better. Going to tweak the baffle a little more and hopefully get it running perfect. Hopefully I'll remember to get pictures next time I have it out. Basically cut triangles out of one end of a piece of pipe and folded them together almost closed off, drilled a lot of random holes in the sides and welded to the piece that hangs out the end of the exhaust. Nothing pretty but it works. Might fully weld the end up, not really sure. I might even try packing it. Not 100% sure yet.

Was riding it around today, and the clutch cable broke so I had to limp it back home and go from there.

Do you have a lot of area to ride?

mr.modified wrote:

Do you have a lot of area to ride?

nope, just ride around my neighborhood, and close by neighborhoods.

Cool bike!! Read the whole thread, maybe I can help. 2 strokes are pretty hinky but I got a good understanding of them. Maybe shed a little light on the subject. OK.....

Problem at high rpm. Seems you got the basics covered. Plug, carb, fuel and oil mix. I usually mix my 2 strokes to where there is a little smoke coming out the exhaust. Any 2 stroke always fouls the plugs at idle, have to rev them every now and then to keep the oil off the plug, and too much oil mixed in the fuel will foul the plug at any rpm but with heavy smoke coming out the exhaust while running. Need good compression on these motors to run right, all 2 strokes are high compression engines. Low compression would have the problem you are having. Maybe do a compression test, or the very least, turn the engine over by hand and good compression would be very hard to spin by hand. You cleaned the carb probably to a point to where you can eat out of it. I'm sure you put it together right, but what about the rest of the intake system? You got the intake and where it mounts to the engine. 2 strokes need a one way check valve in the intake system to keep the intake charge in the crank case. On weed eaters and chainsaw type engines, they use the piston to cover the hole into the engine to hold the intake charge. On the bigger 2 stroke motors, where the intake manifold runs into the crankcase itself has a flapper valve that opens when the engine is sucking and closes to hold the intake charge that it just sucked in inside the engine. Could be this valve is floating at high rpm, feezable because this valve is a flat piece of metal that is a spring and if it has little spring pressure would not close properly at high rpm, and should be flat and smooth to seal properly when closed. Could be as simple as the points bouncing at high rpm, that is if you have points on that motor. If you put new points on then it shouldn't be the issue. Me looking at your pic of your plug, doesn't look too bad to me, sure it's black but not caked up with burnt oil or wet so it should be firing ok. If you pulled it out and was wet then it's misfiring.

Ok, basic tuning of any piston engine is as follows.....
If the engine backfires through the carb, it's running lean. If it's backfiring through the exhaust, it's running rich. Ignition problems will make the engine run rich by dumping raw fuel in the exhaust in effect backfire through exhaust. Timing issues would make the engine run hot or hard to start. Keep in mind, timing and ignition are 2 separate things. The starting point in tuning any engine to run right is as follows... Idle, off idle, mid range throttle, wide open throttle. You can't fix wide open throttle until the engine is running right mid range throttle.

2 stroke exhaust systems. Your bike is pretty mild for exhaust which is probably why whoever removed the baffling in the muffler. By putting that B&S muffler on just helped on low end power with the sacrifice of mid and high rpm power. Engine will run fine with the muffler on there but the exhaust has nothing to do with why it's not running right.

Maybe later after you get the motor running right, I'll tell you how to tune in the exhaust for more performance if interested.

prancstaman wrote:

Cool bike!! Read the whole thread, maybe I can help. 2 strokes are pretty hinky but I got a good understanding of them. Maybe shed a little light on the subject. OK.....

Problem at high rpm. Seems you got the basics covered. Plug, carb, fuel and oil mix. I usually mix my 2 strokes to where there is a little smoke coming out the exhaust. Any 2 stroke always fouls the plugs at idle, have to rev them every now and then to keep the oil off the plug, and too much oil mixed in the fuel will foul the plug at any rpm but with heavy smoke coming out the exhaust while running. Need good compression on these motors to run right, all 2 strokes are high compression engines. Low compression would have the problem you are having. Maybe do a compression test, or the very least, turn the engine over by hand and good compression would be very hard to spin by hand. You cleaned the carb probably to a point to where you can eat out of it. I'm sure you put it together right, but what about the rest of the intake system? You got the intake and where it mounts to the engine. 2 strokes need a one way check valve in the intake system to keep the intake charge in the crank case. On weed eaters and chainsaw type engines, they use the piston to cover the hole into the engine to hold the intake charge. On the bigger 2 stroke motors, where the intake manifold runs into the crankcase itself has a flapper valve that opens when the engine is sucking and closes to hold the intake charge that it just sucked in inside the engine. Could be this valve is floating at high rpm, feezable because this valve is a flat piece of metal that is a spring and if it has little spring pressure would not close properly at high rpm, and should be flat and smooth to seal properly when closed. Could be as simple as the points bouncing at high rpm, that is if you have points on that motor. If you put new points on then it shouldn't be the issue. Me looking at your pic of your plug, doesn't look too bad to me, sure it's black but not caked up with burnt oil or wet so it should be firing ok. If you pulled it out and was wet then it's misfiring.

Ok, basic tuning of any piston engine is as follows.....
If the engine backfires through the carb, it's running lean. If it's backfiring through the exhaust, it's running rich. Ignition problems will make the engine run rich by dumping raw fuel in the exhaust in effect backfire through exhaust. Timing issues would make the engine run hot or hard to start. Keep in mind, timing and ignition are 2 separate things. The starting point in tuning any engine to run right is as follows... Idle, off idle, mid range throttle, wide open throttle. You can't fix wide open throttle until the engine is running right mid range throttle.

2 stroke exhaust systems. Your bike is pretty mild for exhaust which is probably why whoever removed the baffling in the muffler. By putting that B&S muffler on just helped on low end power with the sacrifice of mid and high rpm power. Engine will run fine with the muffler on there but the exhaust has nothing to do with why it's not running right.

Maybe later after you get the motor running right, I'll tell you how to tune in the exhaust for more performance if interested.

The engine has a rotary valve, no reed valve. I don't know if there's any way to adjust that or not. It has points, not really sure how to do anything with them though. Should have good compression, new cylinder, piston, rings and gaskets. What would cause it to misfire and have a wet plug?

You have an 86 bike with points ignition, sounds like that's not the original motor. EPA started getting rid of points back in 74. No big deal though. Never dealt with a rotary valve either in a 2 stroke. I would do a little research on the engine, maybe schematics or tear down pics of motor to see if it was removed when rebuilding the engine that it needs to be degreed when put back in, chances are it being a 1 cylinder, it will only go back in one way and not have to worry about it.

You said the engine is running but when you pulled the plug, it was wet. If this is the case then the plug being wet after shutting off the engine is normal since the engine is still spinning when killing the ignition, there's fuel still moving through the engine till it stops. A misfire though, sounds like points are out of adjustment. The contacts are the round parts that touch each other then spread apart. This is part of your timing also. How far apart the contacts open determine how long they open and close. This gap between the contacts needs to be checked with a feeler gauge. Depending how the power goes to the points and work determines how long the spark lasts, this is called dwell. For example too small of a gap on the contacts and the spark would last half the time it needs to spark, engine would run fine at idle to mid range but at high rpm would stumble because the spark isn't lasting long enough to light the fire or not enough of time to charge up the coil to throw a spark. Check manufacture specs for this gap. Plus look at all the parts to see if they are worn out, holes in the center of contacts, shaft has side to side play that has the bumps on it to open the contacts, shredded wires.

Another option might be to look up a newer engine of same design with electronic ignition to put onto your engine. Usually made to fit engine by just bolting on.

Hope this helps.

prancstaman wrote:

You have an 86 bike with points ignition, sounds like that's not the original motor. EPA started getting rid of points back in 74. No big deal though. Never dealt with a rotary valve either in a 2 stroke. I would do a little research on the engine, maybe schematics or tear down pics of motor to see if it was removed when rebuilding the engine that it needs to be degreed when put back in, chances are it being a 1 cylinder, it will only go back in one way and not have to worry about it.

You said the engine is running but when you pulled the plug, it was wet. If this is the case then the plug being wet after shutting off the engine is normal since the engine is still spinning when killing the ignition, there's fuel still moving through the engine till it stops. A misfire though, sounds like points are out of adjustment. The contacts are the round parts that touch each other then spread apart. This is part of your timing also. How far apart the contacts open determine how long they open and close. This gap between the contacts needs to be checked with a feeler gauge. Depending how the power goes to the points and work determines how long the spark lasts, this is called dwell. For example too small of a gap on the contacts and the spark would last half the time it needs to spark, engine would run fine at idle to mid range but at high rpm would stumble because the spark isn't lasting long enough to light the fire or not enough of time to charge up the coil to throw a spark. Check manufacture specs for this gap. Plus look at all the parts to see if they are worn out, holes in the center of contacts, shaft has side to side play that has the bumps on it to open the contacts, shredded wires.

Another option might be to look up a newer engine of same design with electronic ignition to put onto your engine. Usually made to fit engine by just bolting on.

Hope this helps.

this whole bike seems to be bass ackwards. It had old style rear suspension and 6v power that ran from the beginning of production in the 70s all the way to 2001. I honestly have no clue what the points should look like and when/where to adjust them. I just tried researching what it could be causing this and people said their points on theirs were rusty. I took the cover off where it's supposed to be and everything looked shiny and clean so I just put it back on. All wires are good, no play in the shaft, I'll try and figure out the points thing, and I have a feeler gauge. Just don't know where to find the specs from the factory because for how long these were produced there's little info on them.

Old school it, LOL. Back in the day, to set the points, people would use a book of matches. The cardboard of the book of matches just happens to be the right thickness to set point gaps, well for cars anyways. Would be a good starting point though. Start it up and take it for a ride first to see how the motor runs before doing the points to have a baseline to compare the resetting of the points if possible. Shouldn't hurt anything.

Probably they just stuck with the dual rear shocks and 6v because it was a cheaper bike mostly aimed at the younger crowd and it was still selling. So besides a few cosmetic changes to make it look more modern, they just kept building them. You should find a street legal dual sport and get a motorcycle licence!

mr.modified wrote:

Probably they just stuck with the dual rear shocks and 6v because it was a cheaper bike mostly aimed at the younger crowd and it was still selling. So besides a few cosmetic changes to make it look more modern, they just kept building them. You should find a street legal dual sport and get a motorcycle licence!

that's the plan, keep this one as a really long term project and get a nice street legal one ready to go with a little more power.