ke 100 will not start

[1995dj]

i purchased a none running ke 100 for me and the lad to work on and ride. There was evidence that work had been carried out as there were new gaskets. We were unable to get it started so stripped the engine and purchased a second non runner and built one engine from the best parts. We checked every thing as we dismantled and apart from a bit of scoring on the piston could not see anything which would stop it from starting. It was rebuilt exactly to the haynes manual with new mains, new crank seals, new piston and rings. It STILL wont start or even fire. I've now tried a second carb and new ht coil - Still not even a pop. Today we rigged up a drill to spin the engine over and strobed the timing. it was good a little off very little but still can't get it to fire.
i have changed the plug, it sparks on the head and with the strobe.
The fuel is new and the carb float height is correct. I have tried bump starting down a hill not a pop. I did put some fuel down the plug hole and eventually it fired but out of the carb!!. The ignition is correct and everything is keyed so unless the disk valve in the manual is the wrong way round cant see whats wrong. The piston is 1mm o/s so is the barrel. There feels like there is lots of compression,ill see if i can borrow a tester and see



I'm keen to follow the project through and ride it but am at a loss what else to try.
Can anyone suggest anything ?

[andy_uk]

Is there a spark getting to the plug?
When you take the plug out, is it wet?
Silly question(s)
1) Is there fuel in the tank (and if so, is the fuel filter clean) ?
2) Is the killswitch in the right position?
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Aprilia Classic 125, GS500E, ER5-A1, ER5-C4, ER6 & an XJ6 project frame...

[pepperami]

Silly question but I cant see where you mentioned it, so are you getting a spark? plug fooked?.

Compression? over-sized barrel and standard size piston?
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[st3v3]

I'm guessing mechanically it's fine, so how long have you been trying to crank it over?

Mine has in the past just needed bearing with for a little while, let it alll get wet where it should be.

Have you tried putting a drop of oil/petrol/both down the spark plug hole and then turning it over once or twice?
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[1995dj]

i have changed the plug, it sparks on the head and with the strobe.
the fuel is new and the carb float height is correct. I have tried bump starting down a hill not a pop. I did put some fuel down the plug hole and eventually it fired but out of the carb!!. The ignition is correct and everything is keyed so unless the disk valve in the manual is the wrong way round cant see whats wrong. The piston is 1mm o/s so is the barrel. There feels like there is lots of compression,ill see if i can borrow a tester and see.

[Pete.]

It's firing out of the carb, so I'd re-check both the disc timing and the ignition timing. I'd also check the piston correctly covering the ports at the ends of it's stroke.

These are simple. reliable engines, so if it's not starting with good compression and a spark something fundamental is wrong.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Ichy]

Have you checked the piston position (TDC) against any timing marks?

Have you tried spraying easy start through the carb?
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[1995dj]

I'll test the compression with a gauge then pull the head off and check the ports are being covered. The disc timing is fixed so it's either correct or 180 out. I have put it back as per the haynes manual. The engine does not have TDC marked but does have timing marks. I have taken the plug out and stobbed the marks and they are good. Again the only adjustment on the timing is the points gap, i have tried it correct, with the smallest gap and the biggest gap.
Does anyone know how much vacuum the engine should pull, i could make up a bung and measure the vacuum, this will determine if there are air leaks.

[Ichy]

You need to do a compression test first then try easy start. Virtually anything will run on it. If it doesn't fire then there is a good chance it's an electrical issue. If it runs then it's probably the carburettor.
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[Vincent]

Did you get a magneto with the spare engine that you could try? Same with the coil and condensor?

Whereabouts on the planet are you?
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[bikenut]

:karma: hi dude just to rule this one out, has f/wheel key sheared, yes or no.

disc valve may be 180 degrees out, usin logic check its operation, u sure its correct way round.

exhaust pipe blocked??

rotory disc valve 2 stroke with carb on r/h/s of engine, air hose off, can induction be heard and/or seen with carb off.

air hose off does it start with carb on.

feedback.

[1995dj]

tonight took carb off, placed bag over inlet and kicked over. the bag is pulled inwards but also blows out. Not sure if this is normal ? the disk valve opens just before TDC and closed just after, from memory the key on the disc valve is offset alot so if 180 out then the opening and closing would be totally different. Can anyone confirm what i have is about right? Took the plug out and placed my thumb over the sparkplug hole there is plenty of compression. Took head off to check ports and piston. The piston has the arrow pointing towards the exhaust, the ports are being exposed. The disc valve opens when all the ports are covered approx 10mm BTC. Every thing looked wet inside so put head back on.
Strobed the timing marks again - spot on. The bike only has the black wire from the flywheel coil connected to the HT coil. i have in the past swapped over the back plate and coils from the other engine, flywheel key is present. The strobe does not work if connected in series and only works if connected direct - not sure if this is ok. Finally as my hands were numb i injected 2cc of petrol in the plug hole, replaced the plug and kicked till blue in the face. NOTHING !!!!

[Pete.]

The bag should not be blown back out. Does it come out quite smartly or just a feeble effort?
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[bikenut]

:karma: ok dude im hooked............

so sparks all ok.......happening at the right time...........

disc valve........i would have expected for inlet to be open at bdc ish so a full stroke of air/fuel can be sucked ( pushed in via atmospheric.......) into the c/case...............and closed tdc ish for c/case compression and transfer to combustion chamber............

adding 2cc of fuel, and still non starter ( with good spark )...........

with air hose off to carb and exhaust not fitted......any change ( blocked exhaust so no breathing ).........add 10cc of fuel to c/case and retry..........

are you sitting on bike when k/startin.........any chaffed wired for ign kill circuit.............

TRY WITH EXHAUST OFF feedback please.........

[Vincent]

Just looking in my KE125 W'shop manual:-

"....when the crank chamber is pressurized during the downstroke of the piston, the disc is forced tightly against the intake port in the valve cover, by the gas pressure, preventing gas blowback through the carburetor".

And:-


"Intake open BTDC 115 degrees
intake Close ATDC 55 degrees"

I wonder if you might have accidentaly damaged the oil seal on the rotary disc? Or it might have got caught??
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[1995dj]

my disk valve definately does not open 115 degrees btdc, i will rebuild to other engine and see if placing the disc valve the other way round would open then.
regarding the exhaust, i only fitted it this week end so i could bump start it without attracting too much attension, but valid point.
Reading the manual the spark should jump a minimum of 5mm mine will not jump that far (plug cap off). We will measure the coil to see if it is in spec. Regarding the wiring, the loom has been removed and there is a single wire to the HT coil and a block connector joining it to the kill switch. This has not been connected since the rebuild. Someone at work thought the plug resistance increases under pressure(compresion) and it may be stressing the coil and capacitor. I will un-solder and check.
regarding the crank seals- great care was taken, the seal next to the flywheel may be the wrong way round as i could not find a picture in the manual. I have placed it with the rubber face outwards

[Vincent]

You probably know this but the disc goes with the lettering on the outside. Usualy the same with seals too.

The seal I meant is the one behind the disc, not sure if this doubles up as crank seal...would have thought not.

Something else I've noticed in the 125 manual is that they keep mentioning differences in the disc valve assy between the '74-'76 bikes and the '77 & '78 bikes.
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[Pete.]

The crank seals go with the grooved face inwards, flat face outwards. If you have two grooved faces, poke around in the grooves and find where the spring is - that face goes inwards.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[bikenut]

:D :karma:

so weal spark?? excessive arcing on points??points dirty and badly pitted or white??

suspect condenser ( under flywheel? ) or may be poor coil breaking down under load.

plug resistance value increases under load? more volts needed ( electrical pressure ) to overcome pressures of compression ( wide throttle, more air to compress, more pressure )

[1995dj]

tonight i squirted 5cc of need petrol mix into the crank and kicked and kicked and kicked some more - nothing. must be ignition i thought flywheel off. Points look fine, condenser is not short circuit. I measured the coil resistance and it only 0.2 ohms so removed the coil from the circuit - 2.7 ohms in spec. Dug out other back plate and checked it over, the coil also measured 0.2 ohms connected and 2.7 on its own. Condenser not short circuit. Decided to swap it over, just in case. Did not check HT coil as it is brand new. I checked wire from condenser to HT and fine. Replaced flywheel reset timing and checked with strobe. Decided to take exhaust off, tipped it on its end and fuel drips out. Tried kicking again nothing. took plug out carb off kicked it over and over to try and dry out. replaced carb and plug kick kick kick - ah!
Now totally stuck and disheartened. Anyone any ideas ?
PS have tried 3 spark plugs.

[bikenut]

so with plug in or out you get spark ( enough to trigger neon strobe or battery powered strobe with clip on sensor ), weakish spark??

with plug in no sign of life with exhaust off, even when primed with petrol?

wire from condenser to ht?

you mean wire from condenser/cb points to coil lt connection?

coil earthed?( spark for strobe so somethin ht wise )

so either weak spark insufficient to ignite fresh petrol, ht failure at k/start speeds and pressures ( inside cyl combustion space ), no fuel in combustion space ( wet plug? proves fuel gettin to plug ), spark happenin at wrong time??????? or combination of above?

and youve tried with exhaust off, yes?

eliminate the possibility that its not an ign kill problem when kicking over, or bad contact or something just as silly.

has frame been painted with now poor earths perhaps?

make safe any try pushing with plug out, spark better at higher engine speeds ( one would expect so ), try pushin with all systems go and exhaust off, better spark may allow eng to burst into life.

what year your bike need to check summut on cmnsl? feedback please.

[truslack]

[bikenut]

:karma: :?: thought this bike has flywheel magneto?

[truslack]

[bikenut]

yeah with points, but i'll check also cause im old to.