1975 Kh100 starting problems

bratwurst · L Plate Warrior Joined: 30 Sep 2015 Karma :

i have a 75' Kawasaki KH100 that i cannot get started for the life of me. everything is checking out as far as mechanical goes. Carb float is not sticking, bowl was clean and not gunked up. fuel lines are ok. petcock is functional i am aware that these can be a problem on kawa's. the only thing is electrical.
on the controls, there is a on and off switch for the engine. i think the guy who had it before me tried to short cut the ignition system by only making the handlebar controls work. Only thing is when i test for spark it gives me an OKish spark on the ON and OFF position.

It will not start with choke on/bump start. ive tried different gas mixtures and nothing. the only way it will start is if gas is put directly into the engine cylinder and only for a few seconds.

Is there a problem with the electrical thats preventing the bike from running? points/timing? Crying or Very sad

this is my first two stroke road bike. i've had a few other hondas before never had problems like this. any help is great
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low budget warrior

Oldie · Brolly Dolly Joined: 05 Dec 2010 Karma :

Always best to start off with new plugs. Cheap first step.

stevo as b4 · World Chat Champion Joined: 17 Jul 2003 Karma :

Have you checked what sort of compression pressure your seeing?

the other possibilities if the carb really is clean and fuel flow is ok, as well as the spark looking good are:

1, Crank shaft oil seals may have perished if it's been stored. You won't get any primary compression in that case to draw up fuel/air into the cylinder.

2, The Disc valve could not be sealing or it could be mistimed on the crank possibly?

3, The spark that looks ok, could be weak and breaking down under compression pressure?

Have you had the carb off for an ultrasonic clean and or blow out of all the jets etc? It'd be worth re-checking all the simple things first, before you strip the motor, but a loss of primary compression or an air leak is only really easy to find with a leak down test, which is something you could probably rig up with an air line, some adapter's and gauge etc?

temeluchus · World Chat Champion Joined: 01 Oct 2008 Karma :

My KH100 would refuse to start and need the points adjusting regularly.
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bratwurst · L Plate Warrior Joined: 30 Sep 2015 Karma :

Vincent · Banned Joined: 16 Oct 2006 Karma :

Got a photo of that spark plug? Has the bike been standing? They're not bad little bikes these, if you find it needs engine work, and the rest of the bike is in good nick, I'd get it done. Once sorted, it'll keep going for years. If you're finding it hard to get a spark, you'll need to check the output on the high voltage ignition coil behind the points. There's two there, one for the ignition and one for the lights, IIRC, they both tend to degrade with age.
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bratwurst · L Plate Warrior Joined: 30 Sep 2015 Karma :

[quote="Vincent"]Got a photo of that spark plug? Has the bike been standing? They're not bad little bikes these, if you find it needs engine work, and the rest of the bike is in good nick, I'd get it done. Once sorted, it'll keep going for years. If you're finding it hard to get a spark, you'll need to check the output on the high voltage ignition coil behind the points. There's two there, one for the ignition and one for the lights, IIRC, they both tend to degrade with age.

the plug it seemed there was some graphite colored grainy residue on the electrode it was not wet with fuel/oil. Can't get a picture to work right now
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low budget warrior

bratwurst · L Plate Warrior Joined: 30 Sep 2015 Karma :

Vincent · Banned Joined: 16 Oct 2006 Karma :

Doesn't look too bad, bikes running a bit weak I'd say and there's no trace of any two stroke oil which is a bit worrying. Maybe you should bleed the pump and make sure oil is getting through. When you said the plug had marks, I thought it may have been pre-detonation but it's not.
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bratwurst · L Plate Warrior Joined: 30 Sep 2015 Karma :

Ok update. Got it running! But not ideally it seemed to increase revs with the choke off and no throttle. Not fast like an air leak but slower like Predetonation or something? Not sure fuel mix too rich? Any help is great
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Vincent · Banned Joined: 16 Oct 2006 Karma :

Are you getting plenty of smoke coming out of the exhaust?
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bratwurst · L Plate Warrior Joined: 30 Sep 2015 Karma :

Vincent · Banned Joined: 16 Oct 2006 Karma :

If the bike's been standing, it could be the crank seals that are sucking in air or the rotary disc doing the same.
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