NS125R won't start - any ideas welcome.

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02/07/2004 at 07:52
My son got an NS125R for his 17th birthday a fortnight ago. Yesterday I got a call for help - it had broken down with him. The bike had previously been starting easily and running well. He rolled up to a junction and it had stopped and wouldn't start again. When I got it home and checked it out there were sparks, plenty of petrol, it has compression and the inlet sucks when it is turned over. I tried replacing the plug - no difference. I took the carb off and checked it for dirt/water in the jets - nothing there. I checked the reeds were intact - they were fine. When kicking it over it doesn't fire at all but every 7 or 8 kicks it gives a "Phut" out the exhaust, so it is pumping mixture through and igniting it in the exhaust. This suggests to me that the ignition timing is way out, yet the pickup is firmly attached and the flywheel hasn't slipped on the shaft. Can CDI units fail in this way where the appear to produce adequate sparks but at the wrong time? Any help will be gratefully received, I have a 17 year old new biker who is pretty glum at the moment.
bishbosh
02/07/2004 at 09:20
Is it new? or has miles on it?

It sounds as if he may have just flooded it. (loads of throttle when trying to re-start) Try taking the plug out again, Let it breath, spin it over a few times, let it breath (1/2 hour) then try your fresh spark plug again.

He didn't drop it slightly did he? (just on it side)
Maybe your air box is also full of fuel, take it apart let it breath. clean out the excess fuel.

The two-stroke oil hasn't run out has it?
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02/07/2004 at 09:39
bishbosh wrote
Is it new? or has miles on it?

It sounds as if he may have just flooded it. (loads of throttle when trying to re-start) Try taking the plug out again, Let it breath, spin it over a few times, let it breath (1/2 hour) then try your fresh spark plug again.

He didn't drop it slightly did he? (just on it side)
Maybe your air box is also full of fuel, take it apart let it breath. clean out the excess fuel.

The two-stroke oil hasn't run out has it?


The bike has 19.5K on it and was running fine. It's definitely not flooded and has loads of oil. I'm not convinced it is an ignition problem though, these things usually work fine or not at all. I guess I'll have to lift the head and have a look.
kickstart68
02/07/2004 at 12:24
Hi

I will check the Honda workshop manual when I get home and dig out the info to test the ignition.

However I would say to check the compression on the engine.

All the best

Keith
spottydog
02/07/2004 at 16:20
A long shot............ whip off the rotor cover and have a long good look underneath the rotor, see if there is any sign of fluid coming from the crankshaft, it's just that many years ago I had a kettle that broke down in exactly the same way which turned out to be a crank seal, mind you kettles were renowned for doing that every 20k
Bigjawa
02/07/2004 at 17:23
Crank Seals?
spottydog
02/07/2004 at 20:08
Bigjawa wrote
Crank Seals?

Yes crank seals, seals that seal on the crank
Bigjawa
02/07/2004 at 20:17
spottydog wrote
Yes crank seals, seals that seal on the crank


My god, I never new that!
spottydog
02/07/2004 at 20:28
Bigjawa wrote
My god, I never new that!

In that case smartarse you will know that if one fails or drops out it can cause the symptoms that supersport described so why be such a condescending git?
Either share the benefit of your undoubted vast knowledge and experience and try to help the bloke or shut up
bishbosh
02/07/2004 at 20:37
SuperSport wrote
The bike has 19.5K on it and was running fine. It's definitely not flooded and has loads of oil. I'm not convinced it is an ignition problem though, these things usually work fine or not at all. I guess I'll have to lift the head and have a look.


Also
Take a look at the power valve system, i think there a little fragile?
I think they do a little positioning dance when you turn on the ignition?

I hope it's not your seals.
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Bigjawa
02/07/2004 at 23:22
spottydog wrote
In that case smartarse you will know that if one fails or drops out it can cause the symptoms that supersport described so why be such a condescending git?
Either share the benefit of your undoubted vast knowledge and experience and try to help the bloke or shut up


I said crank seals as the reply, to the original post, so what's your problem, you're the smartarse wanker.
kickstart68
02/07/2004 at 23:24
bishbosh wrote
Also
Take a look at the power valve system, i think there a little fragile?
I think they do a little positioning dance when you turn on the ignition?

I hope it's not your seals.


Hi

It is an NS125R, so unless it is an import it does not have a power valve. The power valve on these was the old ATAC system which used a plunger to open / close a chamber off the exhaust port, and the pluger was moved by a linkage operating under centrefugal force from the end of the crank.

All the best

Keith
bishbosh
03/07/2004 at 08:39
kickstart68 wrote
Hi

It is an NS125R, so unless it is an import it does not have a power valve. The power valve on these was the old ATAC system which used a plunger to open / close a chamber off the exhaust port, and the pluger was moved by a linkage operating under centrefugal force from the end of the crank.

All the best

Keith


Ok, Its not the PV then
are the ATAC systems reliable. KS?
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spottydog
03/07/2004 at 08:53
Bigjawa wrote
I said crank seals as the reply, to the original post, so what's your problem, you're the smartarse wanker.

My god, I never new that! was your smart arse comment dickhead
Bigjawa
03/07/2004 at 11:45
spottydog wrote
My god, I never new that! was your smart arse comment dickhead


Spottydog? You don't seem intelligent enough to be a dog, perhaps you're an amoeba with ideas above your station?
spottydog
03/07/2004 at 13:01
Bigjawa wrote
Spottydog? You don't seem intelligent enough to be a dog, perhaps you're an amoeba with ideas above your station?

Your devastating repartee leaves me almost impressed
baldrick72
03/07/2004 at 15:47
Hello Guys,
in all due seriousness here chaps, this is a workshop thread with a guy trying to get help, pop along & start another thread to argue, so this chap can get some help instead of reading "handbags at dawn".
Bigjawa
03/07/2004 at 18:50
baldrick72 wrote
Hello Guys,
in all due seriousness here chaps, this is a workshop thread with a guy trying to get help, pop along & start another thread to argue, so this chap can get some help instead of reading "handbags at dawn".


And when you make a suggestion you get some twat looking for an argument?

Fuck that.
qwerty
03/07/2004 at 19:04
Brilliant.

05/07/2004 at 07:39
Thanks to those who provided input. In fact lifting the head showed the problem to be due to piston damaged - overheated on the exhaust side due to running it with a cracked exhaust which had just been fixed.
A new piston and rings should sort it out.
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