cbr 125 wont start

niffty · L Plate Warrior Joined: 13 Nov 2014 Karma :

Hi all
I have aquired a 2006 cbr125.

It flatly refuses to fire, i have spark, fuel, compression, vacuum at the carb and crank case, new plug and new cap, valve timming is right, spark is in the right place as piston goes over tdc.

Hot wired the clutch lever switch and side stand switch, both work but i bypassed them any way to make sure, it hasnt got a kill switch, so cant be that.
All the wiring is pluged in and everything works.
New battery and my Sealey jump start pack connected.

I have squirted petrol straight in the carb and plug hole and easy start in both to, lovely spark from a new an an old plug, its not flooding
and it still flatly refuses to fire at all.
Help

john24ssj · Trackday Trickster Joined: 08 Aug 2014 Karma :

oh wow it seems like it's just not in the mood.

From what you have described it might be something electrical. Have you taken the carburettor apart?
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Bikes: Honda CBR600Fi, Kawasaki ER5

niffty · L Plate Warrior Joined: 13 Nov 2014 Karma :

[quote="john24ssj"]oh wow it seems like it's just not in the mood.

From what you have described it might be something electrical. Have you taken the carburettor apart?[/quote]

No carb has not been apart, thats next job and in the ultrasound cleaner.
Only thing electrical i can think is maybe the plug not sparking under compression, but got two plugs, one new today.

john24ssj · Trackday Trickster Joined: 08 Aug 2014 Karma :

P. · Red Rocket Joined: 14 Feb 2008 Karma :

Are you even getting fuel. The vacuum taps are prone to dying on these. That and make sure all your tank breather pipes are routed right, they pinch otherwise.

Also, the CBR has a shit choke that doesn't like to keep itself free. Make sure the choke mech isn't seized and the cable is actually operating it. Those bikes take an age to warm and not use choke in anything under like 15 degrees Laughing

Rogerborg · nimbA Joined: 26 Oct 2010 Karma :

The idle jets seem particularly prone to getting blocked.
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

niffty · L Plate Warrior Joined: 13 Nov 2014 Karma :

[quote="Rogerborg"]The idle jets seem particularly prone to getting blocked.[/quote]

I will set about checking them bits later, its getting fuel in the carb ok and ive put petrol and easy start down the plug hole, old grass track and speedway trick when our zx10 motors wouldnt start cold on methanol.
Surely i should get some sort of bang at some point ??

Taught2BCauti... · World Chat Champion Joined: 12 Jan 2012 Karma :

Back to basics - you need the correct air/fuel mixture, decent compression, and a good spark that happens at the right time.

If something has slipped, you may not be getting the spark at the right time (somewhere near the top of the compression stroke) - so if everything else seems to check out - I would look at the ignition timing.
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Rogerborg · nimbA Joined: 26 Oct 2010 Karma :

Andy_Pagin · World Chat Champion Joined: 08 Nov 2010 Karma :

niffty · L Plate Warrior Joined: 13 Nov 2014 Karma :

Right, i started again from the begining. carb off again and in the ultrasound cleaner, yet another new plug, manually filled the carb with petrol, pencil lead on all 3 plugs, nicked a new coil off the Moto guzzi and wired that on.
Finally i got one back fire bang, just one.
Not a bloody thing since.

Silly thought, it has comression, but whould i have this if it wasnt enough compression.
The bike had been standing without the exhaust on, if the exhaust valve was open, could it be rusty and not closing properly.
I know of a Reliant engine having rusty valves from getting damp, is it possible this could be whats causing the problem.
I have another near complete engine, im thinking of changing the heads over.
Any ideas ??????