Can’t get my Honda cbf 125 to start

[Owen hudson]

Hello there! 
 

I have just bought a Honda cbf 125 that I am planning on doing a cafe racer build with

 

i got it for very cheap as it doesn’t start so needs work being done. 
 

I have got it back to the house to start working on it and I have done all the obvious things like change the spark, new battery, changed the oil and just tonight I had checked and adjusted the clearances hoping that was it and nothing works 

 

the bike turns over, the spark plug fires up strong, there is push back from the pistons. The spark plug smells strong of petrol. The exhaust has push back when turned on. 
 

everything all the other forums say are the issue works fine so I can’t figure it out. If anyone has any idea please let me know 

[Simon Davey]

2 hours ago, Owen hudson said:

Hello there! 
 

I have just bought a Honda cbf 125 that I am planning on doing a cafe racer build with

 

i got it for very cheap as it doesn’t start so needs work being done. 
 

I have got it back to the house to start working on it and I have done all the obvious things like change the spark, new battery, changed the oil and just tonight I had checked and adjusted the clearances hoping that was it and nothing works 

 

the bike turns over, the spark plug fires up strong, there is push back from the pistons. The spark plug smells strong of petrol. The exhaust has push back when turned on. 
 

everything all the other forums say are the issue works fine so I can’t figure it out. If anyone has any idea please let me know 

 

 

Welcome Owen, starting at the most obvious place, so you've probably already done this but....... Have you emptied the fuel completely from the tank and filled with fresh petrol?

It could simply be old petrol.

 

[bud]

If it's an older model with a carb. The pilot jets can very easily get clogged when not used for a while. 

This would make it very hard to start.

[Owen hudson]

2 hours ago, Simon Davey said:

 

 

Welcome Owen, starting at the most obvious place, so you've probably already done this but....... Have you emptied the fuel completely from the tank and filled with fresh petrol?

It could simply be old petrol.

 

I have not tried this yet but the fuel smells very strong but I will try this tomorrow to see if works

[Owen hudson]

2 hours ago, bud said:

If it's an older model with a carb. The pilot jets can very easily get clogged when not used for a while. 

This would make it very hard to start.

It’s a 2012 model. I’m only just getting into to bikes so I’m not sure but it’s got a starter so does that mean it doesn’t have a carb?

[Hairsy]

Definitely do the fuel thing.

 

I believe it's fuel injected (but that's not linked with having a starter motor).

 

Given your experience level, I recommend you invest in a Haynes manual. That should have some troubleshooting guides that you'll find helpful. 

 

As a first step though, do you know someone with a compression tester? I think you mean compression when you talk about exhaust pushback but you need to know there's enough compression - not just 'some'.

 

If that proves successful then, given that you can see a good spark, your injection system would be the obvious place to look.

 

But replace the fuel first ...

 

 

[bud]

I believe it is fuel injected with a quick Google. The give away would be the bike fuel pump priming when you turn the key on. It is doing that right? Making a whirring noise?

[RideWithStyles]

Could be loads of things without more info. 
2012 is a injection. 

Sounds like it’s getting fuel and spark then, sometimes if the gear sensor or the crank sensor isn’t quite quite right on the pick up, if it doesn’t get the right timing from the pick up it wont be doing it at the right time.

 

[Owen hudson]

Update: 

 

We tested the compression and it definitely was not enough so I managed to take off the top end and get a look at the piston and it is fried. 
 

I have fitted the new head and new chamber and will be putting the engine back on the bike today. Need to wait for a new fuel injector cap as I snapped the original one. Hopefully this will fix the problem of it not starting 

[Old-codger]

I take it you mean you have replaced the cylinder head and barrel ? and hopefully a new piston if that was fried as you put it.

[bud]

Any idea what caused this to happen?