Hello, recently I broke down and had a problem with my bike. 

I slowed down after coming off the motorway and it made a loud rattling noise when I slowed down and when I came to a stop it cut out. I pushed it to the side of the road to then try to start it with electric starter. However it was dead, the battery had died. So a garage charged it for me(old bugger charged me £47 to charge the battery!) and he warned me that the bike has a serious problem and it is possibly the low end engine. Crank shaft/Bearings.

He warned me not to start but I managed to get it home and thought I'd try to start it to I can get a better idea to explain what the problem is and when you try to start it the bike has no compression it just pops. Does not sound good at all and I've been told it is most likely the crank shaft that needs replacing and my bike needs checking out to make sure nothing else is affected.

BUT... I don't have a clue where to go from here. My bike is stuck in my back garden and I am in dire need of a mechanic to help me fix my bike.

I will OF COURSE pay for whoever is able to fix this for me and will be so appreciative of it.

And the engine does have oil in but it's dangerously low(it was just due a service).

And I live in Rochdale.                                                                                                                                                                              

You may find it cheaper to replace the engine rather than strip and repair what you've got.
The XR125 has, I am pretty sure, the same engine as the CG125 and there are plenty of these around. £200 tops for a good running engine and a fair bit less if you strike lucky.
Might be worth joining the Honda OC forum, which you can do free without signing up for full membership of the club.                                                                                                                                                                              

it's a DRZ 400 SM 2007                                                                                                                                                                             

Ah. I just took it from your profile!                                                                                                                                                                             

your right garage did rip you of, if there's no compression than it's the top end and if it pops it may be valves, could still be some thing on the bottom end as well, as Wills said look at getting a second hand engine and the seller may put it in for you at a reasonably price though an engine change on a DR is't hard so you could try to find some one to help you. But you must keep it topped up with oil even if it is just about to be serviced.

Paul

A quick google shows that they're prone to big end failure along with conrod issues.  Big thumpers do put a lot of strain through the crank and require very good quality and regularly changed oil.

It's a full strip down I'm afraid.  From what I've read you ought to look at swapping the entire bottom end and the conrod.  Whilst at it I'd be tempted to have the bore and rings checked and rebored / replaced as necessary and the valves checked for seating etc.

This is of course presuming it is the bottom end!  As Bill says some of the symptoms you talk about do suggest top end.

Your only upside is that you've only got one cylinder.

My advice is to find a good local engineering company rather than a bike shop.  They'd be able to very accurately measure the likes of crank runout and smoothness of facing surfaces.  But as well as this they'd be able to very quickly and effectively machine anything that needs it.

A number of years ago, my Dad decided to drop a nut down the inlet of his car and to then attempt to bump start it down a big hill after the resultant cam belt failure (not good).  After a full strip down of the top end I decided it was scrap.  So we bought a secondhand one from a breakers cheaply only to find that although it was in better nick than the original it still needed new valves, new guides, skimming etc.

So I took it down to a good engineering co that I knew and two weeks later and about £100 squid later I picked up what appeared to be a brand new cylinder head.

So, take the bike to a good engineering company and see what they say.                                                                                                                                                                              

 hi paul   you will find it cheaper to replace the engine  as wills said go for it mat                                                                                                                                                                             

New engine about £500-600                                                                                                                                                                             

Geoff, don't ask he how I did it  but I once managed to drop the screw-on thingy (technical term) off the end of a sparking plug into the cylinder of my girl-friend's Mini. 
At least with a Mini a cylinder head lift is only an afternoon's work, but it wasn't how I'd planned for my Saturday off!