A number of broken things.

You can go to any hardware store and pick up a set of ez outs. They are drill bits that when spun in revers cut into the bolt remains and unscrew it. Your alternative to this is to drill and tap it, but trust me the ez outs are cheaper and you can always tap it out if ez outs don't work. Hope this helps with the bolt issue, and if the weld keeps breaking then there is potentially something else wrong. Ask yourself why the stress is being added to that part to make it break, perhaps something is not working properly. I don't know for sure, I am new, but that is what comes to mind.

If you broke the bolt while installing it, it won't be seized or rusted in and it should be easy to get out with the EZ outs or other brand of extractor that you can find locally. Sometimes it's even possible to turn the broken bolt with a hammer and small chisel by tapping around the edge. Once the head is broken there is no tension on the bolt and they often are very easy to turn.

Does the support bracket keep breaking in the same place? If so you may need to add some material to strengthen the repair if the welds alone don't hold up.

The plastic can be welded if you can find a local shop that can do it. I remember finding plastic repair kits on the internet somewhere also. Try a search.

I think the front fender support is spring steel no amount of weld will truly hold it. Replacing it would be my anwser.

Thanks
I am gonna try and get some EZ outs.
I will try to reinfoce the support, if mot i will make a new one out of stonger stuff.
Do you think i could patch/brace the crack with another bit of plastic???

Depends on what you want it to look like, I would try to get a plastic welder when you get the ez outs, it is a two part epoxy that actually breaks the plastic down and when it solidifies it is one piece of plastic again. Your choice ,hopefully it works out for you.

I managed to get the bolt out with some long nosed plires. I am going to reinfoce the support. but i am still on the hunt for a plastic welder.
Thanks for the help.

you can ge a plastic welder (air and electric) form harbor freight for $35 if i remember right, even comes with some rods. i have welded alot of plastic and it works great, tougher than new if done right

Thanks for all the response

Ok i now have yet another problem.
Today i filled full up with fuel and my 400 would not start on the button, it just kept clicking down by the battry, so i gave it a tug on the pull start wouldnt start that way either (just kept pulling and pulling as if there was no fuel) i took the side off by the starter motor and wiggled the wire, when i pushed the buttonit sounded like the motor was flooded then stopped, I eventually got running again (by wiggelin the wire) and kept stalling (as if running out of fuel) got back to the shed and wont start again! what is the problem???

Help would be appreciated!

Start with the clicking you heard. Thats the starter soleloid doing that. You either have a bad connection bad solenoid or low battery. Trouble shoot that then see what you have.

Allhonda is right, you don't have enough power to turn the motor over. That is why it clicks. Check your battery first, then check your ground, if that checks out test your connections, look at the ends. They could be corroded you may even just have a bad contact somewhere? Electrical issues suck so don't be surprised if it takes a while to figure it out.

Thanks I will have a lookinto that.

Ok i took the staror motor off and took it apart and the brushes in the motor were worn, got sum new ones works great
I was speaking to the dearler and he said a new starter motor was $650 and a new transmision $4590

Thanks for the help

$4500.... You can buy a used bike for that.

I no its crazy, but thats the way it is in the UK the bike is like 4000 and the parts are like way more!