Turning over but not firing! Any ideas??

Help!!!

Ive been trying to fire up the GPX 250 Im (STILL!) doing up. Its been sat in our damp garage for about 4/6 weeks. Altho it turns over fine, all that happens is there is a slight puff of smoke/steam from the exhausts and occasionally a HUGE back-fire blasts out of one of the pipes AFTER I stop turning the engine over. Im not sure which tho.

Ive tried with the choke on /off, throttle open/shut and all the various combinations of the above.

The engine is trying to fire but it just wont catch.

Any POLITE surgestions????

My first look would be the battery, I have had it before where a bike will turn over but not start, even after charging the battery. The voltage drops when trying to start the engine. I would guess the backfire and smoke would be unburnt fuel entering the exhaust, rectified by the bike starting. Try putting a known good battery on the bike to try.

I must admit I had to top up the battery water recently as it was very low, but I re-charged the battery and it took and held the charge ok.

Any other thoughts?

Have you got a good spark at the plugs? What do they look like - oily or covered in fuel?

If the fuel has been in the tank for a while then change it as old petrol sucks in condensation.

I don't know this bike - I assume it's got carbs not injection? If it's got carbs and been sitting then the float or needle could be stuck giving erratic fuel delivery and flooding it.

If your based in or near swindon i'm happy to have a look at it Got a GPX myself :)

Up date.

I got a set of new plugs from HAYBALLS in Salisbury (as I was working down that way) and she fired up almost straight away!!!!

Turns out 1 plug was cracked and the other was too wet with fuel!

Thats the good news! BAD NEWS, when I took the tank off to get at the plugs (!!!!) I found a pin prick hole in the tank! I was given as a FREEBIE a tube of tank sealant (Like Araldite!) and it seems to be holding JUST! but any better solutions would be gratefully recieved!

Genesis... Thanks for the offer, Im in Calne.

excellent news...sorta! Are you any good with welding? could weld a small patch over the tank hole?

I might be way out but I'm sure you can get some stuff that you put inside the tank that acts as a sealer and protects from rust etc.

Dabs.... welding and petrol tanks, especially used ones always sounds a bit risky to me!!! :o Anyway Ive never welded before! :-/

Genesis.... Is that a bit like the sealant you blow up tyres with? Any idea on names people???

Try this link;

http://www.frost.co.uk/result_search...FSfxEAodqGoceA

I'm sure Hein Gericke also used to sell a sealant.

Cheers Mike! :)