R125 starting issue

wheelie916 · Derestricted Danger Joined: 15 Apr 2006 Karma :

Hey guy's
Ive just rebuilt my r125 with a new top end and when i tried the first time she started first time on the button and run sweet as a nut.
Since then i cannot get her to start unless i temp block the air pipe then she starts and runs... again as sweet as a nut and will start ok if i swtich of and on again, its only when she is left a while she wont start and I have to block the air pipe and she will start fine.
I have changed the plug, the timing is spot on(checked every time)
The only thing is the fuel its been in the tank for about 3 months.
Does anyone have an idea as to why she wont start unless i block the air pipe.......

Many thanks for any help.

Jas

wheelie916 · Derestricted Danger Joined: 15 Apr 2006 Karma :

anyone help with this problem?

radical · Spanner Monkey Joined: 02 Jul 2010 Karma :

Does the fuel smell stale? if so just empty and replace with fresh petrol

TUG · World Chat Champion Joined: 12 May 2007 Karma :

you've done something wrong when rebuilding it, if your rebuilt it yourself then more than likely you've plumbed things in wrong.

We've done a few of these, let me guess, aftermarket exhaust? didnt change the oil ever 1600 miles?
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Haz ER-5, innit!

wheelie916 · Derestricted Danger Joined: 15 Apr 2006 Karma :

the bikes completly std rebuilt as cam tensoner failed causing bent valves so i replaced the top with a new one and rings, gaskets.
the fuel tank was stored in shed with the lid off for a while would the petrol go bad then?
how do i tell bad fuel?
everything is back as per workshop manual, all the timing is spot on
I cant understand why she starts if i block the air inlet for a short while but wont start without..... she fires up without the need to block air inlet when warm no problems.
when she starts she runs brilliantly with no probs......

Thanks for the help guy's

Jas