Fuel starvation and she won't start!!

[Nitrogenie]

Hi all,

I've been tinkering and searching online and can't seem to come up with a solution to this. It seems a multitude of problems have appeared all at once. I'm new to bikes and this is my first bike and I have many skilled friends who have been teaching me along the way.

A couple of weeks ago, whilst riding the clutch became incredibly hard to change gear. When I stopped I also noticed fuel shooting out of the air box breather tube.
Got it home and had a look. Original diagnosis, carb clean and  new clutch cable.

I have now cleaned the carbs, done a rebuild on the float bowls and replaced gaskets needles etc. No leaks, bike starts ,grand.

The clutch was still screwed so we have now also replaced the friction plates and the clutch is now great too.

Here's the issue. It will run fine for a while then just die. Ok this appears to be fuel starvation of which I have read hundreds of posts and tried everything I can think of.

There was an additional fuel filter on the hose which I have pulled off wondering if this was causing a vacuum issue. I have pulled the entire fuel system to bits. Cleaned and put back together both petcocks and checked for splits leaks etc and there are none.

Now I start the bike on prime and it runs fine. I turn it to res or on and it's fine for around 5 mins then dies whether left on idle with or without choke.

My choke cable only revs to around 1500rpm now where it used to hit 4 on full. I'm wondering if I've not refitted this right but don't see how this would cause issue with the fuel.

The tank is pristine inside and the filter in the tank is great too.
No leaks, but I cannot figure out for the life of me why she keeps dying.

I do have a full tank of fuel also and she's a 1998 model. I've only had her since January but I was advised she had been well kept. I'm finding so far that the only thing well kept was her appearance and mechanically, she needs some work.

If anyone has any ideas that would be great as I am officially out.

Thankyou!

[Big Rich]

First - welcome to the site!

Now I have to ask: when were your valves done last? I don't think it's your problem, but it is very important. Have you checked your fuel level using a clear tube? That's another thing you didn't mention....

In regards to the low idle / choke thing - have you cleaned out the choke circuit and your pilot circuit? A low idle when the choke is engaged usually means something is clogged. And it is odd that your bike will run on prime, but not on reserve. The reserve position (to my understanding) uses the same line as the prime setting. Is it possible you have some fuel / vacuum lines mixed up? The manual isn't correct IIRC.

[lucas]

If the bike will run on prime and not on reserve that means the vacuum operated valve inside the frame petcock is not opening.

Check that the vacuum line is running from the left carb to the frame petcock.  Check that there are no breaks or tears.