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Posted

Hi,

Spent two days on this so far and running out of ideas.

Bike starts and seems to run OK until it starts to warm up. After this period the only way I can get it to rev up is by feathering the throttle, a faster throttle opening leads to bogging, a horrible response in terms of sound. The engine will also die if throttle is opened quickly.

Checks so far include:

Air filter, carb clean (several times), changed oil and flushed (x4) due to traces of water. Generator coils and spark circuit checked. Even had the head off to check timing, valves, tappets etc.

This bike (2008 - 3k miles), seems to be over fuelling. When I take the carb off, there is petrol all over the inside of the inlet rubber.

The choke mech' seems to be functioning OK also. The spark plug, unsurprisingly is sooty & black.

I can't help but think that I am missing something with the carb (float/height checked) but they seem quite basic units compared to the Keihin on my Drz.

All other pointers greatly received.

THX

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  • Moderator
Posted

Sounds like too much fuel. Is the needle valve closing correctly and the floats "floating" or sticking.

Check the needle valve seating, change the needle valve if required.

Check for a pin hole in the float and for free movement.

Posted

Carb does not weep fuel from bowl so am assuming that the needle valve is shutting fuel off as required.

The floats are bone dry and are moving with ease, the only thing I can't check is free movement when the outer case is re-assembled although I can here rattling if I shake the carb.

If nothing else, this is a good fault........

  • Moderator
Posted

Have you tried a different carb on it? It could be the choke playing up so the symptoms would only appear when coming up to temp.

Posted

V/v timing checked and all OK.

Have not yet tried a different carb, this is what I was thinking of doing next. Just got to find one now!

Posted

Thanks for link.

Will bid on this item and let everyone know how this fault pans out.

  • 2 weeks later...
Posted

Hi all,

Update on the fault.

It turns out that the set up was not overfueling but quite the opposite.

A fuel starvation scenario sent me down a different thought route.

The carb was ripped out again and the main jet and emulsifier tube removed.

The emulsifier tube housing/channel revealed a small hole, linked to the the air intake duct and on closer inspection with a strong lamp, was not letting light through. More dirt was suspected, so the orifice was subject to a squirt with carb cleaner and a small strand of strong wire. Light was eventually detected thus some crud removed. The carb was reassembled and reinstalled and hey presto the bike now runs OK.

Just need to find the sweet spot on the air/mixture screw as I fiddled with this during the fault finding process.

So in summary, when you clean a carb, spend some time to inspect thoroughly and ensure that every orifice is perfectly clean.

If I had spotted this earlier it would have saved me a lot of unnecessary work.

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