bigt Posted February 12, 2008 Share Posted February 12, 2008 Bike is an SZR660 Yamaha. The engine is an XT660 single with the twin carb setup. It's in good condition and low mileage, about 8K miles. It's been stood for at least 6 months with fuel in it, I think. The problem is it won't rev at all. It's OK up to 3000 rpm but if I open the throttle too wide it just won't pull, it dies. It starts and ticks over lovely and sounds ace, nice and quiet. I've tried the following :- - stripped and cleaned the carbs, although there was no dirt or gunge to be seen - took the fuel tap off and drained the tank - put fresh fuel in - new spark plug - ran it without the air filter - removed the vacuum part of the fuel tap and run with straight through fuel supply. None of these have made any difference. My best guess is it's a fueling problem but can't find anything obvious. I had expected the main carb (CV?) to be the problem. The diaphragm appears to be in good condition. HELP! Link to comment Share on other sites More sharing options...
Kayla Posted February 12, 2008 Share Posted February 12, 2008 Bike is an SZR660 Yamaha. The engine is an XT660 single with the twin carb setup. It's in good condition and low mileage, about 8K miles. It's been stood for at least 6 months with fuel in it, I think. The problem is it won't rev at all. It's OK up to 3000 rpm but if I open the throttle too wide it just won't pull, it dies. It starts and ticks over lovely and sounds ace, nice and quiet. I've tried the following :- - stripped and cleaned the carbs, although there was no dirt or gunge to be seen - took the fuel tap off and drained the tank - put fresh fuel in - new spark plug - ran it without the air filter - removed the vacuum part of the fuel tap and run with straight through fuel supply. None of these have made any difference. My best guess is it's a fueling problem but can't find anything obvious. I had expected the main carb (CV?) to be the problem. The diaphragm appears to be in good condition. HELP! I've had a couple of these bikes and they are great fun. Have you checked the secondary carb is opening properly? The butterfly should be fully open when the primary slide is fully up. You need to push the secondary slide up whilst opening the throttle to check. There's an adjuster inbetween the carbs if you need to alter it. It sounds worse to do than it is- once you see what's what you'll be ok. Hope this helps Kayla Link to comment Share on other sites More sharing options...
bigt Posted March 9, 2008 Author Share Posted March 9, 2008 Kayla. Thanks for your help. I have tried lots of things over the past 2/3 weeks. I realised the problem was definatley carburation, and stripped, checked and cleaned everything, rebuilt it and no change! I have eventually found if I remove the large diameter pipe from the CV carb it runs OK! Have you or anyone else got any idea why this happens? Bigt Link to comment Share on other sites More sharing options...
Kayla Posted March 10, 2008 Share Posted March 10, 2008 Kayla. Thanks for your help. I have tried lots of things over the past 2/3 weeks. I realised the problem was definatley carburation, and stripped, checked and cleaned everything, rebuilt it and no change! I have eventually found if I remove the large diameter pipe from the CV carb it runs OK! Have you or anyone else got any idea why this happens? Bigt Hi, Do you have, or can you take some photos of the pipe you're talking about? It's been a couple of years since I owned one and it might jog my memory if I saw a few pics. What diameter is the pipe? Is it blocked at all? Link to comment Share on other sites More sharing options...
yoda Posted March 10, 2008 Share Posted March 10, 2008 This is a case of over-fuelling causing a rich cut type of problem. When you are opening the throttle, it is overfuelling so you need to find the cause of that. Link to comment Share on other sites More sharing options...
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