enfieldcr Posted September 16, 2012 Share Posted September 16, 2012 Hi I've got a 350 F2 and am having carb problems. It was leaking petrol from the overflow pipe so I assumed that the vacuum fuel tap was leaking and the float valves were not sealing properly. I thought I'd change the float needle valves and seats in both carbs and try to fix the vacuum tap, which I did with repair kits from Yambits. The tap now seems fine (petrol on "prime" and nothing on "on" or "res" but ever since the carbs just leak petrol straight out of the overflow pipes and the engine just revs to about 5000 rpm with a closed throttle and makes no power. I have checked and rechecked for an air leak and the setting for the float heights but can find nothing wrong - does anyone have any ideas please? HELP!!! I have a Haynes manual and it shows a float height for the earlier YPVS bikes of 21mm and says nothing different in the section for the later F2 model so that is what I have been using - is this correct or is the float height at least part of the problem? (I should have checked the original heights first I guess). Thanks in advance for any help anyone can give. Steve Link to comment Share on other sites More sharing options...
AndyDtr08 Posted September 17, 2012 Share Posted September 17, 2012 You say the bike appears to be revving high on it's own? I had a problem like this and it seems to have settled but still appears when the bikes being run at a contast high speed for a prolonged time. The bikes were known to get an air leak around the inlet. Run it and spray WD around them and see if the revs drop down whilst the WD40 is sealing it. I also gained huge problems when I put the carb slides in the opposite carbs so might be worth testing. Keep us updated with anything you find out and good luck, sorry i couldnt be more help. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 17, 2012 Moderator Share Posted September 17, 2012 If fuel is coming from the overlow pipes no matter how you say it there is something wrong with the float/float height/check valve. Pick any or all but thats the problem to fix first. Then worry about the rpm when the fuel stays on the inside. Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted September 17, 2012 Moderator Share Posted September 17, 2012 +1 Link to comment Share on other sites More sharing options...
enfieldcr Posted September 18, 2012 Author Share Posted September 18, 2012 Thanks for the feedback - I agree that getting the petrol to stay where it should be is the first step and I have checked that the floats are not leaking and replaced the float needles and valves twice. Can any one confirm the correct float height setting for this model please? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 18, 2012 Moderator Share Posted September 18, 2012 Float height for RD350 F II and N 21mm+-.5 Fuel level 26mm +- 1 Link to comment Share on other sites More sharing options...
enfieldcr Posted September 19, 2012 Author Share Posted September 19, 2012 Thanks Cynic - unfortunatley they are the figures I have been using so the problem must be with the floats or the valves, although it is odd that both carbs are overflowing unless I have got the wrong parts (which seem unlikely as I have tried 2 sets purchased at quite a long time apart) or mixed them up somehow. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 19, 2012 Moderator Share Posted September 19, 2012 Pretty standard fare those carbs are on just about everything yam made from 20 -28mm for a decade or more and they all have the same numbers for the float height. Just dug up my old manual, have you been doing it as per page 92. If so what if you tried 23mm instead. Its not perfect but it may help. If the floats have aged badly and lost some bouyancy. Link to comment Share on other sites More sharing options...
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