May 6, 201313 yr I've got an 08 Rev 3 270 which I use with a long ride kit. My friend has just bought a brand new Gas Gas 300 and now that I am riding with him I'm realizing that my 270 seems very thirsty. We rode together today and I must have used close to 4 litres of fuel to his two. We live and ride at altitude, typically riding from 3000ft to 5000ft in the French alps. My bike mostly seems to run well, but I would say it's a sluggish off a closed throttle especially when you are coming down a long decent off the throttle and you dip the clutch and give it a blip of throttle to get some oil flowing. It needs a really good handful before it runs cleanly. My guess is carb setup, but I'm unsure what I should be looking to change. Or are the 270's and the Rev 3's generally considered to be particularly thirsty? I've made sure the air filter is clean, I've cleaned and set the plug gap. Any suggestions? Appreciate any help.
May 6, 201313 yr The angle the carb is at makes it over fuel on a decent I had an 07, the 08 had a KeiHin carb so I don't know if they were better or worse Maybe you are overflowing on downhills, the fact that you run rich on on downhills suggests that Next time stop on a slope and see if you are losing fuel from the overflow tubes
May 7, 201313 yr Author If you are leaking fuel you need the carb set up guide. I thought all those issues were fixed on the 08 model with the Keihin carbs, that's why I'd not really gone down that route? All I saw relating to the 08 carb was to check the float height setting. I will check first to see if I am leaking fuel (I'm gessing I must be given the rate I am getting through the stuff at) and if so get the carb off and have a look at the float height and the carb setup guide for the pre-2008 models. (I assume the pinned thread at the top of the forum on carb setup is the guide you are referring to?)
May 7, 201313 yr Author OK, I've removed the long ride kit and done the "point the bike downhill" test and indeed petrol does dribble from the vent pipes (well, one of them at least). So, I'll check the float hight setting and make sure all is clean inside the carb. If there's anythng else I should be checking and adjusting, do let me know.
May 7, 201313 yr Lap in the float valve with a dab of toothpaste for good contact/seal. Yes it is pinned at the top.
May 9, 201313 yr Well, til we get fuel injection there is only one way to control fuel level in the float bowl If the float is in a position where it can't close the needle then overflow controls the fuel height I think it's possible to stop overflow but then the fuel level would become high and over fuel the motor
May 9, 201313 yr As long as it only drips a tad at extreme angles don't panic. That's normal. It should not leak on the stand or when level though. If it does you need to tweak it.
May 9, 201313 yr Author I've had the carb off (I'm getting good at it now I've done it a few times!) and re-set the float heights now and doing a stationary test with the engine running and the front wheel dropped down a bank it seems not to be dribbling fuel now. I'll go riding with my buddy this weekend and see if my fuel lasts as long as his in his Gas Gas. - Fingers crossed it's fixed, or at least a lot better than it was!
May 11, 201313 yr Author It's still rubbish :-( I'll have another go at re-setting the floats with a view to reducing further the amount of fuel in the float bowl. I can't think of anything else to try.
May 13, 201313 yr Author It's still rubbish :-( I'll have another go at re-setting the floats with a view to reducing further the amount of fuel in the float bowl. I can't think of anything else to try. I've now got the floats set lower than recommended (so that the fuel supply valve is actuated sooner) and it's still using/leaking way more fuel than the gas gas my friend rides. A call to Lamkins next to see if there are any other ideas on what might help.
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