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russeleoin

YB100 Fuel problems.

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Hi all, I am new on here as earlier this year I bought a little YB100 to get my bike licence on(mid 30's and very used to riding in Africa, just dont have a licence here). It is a good little bike, came with a year's mot and a brand new rear tyre however I have had a number of problems with the carb and i am hoping for some ideas from those in the know. My first problem was that is ran lean and couldnt get it past 35mph. It has been in a garage for a number of years so I took the carb out and cleaned it very thoroughly and put a fuel filter inline, that improved things slightly. I took it to the local bike shop on my way home and they were fantastic, moved the needle up a couple of notches and it is so much better. However, when it has been standing overnight it now seems to flood. At idle, within a minute it will start to leak fuel from the overflow pipe under the carb. I have taken the float out and measured the gap with a vernier, I then raised it a fraction, but that has made no difference. On the hot days we have just had it is fine, no leak, but this morning, slightly cooler than the rest of the week, it was leaking again. There are no holes in the floats and the needle and seat fit snugly. Any ideas on what I could do next would be appreciated, as I dont have a lot of money to spend taking it back to the shop, but I really like it when it runs well. Thanks

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Is the tank vent blocked?

Hi Yoda, where would I find the tank vent? I assumed that pressure buld up would just escape from the filler cap, but that may not be the case? As the bike had been standing for quite a few years, anything could be blocked. I fitted the filter to help with the fuel, but I have noticed that the fuel tap is very stiff to turn? Thanks.

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fuel tap, my ft1 had alot of dirt and rust in the tank that clogged the fuel filter on the fuel tap up, flushed the tank out and fitted a new 1 and ran fine, also clean your carb out, check that the float needle isnt sticking

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Latest update. On the way home from the station yesterday there was no leak at all. Bone dry even when breaking hard to a stop. Parked as usual in the covered garage, no problems at all. This morning, within a minute it was leaking again, and I rode switching the tap off each time I come to a stop, luckily I can do quite a few minutes on what is in the carb alone. I will clean the tap/vet this weekend and will also adjust the float height again and see if that helps, it may only be out a fraction of a mm.

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Over the weekend I had the carb off again, and low and behold, I found that the float had some tiny holes in it. I have run a very thin skin of araldite over it and it was fine this morning, well, no leaking. But it now seems flat again and I have no top end power, but I assume that this is due to changing the needle settings to compensate for the flooding and excess fuel. I will change the jetting tonight and hope for the best. Anyone with tips or ideas onn how to tune with the minimum of fuss, please let me know. Thanks

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Adjusted the needle setting to the one quoted in the Haynes manual, still dont seem to have any top end power. Setting is now, Middle notch, I can get 40mph in 3rd gear and power is fine on full open throttle. 4th gear and power dies, cannot maintain 40mph on a flat road. I looked at all the settings and info on the web, and to my mind, full thottle in 3rd should give the same sound/power as full in 4th. Main jet being used, but there is definitly a loss of power. I get the very throaty sound, easing off in 4th doesnt help, but change down, and accelerate and all is good. I am now getting irritated with this. I cant really afford to take it into a shop for repair but if I cant get it fixed I think it might be back on ebay soon.

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You have partially blocked jets, so clean the carb and put it back to the origonal settings.

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Hi Yoda, thanks, I am working from home tomorrow, so the carb will be off and cleaned. I did put the needle at the 5th notch and it was better this morning, but what you say makes sense so that will be done tomorrow. I had initially cleaned the carb, but that was before I put the filter in place to quite possible that I have picked up more dirt. Regards

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also check sproket size front and rear of chain . you bought this second hand and might be geared to high (smaller rear) for eg. this will kill the power off and not let engine rev. you never know a workshop book might tell you the size of each (teeth) fitted as standad.

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Hi All, problem solved. Firstly I bought the Manual as Richard suggested, I checked the bike over and compared it to the standard spec as per the manual. All okay there. Then I had that wretched carb off again. I took it into the kitchen, cleaned and polished the jets, cleaned and polished the needle and low and behold, fiddled with the float again. Using a very techy method, I poured water via a pipe into the feed and holding the bowl in place, I noted where the water level was. I then adjusted the float level until I got to the correct fluid level in the bowl. Hey presto, it worked. I used the bike this morning, and managed to get 55mph without even trying. I only need 50mph as that is the speed limit on the fastest stretch of my journey to the station. I am happy with it now, and started to look around for something a bit bigger for once I have my licence. Regards

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