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Yamaha YB100 1989 - fuel starvation?

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Hello all,

 

I’m a newbie to the forum, bikes and Yamahas.

 

I found an old 1989 Yamaha YB100 Deluxe in a barn on my wife’s farm. It’s been sat there for some time and I managed to persuade her to let me take it home for some TLC.

 

Whoever left it did so with fuel still in ??‍♂️. Going off the DVLA MOT checker it last ran out of MOT in 2014 with the same mileage on the clock as it has now, so has literally been stood.

 

So far I’ve:

 

- changed the fuel filters

- drained the tank

- replaced some fuel line

- cleaned the carb

- cleaned the float and float bowl

- reset the pilot air screw

- reset the oil pump setting

- got it through an MOT

 

It does run and runs fine at low/mid RPM. As soon as I try to go up a hill or give it the beans on a flat it runs out of fuel....the engine coughs and dies. To restart it I need to get fuel back in with a good few kicks before she’ll take.

 

Has anyone else experienced this? I’ve scoured the forums but none with the same issues. Or the ones that are seem to have been resolved but the poster hasn’t said what they’ve done.

 

I am suspecting the float as it’s certainly seen better days but I may be wrong. I’ve cleaned it all the best I can but still the same.

 

A daft question but are the floats supposed to be completely symmetrical? Mine looks a little bent.

 

I just wanted to get a few opinions as to what folk think may be the problem before I start spending money on a load of new bits that may do nothing.

 

Oh also I should add that the right engine cover (housing the carb) has no gasket but it’s on order. Not sure if it will cause massive problems?

 

Any ideas or advice would be fantastic. Thank you all in advance! It’d be lovely to have this little bike running properly again.

 

 

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sOUNDS LIKE FLOAT LEVEL, ,  i would also remove the float valve , and clear the passage

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Thank you for that. I’ll whip the carb off again tomorrow. I do have the Haynes manual which specifies the float distance but being new to all this I’m struggling to find where to measure what?!! Do you have any tips?


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There are loads of "how to's" on youtube. just find the one your most comfortable with and have at it, this guy is setting up a set of floats but the principle is the same.

 

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Thank you for all the help and advice. I think it’s sorted?. So I stripped every bit of the carb down and gave it a thorough clean. I also adjusted the float height. It was already set to the height specified in the Haynes manual so I adjusted it to force more fuel in. There was no scientific method, just trial and error. All reassembled and taken on a little 10 mile test ride and she didn’t skip a beat. I even had her at 45-50mph up a hill (covering the clutch just in case haha)!!! She doesn’t cut out when you pull the clutch in either. Time will tell but I am being optimistic. Thank you again for all the advice, a great response to my first proper post.


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SPammmmmmmmmmmmmmmmmmmm

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Another very quick question, but what mileage should I be getting out of a tank of fuel? I’m slightly concerned that I’ve gone too far the other way now as she’s a thirsty beast.


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define thirsty?

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define thirsty?

I’m getting maybe 70miles from reserve to reserve.


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70miles from what? A 7Litre fill? That's chasing 50mpg what do you expect when its prob flat out 99% of the time.

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70miles from what? A 7Litre fill? That's chasing 50mpg what do you expect when its prob flat out 99% of the time.

Haha very true. That’s what I was thinking as you need to keep it pinned to get anywhere. I was just double checking in case!

I literally have no experience with these bikes so am just checking she’s running as she should be after rebuilding most of it.

Good to know, thanks!


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20 hours ago, blackhat250 said:

SPammmmmmmmmmmmmmmmmmmm

You're getting me worried now Blackie.

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