YBR125

[BBROWN1664]

I have a YBR125 that has stood for a few years since the last owner had a car/bike interface issue. I have rebuilt most of it now ready for my son when he turns 17 in just over a months time but I have a problem with the way it runs.
 
It will start on the button using the choke, and once it warms up (but not before) it will rev OK but it wont idle or start when off of choke.
Using the theory that it was running OK before the previous owner bent a few bits, I suspect that the carb settigns are OK and there would just be crud in the idle jet from where it has been standing. Unfortunately, despite cleaning the jets out with an air line, it still has the problem.

[snooky]

I'd still check the idle and mixture settings on the carb, who knows if it was set right before? Try running without the filter in as well. I've been learning loads on single cylinder bikes recently

[BBROWN1664]

I think I will end up tweaking with the carb screws. I have tried the no air filter route already.

[kebab19]

Not sure if there's anything unusual going on here, mine hasn't ever sat unused for extended periods of time & yet still shows the same reluctance to run from cold.
 I have to leave it with choke on & ride it for about five full minutes before it'll rev & run without stalling. Once she's warm she'll start & run fairly well for the rest of the day, but not before that.

[BBROWN1664]

I may have to try getting it hour rather than "quite warm" before tinkering too much then. I take it you are falling about a YBR125 kebab?

[BIG MAC]

Check the air intake isnt obstructed with waterproofs etc under the seat..check the emulsifier tube in the carb..check the diagprhagm (never could spell it - and have the 5 kids to prove it) Choke probably sets a fast idle bit like the accelerator pump on old carbs if memory serves...check float height also as mixture is irrelevant if insufficient fuel coming through...you could be 'choking down the air flap to let is run rather than enriching) hey I know what I mean even if no one else does.....

[BBROWN1664]

Carb seems ok with clean jets and tubes. Air box is clear. Choke is the plunger type on the carb that increases mix rather than blocking air.

Looking on the intetweb it looks like a common problem but no real answers.

[kebab19]

Yes, just to confirm I have a 2006 YBR125 as well as my FZS1000

Its always been very cold-blooded & will simply will not run without the choke on. The online forums reflect similar owner experiences & I believe the later FI version of the bike doesn't have the problem to the same extent.

It used to bug me sitting in traffic @ 4000rpm, but kinda got used to it now. 

[BBROWN1664]

Well, having spent a couple of hours with GarethG stripping, cleaning and adjusting the carb again, the pronosis was that it was fecced. No matter how much we adjusted the air screw, it made fec all difference to the way that the bike ran. Located another carb on fleebay and have just had a productive 30 minutes in the garage fitting the repalcement and all the panels and it is now ready for its MOT in the morning!

Just hope it passes now as I dont have much time between now and his birthday to sort anything out and I haven't even had the chance to ride it yet due to it not having an MOT or Tax.