YBR struggling to warm up?

I’ve been having some issues with my YBR as of late. After a 2 day break, I took it out last Wednesday and while it was warming up with the choke the bike sounded a bit weird (to me at least). I went out on the road and it kept choking on me as if not getting enough petrol. I let it warm up for a bit more but it still didn’t help. Same thing in the evening when I went home. Mind you I have very short trips.Was slightly better the other morning, it still didn’t feel quite right but maybe it’s just cause I’m sleep deprived. After I got to work (3 minutes later!), in neutral it still felt like the engine was about to die on me. The rev meter was also bobbing up and down a bit which I’m not sure it did before. Got some people to fix the horn on Saturday but I remember it rode fine on Sunday so not sure what happened.
I brought it back to the garage that usually fixes my bike and they kept it for a day and did the following: clean the carb, petrol filter, a new spark plug and adjust the chain. Alas that didn’t fix anything and I was told to warm up the bike some more in the mornings and take it out for a longer. So I tried to do that, rode with the choke on for up to 5 minutes from cold, took it out for a longer ride a couple of days ago and yesterday (ie. more than half an hour) but the issue is still there. Even after the engine is fully warmed up the bike still feels weird.

The rev meter is still slightly bobbing at idle (is is supposed to?)
The throttle doesn’t seem to respond as nicely unless my memory is failing me
The throttle doesn’t seem smooth sometimes around the 2k mark
I don’t think it’s about warming up the engine as it was working fine a couple of weeks ago and it hasn’t gotten that much colder recently. Yesterday was very warm and yet the problem still there.

Any ideas/advice much appreciated!

1st thing I’d do is stick some Redex in there and see what happens. If that doesn’t help:

  • Change/Clean plug
  • Check airbox
  • Check mixture screw
  • Check/clean carb
  • Check fuel line/filter

Ok just actually read the message properly, most of it’s (allegedly) been done

Check your manual to see if they suggest a different plug for cold starts/short trips, my scooter had this problem regularly until I put a lower (I think) heat rated plug in.

Worth checking the HT lead/cap is properly on and not ‘leaking’ spark too.

just needs a good run I think… get it started with no choke, just throttle it a bit to keep it going… get it nice and warm (2-3 mins) then go for a ride but don’t go up into the higher revs

Engines don’t like to be run at colder temperatures, they need to be warmed correctly before they will rev up high. They also don’t like to be left running too long when standing as the engine is designed to perform under cooling ie riding along and having the air cool the engine

I may be wrong but all the YBR’s I have seen are fuel injected so how the the mechanic clean the carb when they don’t have carbs !

I rather suspect either a failed or disconnected air temperature sender, faulty TPS or a partially blocked injector !
I also suspect the wildly moving rev counter is the Yamaha OBD system anouncing a fault look in your owners book or a Workshop Manuel for what senser is faulty The Throttle position one is a favourite on larger Yamaha’s

The 2007 and prior have a carb.

Manual doesn’t seem to say anything about a different spark plug. I’ll check the cap tomorrow morning but I think it’s generally fine.

I was a bit more patient this morning and tried to start it without the choke as suggested alas it didn’t work and after a while I had to kickstart it. After a minute on the choke I turned it off and just gave it gas fairly gently until the throttle was more responsive and the revs actually went over 2000. Then rode off without revving the engine too much and it was perfectly fine after a mile or two.
Is that how you’re supposed to warm up the bike? I used to just put it on the choke for 2-3 minutes and turn that off and be on my way. Worked fine since August! :stuck_out_tongue:

On my GN125 I just hold the revs around 4-5 for 30 seconds or so, test the engine with no revs to see if it’s going to die, if so repeat - 2 rounds of that usually sets me up fine.

I can’t just rev it from cold and after 1 minute or so of choke, I can only rev it to 1500-2000. It just refuses to go any higher until I hold it at that level for a couple of minutes…

Why not, does it cut out? Hmm. I’d like to know the answer to that then, as it was a problem I encountered on my first bike. From cold, revving it to warm up, hit higher revs and it would just cut out?