CBR125R.... Cold start and stopping... Probs a dumb question

[Guest]

OK. Been riding a week now and starting to feel nice and comfortable riding.

Making the transfer from driving to riding however ive noticed theres a couple of sacrifices to be made when it comes to short trips and generally setting off

Firstly, I'm assuming the cold start cutting out is just something im going to have to deal with?

How long should I leave the bike to warm up before setting off?

And secondly when I turn my bike off the is a dull thud or clunk from the back of the bike, not sure what it could be or if its normal etc?

Cheers in advance

Andy

[supersapien]

well firstly welcome to the world of biking

as for warming i up, there isn't really a set time, each bike (size,make,model,age) all have their own min time for warming up. really you'll have to find out ya self, but a couple of mins should do it. my friend starts his and lets it run while he has his morning fag. i only let mine run while i put my helmet and gloves on and walk it through the gate,by the time i done all that it's ready to go (colder mornings mine needs a while longer)

as for the "clunk/thud" do you mean it's backfiring? it won't sound like a car backfire

if it is that, it could be you're bike is running to rich ( too much petrol, not enough air) remove a spark plug if it's fouled. and check ya air filter box (i'm assuming you've got a standard box,not a pod) for obstructions. if the air filter is clean, there is a air/fuel mix screw on ya carb, make a tiny adjustment ( like 1/8th ) and write it down on some paper and put it in ya owners manual or log book or something, just so you know how much to take it back to what it was originally at, if you ever need to

if it's no that, it could be a worn exhaust valve. there's a guy on here called walneyfranky ( or something like that) he'd be best to talk to about that

[Guest]

Cheers for that

Yeah only been giving untill ive got suited up aswell but thought it may have needed more, just too used to jumpin in the car and shootin off hehe

As for the noise I had thought it was more mechanical so ive been thinkin along those lines..... clearly knowing nothing

Ill listen for it again and maybe call on one of my more mechanical minded biker friends.

Still need to give it a good once over anyways so ill check it out then.

Cheers for the help

Andy

[j4ff]

The noise is probably the chain slapping.Even in neutral there is a slight force on the front chain sprocket not enough to move a bike but enough to keep the slop out the chain .When you cut the power the tension stops and it slaps the swing arm.....Just a theory mind,something to look at b4 spending cash.

Cold starting maybe the choke not opening enough,i think theyre manual.Are you actually using it cos in this warmer weather i only need 1/4 to 1/2 for the first fire then i can close it.

[Guest]

The clonk as suggested might be the chain? Id check and adjust your cluch (just incase) and might need new oil.

The cutting out isn't exactly normal. Is it carbed for fuel injection?

Carbs try raising the idle a little, cold starts they are a little harder to get going from cold. I always used to make sure i could rev my bike freely (with out bogging down) before i took the choke totally off, then took it easy for a while.

If its fuel injection, you only really need to wait til the auto choke turns off (revs settle down to normal) then take it easy for a while

Maybe its just you not giving it enough revs when setting off, hence a slightly weak idle and it'll stall (ive done this a few times, especially hard with pillion lol)

But saying that, i never really had a problem with my fuel injected YBR over the winter.

[Ingah]

Firstly, I'm assuming the cold start cutting out is just something im going to have to deal with?

How long should I leave the bike to warm up before setting off?

Read the owner's manual.

In absence of the manual:

You shouldn't have to let the bike warm up at all (not for a 4-stroke 125, which is what you have), just choke on to start it, then choke off immediately (don't ride on the choke) and keep the revs low for the first few miles (to prevent excessive wear to your engine whilst it's warming up) - warm it as you ride. Note: You may need to keep a little bit of throttle on whilst it's cold else it will cut out.

You could choose to pop the choke on and let it warm up whilst you get your helmet and gloves etc on (i start my CB500 about 30 seconds before i set off), then of course turn the choke off when you ride off.

If you keep a little throttle on (even) whilst stationary, it should not be cutting out (NB: Only applicable whilst it's warming up, it shouldn't cut out at all when warm!). If it does, see comments above for ideas on how to fix the problem. Recommed you buy yourself a Haynes manual for your bike, they have good troubleshooting sections and along with a few basic tools tell you how to fix it all.

[Bill_on_a_bike]

As said a bit of choke won't hurt. The clunk I'm pretty sure is the piston having just enough energy left to complete half a compression stroke, then being pushed back down, running the engine backwards half a turn, I think this clunked the starter clutch or something, I remember it on my SR. Don't get it on multi cylinder bikes because there's normally another piston that'll sort it out.

[botham1989]

In regards to the cutting out when started, my CBR125r used to do the same thing. I live at the top of a pretty steep hill and would occasionally get to the bottom junction, indicating out only to find out the engine has cut out on the slow down.

The way i'd get around this (and not a 100% solution) was to leaving the bike running an extra minute before jumping on and maybe playing with the choke

[wilko20]

i have a honda CBR125R also i got mine at the end of may and mine dose both clunk when i turn it off i have no idea what it is its always done it so assume its normal and as for warming up i usely put the chock on full (pull it all the way out) and rev it a little to about 3k for a few secounds as i start it and then let it sit ideling for a few moments wilst i put my golves and helmit on and then its good to go i just push the chock in to turn it off once im about 100m down the road and that seems to do the trick