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YBR 125 Wont start


KimB
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Hi everyone,

I bought a YBR as a non runner, I had to do a top end rebuild on it, everything seemed fine and went well.

It does start but only with easy start ? When it does start the revs seem to sit quite high ? Any ideas what it may be ?

I have adjusted the valves as well so it isnt that.

Any thoughts would be great to hear.

Thanks

Kim

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  • Moderator

You really need to say a hello in the New Members Section as most people don't reply to first post question.

Did you set the timing chain correctly?

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You really need to say a hello in the New Members Section as most people don't reply to first post question.

Did you set the timing chain correctly?

Oh really, I didn't know Sorry.

Yes I did.

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I bought a YBR as a non runner - this means that there could be multiple issues with it not running and makes diagnosing things a little more difficult.

I had to do a top end rebuild on it, everything seemed fine and went well. - Did it run after the rebuild? Why was the rebuild necessary? Did whoever did the bebuild do a proper job and got all of the settings correct?

It does start but only with easy start - This is really a positive, It may rule out major electrical issues however, minor ones may still lurking

When it does start the revs seem to sit quite high - Carb or injection?

Did the re-builder check the bore and piston rings?

The starting may be helped by taking out the plug, while the plug is out, check what kind of spark you are getting, Pour a spoonful of engine oil down the bore and get the piston moved up and down a couple of times - in gear and rock the bike does it. Leave the plug out overnight. tomorrow fit a NEW plug and try again. The bore could be washed out with fuel and there is not enough compression for the bike to start. It takes a faulty plug out of the equation.

Don't forget to say hi.

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I bought a YBR as a non runner - this means that there could be multiple issues with it not running and makes diagnosing things a little more difficult.

I had to do a top end rebuild on it, everything seemed fine and went well. - Did it run after the rebuild? Why was the rebuild necessary? Did whoever did the bebuild do a proper job and got all of the settings correct?

It does start but only with easy start - This is really a positive, It may rule out major electrical issues however, minor ones may still lurking

When it does start the revs seem to sit quite high - Carb or injection?

Did the re-builder check the bore and piston rings?

The starting may be helped by taking out the plug, while the plug is out, check what kind of spark you are getting, Pour a spoonful of engine oil down the bore and get the piston moved up and down a couple of times - in gear and rock the bike does it. Leave the plug out overnight. tomorrow fit a NEW plug and try again. The bore could be washed out with fuel and there is not enough compression for the bike to start. It takes a faulty plug out of the equation.

Don't forget to say hi.

Thanks for the detailed reply.

Hi yes I put everythig back how it was, The previous owner tried to do a rebuild but bodged it and used silicone instead of replacing the gaskets :o. So put all new top end gaskets on.

I forgot to add its a 2005 so carbed model with 8000 miles

I didnt check the piston or ring gap, wish i did do it now !

The spark wasn't too bad. But i will remind myself late/tomoro.

Sorry if im being silly but i didn't understand these two bits of what you said :

in gear and rock the bike does it.

The bore could be washed out with fuel and there is not enough compression for the bike to start. It takes a faulty plug out of the equation.

Thanks again

Kim

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what dirtydt means here is

compression is aided by a film of oil in the bore and around the piston / rings. Repeated attempts to start can mean that the petrol washes this oil away and to some degree the 'seal' needed to aid compression is lost so compression is reduced. Try squirting a little engine oil down the spark plug hole to improve the seal and maximise compression.

Attemp to start with choke and little or no throttle

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what dirtydt means here is

compression is aided by a film of oil in the bore and around the piston / rings. Repeated attempts to start can mean that the petrol washes this oil away and to some degree the 'seal' needed to aid compression is lost so compression is reduced. Try squirting a little engine oil down the spark plug hole to improve the seal and maximise compression.

Attemp to start with choke and little or no throttle

Uhh, Thanks for explaining that. Will give it a go tomorow :) thanks for your help

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Not sure if this help or not but I have seen many people put the slide for the carb in backwards= bike wont start or if it does it revs realy high.

If the bike starts and runs then it kinda narrows it down to a carb issue.

O hi and welcome

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Not sure if this help or not but I have seen many people put the slide for the carb in backwards= bike wont start or if it does it revs realy high.

If the bike starts and runs then it kinda narrows it down to a carb issue.

O hi and welcome

Hi thanks for the input, The bike does tick over low but idles high and goes low, I know i wouldnt have put it in backwards as that was something i was always taught :)

Thanks Kim

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Hi thanks for the input, The bike does tick over low but idles high and goes low, I know i wouldnt have put it in backwards as that was something i was always taught :)

Thanks Kim

So it "hunts for idle" high then low? .I say spray some wd 40 at the intake and check for air leaks

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Hi Everyone,

Okay so I think I had a look at it yesterday, I did the oil in the bore thing it wouldnt start but did have much more compression, I then managed to fire it with a spray of easy start once up and running it was same as before, revs fluctuating quite allot, it seemed to get worse the warmer it got. If I then put the choke on the revs would drop down around tickover.

I also checked for air leaks and totaly stripped the carb again to make sure all of the seals and everything else was fine, which it was.

Once it was warm I could start it fine but as soon as it was cold it wouldnt start. ?

Thanks

Kim

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Its deffinatly that carb kim" the choke should kill it when warm,[ excess fuel] and having to spray to start cold, points to the choke system not working, :eusa_think:

in the carb bowl, there may be a deep well, the choke pipe feeds off this well

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Not sure if this help or not but I have seen many people put the slide for the carb in backwards= bike wont start or if it does it revs realy high.

If the bike starts and runs then it kinda narrows it down to a carb issue.

O hi and welcome

C'mon own up, you found that one out the same way I did.

Bluuugh Bluuuuugh waaaaahhhhhhhhhhhh. Bollocks.lol

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Kim this might sound absoutly nuts but are you shure you not turning the choke the wrong way.Realy sounds like you just having trouble with the choke circut cold once it warms up you turn it off ( but in your mind you turned it on) and the bike idles properly.

I am have trouble gettting this the symptoms of hard starting from cold and increasing revs as it warms is exactly what the bike would do if the choke was on,and once warm if you turn it off it would settle into tick over.

You just did the T/E of the motor R U shure the valves are adjusted properly .002 intake clearence and .004 inch exhaust.

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Hi guys, so I had another look at it today, re checked the valve clearances and they were fine, now that you said the carb seems the issue the only problem i noticed was that as you can see in the photos bellow the two holes that lead to the bottom of the float bowl its blocked ? should that be blocked ?

IMG_2414_zpsf03b8552.jpg

IMG_2413_zps98c704fb.jpg

IMG_2412_zps05298c56.jpg

I put a drill bit down the long bit of the hole and it didnt go all the way to the bottom ? but the hole at the bottom of the float bowl seemed to go all the way to the other.

Also this is choke off ?

IMG_2411_zps3b779ab6.jpg

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