A forum for owners of Yamaha TTR250 trail and enduro bikes!

Seems the recurring TTR problem of dodgy carb jets. 

A lot of this malady has been reported recently. Could it be the additives being put in today's petrol?? 

Ethanol is playing havoc in many older bikes that may have had their tanks Petsealed, or similar.
The ethanol additive also seems to be attacking plastic and rubber carburettor components adveresly.

The cure may be as others have done - a complete carb strip-down and clean, paying special attention to jets.

Martyn

I think Cubber is spot on - blocked pilot jet. Bloody awkward riding the TTR on a combination of choke and throttle full on/off 

MarkShelley wrote:

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Is it usual for the bike to tick over fine if the pilot jet is blocked though?

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Good point - no!

Once the choke is off a blocked pilot would mean no tickover.

Reading the symptoms again (properly this time!) it sounds more likely a droplet of water is sitting near the main jet and is causing the problem.

Brian

MarkShelley wrote:

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does the float bowl have a drain hole and if the water droplet is the problem should that clear it?

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Yes and no....

This thread shows where the drain screw is but, if you have never used it, then it may well be seized in.

If your drain screw undoes, try and catch what comes out to see if there are any water droplets in it.

Draining doesn't always clear water droplets around the main jet for some reason - as someone who has drowned their bike good and proper may tell you. 

I have a feeling you are going to be lucky though 

Brian

If there is water there, and you can't loosen the drain screw and don't want to remove the carb, you could (with a helper) tilt the bike to weird extreme angles and wobble it about, and with a bit of luck the overflow point might allow some water out which normally would be sitting at the bottom of the bowl, being heavier than petrol. This has worked for me on a drowned bike with no tools.

Or if that didn't work you could try just tipping it over etc with the fuel turned off to get most of the fuel out of the bowl, then disconnect the fuel line and tip in a bit of methylated spirit which mixes with the water (and the mix has less density) and might be easier to get rid of, either by more tipping and overflowing, and/or by just riding the bike and letting the mix be burnt as fuel. I haven't actually tried this of course.

Or finally, just being mischievous here have you considered finding a brand of petrol with the highest ethanol content you can get, and running through a full tank of that, and allowing the ethanol to clean out the water?

Stripped the carb today using Brians excellent pictorial guide.
There was no chance of me losing the little brass thingy which is referred to in the guide which can be dislodged when blowing out the float bowl as it isn`t even there!! Obviously lost by a previous owner.
It looks like this part is used to form a link between the float bowl and the little brass tube which sticks up into the carb barrell.
Does anybody know exactly what the function of this is and whether it may be the cause of my stutering?
Is this part available seperately?
Would anybody have one laying around that they would be happy to part with for a few beer tokens?

I also see in the manual that it says the pilot screw should be lightly seated then would out 1 to 1.5 turns whereas the guide says 2 to 2.5 turns. Does it make any difference?

 

 

-- Edited by MarkShelley on Saturday 5th of May 2012 11:42:28 AM

That's the one - very expensive new. Still haven't found the one in my garage