Airhead

I would buy new piston and rings and just run a bit of wet / dry 800 grade round the bore in circular motion to key it for the new rings. doesnt seem that the bore is too bad. new piston & rings, top gaskets set, job done. ...paul rings should be changed every now and again, i bet yours are original

DONT BURN YOUR HANDS!!!

Isnt it a four cylinder bike? I'm talking about feeling the heat in the exhaust header pipes, nothing to do with cans. if a cylinder is not firing, the header for that cylinder will be cold and you should not continue to run the bike until this is investigated and fixed. DOHH

Maybe its not firing on all four!, is it rough and lumpy...cautiously feel the exhaust pipes to see if they all warm up, and of course if they dont then theres your trouble.

1: Yes both bikes were revved mercilessly (almost) 2: What's all this bollocks about emissions? 3; VeZ's doesnt open up...ever 4: It's no slouch but I think i'll challenge him to a race before he fixes it

The four possible positions of the power valve within the pulley have no affect in this case. Both bikes are correctly set up in this regard. With exhaust removed and the slot and hole aligned the PV can be seen to be fully open on both bikes, ie smooth and flat passage along the top of the port all the way to the cylinder / piston. If you think about it then raising the exhaust port is what is done on a tuned engine, now when you watch the videos you can see that my exhaust port is raising with increasing revs, and VeZ's is lowering.

Yes 1 and 2 are the same, with the engine idling both bikes have pulleys at around 30 degrees clockwise of fully open. With high revs mine is fully open, slot and hole aligned. With high revs VeZ's has gone even further clockwise and is now 60 degrees away from fully open. All of this is confusing as his bike seems to go ok though.

Yes they are the same. You see the little hole and the 'Finger' with a u shaped cut-out on the pulley, well when the cutout and the hole are aligned the PV is fully open...Now with mine as the revs increase this begins to happen. And with VeZ's it starts off closed and then goes the wrong way with increasing revs!!! We think he should cross over the cables but cant understand why this is so.

Another couple like mine...as in correctamundo

Welcome Herb I dont know if you will get the snswer you need but I have an idea. Go to the 'Workshop' forum, there you will see a pinned topic 'Parts manuals for yamaha bikes'. There are 25 YZ250's listed there, so you will have to do the legwork and compare the part numbers for your answer. HTH...Paul

No knack, just remove completely the bolt and gently rock it back and forth as you pull on it. Sounds like you will in the very least need a new lever, worst case you will need the shaft too. In the past i have got extra use from a badly worn spline by cutting a section of very thin aluminium from a beer can and wrapping it round the spline as the lever is tapped back on. This will pospone the inevitable replacement for a while. Dont weld it on though thats a silly way out of this fix as you have to saw it off to remove the case in future, plus it melts the seal and leaks oil.

DONT TYPE IN CAPS!! I suggest you investigate the switch on the sidestand or the connections to it may be loose. Get a multimeter and test its operation. ...Paul

Possibly a blocked pilot jet in the carb, It may clear itself but I suspect you are going to have to do it.

I find leaving a tin of sardines in close proximity to the bike usually pays off

Hi Brian Tis Here ...Paul

is there too much air in the fuel tank?

People often complain about the YBR gears being sticky, do a search of the forum and you will see. Have you checked the oil level is correct?

The fact that it still functions as a diode as has been tested, has me thinking its just a bad connection issue...either where the diode connects to its leads, or where it connects to ground. Should be easy enough to check with a multimeter.

Rather than risk blowing a hard to find sealed beam, just connect any old 6v bulb in there first.

You will notice it says A, B and C, It's probably a diagram for a later one and is in the mainn ok for yours' It is a Haynes after all but better than nothing.

Read this topic http://www.electrexworld.co.uk/rg06-regulator-1325-0.html

ok, i dont suppose i'll ever get to see this resistor it does get a mention in a Haynes manual though but not for your 175A...bolted to the frame down tube. If it is in the loom I would think there would be a fair old bump where it resides I would consider a regulator connected between the light switch feed (blue)and battery negative if it were me...an ac regulator that is. http://www.electrexworld.co.uk/rg06-regulator-1325-0.html

Thanks, sure enough that is a rectifier, sorry I was expecting something bigger when you mentioned heat sink. well you may as well do the bulb test with that then. Next thing is there any sign of a resistor...bolted the the frames down tube? Also check your bulb voltages and wattages are correct,

Yes a picture would be good, the rectifier as far as i know is quite small, no particular heat sink and a couple of flat blade connectors, like it is on my bike.

Any chance of a photo before you cover it up again? so did you check this with your diode test too?