Ok, I finally did a video so you guys can hear how it’s just not running right. This is for sound only. All I did was clip my phone to the collar of my Tshirt.

It does clear out and will lift the front end at full throttle but it just seems to stutter at any other throttle range. It starts easy and it does idle now, which is better than the first couple rides. Maybe I just need to keep thrashing it for a while to clear it out.

I installed an HPI ignition and timing is set at 2mm BTDC. Maybe I need to play with the timing a bit. But should I advance it or retard it? Or maybe try it both ways and compare?

I welcome your suggestions please…..

needle jet and needle in good shape?

I did notice the needle looked questionable being discolored in areas along its length which I assume is wear patterns. So I’ll make that the next step. Thanks for the suggestion.

How do I know which part number to use​​​​​​? There is more than one choice.

imgur.com/a/SZzeHi8

Edit…
never mind…..I see (MX250A) noted by the number.

I have been fighting mine doing the same thing at intermittent times and mine turned out to be the float not closing off the gas flow so I was running rich everywhere except at close to wide open, as I was using more fuel than the float was allowing to seep by. Still fighting with it.

Yamaha parts list for 73 MX250 and 360 Yamaha parts list same as 74 MX 250 @ cmsnl.  The following from Yamaha parts list for 1973. 

MX250 239-14116-05 Needle 6F5-3
MX360 239-14116-15 Needle 6F15-3

MX250 249-14141-45 Nozzle P-5
MX360 249-14141-40 Nozzle P-0

Either way.  That thing sure sounds nasty like its getting ready to take a big bite of the grass. 

@pabdt
That’s the needle I just ordered but I found the nozzle to be part number 239-14141-48-00 and that’s what I ordered. I guess we will see how this works out. It’s my first order with CMSNL.

@Dogboy
I will check into that when the new needle and nozzle arrive. The bowl does overflow on occasions…..

full disclosure, I am not sure which ones your bike came with. was looking around and found this though on the legends site.

www.legends-yamaha-enduros.com/_files/ug...3ba99.pdf?index=true

I'd love to hear RT325's opinion.  

Sounds pretty darn good to me after it warms up a little, it's a race bike and was designed to be ridden hard.  They tend to be jetted a little rich at lower throttle settings from what I remember?  If you get it out on a track and ride it like intended, you need that extra richness when off the throttle during a race.

Stock timing was 2.3 mm

Do you have the stock silencer?  In 74 they were pretty loud and Yamaha went to a Skyway "super muffler" and airbox mods to quiet it down and pass the new AMA sound requirements. 

It also looks like the early 74's had a VM30 (up to VIN 025238) and the later had a VM34.  What's your carb number?    They had different jetting specs.  



 

Thank you for your efforts finding that manual. I will get it printed because I’m a hard copy guy.