Plug issues

[OverTheHill]

i'll keep out of it now & if i'm wrong i'll go stand in the naughty boy corner but put my money on simply [1] plug too cold for how bikes being used [2] carburetion's set up far too rich etc. Even had [years ago] someone playing with throttle slides in a yz80 & was trying a slide fron an RD350 [or earlier R5] chrome slide & had got hold of a RH slide instead of left hand consequently the cutaway ended up pointing forward instead of back making it run 'super rich', is just a thought but not likely i know with a modern 85cc. Just [from pics & video] looks like the oil gets baked on to insulator then tracks down the side to earth--not really a fault of the plug as such but ends up being reason it stops. Hope you get it sorted. Have a good day--[pretty depressing weather in this part of NZ lately]

[evo550]

Update, Update, Update.

Something Overthehill said triggered my memory about a something I read about YZ 85 slides and the fix was replace the whole carb with one from a kx 85. Apparently the slide and needle are way wrong in the standard Yamaha carb.
So onto ebay I went, secured a carb and fitted straight up, and to our complete jubilation (mine and the young fella's) IT WORKS.

He can't beleive the difference in throttle response and best of all we've been riding every day on the same old plug. before the swap we would have gone through 3 or 4 plugs by now. Fingers crossed it's all clear sailing from now on.

Thanks to all for advise.

[OverTheHill]

I'd say you sorted that one yourself [good on ya], good idea though tossing different ideas around for a bit & hearing how others have overcome their problems, till something rings a bell. Cheers.

[Lozza]

Chalk one up for 'Over the Hill'  What's the new needle/slide combo?

[evo550]

Stanadad YZ 85
3 slide
nbkf needle
48 pilot

Standard KX 85
3.5 slide
nape needle
45 pilot

I had already dropped the pilot on the YZ to 45 before the carb swap, so it was just the slide/needle combe change.

I'm not to bad at picking up needle clip and jetting issues with carb settings, but slides are a mystery to me.