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00' YZ 125 jetting jeadache...


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Ok so I know this has been discussed over and over again and Ive read the sticky and used just about every resource I have avail to me. However this jetting has got me stumped. I had the bike jetted slightly rich for winter. Bike ran perfectly before, since Ive returned the bike to stock jetting and it still ran perfect and jetting seemed spot on. Well I replaced the top end and after the break in period (which it seemed to run fine) I went to the track and the bike started bogging terribly. Upon further inspection the plug was black and silencer was covered with spooge and it was also pouring from the breather tube. Although I ran stock jetting in it last summer and it was absolutely perfect with the exception of the needle clip position which I had at the 2nd notch.

Got the bike home and started the jetting process all over again with stock jetting by returning to stock jetting... per roccomendations from JD himself.

MAIN...350...stock

PILOT...35...stock

NEEDLE...6DHY53-75...stock

CLIP...3rd

AIR SCREW...1.5 turns...2

40:1 yamalube 2R

Im at 1100 ft and temp is currently around 70 deg F

Mid pack intermediate MX rider.

and low and behold it took care of the bog but Im still getting mass amounts of spooge but the plug looks perfect in color through all ranges of the throttle. Ive never experienced this much trouble jetting this bike and its starting to frustrate me. I have the jd kit and Ive been messing with it for a week straight now and no combo I have tried is getting rid of this spooge factory of a bike I have on my hands. It seems like every time I go any leaner on any of the circuits its extremely lean in that range.

So my question is, is there something I am missing or what? Im beginning to think that it has something to do with the top end I put in but the bike pulls hard now that I have returned to stock but theres gotta be a cure for this spooge... I know its gotta be hindering the performance since Ive repacked it 3 times in the last week and the packing is completely saturated and seems to weigh 10 lbs after each ride...

Someone please point me in the right direction!

Also note Ive rebuild carb, replaced air filter 2x, and replaced reed petals...👍

Edited by ftball90
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Not much but have to ask...did you clean out the header real good? It may have a bunch of oil sitting in it just waiting to be cooked enough to spit it into the silencer. Other than that, if it's running great and the plug looks good...maybe it's ok and just a byproduct of the new top end???

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Yes the bike was meticulously cleaned this winter along with the rest of the bike... including cylinder replate so the cylinder was spotless when I got it back, cleaned exhaust to the best of my ability and repacked silencer, fresh seals and bearings everywhere!

Update: I took another crack at this last night and upon further inspection it looks as if its tranny oil, any possible causes for this that wouldnt effect performance? I may be wrong but if trranny oil was getting into the top end I figure Id see some loss in performance and power... maybe I should just start over, but I hate to waste all these fresh parts I just paid for and spent the time to install. I had to make a mistake somewhere...👍

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Constantly check that oil level from here on out if you are losing oil and your bike is blowing blue smoke it could be the right side crank seal which would mean you have to split your cases and install a new one. I'm pretty sure it's not your fault I don't think there is too much you could have done when putting a newtopend in to cause that to happen it just did. I have friends who's bike has tons of oil dripping from the exhaust and they corrected it by cleaning the pipe out and getting that jetting good and about a week or so of riding and the dripping went away on it's own so it could be as simple as that.

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