2009 YZ85 Has me Stumped

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7/3/2019 4:57 PM

After what seems like probably 25+ Hours of time into this, I finally wave my white flag and have to seek some help. I had someone deliver this minicycle roughly a month or so ago. It showed up in parts and ziplocs, an absolute mess. The father of the boy had split the cases and completely disassembled the bike in the least organized fashion possible. I inspected most every single part and began the rebuild. Old crankshaft bearing was a mess and needed replaced. I just purchased a new OEM Yamaha full crank assembly as well as new bearings, gaskets, top end, and all fluids. I’ve never done a project like this and have spent quite a good time fiddling and repairing my own bikes but figured it would be a good learning tool. I cleaned, inspected and greased everything correctly and followed most strict instruction on putting it together. The transmission was a task but I figured it out (at least I’m sure I did) I replaced the shift shaft assembly due to a small broken edge off the piece. I also noticed the push rod assembly for the clutch was missing. So I had a piece of drill rod machined to spec, but have since put an oem push rod in now. Here is my issue, the bike runs, and runs awesome. Starts first kick, idles, runs clean. But I have zero movement. Everyone I have explained the issue to thinks it’s a clutch issue. I am able to pull the clutch lever in, out the bike into 1st gear, and it will lurch forward much like you would do before say a practise start. But when you release the clutch, nothing happens. No movement. I am lost? It has to be a transmission issue, splitting the cases again just gives me anxiety after all the work I did. But figured before I get there maybe someone can think of something small I may have missed. Photo
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7/3/2019 6:03 PM

take the clutch cover off and pull the lever in and watch the pressure plate it will move in and out if its not seating correctly or if its worn down to far the bike isn't gonna move that pressure plate may only go on one way like some older yamahas and it may not be comtacting the plates completely
did you try with the wheel off the ground and the engine not running, shifting it threw the gears? does every gear work,i think its the clutch just like your buddies told you

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7/3/2019 6:10 PM

pete24 wrote:

take the clutch cover off and pull the lever in and watch the pressure plate it will move in and out if its not seating ...more

I’d agree sounds like a clutch engagement issue... I’ve also come across new fibers before that were too thin and the pressure plate would never contact the fibers completely...

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7/4/2019 10:01 AM

What type of fluid did you put in transmission? We had a CR80 years ago that accidentally got some Honda oil with Molly put in it (the CRF450 we also had at the time used it) and would never work right until we had to complete rebuild the bottom end and get every smidgen of that oil out.

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7/4/2019 1:19 PM
Edited Date/Time: 7/4/2019 1:30 PM

Are you sure you have the correct number of fiber and steel plates in the clutch? If it's short even one plate, or if the fibers are worn too thin, the bike will lurch a bit like you describe when you put it in gear, but won't move when you let the clutch out. Also, you didn't forget to install the washer behind the clutch inner hub, did you?(There's one that goes behind the outer basket, then another that goes between the inner and outer baskets) I don't know if they are the same thickness, but if not, it might be possible to install them in the wrong position which could also cause your problem

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Many thanks to everyone helping me out this GNCC season: SRT Offroad, Acerbis, FCR Suspension, O'Neal Racing, Evans Waterless Coolants, Rekluse, Twin Air, Braking Brakes, Carbsport

Profile image credit Ken Hill Photography

7/4/2019 1:33 PM

wwoberg wrote:

What type of fluid did you put in transmission? We had a CR80 years ago that accidentally got some Honda oil with Molly put in ...more

I just used genuine Yamaha fluids for everything with maxima assembly lube for all bearing and seal surfaces! But as to what was ran before I honestly would not have the slightest idea. I did clean and inspect everything quite thoroughly before assembly.

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7/4/2019 1:36 PM

harescrambled wrote:

Are you sure you have the correct number of fiber and steel plates in the clutch? If it's short even one plate, or if the ...more

I’m starting to think it must be a clutch issue. I will measure the fibers tonight when I’m home from work and check that they are within spec and see. The boy told me that it basically got stuck in second gear and then eventually died. I appreciate the answers!

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