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2007 Honda CR85RB Build

  1. #1
    Lifer Tekime's Avatar
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    2007 Honda CR85RB Build


    As interesting at mattresses are, figured I'd start slinging some pics up of my current project. This is my first full 2 stroke rebuild. I'll probably end up trading/selling it in the Spring but not until I have some fun with it. This one is for sanity and educationamal purposes.

    I originally had my winter slated for rebuilding my DR350 (again), but chanced upon an unbeatable deal to replace my adventure bike and get a new top end for the old DR. Now that I have a DR350S in decent running order I'm procrastinating that rebuild. So I was on the lookout for a good winter project that didn't involve disassembling my true love, the KTM, or further mucking with the perfectly good running SV I built last winter, as I had originally planned to do.

    Stumbling upon a pile of parts that once resembled a 2005 CR85 for $200, I had to have it. Loaded the heap up in my truck, convinced my wife it was absolutely the smart thing to do (she resists but I know she secretly would want to kill me if I wasn't tinkering in the shop for half the winter), and my fate was sealed.

    I don't know exactly what I'll do with it except maybe race my buddy on his CR in the pits somewhere, and maybe annoy my neighbors from time to time. But, I like my neighbors, getting my buddy off his ass to ride is next to impossible, and when I do have time to ride I usually head straight to the trails. So yeah, I hope to come out of this with a sweet bike, a better understanding of 2 strokes, and I'll be happy.

    Anyway, the bike:

    Pretty much a complete bike aside from a blown top end, shagged crank, and missing bolts/washers/etc. It was originally a CR85R Expert (2005 frame marked RB) with the big wheels, but someone attempted to rebuild it in the past with the small wheel kit and just gave up. Pretty much all stock. With the exception of the forks, pretty much nothing was bolted together. Wheel spacers missing, swingarm bolt long gone, just dozens of little items. On the plus side, basically brand new factory seat and plastics, and all the major parts there.

    This is the only pic I got of the actual bike after cramming it in my "shop":



    The crank had about six feet of vertical play so I kind of knew what I was in for, but first order of business was splitting the cases for a look:



    Gorgeous. Anyone want a lightly used crank?



    I especially love how the iPhone flash really brings out the rust. It actually ain't that bad. Lots of cleaning/detailing to do though.

    Action shot:



    Fully disassembled, all the bits and pieces bagged up and stored, and a few solid evenings of cleaning to get the cases back in usable condition. used my handy little Goodwill toaster oven to drop all the bearings without too much fuss. Midway through cleaning after bearing removal:



    Around that time my Wrench Rabbit kit showed up. Went with the WR because I didn't want to drop tons of money into it, it has the most solid reviews for an aftermarket kit, and uses a Vertex piston.

    I'll be using OEM crank bearings though, but more on that later.



    Cases fully cleaned, bearings installed, time to drop the crank in. Damn I love this tool.





    And sealed:



    It was at this time that I was inspecting the left crank bearing for the third time and identified what I can only describe as a nearly-imperceptible lack of smoothness. I suspected maybe some stray dirt or something made its way in (despite keeping it covered) but after cleaning and fondling it for many minutes I can't get over it. It should be dead smooth, but it's not.

    So, my OCD-ish-type-self can't live with that, and I've elected to backtrack in favor of OEM crank bearings & seals. Another $40 and a few hours lost, but why go all this way and skimp out I guess.

    Plenty to do while I wait. So far my sixth order from Rocky Mountain came in today so what's a seventh. Full inspection of everything amounts to a total of about 30 bolts, washers, and other miscellaneous items ordered up, some more critical than others (like a stray missing thrust washer in the transmission, maybe why it tanked in the first place??).

    That all aside, two important notes:

    1. Yes, the thread says 2007. Yes, it's a 2005. I found a cheap 2007 RB frame with a kickstand and decided to grab it. Now technically I'll have a 2007 (the last year of production for the Honda 2 strokes) and I can start frame cleaning/possibly painting/coating, then sell/keep the spare.

    2. Found an unbeatable deal on a big wheel setup last week and it's in the mail now. Excel rear, stock front, and big swingarm, so I can do the full big wheel setup and have a spare set of small wheels to boot.

    Having quickly giving up on this being a dirt-cheap project, I'm still doing pretty good budget-wise, so it shouldn't break the bank.

    Work is insane now, and next phase is cleaning/prepping the top end, carb rebuild, and some more disassembly/inspection. I'll update again when some actual progress is made.

    Can't freakin wait to get her started up, but either way I'll have something to do in the evenings for the next few miserable months.

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  2. #2

    Re: 2007 Honda CR85RB Build

    1.) 2 strokes are rad to rebuild
    2.) dammit

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  3. #3
    Soul Rider Paul_E_D's Avatar
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    Re: 2007 Honda CR85RB Build

    Great thread. Nice return to topic!

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  4. #4
    Lifer typeone's Avatar
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    Re: 2007 Honda CR85RB Build

    awesome ! sub'd for more ... great project

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  5. #5
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Thanks!

    Got a nice little package in the mail today.


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  6. #6
    Lifer typeone's Avatar
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    Re: 2007 Honda CR85RB Build

    loves me some Man in Brown. nice score.

    parts are starting to stack up over here as well, you've inspired me to turn wrenches tonight.

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    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Nice. Do it! I've been relegated to the computer the past week but making some time this weekend for sure.

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    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    2005 frame totally stripped and bike is 100% in pieces.

    2007 RB frame w/ kickstand mod arrived today.

    Lots of cleaning ahead. Tempted to powder coat but might just touch up with spray a bit...


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  9. #9
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    "just a few things"



    Went ahead and pulled the crank again and removed Hot Rods crank bearings I had installed. Installed new OEM crank bearings and got new seals to throw in. Crank is going back in, and I should now have everything to button the bottom end up.

    Side note: the service manual never calls for assembly lube, but rather a "molybdenum oil solution" for certain transmission parts (a 50/50 combination of engine oil and molybdenum grease). Other parts call for 3% molybdenum grease or 40% molybdenum paste. Was thinking I'd stick with a 50/50 mix of straight high-moly grease + motor oil for the trans, then assembly lube for the other stuff. What do you guys think?

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    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Hell of a time getting the cylinder locating pins out. PB blaster, heat, and pliers managed to loosen them slightly but completely destroyed them in the process. Had to dremel them off about 2mm above the surface so there was no material left to grab. In an act of desperation I grabbed my helicoil kit and had a cutter for an M8 insert that was just the right size (hair under 10mm). Got a bite in the first one and as I turned the cutter it sort of pressed the pin out through expansion. Second one was even more stubborn, but I got enough thread cut on the ID to get a bolt threaded on, then slid a punch through the top and hammered it out. Heck of a nice trick for the next time this happens - if I had to repeat I'd put a small collar around the exposed pin OD to help keep it from expanding too much and cracking the head (was nervously waiting for a crack to suddenly appear..). Would probably also start the helicoil before I mangled the pins.



    Motor's coming along and should be buttoned up this weekend.






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  11. #11
    Development Rider scottieducati's Avatar
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    Re: 2007 Honda CR85RB Build

    Kick ass man!!

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  12. #12
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Motor is done! Just need a few bolts to put the water pump cover on, then clean up the left cover.





    Of course, always an obstacle when you're pinching pennies: one of the swingarm pivot bearings in the RB swingarm apparently spun out and embedded itself in the softer aluminum. I got the swingarm so cheap I may just write it off and order a new one, but I'm also thinking about possible fixes. If I can cut out the old bearing race, get a weld dropped in there, and have it machined back... just maybe. Asking a local shop w/ a Bridgeport to see what could be done.

    I did briefly consider some JB Weld to fill in the groove, honestly I feel like it'd be a passing solution as long as the interference fit was still tight, but.. yeah. JB Weld.


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    Lifer loudbeard's Avatar
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    Re: 2007 Honda CR85RB Build

    Jim ran Daytona with a spark plug JB Welded into his head.

    Why he was installing spark plugs with a 6 ft. breaker bar is a different matter, but it worked.

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    I went to MMI I know what Im doing here chief

  14. #14
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Ha, wow.

    JB has impressed me more than once. Gonna cut the old race out and see what the damage is, all it needs to do is fill in the damaged area and make sure the new bearing isn't slipping around. Relatively speaking it's a pretty low-stress area.

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    Lifer typeone's Avatar
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    Re: 2007 Honda CR85RB Build

    man, that motor looks pretty ... funny how docile they look sans fuel + fire + fury ... pretty sure i broke a rib on the 80 New Years Eve still hurts to sneeze/cough

    bummer on the swinger but hope you get it sorted cheap!

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  16. #16
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Oh man, ribs can take a while to heal up! Yeah, this little guy is so unassuming on the bench... can't wait to hear it come to life and try to murder me. With the internals all cleaned up and reassembled it really is a sight... art with a purpose.

    Tackled the swingarm.

    That old bearing was completely jacked up in there. Had to dremel away some of the race and sacrifice a bit of the aluminum where the race was crushed into the swingarm. After the cut I was able to torch it and beat the old race out. Suffered some nasty galling in the process, but all in all I decided I'm cheap enough to work with it.





    That deep groove was already there, the nasty cut in the middle was my work. Despite the hideous nature of that last pic, 90% of the bearing mating surface area is smooth. Getting a weld in there would be ideal, but a lot of work for something with a pretty simple job. I went ahead and cleaned it up, mixed up some JB weld, and filled it in. Letting it set, then I'll smooth it out. Luckily my 18mm socket has a 22.5mm OD and the bearing is a 23mm OD so it's just about perfect. Pretty sure a new bearing would fit snug even without the JB, but my concern is the gaps causing damage or allowing moisture in. If the new bearing gets a tight fit in there I'm 100% happy and it should be a pretty reasonable mostly permanent solution.





    (Yeah, I cleaned that random glob of JB off in the last few pics)

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    Last edited by Tekime; 01-24-19 at 11:38 AM.
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  17. #17
    Lifer loudbeard's Avatar
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    Re: 2007 Honda CR85RB Build

    That thing is ready for Daytona!

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  18. #18
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Pivots cleaned up nice and got a superbly tight fit with new bearings. Interestingly, spec calls for a 9mm inset and most of the damage was shallower by ~2mm - the older bearings being installed (incorrectly I assume) to about 7mm. Which slightly worked to my advantage since the new bearings (and all the load) sits mostly in the undamaged area.





    Another unflattering picture, but this was pretty darn straight and clean, smoothed down to 1200 grit.



    The '07 frame had a few things. Steering stop was banged up, so I cut/welded a new one:



    Those stem races need to be replaced.

    Cleaned up, prepped, fresh paint:



    And reassembly is finally underway:



    Pretty much all new mounting bolts, swingarm pivot bolts/washer/etc and feeling really snug and smooth, pretty happy about that:


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  19. #19
    Soul Rider Paul_E_D's Avatar
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    Re: 2007 Honda CR85RB Build

    This is coming along nicely.

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  20. #20
    Lifer typeone's Avatar
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    Re: 2007 Honda CR85RB Build

    sure is. nice work!

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  21. #21
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Thanks, a lot of the grunt work is done, on to the suspension and wheel setup.

    50 days until spring (not that that means anything) but might even have time to get at some other projects before the snow clearsp

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  22. #22
    ^ It's my bike and my car tls25rs's Avatar
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    Re: 2007 Honda CR85RB Build

    You are not making it easy on me........................I have a '91 CR125 in my garage that I would really like to give a similar treatment to what you are doing to this bike but don't ever make the time to do. Your photos of the progress remind me of how cool it would be to make that bike closer to new condition instead of just making it mechanically right but still looking like it is a 28 year old dirtbike. Some day.

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  23. #23
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Definitely a lot of work but I enjoy it, especially after sitting in front of a computer most of the time. Working on bikes has taught me a lot about patience, haha...

    Kung fu = hard work over time. This is my dojo

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  24. #24
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    Carb clean & rebuild, linkage clean/repack/rebuild, shock cleaned up, and rear suspension together:














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  25. #25
    Lifer Tekime's Avatar
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    Re: 2007 Honda CR85RB Build

    New tires, tubes, and sprockets are in.

    Cleaned/prepped/painted footpegs, kickstand + hardware, and subframe. Cleaned the crusted up triples, forks, wheels, and removed a bunch of old paint from the front rim. Few other bits installed, tubes & tires mounted.











    Mounted up to get all the spacers etc. sorted.



    Talon hub requires shorter sprocket bolts than stock so I'll probably cut some new ones.

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