Supporting Member knyte Posted November 1, 2021 Supporting Member Share Posted November 1, 2021 ...anyone here familiar with these bikes? I've got the Clymer manual, and installed a BBR Big Bore Kit (so the XR100 is now an XR120 lol), but it's still burning oil, and I'm not sure why. Next step is (I guess) to pop the jug off again and check the rings; ensure they're indexed, but they should be. 2015 FJ-09 / FJR touring bags / oil plug mod / Evotech rad guard / SW Motech bash plate / VStream touring windshield / Seat Concepts: Sport Touring / Vcyclenut ABS rings (speedo correction) / Cosmo RAM mount Link to comment Share on other sites More sharing options...
Supporting Member texscottyd Posted November 1, 2021 Supporting Member Share Posted November 1, 2021 @knyte - What year, and how much oil? These little air cooled singles tend to be set up a bit loose, and I’ve seen them burn some oil just as general operating procedure. It shouldn’t smoke, but if it runs well I wouldn’t be overly concerned about a little oil loss A quick compression/leak down check couldn’t hurt… 1 Link to comment Share on other sites More sharing options...
Supporting Member knyte Posted November 1, 2021 Author Supporting Member Share Posted November 1, 2021 1987. Running dino oil and premium fuel as recommended by BBR. Used assembly oil (motorcycle oil) or moly disulfide grease where instructions called for it. Replaced: Connecting rod wrist pin/piston/rings/cylinder/valve springs/rockers (all part of the BBR kit) Any/all gaskets and seals along the way, including valve seals. After reassembly the jug / head of course was all clean - it ran GREAT (first kick) for about 20 mins / 1/2 hour and the plug fouled with oil. Cleaned it up and ran it again for about 10 minutes. Pulled the plug and it's black again. The only place I think of where oil might get into the chamber other than valve seals would be rings. I think it was running rich, too, so leaned it out with smaller jets and turned the mixture screw in a bit (I'm at ~2000 feet and it was all stock jetting, which I think is meant for closer to sea level). I think it's too lean now, but ez enough to enrichen a bit more. It's a bit tough to read the plug with all that bloody oil all over it. 2015 FJ-09 / FJR touring bags / oil plug mod / Evotech rad guard / SW Motech bash plate / VStream touring windshield / Seat Concepts: Sport Touring / Vcyclenut ABS rings (speedo correction) / Cosmo RAM mount Link to comment Share on other sites More sharing options...
Supporting Member texscottyd Posted November 1, 2021 Supporting Member Share Posted November 1, 2021 Sounds like a fun build! I guess asking which cylinder is fouling the plug isn’t necessary… Assuming nothing is cracked (highly unlikely), it’s either coming down a valve or up past the rings. Is it smoking, and is the plug wet with oil? I assume it’s not overfilled with oil… they hold less than a quart, if memory serves. 1 1 Link to comment Share on other sites More sharing options...
Supporting Member knyte Posted November 1, 2021 Author Supporting Member Share Posted November 1, 2021 54 minutes ago, texscottyd said: Sounds like a fun build! It has been, very much so We're basically in it for a full on restore at this point, lol. I've only listed what went into the engine (so far). We've already done tires / chain & sprockets, throttle & cable, carb kit & jets, petcock, fork seals, brakes, and a folding shift lever. All that's left is paint and some plastics, and triple tree bearings. I don't think anything is cracked...what with a new cylinder, and all. It's not smoking much, just a wee bit with some throttle. The plug comes out...coated, but not exactly wet. Almost like a black dust. And yes, I intentionally underfilled it a wee bit just in case. One thing I haven't done yet, and will soon, is check the oil screen - although I can't see that being at play? 1 2015 FJ-09 / FJR touring bags / oil plug mod / Evotech rad guard / SW Motech bash plate / VStream touring windshield / Seat Concepts: Sport Touring / Vcyclenut ABS rings (speedo correction) / Cosmo RAM mount Link to comment Share on other sites More sharing options...
GTO MIKE Posted November 1, 2021 Share Posted November 1, 2021 What type of cylinder prep was done for the big bore kit ? An over bore for sure and assuming the rings and piston was the proper size. ? Yep the ring line up is important in the sealing .Also make sure the valve seals did not pop up on the valve or that the crankcase is venting properly. It should not be burning any oil if all is right and definitely not oiling the plug ! Hope you get it figured out. MIKE 1 Link to comment Share on other sites More sharing options...
Supporting Member knyte Posted November 2, 2021 Author Supporting Member Share Posted November 2, 2021 The kit comes with all of that, so all components are already right-sized and ready to install as-is (with assembly oil of course): https://bbrmotorsports.com/Products/Products.aspx?Prod=411-HXR-1001 1 2015 FJ-09 / FJR touring bags / oil plug mod / Evotech rad guard / SW Motech bash plate / VStream touring windshield / Seat Concepts: Sport Touring / Vcyclenut ABS rings (speedo correction) / Cosmo RAM mount Link to comment Share on other sites More sharing options...
Buggy Nate Posted November 2, 2021 Share Posted November 2, 2021 Is it black smoke (rich) or white smoke (oil)? As you have increased displacement and the vacuum being pulled through the carby you are now massively rich. You will need to go smaller on the jets to compensate. If it is white smoke, some aftermarket valve guide seals are junk. Those motors also commonly cracked heads and sometimes guides. Careful inspection and or crack testing may be in order if all the proper o rings and gaskets are in place. 1 Link to comment Share on other sites More sharing options...
koth442 Posted November 2, 2021 Share Posted November 2, 2021 I'd be looking at the valves, seals and guides as others have mentioned. 1 '15 FJ09 Link to comment Share on other sites More sharing options...
Supporting Member knyte Posted November 2, 2021 Author Supporting Member Share Posted November 2, 2021 Thanks for the suggestions. Gives me some leads. 2015 FJ-09 / FJR touring bags / oil plug mod / Evotech rad guard / SW Motech bash plate / VStream touring windshield / Seat Concepts: Sport Touring / Vcyclenut ABS rings (speedo correction) / Cosmo RAM mount Link to comment Share on other sites More sharing options...
peteinpa Posted November 2, 2021 Share Posted November 2, 2021 Ring end gap checked? Can the crankcase breather handle the extra volume? 2 Link to comment Share on other sites More sharing options...
Supporting Member texscottyd Posted November 2, 2021 Supporting Member Share Posted November 2, 2021 45 minutes ago, peteinpa said: Can the crankcase breather handle the extra volume? I wondered about that, too. I would expect that BBR would provide for that in their kit, as they sell a ton of these. From what I've read, the stock crankcase ventilation is fine for up to about 120cc, so I would be surprised if there's enough internal pressure to push oil up past a new set of rings... Off topic, but we built a 185cc XR-motored YSR 50 to endurance roadrace awhile back. I've blown up LOTS of XR/XLs trying to get them to live at high rpm for extended periods of time... 1 Link to comment Share on other sites More sharing options...
Supporting Member knyte Posted November 2, 2021 Author Supporting Member Share Posted November 2, 2021 BBR says the stock breather is fine up to 120cc, which this is now. 14 hours ago, Buggy Nate said: Is it black smoke (rich) or white smoke (oil)? It's black, but I'm sure it's oil because I installed smaller jets (one size down from stock - BBR recommends one or more size up, but I'm at a bit of altitude) and leaned out the mixture screw to 1 turn out (stock is 2 3/4 turns out). The plan is to pop the jug off and try something different with indexing the rings. I noticed a puff of air from the oil filler tube last night when pushing the kickstarter down, so I'm 99% convinced I've screwed up the ring indexing. 1 2015 FJ-09 / FJR touring bags / oil plug mod / Evotech rad guard / SW Motech bash plate / VStream touring windshield / Seat Concepts: Sport Touring / Vcyclenut ABS rings (speedo correction) / Cosmo RAM mount Link to comment Share on other sites More sharing options...
Supporting Member texscottyd Posted November 2, 2021 Supporting Member Share Posted November 2, 2021 1 hour ago, knyte said: The plan is to pop the jug off and try something different with indexing the rings. Good news is you can have an entire XR100 disassembled in less time than it takes to get to the plugs on your FJ. Keep us posted! I freaking LOVE 4-stroke singles, regardless of the displacement... 2 Link to comment Share on other sites More sharing options...
Supporting Member knyte Posted November 2, 2021 Author Supporting Member Share Posted November 2, 2021 yeah, the first tear-down was with the engine removed, but now that I've done it once it's clear it can be done with it still in the bike. These things are pretty simple little bikes. It's what...7 bolts to get the cover, head, and cylinder off. 42 minutes ago, texscottyd said: I freaking LOVE 4-stroke singles I bet you wouldn't say that about a certain '03 BMW F650GS I know, haha...those Rotax engines are unlike any other when it comes to maintenance and troubleshooting, SHEESH!! 2015 FJ-09 / FJR touring bags / oil plug mod / Evotech rad guard / SW Motech bash plate / VStream touring windshield / Seat Concepts: Sport Touring / Vcyclenut ABS rings (speedo correction) / Cosmo RAM mount Link to comment Share on other sites More sharing options...
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