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About GSjimmy

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  1. completely cleaned the carb, blew out everything with compressed air. Still will not start
  2. Ok, I can try that tonight. But even a few drops of gas in the plug hole isn't doing it. Think I have more gray hair now.
  3. Have cleaned & soaked the carb 2x now. Motor has been out on the bench 3x to verify mechanical timing/cam & piston position. Last night I pulled the flywheel & reset the timing to .016. Last time on the carb I sprayed carb cleaner through the carb jets & all passages. Compression is over 100lbs. My only change on the bottom end is the flywheel. Correct p/n for the engine. Makes tons of spark. I resealed the intake @ the head & carb to eliminate a vacuum leak. I also tried starting fluid to eliminate the carb as an issue. Still nothing. Tried to bump start on the hill, no-go there as well.
  4. GSjimmy

    Stumped on a big bore XR80

    OK, I'm officially stumped. Have the motor built since February, but can't get it to fire up. 1984 XR80, bored 200 over and running a CB400F piston. Bike ran fine before the new top end went on. I did swap the flywheel Have fresh gas, fresh plug, verified the timing 3x, set the point gap to .016, Verified TDC on the piston vs. the "T" mark on the flywheel. Cam is set with the lobes in the down position (8 & 4 o'clock lobe positions). Spark checker says I have a good strong spark. Carb is a 2003 XR100 unit. Plug is NGK CH7HSA Have tried starting fluid as well, nothing. Best I have gotten is a pop out the carb or pipe. Jim
  5. OK, I'm officially stumped. Have the motor built since February, butcan't get it to fire up. Have fresh gas, fresh plug, verified the timing 3x, set the point gap to .016, Verified TDC on the piston vs. the "T" mark on the flywheel. Cam is set with the lobes in the down position (8 & 4 o'clock lobe positions) Carb is a 2003 XR100 unit. Plug is NGK CH7HSA Have tried starting fluid as well, nothing. Best I have gotten is a pop out the carb or pipe. Jim
  6. GSjimmy


    Genuine Mikuni carb runs about $75 - 80 bucks BTW - there is an adapter to run a non bolt-on carb that runs about $20. Not too sure if it will fit. Check out ebay
  7. GSjimmy


    In theory you could, BUT, the CR carb is mounted using an intake instead of the XR/XL flange mount. The CR carb attaches with a band clamp into a rubber intake manifold. Your XL has a 2 bolt design onto a vulcanized rubber & aluminum intake manifold. You would need to be able to turn out a new manifold to mount the carb. Runner volume also comes into play in regard to jetting. I think you would be miles ahead using an XR/XL 125 carb. Same mounting system, and is a 4 stroke carb to begin with. Then jetting will also be very close. Are you thinking of the Big Bore kit? I just assembled the long block on my XR95 last night. Very easy mod. The over bore left plenty of material on the cylinder to do a couple more over bores if needed!
  8. GSjimmy


    Some guys just want to be different. But as soon as he has power, the suspension and weight will be the limiting factor, just sayin'. When my kid got faster, we picked up a KX80 roller and did an XR conversion to it. He is fairly fast on it, good suspension & weight for what it is. We are now moving up in HP (9 to 13-14). After that he will be tall enough for a CR125.
  9. GSjimmy


    Depends on what you plan for the bike. Vintage racing or just a fun trail bike? Check out XRMINIRacer for hop-up ideas, also take a look at Planetminis.com, under the vintage section for JDM verticals (XR75-80-100). I'm on there, look at the KXR80 conversion bike. A stock '79 XR80 has about 9hp and a 100 is about 11hp. The XL's are geared towards road riding and have a lighting circuit on the stator. Since all engines are just an air pump, it matters what you put in and can get out of the engine. Couple ways to do this, install a bigger cam that has more lift & duration. Look at the Hot Cams Stage 1 or Stage 2 cam. These can be installed with out major head work/new springs. Next would be to increase the displacement of the engine. BBK makes a 120cc kit for around $250 or so. Includes a new cylinder, cam, gaskets, piston/rings. This will wake up the bike. [no replacement for displacement] Now after doing this stuff, the bike will need to hook up. Condition of the rear tire is important. You should also think about the gearing on the sprockets. By going to a 13T counter and a 50T rear, the bike will have more grunt out of the hole. Be sure to get a new chain. This should be done at the same time as a clutch kit. Put in a good HD clutch & stiff springs. This reduces parasitic loss due to clutch slippage. Expect to spend about $60 for a good set up here. Last area is weight & suspension. On a '79 XR80/100 the shocks are weak as is the front end. Couple easy fixes here. Forks - go to an '85 & later XR80/100 front end. Total bolt on, just be sure to get everything from the seller. Shocks - look on ebay for piggyback shocks (12.1 or 13 inch) again a bolt on deal, no fitment issues (I did both on my '79 XR80). As for weight, best thing to do is add in CR80 rims and get rid of the steel rims. BTW - an XR100 transmission has better ratios for dirt riding. Jim Remember, it's just money!
  10. Thanks for the reply. I'm picking up the cylinder today and hope to have the long block done tonight. Going with the Mikuni as I have had good luck with them (CR125's & 250's). Jim
  11. Building a new motor for the KXR80 conversion bike. Doing a 2mm+ overbore to the engine and running a CB400F piston. This increases the cc's to 95, requiring an XR100 head gasket & carb. So I am looking at a (Jap) Mikuni 22mm. Is this the right carb to be running for this size engine? We may step up to a hot rod cam in the future as well. We tried the China Keihin carb (eBay $25) and had poor luck with it. Rider on this bike is 120# and still learning. Jim
  12. GSjimmy

    Jetting or bad crank seal?

    It's seals, time to tear it down and do the bearings & seals on the crank. Check the other internals while your there just to be sure (think lower end rebuild). In therory you can replace crank seals w/o tearing the whole thing down, but I've never had any luck doing it.
  13. GSjimmy

    1979 XR80 run problem

    Hey, I'm building a conversion bike ('85 KX80 / '79 XR80 engine) and have run into a problem that is stumping everyone. Had low compression and the bike finally quit running. So in went a new piston/rings on a fresh bore (48.5mm). Kept the stock Honda cam & timing chain. New Honda points, new coil, new condensor. Bike wouldn't start. Messed around for a couple weeks and then took it in. Again, swapped over everything with known good parts, same result. But now it runs. It will not take throttle at all (bucks and dies), she idles great though. So out came the engine to check mechanical timing position. Found that we had set the bike to the "F" position and then adjusted to the "T" position. Starts easier, but still won't take throttle. My next step was to replace the petcock to eliminate an air bubble that was in the line due to routing of the line and a bad OEM petcock. No change. I am thinking that this is a timing issue and not a fuel issue (tried 3 different carbs). Has anyone else had a simular issue on an XR80/100? I'm stumped, my mechanic is stumped.....everything is set to the book and we are still at "no run" under load. Thoughts? Jim
  14. GSjimmy

    KXR80 conversion bike

    I am in the middle of building a little thumper for my 11 year old. Took a '79 XR80 driveline and put it into a '85 KX80 chassis. Fairly straight forward build with nothing too wierd going on, until I tried to get it running. I had to build a straight intake to clear things and keep the carb from tipping towards the rear. We rebuild the top end with a new Wiseco piston (48.5mm). Set the timing to factory and got it to idle. Then the trouble started. 1. When tipping the throttle in to anything that is "off idle" the bike dies. 2. took it to the local mechanic thinking I did something wrong on the rebuild. a. $80 bucks later it idles like a champ. Still can't ride it. Swaped out everything: flywheel, intake, carb (new), all of the ignition, even the keyway. Same problem everytime. Idle is fine, but tip in the throttle and it dies. 3. Now it looks like a tear down again. The mechanic did get the idle spot on. I'm leaning towards the timing chain being off by a tooth for timing. The tip in is acting odd. It bucks & pops like a miss, so I guess it doesn't totally die out anymore. Any ideas I have not tried yet???? Jim
  15. GSjimmy

    XR100/ KX85 Conversion Build

    Thanks, I looked all over the net yesterday thinking it might be under that name. Anyway, I had my oldest come over and take a look at the KXR 80 and see if he could think of anything to relocate the carb under the tank. He takes the intake spins it 180*, placing the rubber isolator end against the block and says "Like this?" Everything lined up in the ports like it should of. Put the carb on and it seemed a bit low, but no suspension on the bike right now so I can't be sure if its wrong. Might just be a simple float adjustment to solve a possible non-issue. So that puts me into the dumb _ss catagory at the moment. Carb runs right next to the frame with plenty of clearance all around. At least I'm moving forward again. Jim