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About mrmikkelsen

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  1. mrmikkelsen

    1979 rm125 DG head to 1978 rm125

    I don't know if that will fit Ben. But I found your post because I am searching for a DG head for my 1979 rm125. If you have one, would you like to sell it to me? Thanks, Jon
  2. mrmikkelsen

    SL 100 Mods

    OMG that J6 bike is so cool. I think I saw you at Hollister a couple of years ago on that bike and you were flying!!!! I love those Elsinore sidepanels. How did you get them to fit that bike? Is that a custom exhaust? I've never seen one like it. Good luck with the engine cover. It looks like you have the right one in your picture. Jon
  3. mrmikkelsen

    Putting a SL125 motor in a 1974 Honda XL125 Frame

    The XL stator and rotor will bolt right onto the SL motor. You can then use the same ignition and your wiring will all match up. ENjoy!
  4. mrmikkelsen

    Cam/crankshaft gear/sprocket size options

    The cylinder height is perfectly matched to the piston deck height. To accomplish that miracle, I started with a stock xr185 cylinder and had a big slice cut off of the bottom. The cylinder is still slightly taller than the stock sl125 cylinder, just right for the slightly taller piston crown height of the big bore piston from the xr185. That is why the cam chain is too short. I did think I could solve it with a full link added, so I spliced in another full link and put it together. The longer chain is too long though, and the cam chain adjuster does not have enough travel to take up the extra slack. So now I am looking for information leading me to a source where I could find find smaller cam chain sprockets to fit this crank and cam. If anybody knows if the Chinese bikes' 14/28 gears will fit these sl125 motors that would be great. OR, if anyone out there knows if I half link is okay to run in a cam chain, I'd love to hear about that too. I understand that a half link is not as strong as the normal full width links. What do I know though? Just playing around trying to learn and make this old rig go again. Thanks! Jon
  5. Need some help from folks who know. I have an old Honda SL125 motor with a few non-standard parts in the top end. The big bore piston fits perfectly into the cut down cylinder of an xr185, but there is cam chain trouble. The piston deck height was a bit taller than the stock sl125 piston, so I had the 185 cylinder cut 4mm taller than the stock sl125 cylinder. That is just enough extra height so the cam chain is now too short. One full extra chain link and the chain is too long. A half link would fit perfectly, but I am scared to death that will be too weak of a link and the chain will snap at some point. So, I am looking at possibly running a 15/30 crank drive and cam drive sprocket set up. Or maybe a 14/28 that I understand comes on Chinese pit bikes and maybe???? on xr50's. I could sure use some direction here. Does anybody even make 15/30 sprockets? Maybe some tips as to whether the smaller sprockets fit on the crank and cam properly, or if the easy half link really should be safe? Safe enough? Any tips or help you can think of, I am all ears, or well, eyes I guess. Thanks! Jon
  6. The 4289m06500 Wiseco piston I have is too tall for the conversion I am doing. I didn't know it until now, but Honda's 185/200 pistons have different deck heights, and I need a shorter one to fit the custom application. The measurement I am trying to shrink is from the center of the wrist pin to the top edge of the piston crown. The Wiseco tech rep says he can't reveal that information, and no amount of begging seemed to help. If anybody knows a different go-to source for the specs for any maker of pistons, I could sure use them. Thank you, Jon
  7. mrmikkelsen

    xr200r cranking pressure allowable overages

    Thanks for the reply Lead Head. Yep, I do have a Web Cam mid-range cam in there, maybe could have popped for more of a high strung cam, but I am old and would like some measure of low rev power to assist when I let it fall off the bubble. 225, if it is okay with race gas, or better yet 50/50 race/pump I'll happy as a clam. Anybody else out there got a second experienced opinion? The more more merrier. Thanks again! Jon
  8. So, I am somewhat experienced with these two valve Honda motors, but not in the area in which I am playing around now so I could use to technical input. Situation: I am building a 150cc motor mating a 1982 xr125s lower end with an atc185 top end to run in ahrma's pv 125cc two stroke class. So far I have cut down the cylinder to match the short stroke. Recut the piston dome to match the deck height of the littler piston, including recutting the outer circumference of the pop-op portion of the 10.5:1 Wiseco piston. Installed Kibblewhite valves and heavy duty spring. Installed a Web Cam mid-range cam. Confirmed clearance for head/valves and piston dome. In comparing the atc head with the xl125 head, it appears that the atc head may either have been milled, or came stock less extra material on the sealing surface. My guess is that it has been milled. SO, I kick it over and it builds 225 psi of cranking pressure. Stock 200r specs call for 200psi. I expect to be over stock, but I have no idea what this motor can tollerate. Am I in the ball park for a moderately modified motor at 225? Or is this thing really pretty mild still? Or is it crazy high on cranking pressure and going to lead to an early death? Thanks for any input you have!!! Jon
  9. mrmikkelsen

    xr200R Mikuni Vm Carburetor specs

    The current downtubes running into the engine cradle are that size. I need to intersect the single downtube higher with the split to give the exhaust somewhere to go. Sure would like to come across those jetting specs for a 28mm Mikuni old-school round slide carb.
  10. mrmikkelsen

    xr200R Mikuni Vm Carburetor specs

    AHRMA okay'd the project, to put the 150cc motor in a 1983 CR125R, being legal against the 125cc two strokers of that era. Sure, I would have loved to find a proper 125cc two stroke motor for the really clean chassis I came across, but I just couldn't find one. This one should be more interesting anyway. Absolutely bottom dollar project here: Skimming the regular sources for long forgotten parts and knowledge: A cut down atc185 cylinder, an atc200 head, a used atc200x race pipe, close-out pop-up piston, a "mid range" race cam of uncertain origin that was "lost behind the shop counter for the last 20 years" are keeping the thing mysterious and affordable. The engine cradle and under-the-foot-peg brake lever fabrication are making it interesting. There's that word again. I hope to have the bike ready for the Tulare, CA AHRMA race sometime in October. I hope my knee and hand are operational by then too, but I can't do much about them except keep my moto activities to the garage for a while. Those 1 1/8" chromoly tubes better get here quickly! Now, off I go to find this Shortline10 fellow. Thanks!
  11. mrmikkelsen

    xr200R Mikuni Vm Carburetor specs

    Great info in that OldRice Powroll page. Thanks! narrowing to 28/30 helps too. It's motivating to grab a lead and have something to follow up on. I am runnning an atc 185 top end on an xl125 lower end, and if this thing is going to spin up some rpm's, I figure it had better breath freely to make respectable power. Powroll says 20% + better flow from porting the heads, so now I get to look into that detail too. Danger. Thanks! Jon
  12. mrmikkelsen

    xr200R Mikuni Vm Carburetor specs

    Good news on the ease of finding a manifold. Thanks! Anybody who knows what the proper hot rod sized Mikuni vm series carb was back in 1983 and what the baseline jetting was to suit, I'd sure love to see that!!!! Thanks folks! Jon
  13. mrmikkelsen

    xr200R Mikuni Vm Carburetor specs

    Thanks for posting Mark, and for the 26 recommendation. I don't yet have the carb. My goal is to duplicate the set up I had on my 83 back in 83, I just don't know what it was. Our local parts guy - back then, and when I used to live back home - he and some buddies raced ATC200X's and they had manifolds that adapted to a round clamp style carb outlet. I bought the manifold at retail, got the right sized carb, and used the same jetting all of those guys were using. Then 30 years passed by and here I sit hoping to find somebody who knows what size carb is good for a cammed, high compression engine running a large diamater header. That carb will breath through a huge two stroke style air cleaner, so other than any head limitations, I'd like it breath as well as it can.
  14. mrmikkelsen

    xr200R Mikuni Vm Carburetor specs

    Back in 1983 I put a Mikuni VM carb on my xr200r. It was a simple round outlet model, using a special manifold. The Honda dealer parts guy knew exactly which size carb I needed, and gave me great starting points for all the jetting. That was a long time ago, and I have no idea what size carb or jets that conversion took. All I remember is that the bike ran great! If anybody is familiar with that setup, I could sure use the specs again. That parts guy has got to be 80 years old by now, and he is no longer standing behind the counter waiting for my silly questions. Thanks, Jon
  15. mrmikkelsen

    short stroke XL125 ?rod?

    Aah, yes of course. I seem to be overlooking some details don't I. Shorter rod just means the piston won't go up as far, but it come down farther won't it then. Somehow I had convinced myself otherwise. I am not looking forward to the expense and complexity of having a crank destroked, though of course the would be the proper way to go. I'll go back to exploring other unknown options. I quite like the idea of using the 65mm stock bore of the atc200 with the big fins and of cutting the bottom of that cylinder to match the short stroke of some unknown other Honda single that may or may not exist. I'll have to check around and see what turns up. Lord knows Honda used a million different spec cranks in that lower end. Hmm, Chinese crank...... Know of any 15mm piston pin model cranks that I might try for a shorter stroke? The hunt is on, and the learning is happening. Thanks folks.