Vintage Dirt Bike Q & A

hello i'm new here. last week i bought a 1975 mt125 elsinore for $475. it's my first motorcycle.



needs a carb, kickstart lever, cleaned gas tank, probably throttle and clutch cables, grips, mirrors and signals, chain, and side covers. maybe more but so far i have that list for it to be street legal.

looking at a mikuni vm 26mm carb, that a good size for a 125cc?

also looking info for kickstart levers. any interchangability between mt250's, cr125's etc?

thanks! glad to be a part of the community!

Welcome! I too am an mt125 owner. mines a '76 I'd recommend a keihin carb. In my little experience, they're easier to work on and their design makes more sense to me. Of course you probably shouldn't listen to me, because I've yet to get my bike to run consistently. But either way, welcome. One thing you may want to do is check to see what kind of shape your wiring is in. when people take the lights off they like to attack the wiring with a wrecking ball. It maybe be a ton of work. But yeah, dont go on just my advice, because i am a pretty big noob. One thing i can recommend with absolute certainty, is if you're trying to get a bike to run you should try to find a padded kickstart lever, one with a little rubber on it. It could potentially save your ankle/leg, esp if its your first bike, and esp if you dont have more experienced help. Now that i've said that, i have no idea what padded levers fit mt125, but the stock isn't padded, so if you don't get a padded crank lever, you may want to wrap it in tape or some kind of cushion while you're first adjusting the carb/getting it running. I know it's been a huge help to me.

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1976 Honda Elsinore MT125
1990 Toyota Celica

Welcome!

Re the parts you're looking for... the stock 24mm carb shows up on eBay quite often (it should have 021A stamped on the body, near the choke lever) and is probably your best bet if you're planning on keeping the oil injection and using the stock intake manifold, throttle cable, airbox, etc. I'm assuming you're looking to get the bike running ASAP.

Any MT125, CR125M ('74-'78), or MR175 kickstarter will fit the shaft splines. There's the slightest possibility that a '75-'76 MR175 unit will hit the top of the brake pedal, but I doubt it (a lot of eBay sellers have return policies now, so you could always buy and try). To add to Maximilian's suggestion about the kickstarter foot; some of the kickstarters mentioned above have longer foot sections than others, and are less likely to slip off your foot while kicking (in general, later-model kickstarters have longer foot sections).

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Lol your shin gets used to the whack of the steel kicker levers after a while. Just wait till your shin comes down on the foot peg that really hurts as its got teeth on it. Funny thing I never got the mikuni on my mt250 to work very well went to a kehin and it works great. I have no oil injection and it sucks as I have to carry oil and a ratio right cup with me in case I need gas. These are great on the street everyone looks at you when you go by.

thanks for the responses guys! haven't checked this in a while, i didn't think anyone would reply haha.
anyways i've recently bought a keihin carb and an mt250 kick start lever. i've yet to install them, though. but i will return with fitment results later.
if anyone is interested, i can take pictures of my progress to follow my build.

well here i am a month later with little progress.
installed the kick lever, found out the piston has siezed. finally got around to taking it apart today.

turns out the piston pin siezed also. since the piston couldn't rotate around the pin, the piston couldn't go up or down the cylinder. some good ol' ring expansion didn't help either. took a little careful persuasion, but i got it done without breaking anything!
probably going to have to get the cylinder bored out. probably a .50mm over and i think i'm gonna go with a wiseco piston kit.
bottom end is currently bathing in some ATF to clean out the gunk and work its way into the bearings. so far it feels a lot better. crank to con rod bearing feels quite good actually.

Unfortunately you should probably split the cases on that one. I just went through this with my CR. It's easier than you might think. Having a service manual will make it a breeze.

i would recommend you a complete engine rebuild with all bearings, seals, piston, conrodkit etc.......

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80 CR250Ra
80 CR250Ra
78 CR250R
80 CR80
82 Bultaco Sherpa 340
78 Bultaco Pursang 250 MK12
76 Bultaco Frontera 370 MK10
76 Bultaco Alpina 250
73 Bultaco Lobito 125 MK6
76 Suzuki RM125A
90 Kawasaki KX250

you're probably right. since i have the whole thing apart it just seems logical to do that. not replacing the bearings would be just as irresponsible as the previous rider who left oil out of the transmission and overall didn't take too great of care for this bike.

anybody got any tips for removing the engine? had some trouble today. got all the bolts, wires, cables etc removed but there's a notch on the engine case coming in contact with the upper rear mount. i have been trying to lift the front of the engine and slide the bottom from underneath.
how have you guys removed your engine? i must be missing something here

nevermind. i got it worked out.
well here's some progress i've made
some new parts. wiseco piston kit, NOS gaskets and top end bearing



got the cylinder bored .50mm over




got the engine out with the bike upside down


took off basically everything to clean up


got some more cleaning to do. my dad and i are going to tidy up the wiring harness as well. doing a lot more to thsi bike than i planned but it's a good experience. can't wait to finish it!