The RM125 is RUNNING! But We Have a Problem 

Honestly you should buy an entire new carburetor because that carb is going to make that bike blow tf up 😂

That thing is running major lean. You will blow it up if you keep running it like that. If cleaning up the carbeurator does not fix that it is definitely an air leak, Either a gasket/seal is not sealing or something has warped. Spray some starting fluid, carb cleaner, or wd40 around the engine and if the revs change, you have found your leak. It could be the base gasket, head gasket, case seal, or crank seals. I doubt it would be the crank seals since it is a freshly rebuilt engine, but Id also check that you didnt warp anything such as the cylinder or head(which i doubt you did, but still something to check.) But before checking for air leaks i'd clean the carb cause the jets could be clogged not allowing enough fuel through causing it to run lean. Hopefully it is just the carbeurator and not an air leak. Hope you get it fixed soon!

The reason it runs good on choke but fast off choke is because it's too lean. Choke has a richening effect.

I’m glad it’s running, you’ll get the problem fixed soon man. Almost there!!

Can't wait to see u rebuild the whole dirt bike 💯

That coolant bottle said concentrate.. I hope you mixed it 50/50 with water before putting it in the bike..

You don’t need to give it gas to start it while it’s cold

You have a air leak in the boot that goes from the carb to the reed it’s letting air in causing it to run lean and rev up the hose clamp might have cut its way through the boot at least that’s what happened to my dads 89 rm 250 of course in the middle of a trip to West Virginia 🤦‍♂️

The slide in the carb are stuck

LEAN LEAN LEAN LEAN LEAN LEAN LEAN LEAN LEAN LEAN Lean is the best way to kill your engine especially in 2 strokes as they use gas premix to provide lubrication so when it's not getting enough gas it's not getting enough lubrication

you need to put the rest of the plastics on and the seat because it is running lean with the air filter being exposed that is your problem ( i tested this theory on my own bike to make sure it was correct and it was)

Like the vids man! But easy with the gasket maker. I like to put a little bit on my fingers and smear it all around and add to the finger here and there and just do a thin layer with maybe even the old gasket (or new) just to help and always make sure to wipe away any excess that looks to be on the inner edge of the cases where they mate. Really don't want any of that smooshing down especially with how much you put on it'll smooth alot and could always end up breaking off and going somewhere it shouldn't. Keep it up it'll be a beast soon!

I have to agree with angel. I would try rebuilding the carb first since that is cheaper then buying a new one. It’s not hard to rebuild those carbs. I would spray carb cleaner thru all the ports in the carb when u have it apart to make sure they are clear and free of any deposits.

It's good to have a good mixture for it if it is adjusted right

you either have an air leak somewhere or you need to really adjust your jets because if you have warmed up your engine and it revs high with choke on its running lean

I had the same problem TODAY actually, my pit bike. I put in the throttle slide wrong and I re-did everything with the throttle and it worked perfectly.

1) Find TDC and kick it harder 2) Stop opening the throttle unless the bike is flooded and you need more air to even out the mixture for start up 3) Tilt the bike Oberón the left side all the way over for a few seconds to put gas in the carb 4)Turn off the choke immediately after you start the bike I’m 16 and I race 2 stroke dirt bikes so please take this advice it should help you a lot with your bike and future issues you might have.

you have the wrong size needle for the seat

Lean as hell, Definitely clean/rebuild the carb. You may also need a new float sounds sticky

I had the same problem with the throttle being sticky, make sure you grease the bar and throttle cables, also spray a tad of WD-40 Inside the throttle tube and it’ll be snappy 👍🏽

She's running lean either intake leak or jetting issue

Oh and try tightening the fuel air screw then turning it left two turns go from there left lean right rich

Funny enough im having the same problem with my 1995 kx100. Its fine then all of a sudden bounces off the wall. My mixtures perfect (Ive used the gas in other machines that love it) and my carburetor has no problems that i know of. I knew it was to much air as well, just cant track where it is. Hopefully you and myself will fix the problem soon!

Its running perfect on the choke because you have the airbox open and its sucking in a lot more air so the extra fuel from choke is actually lining the mixture out. You always want to adjust the carb with everything in place because a 2T is sooooo touchy with adjustments. That could be the issue with the boggy throttle too. Id put the airbox cover on then try again before you take anything apart or buy anything

You either have an air leak or your throttle cable is catching somewhere. Check to make sure its routed properly and not catching under the tank and make sure it slides freely in the carb. Also double check for air leaks. 🤞

Keep it simple: check carb for leaks, clogs, jetting, generally anything that does not look right and adjust/fix if nessesary. Then check for air leaks..

@moto migs your bike runs wfo because of an airleak or lean pilot, look up jetting specs and order those jets and work your way down, better to run rich then lean, working your way down from rich is better as you will find your sweet spot in jetting, as for your gaskit maker job a very little bit goes a long way with building engines, a very thin film put on with either a stiff paint brush or a q-tip will work fine, then wipe excess off that you see on outside of engine case, it will look much better. Your in the right direction my friend as inwas in your boots at one point, brand new to dirtbikes which i thought was absolutely amazing and i still do, i race a 01’ cr125r to the rod and do all my own work from engine to fork seals, you pick up things the more you do it and i think by far jetting was the hardest for me because it would always load up and foul plugs and finding that sweetspot is very hard even with jetting soecs as it may be running rich with the called specs

Check your pilot jet and your air/bleed screw. The pilot controls idle-1/2 throttle, and the main does everything else. If you don't have a bunch of jets, buy some, they don't really wear out. If your throttle isn't snapping back closed, you might need to loosen the grip and move it outward a bit. Check for pinched cables. Lastly, be sure the slide is properly installed. GOOD LUCK, you have brought this thing back from the dead, now finish it off!

I like the long videos

You need a new float valve seat gasket and needle, my 1984 IT200 did he same thing, made me too scared to ride it

Hey migs loving this built so far but it sounds like to me the spark plug it fouled. If that doesn't work the stator might be stuffed Couse that's what happens to my bike.

I’d definitely take a look at that rev cable and see if that’s the issue if they get stuck they can max Rev make sure the cable is lose and not tied tight to the frame

I wonder if the problem is that the bike hasn’t been tuned with the right jet for the v-force reeds, pulling in too much fuel for the current jet.

You need the airbox sealed. It is tuned to run sealed up. Just pulling the side cover off my bike (ktm has side cover over air filter ) and the bike dies. Causes it to lean out

Yeah you might use gasket maker on your small engines but you should use real gasket for high-powered dirt bikes

Find your air fuel screw on the carb. Look up the stock settings basically how many turns out it should be . After you have that number from were it is right now count how many turns you go in and see if your at the right number for turns out

Are you going to get a new pipe and shorty for it?

Seat on when starting ur bike always migs needs seat or too much airflow thru the airbox= lean thumbs up so he sees!

Hey dude, I had an old honda 2 stroke and it had the same problems, I would say to get new reeds and clean the carb, that's what fixed my bike that had the same exact problem.

Running too lean. I can’t remember, but was the air filter pre-oiled? If not, you need to do that ASAP. That could be causing a lean running condition. If it’s not that then probably an air leak.

Did you put in a new sparkplug?

It runs way to lean but maybe put on the airbox so you dont allow it to suck that much air because it doesnt have any resistance without the box which allows it so breath a lot more air. Then that screws up the air to fuel ratio.

Put on all the plastic. Seriously, that cuts down the air flow and will make it run better. Right now with the air filter exposed 100% to the open air it will have that high, hanging idle. Put all the plastics on, that way the air filter isn’t 100% exposed and is sort of “choked” on air. I was working on a buddy’s bike and if I would have the plastics off it would do the exact same thing. But when I put them on it didn’t rev up as high and was able to tune it out with the screws

check for vacuum leaks everywhere spray carb cleaner when it's running around the carb and intake

I just read that you already had it rebuilt so that rules that part out. Honestly, the next step, I would be checking your throttle and throttle cable to make sure they aren’t binding in any way. That throttle should be snapping back.

I had that problem sometimes you bars are to fare to the right and I pulls on the throttle when you tilt check that it could be the problem

You need to change the spark plug and get a new throttle cable

I hope you did a 50 50 mix of the antifreeze and distilled water and not straight antifreeze

Very very lean. Clean carb first but in willing to bet it's a air leak causing it to lean out.

I think half the reason its running so shitty is because of your air box you might have a vacum leak plus the thing doesn't even fit the bike properly

There is a like a special tube in the carb that’s plugged it did this same thing on my Yamaha blaster

At this rate id of bought a new bike, you’ve spent loads of time and money on it should have bought a good working one !

might be an air leak this happened to my cr125 check reed gasket.. all boots on correctly. may sound stupid but piston could be in backwards.... i would check all gaskets

Lube your throttle cable and also it seams lean to me

I hope you mixed that coolant with water because that is not mixed. 9:23 you can see the coolant jug says concentrate.

Question... how did you learn how to fix bikes. I’m getting my first bike soon and I want to be able to fix it my self!

Buy a new carb or get a carb rebuild kit

Get some starting fluid or brake clean start the bike and spray it around the intake boot closest to the engine if the engine revs up its has a leak causing it to go lean

You have to put oil in the gas can then mix it

Check for air leak bro, check Carter key on magneto side, you may have sheared it if you didn't tighten magneto to oem specs

Hey I need help with my 90cc repsol super pocket bike. I want to buy exhaust but don't want to water buying wrong type. Can you help with that

I thing the float in the cab is just sticky and is holding itself open so heaps of gas is puking up in the carb

Very lean

What clutch plates do you use

You have a air leak somewhere from carb to reed or head gasket

Please stop saying driving 😂 it’s riding lol. Nice build tho

do u use stright up gas o mixed?

Your throttle cable is adjusted too tight Thats why it doesn’t snap anymore when you release the throttle. That snap is the slide hitting the bottom of the carburetor shitting off the gas so since its not doing that, the slide is up a bit and letting gas in

Does your gas wire are too tight?

you probably have an air leak. to test this you should spray some soapy water on the intake boot and on the boot that's connected to the air box and if it starts bubbling a lot while it's running it means there's an air leak. if it's not that then your carb slide might be stuck or something.

You need to have a better air to fuel mixture for better idle and giving it throttle really fast

You need to mix your petrol an air right it sounds like there’s too much air been taking in think about it. Runs fine with the choke on so there’s to much air been takin in

Full on Carb clean/ new carb?

Don’t bump start it if it’s stuck open I learned that the hard way lol

U don't drive a bike u ride the bike lol😂

Crankcase not sealed and you need to keep radiator cap off and run the bike till bubbles stop

Use the air mixture screw and richer it up a bit

i'll recommend that you file down the clutch basket :D

Check the throttle at the engine. Where the cable meets the engine. That’s your problem. Something would’ve come loose/out

Leave it on choke and try messing with the idol screw to get it to idol down

U need to adjust air mixture screw if that doesnt fix the problem you have an air leak somewhere

Yo your floats are stuck or air fuel mixture is completely dickered.

It'll be fine

Run a 50:50 or 60oil and 50 gas ratio, and check your reeds for any chips or cracks

I think you have a air leak, i had the same problem with my Cr.

Never leave the choke on that long on a 2 stroke and it’s running extremely lean since you didn’t seal the crankcases and cylinder right

Just do a carb rebuild, something wrong with the slide I reckon. Clean out the carb and rebuild it. Should be sorted!

like every body told you, the bike is running lean, try to clean the emulsion tube, maine jet, ferify the screen in the fuel inlet, check you float hight. try to presurise your crank case, plug the exost port remove the spark plug and put some presure inside, less than 1 bar, the pressure should stay, if not you probably have a spy leak or anything else. spary some carb cleaner on the carb to cheak for leak. rtv kill bike by cloaging the oil screen inside the engine, your bike is a 2 strock so not that important.

Turn the air fuel mixture screw in to richen it up

Recheck pilot jet to make sure it’s not clogged.

Lube your cable and do 2 1/2 turn out on the mixture screw

I would get a new carb I think it’s your best bet and so you don’t have to keep messing with that one

You do realise that when you starve a 2 stroke of fuel the engine isnt lubricated so it could easily cease up. You could have put the choke on and it would have cut out👌

Your float level is high why it’s idling high even with the screw down and bogging because it’s not getting right air fuel mix adjust the floats

Did you put 2storke gas !!! It's the float bowl needle. It's probably getting stuck from all the years of sitting. You might just need a new carb

Leave choke on and don’t give it gas when kicking for startup

It may smoke a little bit it's ok just adjust the i idle to down more and yea

I know a good way to get the dent out of the pipe, fill it with water then freeze it, it will bump the pipe out

Rebuild ur carb and adjust ur floats same thing happened to my yz

The shop you sent the carb to never rebuilt it carb needs a good going over the thing came back dirtier than it went in 😂