RM125 build.

finlay vanmulbregt
Edited Date/Time 5/16/2020 9:52pm
Starting my rm125 build. Have started tearing it apart and cleaning. Once quarantine is over I’ll be able to get on with powder coating and order parts!!




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Ryan625
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Lynnwood, WA, USA
Ryan625 4/1/2020 8:10am
4/1/2020 8:10am
I’m here for the cat.
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finlay vanmulbregt 4/3/2020 6:03am
4/3/2020 6:03am
Ryan625 wrote:
I’m here for the cat.
Barney the “cat” is great with the tools so he will remain in my build series Wink
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finlay vanmulbregt 4/3/2020 6:05am
4/3/2020 6:05am
Have ordered a few parts. Got in contact with the post company and seems they are still up and running Smile so hopefully I’ll have some more stuff to post over the next few days.
finlay vanmulbregt 4/3/2020 9:41pm
4/3/2020 9:41pm


Bikes basically down to the frame. Made a silly mistake and took the forks off before loosening the triple clamps and now they are really stuck on there! Anyone have any tips plz commentSmile
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The Shop

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finlay vanmulbregt 4/3/2020 9:46pm
4/3/2020 9:46pm



Front brake caliper bracket bolt stripped. Don’t really want to buy a new one as it’s going to get Vapor blasted and look like new. So might get the bolt welded on. Anyone have ideas plz comment or a cheap bracket.
finlay vanmulbregt 4/4/2020 1:08am
4/4/2020 1:08am
I don’t now much about jetting that’s why I was considering getting a lectron but while I save I need some help. How does this spark plug look? Does the carb need to re jetted.


Rob YZF250
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Essex, GB
Rob YZF250 4/4/2020 7:47pm
4/4/2020 7:47pm
Plug looks like it's running richer than Bill Gates.
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finlay vanmulbregt 4/4/2020 9:58pm
4/4/2020 9:58pm
Rob YZF250 wrote:
Plug looks like it's running richer than Bill Gates.
Comment just made my day hahah. But yea I thought it was. Considering getting a lectron so I don’t have to deal with jetting
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finlay vanmulbregt 4/4/2020 10:13pm
4/4/2020 10:13pm
Forgot to take a photo of before but spent hours cleaning up the swing arm today. It’s in bad shape so I have tried my best. I might Vapor blast it and some other parts will just see how much it will cost.


Rob YZF250
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Rob YZF250 4/6/2020 7:50pm
4/6/2020 7:50pm
Rob YZF250 wrote:
Plug looks like it's running richer than Bill Gates.
finlay vanmulbregt wrote:
Comment just made my day hahah. But yea I thought it was. Considering getting a lectron so I don’t have to deal with jetting
Laughing I hope you get it running spot on and look forward to seeing it finished. Cool
finlay vanmulbregt 4/8/2020 3:01am
4/8/2020 3:01am
wondering if you can vapor blast front andrear axle bolts, linkage and swingarm?
ledger
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ledger 4/8/2020 3:20pm
4/8/2020 3:20pm
finlay vanmulbregt wrote:
wondering if you can vapor blast front andrear axle bolts, linkage and swingarm?
Yup. The work done to swingarm looks great.
Dangerbois666 4/8/2020 6:52pm
4/8/2020 6:52pm
Rc Bikes in Tauranga will probably have a brake caliper bracket for you. Whatever you do, don’t change the carb, the mikuni power jet carb with throttle position sensor you have is great. I have my jetting setups from 2007 when i was racing my RM125 around NZ. I will try will try to find the book that i wrote them down in. Standard expansion chamber with PC304 muffler was the best set up on the dyno with stock porting.
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Phillip_Lamb
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ORANGEVALE, CA, USA
Phillip_Lamb 4/8/2020 8:57pm
4/8/2020 8:57pm
If you have a manual they do provide good information on basic tuning. Your plug is pretty wet so a few things could be going on.

Your jets are too big and need to downsize a little,

the fuel/oil mixture could be on the heavy side and the prior owner could be 'loading' it up, essentially not running it hot enough to burn off the excess oil in the fuel


Carb tuning isnt too hard but it can be a little finicky with some, Ive had multiple RM125's and never had too much trouble with them myself YMMV

I would open up the carb to access the main and pilot jet to see what you simply have first.
(assuming you have an 07) this should be the base settings:

Main Jet: 370
Pilot Jet: 40
Needle: 6CHY17-60
Clip: Second from top
Air screw: 1-3/4 turns out

also try running the fuel oil mixture anywhere from 32:1 up to 40:1
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finlay vanmulbregt 4/9/2020 4:17am
4/9/2020 4:17am
Phillip_Lamb wrote:
If you have a manual they do provide good information on basic tuning. Your plug is pretty wet so a few things could be going on...
If you have a manual they do provide good information on basic tuning. Your plug is pretty wet so a few things could be going on.

Your jets are too big and need to downsize a little,

the fuel/oil mixture could be on the heavy side and the prior owner could be 'loading' it up, essentially not running it hot enough to burn off the excess oil in the fuel


Carb tuning isnt too hard but it can be a little finicky with some, Ive had multiple RM125's and never had too much trouble with them myself YMMV

I would open up the carb to access the main and pilot jet to see what you simply have first.
(assuming you have an 07) this should be the base settings:

Main Jet: 370
Pilot Jet: 40
Needle: 6CHY17-60
Clip: Second from top
Air screw: 1-3/4 turns out

also try running the fuel oil mixture anywhere from 32:1 up to 40:1
Ok thanks I’ll have a look into to it.
finlay vanmulbregt 4/9/2020 4:18am
4/9/2020 4:18am
Dangerbois666 wrote:
Rc Bikes in Tauranga will probably have a brake caliper bracket for you. Whatever you do, don’t change the carb, the mikuni power jet carb with...
Rc Bikes in Tauranga will probably have a brake caliper bracket for you. Whatever you do, don’t change the carb, the mikuni power jet carb with throttle position sensor you have is great. I have my jetting setups from 2007 when i was racing my RM125 around NZ. I will try will try to find the book that i wrote them down in. Standard expansion chamber with PC304 muffler was the best set up on the dyno with stock porting.
Hi if you could find the jetting Info that would be great thanks
finlay vanmulbregt 4/9/2020 4:19am
4/9/2020 4:19am
Have just counted the gearing on it. And it’s 12-48 and have had a look at the stock gearing and it’s 12-51. That’s pretty far off from stock, thinking of going upto 12-50. Is that a good idea? What are other people running?
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Phillip_Lamb
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Phillip_Lamb 4/11/2020 12:29am
4/11/2020 12:29am
i would put gearing back to stock or +1 tooth more on rear
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Pit Row

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finlay vanmulbregt 4/13/2020 2:55am
4/13/2020 2:55am Edited Date/Time 4/13/2020 2:57am
Doing the best I can with what I have, as we are in lockdown so can’t go to the stores






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STStevew199
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STStevew199 4/13/2020 6:13am
4/13/2020 6:13am
Swingarm looks great!
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pizza4breakfast 5/2/2020 10:39pm
5/2/2020 10:39pm
I am doing an 01 rm125 as well right now so this is relevant to me.
Im doing a full engine rebuilt. new clutch, wiesco billet basket, crank and top end. suspension is done, will need some fresh plastics and graphics but its a super budget build for me.
finlay vanmulbregt 5/2/2020 11:33pm
5/2/2020 11:33pm
pizza4breakfast wrote:
I am doing an 01 rm125 as well right now so this is relevant to me. Im doing a full engine rebuilt. new clutch, wiesco billet...
I am doing an 01 rm125 as well right now so this is relevant to me.
Im doing a full engine rebuilt. new clutch, wiesco billet basket, crank and top end. suspension is done, will need some fresh plastics and graphics but its a super budget build for me.
That’s awesome man🤘Always awesome seeing an rm brought back to life.
finlay vanmulbregt 5/2/2020 11:35pm
5/2/2020 11:35pm
Found a photo of the brake caliper when I first got the bike and here is it now all cleaned I
Up

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finlay vanmulbregt 5/16/2020 9:52pm
5/16/2020 9:52pm
She’s coming along quite nicely. The wheels are temporarily until I can afford some new ones 😂
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