Hey y'all!
After a few years completely off due switching to cars working as a technician in Hyundai Motorsports WRC, I felt the itch back into dirtbikes since i'm back in Spain, so its about time I get back to the ole old days of wrenching in MXGP and in the US down at MTF.
The last bike I did own was an RM125 so for the last 3 months I've been in the scope for one but couldn't find anything interesting. The other day scrolling down Wallapop (Spanish Craigslist) something caught my eye... I came across a frame, swingarm, subframe and a few other bits of a 2020 Suzuki RMZ250 for a couple of bucks, 550$ to be exact.
So yup, after a couple of hours I was already the new owner and down to search for more parts.
Found a good deal on a set of forks KYB forks of a 2023 RMZ 250 for 200$ and a KYB shock off a 2008 KXF450 listed for 70$, set of plastics for 70$, triple clamps for 30$ and a few other parts like an ARC lever, footpegs with brackes, a few axles, a Renthal 998, and a front brake MC from a CRF 450 with a braided line that my buddy and former boss Javi Garcia Vico (former MXGP winner in Everts, Smets era back in 2000's) handed to me.
I'm also waiting for my Suzuki dealer to pick up a bulk order of bolts and axles I did last week.
As for the engine, I sold one of my spares 125 to a friend from the races back in 2016. Called him the other day in order to know if he still has it or if he knew somebody and for my surprise he still has it in the same box I did sell it to him, so I'm going to pick it up today.
Here are some pictures of the parts and the little to non progress of the last few days, the plan is to build and make all the adaptations first and then proceed to rebuild everything once the base is set. Planning to do a full race engine, REM Isf trans, full mod top end or even going up to 144cc, cerakote some parts and add a bit of factory looks and bits, with Ti bolts and so on.
That's the parts I found listed in Wallapop.
Stay tuned, more progress coming soon!
Sooo made a bit of progress over the last two days, went to pick up the engine and a few parts more.
First of all I put the engine on the frame to take some measurements and sketch a few things to prepare all the necessary brackets for the engine. I will post everything once I’ve got it done. The tab for the brake pedal soring needs to be removed, along with the casting mark on the right side of the swing arm as it is close to the engune case.
The engine is already open in order to speed up a bit the process so today I went ahead and started to apply some elbow grease to the cases and sandblasting the big clutch cover, exhaust valve covers and water pump cover to send them to cerakote next week.
Engine before
After some elbow grease:
Whatever you do - go check the original relationship of the 4t Countershaft center to the Swingarm pivot. And try Very Hard, to match it.
That's a VERY Important part of Handling / Suspension.
So many conversions f**k it up, through, mostly, too high a CS center positioning. Creating so much 'Squat', and suspension interference.
And, far to many 'convertists' build for the ancillaries, not the correct engine placement.
In that picture, though, not a perfect, side on view, the CS center that the engine is in, looks to be a bit High.
The Barrel / Head does look (very) close to the 'Y' / Downtube, but it's not hard to get clearance there, with bit of cutting and plating - I doubt you need to do a new 'Y' with a 125 engine being used.
A side note : I'm not in favour of removing the original mount 'saddles' on the cradle, when it's possible to retain them. Just cutting off the vertical part of the mount, then putting on a new vertical mount To The Existing Saddle- if possible, using RA, with an inner radius. But, with the 125, the case mount is further back than the original mount, so you'd have to 'cantilever' it back a. bit. But, I'd Still do it that way. You're making use of an existing, well made mount, and not weakening / damaging the frame area by removing it. I've done many AFs since '97 - and other , steel frame engine conversions, since the 70s.
Hey mate!
Thank you for the inputs. I did take all this in consideration prior to making/designing anything as I do not want to interfeere with the Kinematics of the swingarm/engine. Tomorrow im going to check the 4t cases alignment and measurement to swing arm pivot in order to replicate as exactly as possible to the 125 cases, however the position on the picture is not what it is going to be as I was only holding the engine with the hammer!
Another key point is the alignment of the front sprocket, I've seen some using and offset front sprocket but I would like to go a different way. I will check on that later in the project tho.
Thanks!
Very cool!
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Luxon 4-Post Bar Mounts
$189.95 - $239.95
Free shipping: VITALMX
This will be sweet!
Here's my last gen RM125AF - currently top ends stripped down as I got the cylinder machine out to a 135.
Compared to my 05 RM 125 and super heavy 99 KX125's this is thing is light as a feather.
Hey mate!
Such a nice one, buddy! Congrats on the build.
As for the 134cc are you going straight to the 56mm wiseco piston? why didn't concider to go 58mm using the wiseco 58mm piston from the YZ? I'll send you a pm so we can chat about it!
I'm gathering a lot of parts and spares at the moment, and i have some bits cerakoting, but I will post more updates tomorrow!
Who's doing the 134cc conversion?
I'm in the UK with an RM125, so I'm curious to know
Hey dude! @bestmx is doing it, i'm doing mine aswell but didn't decide if 134 or 144.
You need to bore out the Cyl up to 56mm, but the best is to go with the piston to the machinist so then they can calculate and double check the tolerances to run. I order to bore it up to 134 or 144 you also need to modify a bit the front part of the cases (where it matches with the cylinder) and the powervalve!
Here is the piston link: Shop High Quality Suzuki RM125 Wiseco Piston Kit Piston Kits - Wiseco SKU 641M05600 PS: Check and order acording to your model year etc.
Let me know if you need further info!
Thank you!
I actually sent my cylinder off to WS-Zylinder in Germany as it popped up on ebay as a complete kit with a matched Wossner piston (55.95mm) and was a decent price. Just make sure you pay attention to import duties and don't put the value of your faulty cylinder as the cost to replace it or they'll be very grumpy with you lol. I was equally grumpy when their "complete kit" didn't include a small end bearing.. 🙄
Was relatively quick turn around. Biggest hold up for me was getting power valve assembly over from Japan - I suspect a small war and diversion of boat was the culprit for the delay. The two scroll/ worm gears from my original one were toast - just holding the power valve stuck half way - reason for the rebuild.
I did get a new power valve, but - I've used the original as it isn't worn and you will need to grind it back, as it does protrude into the bore of the cylinder - least it did for me. I'll drop photos below of how it was and the valve ground back to match the cylinder - friends handy work who's considerably better than me!
Do look forward to seeing how it comes out and rides because I never even got to ride it myself prior - just my friend who did about 3 corners and had no power, so parked it up. "Freshly rebuilt" by the trader who sold it to me - just with a stuck power valve and a head that had eaten an electrode. Tremendous. New head - was hard to stop myself buying a shiny VHM (have one on my other RM 125 - which I also haven't yet ridden), 135 kit and new power valve, should be a ripper!
I'm pretty slow, so 125's are great for me as I can almost make them sound fast (almost). 🤣
Honestly, I purchased a Vertex kit but that was £144 and I felt like the bore should be re-sleeved and that was going to cost £200-250 on top.
Then this 135 kit popped up for like £290 (not sure why my screenshot below says £306 now) and I just figured this is already a bit of a frankenstein bike, so upping the displacement a little bit kinda fits the bill, it's cheaper and at 135, I think it'll just feel like a fast 125.
They've upped the price of it now, but here's the link: https://www.ebay.co.uk/itm/313744098800
Here's my decision making process:
Thanks for the reply!
This is irritating, I brought a brand new OEM cylinder from Japan for my 06 RM125 a few years ago, as the original had cracked across the exhaust ports. I paid the same if not more for the brand new 125cc cylinder, so I would have definitely gone this route had I have known!
However I have kept the old cracked cylinder so will probably go this route if I choose to do so. 134cc is still more than a 7% increase in displacement, on a 125 this is going to be noticeable and effective. I often read mixed reports on 144cc, some love it, some say it doesn't rev quite as well/bit less top end but more torque. I guess it depends how you ride it.
Yeah, I actually have a 2005 RM125 as well now that I plan to build into a 01 Pastrana bike.
That’s been built up by Middlesex MX with the VHM head, V force, lectron carb, so it’ll be cool to compare the steel frame 125 vs the ally frame 135.
Sooo let’s keep up with the progress, as today I did receive some goods. A Wiseco crankshaft, all the engine bearings, transmision included and all the seals. Also I did and order to the Suzuki dealer in form of bolts and shafts.
I also got an ASV factory clutch perch with the lever from my good friend and former GP rider Garcia Vico.
The plan is to start with the buildup of the engine over the weekend. I’ll be cerakoting a few parts during the week as well in order to finish the engine or at least the bottom end next week.
Here are some pictures:
New updates on the engine side.
Rebuild the right case and installed the transmision and crank. All new bearings and its currently waiting for the left crank case as I did mill 3,5mm on the face of the swingarm pivot in order to move the engine to the left side and align front to rear sprocket.
After doing that, there is an space of 7,5mm in the right side between the case and the swingarm, the plan is to make either an spacer or a new complete bushing plus 7,5mm in order to fill up the space.
The plan is to not make adaptations in oem parts that needs to be serviceable, as front sprocket, or swingarm bearings…
Here is a couple of pics:
As you can see there is enough material so you can mill safely. I used a 40mm milling bit on diameter, and milled 3,5mm out of it.
The plan is to rebuild the left side case and close the engine so I can fit the engine to the frame and finish the lower and top mount.
Hey y’all!
Had a bit of time to work on the bike during last week. Bottom end was finished enough to be fitted on the frame to check my calculations and see the alignment between front and rear sprocket, and greaaat successsss (Borat’s voice)
I’m still in the process of cerakoting parts, so I assume I will be able to finish the complete engine during the upcoming weeks, still didn’t decided what to do with the cylinder, if going 134cc or 144cc or keep it 125 and do some porting/adding material (intake port in the 2003 is too big compared with the 2004 onwards that is smaller and has a bump).
Here is a couple of pictures (mind that all the swingarm bearings and so on will be new once I start building the finish setup!)
Hi y’all!
Been doing some cerakote work these last week and here it is the result. I did both oem clutch and ignition covers as im planning to ride with these but for the display and pictures I will put on some PC’s.
I’m also waiting for some bolts from Suzuki and a few more parts so I can fully finish the engine.
Meanwhile some pictures down below.
Post a reply to: 2020 Suzuki RM 125 AF