I'm 'looking after' my brothers 2006 Suzuki RM125 as he is no longer riding. I haven't properly ridden 125's since I was in the youth 15-18 class (now 32). Had a few good rides on the bike and as an avid tinkerer, I'm looking for tips and advice on making it better.
Bike has just had a brand new barrel. Running a full HGS Exhaust. Otherwise its completely stock. 51 Tooth rear sprocket. Jetting is 42.5 Pilot, OEM needle in #3, 370 main. Runs okay but isn't super crisp in the lower half of the throttle.
I have a V-Force reed block but haven't fitted it yet, is it actually better than stock? To me the V-Force block looks more restrictive.
Timing wise, what's the best way to go with 125's? As far advanced as possible without detonation?
What about squish? Will tightening the squish gap improve lower/mid at the cost of top end?
Should also mention the suspension is sorted. Sprung and valved. No complaints handling wise.
Need an Excel Yellow rear rim if anyone has one!
Getting the squish tightened up to a degree shouldn’t really effect your top end, but it will definitely help the bottom end punch out and probably help clean up your jetting as well. For the cost to gains ratio, some mild port work, proper squish, and quality fuel is really the way to go IMO. Still plenty reliable, relatively same service intervals etc.
The V-force reeds will help in throttle response more so than actual power. Still, very welcome. You may have to run a larger pilot jet. This mod may clean up the low-throttle crispness you are mentioning.
I had a well-ported 2001 YZ125 with V-Force reeds in it once that I spent a lot of time jetting. After that, it was so good that you couldn't even say it barked; it simply "arked."
I'm planning to buy another inlet rubber. The current one is mega solid, but needs to be modified to take the V-Force block. With 2 I can test both and see any difference.
Completely agree on jetting! Will keep playing with it, but there isn't tons of info around. Seems like most people have good luck with the stock needle to will keep trying pilot/air screw combos to get her crispy
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had a 2005 rm 125. great bike! made it a 144 and it was awesome.
If you want a simple way to make a lot more power everywhere, but want to keep the engine stawk. For a few years now I've run the STIC Super X PWK carb. Internally it's a completely different design. Even with the weaker small bore vacuum signal, this 38/40mm carb has a potent uptake of fuel at low RPM, thus making power available right off idle. In short, I know a couple of 125 riders that removed the STIC, bc too much was happening, way too soon.
A few years back @Tracktor ran the older, less potent version for his kids practice TC125. He described it as favored over their fully race built TC125 costing a small fortune. Another dad told me, the boy suddenly gets top 3 starts at Ponca Nats, against faster boys with full race builds.
BTW, I believe cost is below $700 for the Super X 38/40mm. Contact is vortex@sticfuel.us.
Continuing on with this as I've made a few tweaks.
Fitted the V Force along with a new intake rubber. The carb comes on/off nice and easy now. Bike doesn't feel much difference power wise but does seem more 'peppy' on the throttle on the stand.
I removed and fully rebuilt the carb. Replaced the jet block gasket. I also performed the 'Jarvis Mods', drilling the bowl to help fuel get into the bowl cap. Drilled the plastic jet shroud and altered the brass breather tube. I also filled a small round notch into the slide.
I'm currently running 40 Pilot, 6CHY17-65 moved to clip 2 and a 360 main. It was a hot day for the UK when I rode last. 28/30C. Around 350 feet above sea level.
Plug colour is good. The initial throttle crack is still fluffy. I think its rich so I have since ordered and fitted a 37.5 Pilot. Hoping this gets it right. Everywhere else the jetting feels about right.
Calling @digger for his jetting expertise, do you have any recommended settings for an 06 RM125?
Measured the squish, took multiple readings and they were all very close, with a 1.06mm average (0.417 freedom units). Tempted to skim this a tiny bit, 0.1mm to bring it to 0.95mm. But from general internet browsing I don't think 1.06mm is bad for a 125.
Russ, what you have listed looks pretty close to what I would expect it to be. The notched slide, depending on how big the notch is, usually requires a leaner pilot, than a non notched slide. You may want to order a 16-66 needle to test with as well. This is assuming that you're using a #5 slide. What size nozzle jet are you using ?
Yeah it's not far off and is certainly ridable. This bike seems to like Clip 2 in the summer with a 360 main, and Clip 3 in winter with a 370 main.
That makes sense with the notch, as I guess its pulling more air directly over the jet. It is the OEM #5 slide and I'm assuming the OEM nozzle. I haven't checked to see what it is. I will have a look to find out. The bike/carb has done a lot of hours so I imagine it could be worn. I will also look to replace the float as I've heard these can go bad with age and throw the fuel level off even when they are set correctly.
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