Hi,
Was hoping someone could help me with some jetting advice,
I have an RM125 2007 running the following jetting:
Main 390 (stock in the manual says 370) - but FMF say 390 with their pipe
Pilot 40 (stock in the manual says 42.5)
Standard needle clip 3 - this is stock setting
2 turns out on mixture screw - this is stock setting
The engine is completely standard, but have V force and full FMF system installed,
I typically ride at the altitude and temperatures in outlined as the standard jetting in the manual.
My manual in europe actually says to use main 370.
The issue i'm having is the plug looks dry with a nice golden brown colour but the electrode is marginally on the white side indicating it is a little bit lean, but there is also a bit of oil out the tail pipe (nothing crazy) and a bit of spooge running out the overflow of the powervalve,
I'm not very clued up with jetting but what i'm seeing indicates that its lean at a certain part of the rev range and rich in another in and i'm unsure how to work our which jet needs to be made leaner and and which needs to be made leaner,
Common sense would say to try putting the pilot back to 42.5 to start with, but that doesn't adress the richness at part of the reve range, it could potentially only address the leanness.
The other slight issue is it will idle slightly faster than ideal for a number of seconds before eventually retracting back to a slower idle where it would eventually stall
Any help or suggestions would be much appreciated,
Little bit lost,
Thank you in advance
What premix are you using?
I am running Putoline MX9 oil at 40:1 with pump petrol
My thinking was to try an oil that burns off more easily, but I know nothing about Putoline to be honest. Some oils, such as Honda HP2 in my experience, spooge a lot more than others. Motul 800 has burned cleaner for me.
You are running a near identical set up to me (UK).
I have a 370 main, actually about to try a 360. HGS Pipe. Everything else stock.
I have also switched from MX9 to Motul 800. Its about the same price, but so far it does seem to be a cleaner oil. I had no issues with MX9 other than the black sludge, even with good jetting.
Another thing to note... order and replace the jet block gasket. I just replaced mine and it was toast. I have not ridden the bike since but I expect it can only be an improvement. It's a very easy job to do. Just need to fully remove the carb.
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This is how mine looked. You can see its completely distorted and likely causing a slow fuel leak. This could absolutely mess with the jetting.
I'm looking forward to getting back out on it to see if theres any improvement.
My jetting has always been fine but never super crisp, I'm chasing the last 10% so will post back with any progress.
I will try a different oil and inspect the part suggested, thanks,
I'm still unsure how to address leanness (slight white electrode)
How old is the plug? Is the colour you're describing from a full throttle plug chop run or just general running condition?
Your high idle to stall issue may be fixed with the air screw. If you find an air screw setting that cures the idle, the position will tell you if you're pilot is too rich or lean. I only ever play with my air screw after I've ridden the bike, as it reacts differently when its truly hot as opposed to just revved up on the stand for a few mins. I think I'm at around 1.25-1.5 turns out with my 40 pilot
The plug is pretty new, maybe 8 hours - no, thats not at full throttle plug chop that's just general running, ok I'll have a play with the air screw and see how that improves things,
Just out of interest where about in the UK are you so can see if we're running at similar elevation
8 hours is okay, hard to read a very fresh plug as it takes some time to colour.
I'm Worcestershire. Ride at Apex, Brookthorpe, Bushton, Arncott etc etc.
From my experience temperature makes more a difference to my bikes than altitude. I'll go at least 1 step richer/leaner on the main, 1/2 step on the needle and 1 step on the pilot on my RM250 between winter/summer
If the electrode is white, your main jet may be too lean. Try one size larger and possibly go back leaner one position on the needle clip. There's some overlap between these two settings, so you may find a sweet spot there.
As for your idle problems, I am 99% sure your pilot is too lean. Turn your airscrew in all the way and see if the idle problem goes away. I bet it will. (The stalling might persist without adjusting the idle.) When you have higher-flow reeds, you often need to go up one size on the pilot. Since yours is smaller than stock, it is a likely suspect. I'd start with the air screw test I just mentioned, then if I'm right, change back to the stock pilot and go one turn out on the airscrew as a base setting.
Thanks I’ll try that this weekend
If you go down one main jet and it makes more power then you were too rich, and vise versa. Jet for best power.
If you have excessive spooge that means you’re putting too much oil in. No spooge means not enough. I like to see just a little oiliness in my exhaust manifold.
Timing will also effect jetting and spooge. You have to work with all three.
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