2003 rm 125 tuning/jetting, who knows a lot about

I've never really done any jetting since the last few bikes we bought were pretty close so I have a few questions for when I start playing with it on the 03. First I have done all the pre-reading of the important jetting threads and think that I have a basic idea of what I'm up against but I have 2 main questions I want to clarify. First if I recall the special plug spec'd in the RM's is between an 8 and a 9 heat range and while I don't mind running a $20 plug for safety I'm certainly not going to sacrifice a case of them to do plug chops to work my main from a 560 to the 440-460 range most of you are running. So given that the heat range of the stocker doesn't really match an 8 or a 9 how do I proceed? Secondly for WOT plug chop I always thought that you warmed up the bike then changed plugs and then tried to find a slight uphill to put a load on the engine and then ripped it through the gears until you were WFO and then grabbed the clutch and killed the engine, however in a recent thread on jetting someone mentioned that you can get to WOT in 1st gear. Do I need to just pin it in 1st for 15 seconds and then kill it to get an accurate chop?

My plans for now are to break the bike in on the OEM brass, then deal with the pilot and needle before finally progressing to some WOT plug chops to dial in the main.

Our conditions here are 785 feet above Sea Level and on average summer riding is 70-80 deg with anywhere from 45-100% humidity. Plan to run the bike on Yamalube 2R @32-1 with premium pump or at best 50/50 pump/race fuel.

Originally posted by bclapham
Chilli:

for what its worth, those main 560 jets sound massive- around here 80-100deg and 1000-4000ft i have seen rm's running in the range of 430-490 but i dont know what physical differences there are with the bikes so take those comments with slight caution.

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Bruce that is what has me baffled I don't think there is any physical differences with the bikes other than the jets in the carb. I'm at work so i don't have my manual with me but it is worded something to the effect that if you have a USA model it has these jets if you have a rest of the world model it has these jets. Just seems odd to me that they wouldn't send the USA specs to Canada since the guy that buys one in Pembina ND is running under the same conditions as I am since we are less than an hour away. That being said I'm reluctant to just drop it from a 560 straight to the USA spec of a 460 so I will most likely work my way down through the jets over time.

As for the 50/50 race gas I should probably start this in another thread but the gist I got from another thread was that you were wasting your time and money running 50/50 unless you were simply trying to avoid detonation. Since I can't afford to run straight race gas given the amount of fuel Troy uses and the $15 a gal price tag of C-12 up here I've simply stuck to premium pump in the past. In discussion with a race mechanic I respect he's telling me that it would be a waste running straight VP as none of the bikes have high enough compression to need straight race gas so he recommends 50/50, feel free to color me thoroughly confused :confused:

Originally posted by bclapham
as for the race gas, $15 a gal of C12 seems massively high, but if that the cheapest you can find then thats a shame.

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I'm going to do some serious shopping yet but I've checked pricing at the two most likely suppliers for VP and both were $75 for a 5 gal drum. I can get it for $11 a gallon if I buy the big drum but then I'm into worrying about storage and keeping it fresh. Keeping in mind these prices are CDN funds, with the $ improving of late it might be worth me making a trip down to the USA to get some fuel although I'd have to check into the regulations against transporting it across the border etc.

Marcus - thanks for the reply. Have been out of town and just noticed the post this evening.

Bruce I'm at work for the night shift but I'll take a peek tomorrow when I get home and post back.

Bruce sorry for being tardy with the reply. The 03 manual lists the 6BGY-27-79 as the leanest needle, however I imagine that is simply the leanest available from Suzuki.