Quote:
Originally Posted by Weldangrind
The jets don't necessarily dictate the fuel economy. The efficiency of the engine in good running condition determines the fuel economy.
As you indicated Hector, the plug colour is a very good indicator. If you intend to check the plug, one way is with a plug chop. Find a level road (on a day that is not windy), cruise at whatever speed you would normally use (80km/h is a good baseline) and shut the bike off without letting go of the throttle until the engine stops. Once the engine cools, remove the plug and you'll see the colour for that specific condition. If it is tan-grey in colour, you're right where you should be.
The way to increase economy after that is by making changes that improve effiency on the intake and exhaust side, removing weight, using synthetic oil; stuff like that. Every time you make a change, it's wise to do another plug chop.
Ideally, you'll increase efficiency to the point where you can cruise at the speed you wish with less throttle than you do now.
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Hi Chineros, I've been buying different used main jets (mikuni, dynojet, and keihin) trying to get the right plug color and best acceleration. I haven't found the mikuni 132.5 but found the mikuni 137.5 with poor results (can't reach 80 km/h or full throttle) white plug. Bought the dynojet 142 equivalen to mikuni 132.5 and could not reach the 75 km/h, white plug. I used the keihin 140 equivalen to mikuni 122.5 and could reach the 80 km/h but start to stall after the 80's,, white plug. One step down, right know using the 120 mikuni with no problem (can get 100 km/h and full throttle with no problem), start tan-grey in color. My conclusions, the bigger the jet (132 and beyond), the poorest the acceleration. Check the pics below after running at 80 km/h and done the plug chop (used plug 'cause is sunday and nobody opens).
I wonder if I can conmute to my work (46 miles round trip) at a cruising speed of 60-70 km/h (half throttle) without causing engine damage. I will order the mainjets online and pick them up in Cruces 'til late June when picking my PhD's diploma at NMSU.
