Shimmed my needles, but didn't need to.

[peteypetepeep]

Today's project was to shim the needles on my 2009 250r. As first time ever taking off my gas tank, had some difficulties on some hoses & weird clamps. When I got to the carbs, I carefully tried to not strip the screws as everyone had advised, lol. Then when I pulled the cover & spring out. I took out the diaphragm, just to check if it was shimmed already by the previous owner. & Unfortunately, it was & had 2 washers ! Meaning, I didn't even have to go through the trouble of tearing the whole bike down, but hey... I know how to do it for the future. I would make a video the next time I do it, for those who can't seem to trust themselves to do it. I ended up just adding 1 more washer, because my DanMoto Exhaust comes in tomorrow.

[DaBlue1]

Checking to see if the PO removed the snorkel or not would have been a good hint.

[peteypetepeep]

Originally Posted by DaBlue1

Checking to see if the PO removed the snorkel or not would have been a good hint.

No, it was stock. I removed the snorkel.

[DaBlue1]

Originally Posted by peteypetepeep

No, it was stock. I removed the snorkel.

So, how does it ride now?

[peteypetepeep]

Originally Posted by DaBlue1

So, how does it ride now?

A lot better, it was a bit boggy without that third washer. It ran fine with the two washers & snorkel in, but when I took the snorkel out it was .... Ehhhh. So, I should be good when I put my slip-on tomorrow.

[Joshua95]

I have couple questions what does shimming? how does it affect the bike?

[alex.s]

Originally Posted by Joshua95

I have couple questions what does shimming? how does it affect the bike?

The engine burns fuel mixed with air. The ratio needs to be correct for optimal power. As the engine rpm increases, it draws more air through the Intake. To accommodate this, the Carbs must increase the fuel going into the air stream to maintain a correct air/fuel ratio. Our carbs work by using what's called a vacuum slide which uses vacuum from the engine intake to raise a tapered rod called a Needle out of a hole called the Needle Jet. as the needle raises, the space between the needle and the jet increases, allowing more fuel through into the intake. adding a washer effectively raises that needle, increasing the fuel/air ratio. depending on what kind of intake and exhaust setup you have, this could be beneficial or not. with a stock setup straight from the factory, the bikes come a bit lean and adding a washer richens the mix up a bit. these carbs have 3 jets total, the needle jet which i already mentioned. the other two are the Slow-Jet (aka Pilot-Jet) and the Fast-Jet (aka main-jet). the slow jet is very small and is always open. this provides the "minimum" amount of gas that the carbs squirt into the air stream. the Fast-jet is after the needle jet, and limits the "maximum" amount of gas the carbs squirt into the air stream.

so to recap, pilot jet determines the lowest amount of gas going into the air stream which is typically at idle with no throttle. the main jet determines the largest amount of gas going into the air stream which is typically at max rpm wide open throttle. the needle shape and height determine the transition between those two jets.

gasIntoIntakeTotal = slowJet + ( fastJet * (needleTransition+needleHeight))

where needleTransition is 0.0 to 1.0 based on the vacuum range of the engine and the needleHeight is your change from washers or clips which is a percentage of the total needle travel (also in 0 to 1 domain)

[Kscreations08]

Guys... Its a serious and informative post from Alex.s Anyone have a thermometer?

[alex.s]

current temperature: Drunk as a Skunk!

[Kscreations08]

Keep it tipped lol

[Joshua95]

Thx Alex for the info I had to look up all the terms you said on google so I could understand more haha

[evidens83]

Nice. I was hesitant at first when I shimmed mine because I felt I wasn't as mechanically inclined as I thought. But all went well and now I feel like I'm that much more closer with my bike now The DIY threads here are awesome!