Arizona: Jetting an '05 EC250 for 7K

[AZRickD]

Howdy,

As you know, I bought John Goss's EC250. He had forgotten which jets he had in there so tonite I took it apart.

With the aid of my magnifying glass it looks like I have the following:

MJ = 178
PJ = 45
Needle = "DD" (I saw no other etchings)
Clip on 2nd from top (leaner)

His carb has both the Power Now and Power Now inserts.
He said it had an LTR jet kit.
Stock reeds, I believe.
LTR Powervalve cover.

As jetted, the bike has been running great from February to including now, so I have a good baseline. I'm pretty impressed that I don't need more than a half turn or less of the airscrew to get it to peak performance during these warming months.

With May brings 100F temps so I will find myself driving to Flagstaff and Utah this summer (Elev = 7,000 and 20-30F cooler), so I want to ballpark some likely jetting choices as I do plug chops.

Near the outskirts of Phoenix, the elevation is usually 2,000 to 3,000 feet where we ride. Temps in Phoenix in the wintertime can be as cold as 30F and as warm as 60F. Temps in May reach 90-100F with morning (when we ride) at around 60F. We're approaching the time when some desert dawgs go north or don't ride much.

So, using the Carb Correction Guide in the on-line manual:

I'm already at a correction factor of .99, so I'll just ad .01 to each elevation/temp combination on the chart.

If I use a temp of 104F at 1,500, I get a factor of 4% (MJ175 x .96) = 171 and PJ45 x.96) = 43 for hot riding around Phx.

At Flagstaff at 7K' and 80F, MJ175 x .93 = 163 and PJ45 x .93 = 42

If I wanted to get an extra set of richer jets for cooler temps around Phoenix in the wintertime (say, 50F and 2K'), I'd need a factor of 1.02 or
MJ175 x 1.02 = 181.5 and PJ45 x 1.02 = 46

Or maybe I'd just drop the clip one richer and open the airscrew.

So, how's my GG math?

Thanks,

Rick

 

[AZRickD]

I bought four MJ and four PJ staggered on either side of my current set up.

New MJ = 172, 175, 180, 182

New PJ = 40, 42, 48, 50

Yeah, I'll never need most of them unless I travel up to Colorado or back to Houston. When the daily highs start to tickle 100F (about 80-ish during morning ride times), I'll re-jet down to 175/42 and see what the plug chop shows me. Then I'll have to decide what 7,000 feet in August will require (172/40?).

 

[Nick]

I have ran a 168 here at 5-9000ft in the summer and 172 in the winter. We have two seasons here, winter and the fourth of July.

 

[AZRickD]

Hmmm. So you're suggesting the possibility of one jet leaner for Flagstaff (maybe 7-9K') and Monticello, Utah, this thus summer, eh?

Too bad I won't have an opportunity to do a decent plug chop (maybe I should bring a hacksaw).

 

[AZRickD]

I finally got out of my sick bed (yuck) and took the family up to Flagstaff to play and see how things were at 7K (temps at 75F).

I rode with the MJet at 172 with the PJet at 42. Airscrew didn't seem to make much difference.

The off-idle to mid-revs were very nice (I might be able to go one leaner on the pilot).

But just when the Gasser was about to come up on the pipe, the gain in revs abruptly ended and it started to blubber. Not as bad as my ride a few weeks ago at 7K, but I was short-shifting the entire day.

At first I thought it was a float problem (fuel starvation), but when I got it back down to Phoenix (1,200' and 102F), It ran like a raped ape.

Looks like I need to buy a 168, eh?

 

[Eric K]

It looks like you are on the right track with the smaller main jet. I would get a few more main jets so you can tune it as needed for the conditions. They are easy to change with the right tools.

 

[Loosenut]

With my jetting set how I like it for Sea Level to 3000 ft., changing for elevation has been very easy to ball park. This is how I will leave the house and then adjust as needed at the site.

For 3000-6000 ft
pilot - no change
main - down 1 size


For 6000-higher ft
pilot - down 1 size
main - down 2 sizes
(possible switch to different, leaner needle or clip position depending on conditions)

I not a huge rever, but I jet my bike to pull clean onto the pipe.

 

[AZRickD]

I took your advice and got both a 168 and a 165 MJ and a 38 pilot. Apparently I might need that if I ever get to Colorado and 10K'. Of course, while Flagstaff starts at 7K', some of the mountain loop trails climb to 9K and higher.

Amazing what a dirtbike shop has to charge for a piece of machined brass.

 

[AZRickD]

I was able to try the 40 Pilot and the 168 MJ. The off-idle was good but the MJ was still a bit rich. I was able to go wide-open throttle but when it got to the upper revs, it started to blubber. Next time I'll try a 165 or just dropping the needle. Not sure which the LTR needle would mandate.

 

[Eric K]

If the 1/4 to 3/4 throttle operation is good, I would leave the needle alone and change the main jet.

You may have to go smaller than a 165 for optimal performance at your elevations.

 

[AZRickD]

Yep, off-idle to mid throttle was fine. Even pretty deep into the main jet was okay. Just the very top-end of the revs were troublesome, though I'm sure power was diminished throughout the mainjet circuit.

As luck would have it, a buddy gave me his 162 MJ from his KTM300 -- he had three of them in his jet box. He was using 155/38 at 7K' by the way. I don't think I'll need it at 7K in the summer. Maybe 10K in Colorado if I ever get up that way (and I'll drop in the 38 pilot and crank out the airscrew).

 

[Nick]

keep your bigger pilot jets handy as when you start getting way up there in altitude the pilot circuit will fool you and you will be better off with a bigger jet.

 

[AZRickD]

I've heard that before but I've never gotten an explanation.

 

[RBD]

The RB carb mod could help too.....

Ron