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Jet size recommendations

5 posts in this topic

Ok, I did the dave carb mod (slide drilled, needle shimmed 26k, 55 short pilot, 158 main, idle mix tab removed and 2 1/4 out) and it made a huge difference in the midrange power, driveability and overall performance.

But I still have a slight bog right off idle.

Bike is a 01 XR650L at sea level with snorkle removed, K&N filter, big tube header, W/B e-series with 8 discs, IMS desmogger and the canister removed. Single vacuum hose from the diaphram on the right side of the carb to the port on the front of the carb.

I did some searching and found a similar combination that is using 58 pilot and a 162 main.

Anyone else have a similar combination and care to share some jet recommendations?

Thanks in advance for any help. :D

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Ok, I did the dave carb mod (slide drilled, needle shimmed 26k, 55 short pilot, 158 main, idle mix tab removed and 2 1/4 out) and it made a huge difference in the midrange power, driveability and overall performance.

But I still have a slight bog right off idle.

Bike is a 01 XR650L at sea level with snorkle removed, big tube header, W/B e-series with 8 discs, IMS desmogger and the canister removed. Single vacuum hose from the diaphram on the right side of the carb to the port on the front of the carb.

I did some searching and found a similar combination that is using 58 pilot and a 162 main.

Anyone else have a similar combination and care to share some jet recommendations?

Thanks in advance for any help. :D

Jetting is not an exact science. It takes some experimenting along with some trial & error. I just rejetted the carb on my '98 last night. My previous set up I had here in So Cal at sea level was a 155 mj, 55 pj & the ps was set at 3 turns out. Now I have a 158 mj, a 55 pj & the ps is now set at 2.5 turns out from 3 where it was before. My bike has all the carb mods, no smog, desnorkled, Uni-filter , no headers, and no engine work.

Do you have an aftermarket air filter, or are you planning to get one? That'll change the overall jetting requirements. For now, start by adjusting the pilot screw in 1/2 turn increments, first out, then in, but not more than 3.5 turns out or else it'll fall out. Don't ask me how I know... :D If the bog gets worse (which I doubt), turn it back 1 full turn in and see how it performs. Once you get the best results you'll know right away if the pj is too large or too small.

My pj was too small since I was overcompensating with the ps set at 3 to 3.5 turns out. Shouldn't be more than 2.5 to 3 total.

For the main, I'd go up one at at time and start with a 160, ONLY if the bike is leaning out before reaching top speed. Too rich and it'll bog at 3/4 to full throttle. Mine leaned out around 85 mph so I went up one mj size & added 2 more discs, 9 total, to my Trapp. Now the bike is running SWEET!!! :D

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Rule of thumb on turns out is to get engine fully up to temp, adjust for max idle speed, then back in slightly. If that doesn't do it, maybe shim the needle a little more and try again.

I know on mine, I can not run more than 155 main or it really cuts out. I have an opened up air box, opened up head pipe, IDS2, no disks, UNI filter. It runs perfect with the 58s and 155. And I'm in Florida so low alt.

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might have been the DynaJet kit you saw ... my DaynaJet kit has the 58/162 jets ... BUT ... they have their own numbering system, is the same as 55/158 in the Keihin jets ...

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Got it! :D

I changed things around a little bit, and it worked out excellent.

I scrapped the discs on the W/B E-series in favor of the straight through turn down tip.

I shimmed the needle to 50k, and used a 58 pilot and 160 main. 1 1/2 turns out on the idle air screw.

It is a little bit louder than it was, but when you take it easy she purrs like a kitten with a rock solid idle.

The bog is gone... :D

Just to recap, this is an 01 XR650L at sea level with snorkel removed, K&N filter, big tube header, W/B e-series straight through turn down tip, IMS desmogger and the canister removed, 58 pilot and 160 main, 50k needle shim, slide drilled and a single vacuum hose from the diaphragm on the right side of the carb to the port on the front of the carb.

happy happy joy joy :D

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