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Jetting experience? XR400

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Can you give me a head start? I ride at 3000 feet and up (Alberta's Rocky Mountains -awesome), 60 degrees and warmer. I just finished uncorking and have the bike starting and running well with a 60 pilot. The mixture screw is 3 turns out, needle clip stock, main jet still stock (142?). It's winter here so trying to get the main jet sorted out will have to wait for warmer air since everything I read says air temp does affect leanness big time. I can run the bike indoors with warm air to get the pilot set right, but the main needs riding outside.

Most of you seem to need the main up in size as well. Are there some of you who need to increase the pilot, but find you're rich enough in situations like mine with less increases in the main jet size? Are the odds overwhelming that I will need to go up about three sizes on the main as well or should I ride as is and go up only if the plug looks lean? Would you ensure you started with the bigger main jet and then lean it out if you're too rich?

thanks. Tedd

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Tedd,

The likely pilot range will be 52/55/58/60, the 60 pilot isn't stock so I assume you made the switch. The 60 will be close but it may be too much for 3000' and up. I wouldn't want to swap the pilot out that often so I might go with a happy medium, say a 55. The fuel screw should be set 1/4 turn out from max idle.

Switch the three float bowl stock Philips head bolts for Allen head bolts for easier access, I think they're #4 x 16mm.

For the main, the range you should be in is the 152/155/158/160 range, however the 160 may be too much also. These are easy to swap out and only take a couple minutes. I would probably carry whatever jets I didn't use especially the leaner jets so as when you go up in elevation you can go leaner if need be. Also carry a couple extra Allen head bolts in case you drop one along the trail. The proper main should pull hard and strong on acceleration.

While you’re at it I would recommend safety wiring a 15mm piece of transparent fuel line 10mm onto the pilot, the fuel line I use is transparent blue, the idea behind this is that it helps deliver a consistent flow of fuel while ripping over rough terrain. Another advantage to this is that when crashing the bike it will continue to idle while it's laying on one of its sides, I can't remember which side right now, but I'm sure I'll be reminded once spring comes. :) This could prove to be quite beneficial considering you ride among hungry bears.

Make sure your float level is set between 14mm and 19mm.

Leave the needle clip in the stock third/middle position.

Always run cool clear 92 octane fuel.

Then life should be good on the XR4.

:) (I've never used the happy banana guy before and thought this might be an appropriate time)

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Not trying to steal the thread... but does all that same info apply to a California model 2002 XR4? Wasn't sure if the needle was different than on the 49 state model, and would require changing after uncorking?

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It's getting worse not better.

I did put a new plug in when I started all this modifying. It's still in.

My pilot is 60. Everything else in the carb has been stock although I did put a 152 main jet in for fun. The stock is 142 and I will have it back in right away.

I use starting routines like many posted on this forum. It takes kicks with the decomp pulled and some throttle, followed by full choke, no throttle and hard kicks from TDC. It takes a bunch, and if it doesn't start in 4-5, I pull the decomp again and give it throttle before trying again. What a pain.

Then when it's running, I have to feather the throttle and watch the choke. It won't idle cold unless I am working the throttle and even then, I get a pop backfire at the carb and it stalls 4-5 times before it's warm. Bummer. It takes me 4-5 minutes to get it running. Does this pop backfire and stall tell me anything about the carb setup?

Valves were setup by a mechanic last fall and I ran it only about 6-8 hours since then.

I'm at 3000 feet, inside a cool shop - about 60 degrees F. Thanks.

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I'm definitely no expert, but you may want to check the valve clearances again. The mechanic may not have set them properly. My bike was a hard starting beast too until I set the valves properly, and now it starts rather easily (I hold the decomp lever, wide open throttle, and kick 10 times before trying to start it, and it works flawlessly). I too have to feather the throttle for a minute or so to keep it running, but I am still trying to dial in my pilot jet and fuel screw setting.

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Like Team Burk said, I think you're too rich. Try a 55 pilot and set the fuel screw at 2 turns out to start.

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I have to agree with team burk. 55 is probalbly a good spot for the pilot. You should also reinstall that 152 main and reset the air screw around 2 1/4. the other thing is needle position. You may want to check and make sure it is in the middle notch.

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Call Baja Designs, They are the XR400 gurus, I called about my '96 XR4 and the guy fixed me up, It's been 4 years since I did the changes, but my bike will start up first kick, hot or cold, upside down, under water, It is awsome. good luck.

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A very common set up for sea level is 60/160. I ride at 5000 to 8500 and run a 55/155 setup during Spring through Fall. You need to make sure you are isolating your testing to each circuit i.e. Pilot up to 1/4 throttle. Main 3/4 to full. You are most likely cleaning your plug during the 1/4 to Full operation encountered during most riding conditions. Keep at it!

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