Jetting 1986 xc500

[cworobec]

Hi guys, I have an 86 Husqvarna xc500 and it starts OK, I've got the needle clip on the 4th from the bottom so needle is close to all the way down, and that seems to help the mid but it just bogs and hangs up top. I was wondering what the stock pilot and main jet and needle clip positions are for sea level. I ride mostly at 2500-5000ft above sea level. I know most can't tell me what jets I'll need for that but even if someone can tell me what the stock jetting and air screw settings are at least I will have a starting point. Thank you for your help.

 

[suprize]

just drop the main a couple of sizes then look to lift the needle as the main cleans up.....

check your float level isn't too high and flooding the engine a bit. check the exhaust for blockages.

try a different plug

 

[cworobec]

It's running the stock plug, b8es, right now it has a 470 main. How many mm is the float arm supposed to fluctuate?

 

[86 400 XC]

I set my floats parellel with the gasket surface for the bowl.

Steve

 

[justintendo]

it bogs and hangs up top? be careful with dropping the main leaner..bogging sound lean already.

 

[suprize]

yeah, I read that to mean its blubbering like the choke is on....especially as he was cleaning it up leaning the needle off.

if its dragging ie feels like the brake is slowly being applied as it starts to rev up, its lean...should feel like its running out of fuel if its lean.

a plug chop is difficult on a 500. do you know how to read a plug? we can help if you dont

the old a/c 500 parts manual says 470 is the biggest main so 440 should be ok. how is the air filter? clean and freshly oiled?

HVA Factory.com have all the parts manuals online free so look em up. my inet connection is too slow to dload the 86 manual

 

[Four Digit]

I have an 85 500 motor in my 86 xc frame. The 85/86 motors are basically the same except perhaps for an extra screw location on the 86 clutch case. That a side, when I started to put the bike together (from the three hulks I purchased) I copied the following jetting from an online spec sheet for the 500 running a 40mm Mikuni carb:

Main Jet 350, Needle Jet AA5, Idle Jet 55, Needle position is 3 (middle), Air Jet 0.7, Jet Needle 7DH3, Throttle slide 2.5 and 1.5 turns on the air screw.

I normally ride in an area where the elevation is listed as 3000 feet but with some of the trails I could be near 3500 feet. My jetting is the same as above except that I am running a AA2 needle jet and my pilot jet is 35.

The jetting seems correct for my style of riding ( a 72 year youngster) who only occasionally "whacks" the throttle hard. The motor runs with great power and quickly reacts to any throttle whacking be it lugging down a trail or wailing through the gears. Now if I was a pro rider or some delusional soul who thinks he rides "wide open" all the time then a larger Main Jet would seem to be appropriate but my feeling is most people are riding in the 1/2 to 2/3 throttle range which makes the 350 main fine. I constantly am checking plug color just to ensure I am not running the motor in a lean condition.

Finally, spec says the float measurement is set from 17-19mm. I also measure from the carb gasket.

Hope this helps.

 

[ajcmbrown]

Have you disassembled the carb and checked for cleanliness? I recently found a large flake of crap in the big brass nut on the bottom of the float bowl that was causing similar symptoms, after revving cleanly through the first three gears my '88 WR400 would bog like it was starving, it seems that since the main jet protrudes into this brass nut, it was sucking it up against the main jet and starving the motor.
After a thorough cleaning it now behaves as it should.
I hope you find your issue, Tony.

 

[cworobec]

Thanks for all your help guys. I will have him double check floats and carb cleanliness and it's bogging on top cause it's way to fat I know that much by listening to it.