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Discussion Starter · #1 ·
Just got the SMR 510 and have a surge/hesitation problem. Previous owner said he set the bike up according to the JD jetting instructions. Any of you riders had to address this is problem? I'm pretty much at sea level. My first step is to check a/f mix and then look at pilot jet size. Any ideas?
 

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Surging idle or surging while riding? The pilot only effects idle to barely around 1/8 throttle. If you're surging at cruising speed then needle straight diameter should be the first thing you look at. If it's surging more towards the top of your cruising speed or around 1/4+ throttle then you can try going 1 richer on the clip for the needle.
 

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Kan, how would you diagnose the needle diameter and figure out what needle you need?

I read in a few places that everyone was really happy with the JD needles. At sea level you should be using the blue needle
 

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Without a dyno or a/f gauge, the best way is to mark your throttle in increments of 1/4 or better. From there you can figure out the area that you're having a problem with. If it is around 1/8-1/4 throttle then the needle diameter would be the first thing to change for most carbs. You would need to find out the diameter of the needle and then go up or down one depending on rich or lean. Most needles I've seen tend to change in .01mm increments. For example, on a Keihin PWK 2T carbs if you were using a DEL needle you would move to a DEM if you wanted 1 step leaner.

Generally, cruising speed is on the straight diameter of the needle but it depends on your gearing and number of gears. Sometimes you're actually on the taper at these speeds so changing the clip position can be a quick test to see if the problem goes away.

If you feel the needle should be the right one then I'd try the clip position first as that could be your problem.
 

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Discussion Starter · #5 ·
Okay riders, this is what I did. Sometimes ignorance comes in handy. After removing side panels it looked like the airbox is way too wide open. Actually I thought previous owner had removed sides to airbox and never put them back on. It looks like there is attachment points to me. As an experiment I used duct tape to close up the sides. According to parts fiche, there are no sides. At any rate, I took the bike out, it runs 100% better. It was quite obvious the bike was way lean before. There's no doubt that Husky engineers are way smarter than me, but I've never seen an airbox that is this open. Tomorrow I'm going to raise the needle one clip and remove the tape and see what happens. I'm sure there is something wrong with what I did.
 

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Okay riders, this is what I did. Sometimes ignorance comes in handy. After removing side panels it looked like the airbox is way too wide open. Actually I thought previous owner had removed sides to airbox and never put them back on. It looks like there is attachment points to me. As an experiment I used duct tape to close up the sides. According to parts fiche, there are no sides. At any rate, I took the bike out, it runs 100% better. It was quite obvious the bike was way lean before. There's no doubt that Husky engineers are way smarter than me, but I've never seen an airbox that is this open. Tomorrow I'm going to raise the needle one clip and remove the tape and see what happens. I'm sure there is something wrong with what I did.
Thats a great way to experiment :clap: Way to think outside the airbox :lol:
 

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Discussion Starter · #7 ·
To follow up; I pulled the carb. out and checked everything. Previous owner had given me the jet kit with extras and instructions. Carb. was setup according to the instructions. I left needle where it was as that was suppose to be correct. All jets were sized according to spec. Only thing I found that even remotely looked like an issue; primary jet may have been varnished a little. Removed and hit it with carb. cleaner and compreesed air. Seated a/f ratio screw and backed it out 1 1/2 turns. Removed all my duct tape from sides of airbox and took it out for a ride. Pretty much carries the wheel through 3rd gear. I really don't know what cured it, but initially it was dangerous to ride on the street it was so weak.
 
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