Engine missing at sustained 50mph

I just purchased a used 06WR 450 with the boyeson carb kid, DRD pipe, no toil type air filter, and a bunch of cool accessories. The bike runs really nice, and feels very well sorted with one annoying exception: at sustained speeds on pavement it has a little miss you can hear and feel, occurring every 20 seconds or so sometimes. Other time every 10 seconds, sometimes once a minute. It seems not to be engine load related, but I don't feel it on full load acceleration. It just occurs on simple comfortable rpm sustained speeds and may or may not be present at any given time. I did change a spark plug to no avail. I have had to loosend and retighten the header to get the dang oil filter screw out and thought perhaps I had some koind of exhaust leak effect, but it runs so good I do not think that is the case.

Any ideas?

My 06 did the same thing after installing a YZ pipe and low throttle on roads here in Colorado. I had already richened up the pilot and main jets so I raised the needle one clip position for a little more fuel.

Check into the Throttle Position Sensor (TPS) re-calibration/adjustment. It is an often occurance to have these bikes have a "mis-fire" around 1/4 ish throttle and steady speed. I've never bothered to adjust my TPS on my 2001 WR426 and it has had the steady throttle hesitation for 11 years and the bike runs as strong today as the day I bought it new. This also assumes all your jetting is proper for your elevation. On the trail you probably would never notice because its not very often you hold the throttle steady.

These bikes don't cruise well at steady speeds. They like the throttle to either be on or off mostly due to the TPS system.

These bikes don't cruise well at steady speeds. They like the throttle to either be on or off mostly due to the TPS system.

Mine cruises great I've taken it on lots of constant speed rides

I just purchased a used 06WR 450 with the boyeson carb kid, DRD pipe, no toil type air filter, and a bunch of cool accessories. The bike runs really nice, and feels very well sorted with one annoying exception: at sustained speeds on pavement it has a little miss you can hear and feel, occurring every 20 seconds or so sometimes. Other time every 10 seconds, sometimes once a minute. It seems not to be engine load related, but I don't feel it on full load acceleration. It just occurs on simple comfortable rpm sustained speeds and may or may not be present at any given time. I did change a spark plug to no avail. I have had to loosend and retighten the header to get the dang oil filter screw out and thought perhaps I had some koind of exhaust leak effect, but it runs so good I do not think that is the case.

Any ideas?

The problem is caused by the ignition "timing" map. it feels like a Studder at part throttle low throttle opening felt mostly on pavement or hard smooth dirt road. You may not be able to completely cure the issue but you can but you can minimize the issue.

Here is what worked for me:

Adjust TPS to upper voltage range, set idle speed and mixture perfect first.

Raise needle one clip to richen (smooth) small throttle opening at constant throttle.

An intermitent stutter at constant highway speed is normal for these bikes.

Mine (04) does the same thing.

I wouldn't waste any time on the issue if it runs great under every other scenario (mine does).

There are probably lots of other issues that would benefit far more from your time.

My two cents.

Mine does it too, and it's driving me nuts. Just doesn't make sense why it happens.

The problem is caused by the ignition "timing" map. it feels like a Studder at part throttle low throttle opening felt mostly on pavement or hard smooth dirt road. You may not be able to completely cure the issue but you can but you can minimize the issue.

Here is what worked for me:

Adjust TPS to upper voltage range, set idle speed and mixture perfect first.

Raise needle one clip to richen (smooth) small throttle opening at constant throttle.

How do you adjust the TPS to the upper voltage range? I loosened the screw and turned mine, but it will barely move. How far is the TPS supposed to rotate? Mine only rotates a tiny amount, like 1/8".

I ened up unplugging the TPS, but it's still "not right".

I don't know how mine works good on the highway... Never misses at 60mph when I cruise for an hour or so , this is the only time it doesn't overheat though

Mine does it too, and it's driving me nuts. Just doesn't make sense why it happens.

The manufactuer manupulates the ignition timing map to pas sound and emmissions testing for specific Government required tests

How do you adjust the TPS to the upper voltage range? I loosened the screw and turned mine, but it will barely move. How far is the TPS supposed to rotate? Mine only rotates a tiny amount, like 1/8".

I ened up unplugging the TPS, but it's still "not right".

Now for sure your going to need to read in your manual how to do it. It has been explained here at least 20 times

http://www.thumpertalk.com/topic/609247-throttle-position-sensor/page__p__5915199__hl__tps%20adjustment__fromsearch__1#entry5915199

Now for sure your going to need to read in your manual how to do it. It has been explained here at least 20 times

http://www.thumperta..._1#entry5915199

I guess you didn't understand what I was asking. How far will the TPS rotate? Mine will only turn about 1/8", maybe a tad more. Is that correct, or should I be able to turn it farther than that?

That is how it's adjusted, right?

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