Hunting idle?

[the_Journeyman]

Ok, new plugs are going in as soon as I figure out what the gap is to check the new plugs.

JM

[the_Journeyman]

Fresh plugs and it idles much better.  I'm going to check plug color and see if it indicates rich or lean.

JM

[the_Journeyman]

Idle is good, actually responds to fuel screws.  I went in a half turn and got a slightly faster idle.  Seemed to run ok & idle ok.  Back to fussing with the needle shims.  If feels a little lazy in the midrange.

I'm amazed at the difference new plugs made.  

Plug deposits are very white, so I'm going to add an additional shim under the needle and see what happens.

JM

[the_Journeyman]

After trying a few different things, I wound up nearly tripling the needle height from OEM.  Currently at 3.5 turns out on the air screws, might go back to 4 though.  I'm thinking the main needs go be larger too.  I do have BCM filter & Termi pipes, so that makes the factory lean settings probably more noticeable and harder to tune without adding a jet kit.

So, here's where I wound up:
1.  Full throttle is weak, as you roll off, the bike pulls better.  I think that means lean.
2.  It pulls strong and smooth in mid-throttle & RPM with reasonably crisp (Not quite FI crisp) response.
3.  It is idling steady, but I get a lot of popping when I decelerate with a closed throttle.

Plugs still indicate lean, but it's running much better.

Starts easier too, probably the new plugs help with that. 

[akmnstr]

After trying a few different things, I wound up nearly tripling the needle height from OEM.  Currently at 3.5 turns out on the air screws, might go back to 4 though.  I'm thinking the main needs go be larger too.  I do have BCM filter & Termi pipes, so that makes the factory lean settings probably more noticeable and harder to tune without adding a jet kit.

So, here's where I wound up:
1.  Full throttle is weak, as you roll off, the bike pulls better.  I think that means lean.
2.  It pulls strong and smooth in mid-throttle & RPM with reasonably crisp (Not quite FI crisp) response.
3.  It is idling steady, but I get a lot of popping when I decelerate with a closed throttle.

Plugs still indicate lean, but it's running much better.

Starts easier too, probably the new plugs help with that.  

Your jetting is getting a little disorganized.  I'd suggest that first check for leaks in the intake as I suggested earlier.
Also check for leaks in the exhaust.  Leaks at either intake or exhaust can cause lean running and are problems you will never solve with jetting.  Your symptoms at idle sound more like a leak issue than a jetting one.

If you have no leaks and your bike still has problems as described start by solving the WOT problem first by changing the main jet.  Get WOT sorted first!  Your symptoms sound like a rich mixture to me.  In my experience a lean mixture results in hesitation or popping.

After that, if you have problems with partial throttle openings adjust the needle.

Adjust ideal mixture last by adjusting you air screws.  


Also you could use an AFX air-fuel Monitor http://www.ngk.com/afx/ to help you sort out your problems if you have no leaks.

[koko64]

It wouldn't hurt to check for manifold leaks as AKMNSTR suggested.

It's good you are considering a Factory Pro or Dynojet jet kit with that high flowing filter and pipes. It will give you a tuning range you dont have at present. If you can get main jets cheap enough you could try DPs needles. There is such a minor taper on the stock needle that shimming it has less effect than you would hope for.

I have seen decel popping from manifold air leaks, too much (rich) fuel burning in the exhausts and also from too lean a setting, so try half a turn out on the IMS and see what happens.

Sounds like you are learning heaps and making progress. I like how you picked up on the main jet being lean. ( I have seen similar WOT symptoms with too rich), but your plugs are white and you have a freer filter and pipes. It's great you are reading your plugs too.

Us older guys brought up on carbed bikes all went through this.

[Howie]

Full throttle is a main jet issue.  Rich or lean can difficult to determine with the butt dyno, but too rich short of stupid rich is smooth but may have noticeable power loss.  Lean usually results in ridability problems.

[ducpainter]

Lets not forget this is stock jetting.

I doubt any part is rich.

[akmnstr]

Full throttle is a main jet issue.  Rich or lean can difficult to determine with the butt dyno, but too rich short of stupid rich is smooth but may have noticeable power loss.  Lean usually results in ridability problems.

All true.  The main jet also influences all of the other settings and is why I suggested sorting it before other adjustments. 

It's good you are considering a Factory Pro or Dynojet jet kit with that high flowing filter and pipes.

Maybe the best advice given here.  The kits suggest jettings that have been worked up for your engine setup.  I didn't realize earlier that you are working with carbs with the stock jetting. 

[Howie]

All true.  The main jet also influences all of the other settings and is why I suggested sorting it before other adjustments. 

Maybe the best advice given here.  The kits suggest jettings that have been worked up for your engine setup.  I didn't realize earlier that you are working with carbs with the stock jetting. 

Absolutely!

[the_Journeyman]

Got back from a riding vacation last night.  Here's my observations.  It's obvious I need a jet kit, that'll come in this winter when I have time to disassemble the carbs again.

In the mean time, here's how things run.

Bottom end through mid throttle is great.  Very strong pull from idle.

Top end is in bad shape.  Chasing down some of the fast guys required a couple seconds of WOT.  This resulted in a NASTY forward surge as I closed the throttle.  Likely a lean surge I'm guessing.

JM