Author Topic: carb jetting/plug chop  (Read 13939 times)

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guss,guss

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Reply #30 on: July 03, 2015, 12:01:53 am
OK.   Its a new carb.  i pulled it and blew out the pilot system. i had carb cleaner and air blowing up thru the jet, out both holes in the throat and out the air hole in the front, and back. i have a new tank with new fuel tap with strainer in the tank, and an in line filter. fuel is BP high octane. the fuel flow very well to the carb when i cut the valve open. the float looks good to me. my gauge is set on 15/16 in the pick.
 i have put the P-6 , 2.0 slide and 35 pilot. started with the needle clip in center.
it still ran hot in 1/4 range. when i say hot, i mean after only a mile, plug is Bright, exhaust tics, and it doesn't want to start again.
 i moved the clip down, and it was better in the low range but still hot. when i move the clip all the way down it runs good at lower range but at 1/2 it sputters and stutters a little. then the plug is black around the ring and electode bend, but the end of the electrode is yellow.  i am letting it rest. i don't know if the P-8 will help. i think the needle is too thick at the top. there is a chart on jets r us in the mikuni needle section that shows the diameter at 10 mm increments from the top. if i had one smaller diameter at the top but close to the same lower it would let more fuel in at the lower range.  i have a 6DH2 now, I ordered a 6FJ6 and a 6F13. i don't think the P-8 will help but i can try it later or in the morning. where should i start the clip at? center or lower?  thanks for the help.   i forgot this, the plug is a little wet, i think with oil around the ring when i check it.
« Last Edit: July 03, 2015, 12:13:24 am by guss,guss »
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ace.cafe

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Reply #31 on: July 03, 2015, 12:26:47 am
Okay, so you are getting a rich stutter with the needle up too far, so that shows that you are getting in the right area at 1/2 throttle. You can put that back where it was before, so it doesn't stutter at 1/2.

Since you have the P8, go ahead and try it. That is the jet that has control over that 1/4 throttle position. The needle has very little effect at 1/4 throttle position. Yes, it does have some effect, but the needle jet is by far the predominant factor at 1/4 throttle. So, try it with the P9 and see what happens.
It would not be the first time that I have seen a bike act different than others do. Maybe it just wants that rich needle jet for some reason.
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guss,guss

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Reply #32 on: July 03, 2015, 03:35:41 pm
OK. P-8 in. needle clip center.still have 35 pilot 2.0 slide. got 50 yards from the house, stop sign it died. looked at the plug, black. went for a quick ride anyway to see what happens. stuttered in 1/4 range. ran good at 1/2. pulled over. changed pug. bike was hot, didn't want to start . got it going. got a good run at 1/2 throttle, plug was clean, electrode had bronze tint.
  this morning, put 30 pilot in, clip one dwn f/center. idle, plug was good. went for a run, stuttered in 1/4 range.got home plug was black.here is where i am now.
 i changed the slide back to 3.0. left all the rest, P-8, 30, clip one dwn from center. went for a mile run mixed throttle range, ran smooth. plug was clean, electode had bronze tint.i think i will try to darken the plug a little by putting the clip all the way dwn. or put the 2.5 slide and see what that does for the lower range? whatever i do it will be later or Saturday.  it rained on me on the way home. i got drenched.
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ace.cafe

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Reply #33 on: July 03, 2015, 03:54:42 pm
What about the timing?
If it is too advanced or too retarded, that can make it run hotter. Maybe check the timing, and be sure the advance bobweight mechanism is working good.
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guss,guss

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Reply #34 on: July 03, 2015, 09:02:12 pm
the only way i can check the timing now would be with the old TDC finder and a light setup. i tried a couple months ago and never could get it to ping. at that time i wanted to get the timing worked out before i put the electronic ignition on. i put the electronic ignition on and set the plate in the center. it ran great, not hot. that's were it is now. i checked the weights again, they are free.
 i just took it for a run to get better 1/4 and 1/2 readings, it runs hot all over the range.when i change the plug, its hard to start. it idled great before i left. but if i stop at a light it will die on me. i get to my driveway and let it idle, it dies.  i hadn't moved the clip yet. I'm gong to let it rest, set the clip all the way down. and try again.
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ace.cafe

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Reply #35 on: July 03, 2015, 09:16:40 pm
Tune it while it is hot, and it won't die at a light.
  I'll bet the timing is too retarded if it runs hot and you can't get it to ping.
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guss,guss

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Reply #36 on: July 03, 2015, 10:54:48 pm
 i just tried to advance the timing and it wouldn't start. backfired. so i put ti back in the middle. so i put the clip in the bottom place and it actually was a little rich and stuttered in 1/4 but at 1/2 throttle the plug was white and it ran hot.
 i cant figure this out. 
 could it be something like a crack in the head? if it had a blown head gasket it would have loss in compression and would run right.   right?
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ace.cafe

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Reply #37 on: July 03, 2015, 11:05:06 pm
i just tried to advance the timing and it wouldn't start. backfired. so i put ti back in the middle. so i put the clip in the bottom place and it actually was a little rich and stuttered in 1/4 but at 1/2 throttle the plug was white and it ran hot.
 i cant figure this out. 
 could it be something like a crack in the head? if it had a blown head gasket it would have loss in compression and would run right.   right?
Yes.
But, I have seen a leaky decompressor valve cause some air leaks.
It seems that your symptoms are moving around, and that is really pointing toward some form of air leak or exhaust leak.
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cafeman

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Reply #38 on: July 04, 2015, 01:22:33 am
Scanning through your posts it seems you never mentioned what heat range of plug you are using. Also, have you written  down results of how it runs at various throttle positions with the changes you've made to jetting? You know the carb is clean, and have good clean fuel and flow, but the timing is not for sure set at a known good baseline, we're not clear on what plug you're using, it may be too hot a plug, it may be fine? And can you remember the jetting combo where it ran best? You valve to whittle things down and establish a baseline and go through a methodical process of elimination.


Arizoni

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Reply #39 on: July 04, 2015, 05:09:10 am
More than a few times, guss,guss has changed more than one thing at a time.  (jet size, needle size, clip location.....)

When more than one thing is changed at the same time there is no way of knowing what any of the changes did to the actual outcome.
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guss,guss

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Reply #40 on: July 04, 2015, 03:40:42 pm
 plug is NGK BR8ES  gaped  .027.   i am going to check for exhaust and intake leaks again if it ever stop raining. i got some starting spray to do it this time. but i don't think that's it. i will look all up and down the exhaust pipe for holes. i did that already too. then i will break out the TDC finder and test light to make sure its at a good reference point. i assume that process will work with electronic ignition.   could a sticky exhaust valve cause this problem?
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ace.cafe

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Reply #41 on: July 04, 2015, 04:02:54 pm
plug is NGK BR8ES  gaped  .027.   i am going to check for exhaust and intake leaks again if it ever stop raining. i got some starting spray to do it this time. but i don't think that's it. i will look all up and down the exhaust pipe for holes. i did that already too. then i will break out the TDC finder and test light to make sure its at a good reference point. i assume that process will work with electronic ignition.   could a sticky exhaust valve cause this problem?

To find TDC, you must find the center point of the "dwell" of the piston at the top. There is a point where it seems to stop coming up, but the crank will still turn a little bit before it starts to go down. This is the "dwell" at TDC, you must split that distance to find the center, and that will be TDC. This can make up to 20 degrees of variation in timing, depending upon whether you get this actual TDC in the middle of the dwell, or not. This is the most common timing mistake in Bullets.
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Tarnand

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Reply #42 on: July 07, 2015, 12:57:31 am
Quote
More than a few times, guss,guss has changed more than one thing at a time.  (jet size, needle size, clip location.....)

When more than one thing is changed at the same time there is no way of knowing what any of the changes did to the actual outcome.
Precisely.  It seems like setting the proper timing would be the first thing to start with.  Then changing the carb settings "one thing at a time".

Last Friday we worked on friend's Softail.  The plugs were sooty, the engine was overheating and choking on high rpm and he blamed the S&S carb settings.  What can be wrong with S&S?  It did not take us long to find out that someone has messed with the pickup coil position.  We turned the plate CW to max advanced position (typical) and all the problems went away in an instant.

If it helps, this is how I have set mine 4 years ago and have not touched it since then.

« Last Edit: July 07, 2015, 01:04:59 am by Tarnand »
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Blltrdr

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Reply #43 on: July 07, 2015, 02:52:15 am
Showing a picture of your distributor plate will not help him. Depending on who installed the Boyer unit, if the distributor cam was removed and reinstalled incorrectly you can run out of room for adjustment. The best thing he can do is start over from scratch and reset the cam so he has sufficient room for adjustment. Hitchcock's has a write up for setting ignition timing for a Boyer ignition.
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Tarnand

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Reply #44 on: July 07, 2015, 11:37:57 am
Good point Blltrdr.  I did not think of that.  :-\
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