Welcome, Guest
Username: Password: Remember me

TOPIC:

Jet needle improves acceleration. 10 Jul 2011 13:01 #462049

  • mark1122
  • mark1122's Avatar
  • Offline
  • Member
  • Member
  • Keep twisting it
  • Posts: 5350
  • Thank you received: 107

calvin17d wrote: Driving in first and observing engine performance I noted surging most noticeably at 2K rpm's. It was however present at 1-3 & 4K as well. Approaching 5K the surge went away. I assume this was where a transition was occurring. Prior to heading out, I did in fact tune the mix screws as suggested. After Finding the optimum rpm at idle how would one begin tuning after a driving test that revealed a rich condition?

Lean all screws an 1/8 a turn and try the riding test again?

YES , but i would encourage u to try it booth ways to be sure u are going the right way the first time. this is all about u learning what rich and lean feels like . don’t be afraid to go too far for experimental purposes so u can REALY FEEL the dif.

If I understand this, we are saying that a good idle tune of the mix screws may not directly translate to a good tune under load?

it usually does but obviously, not always. Also a carb sync helps to smooth things out, after jetting is done.

Not all Carbs have AIR SCREWS. Some have FUEL SCREWS, it is important to differentiate as to which one you have. This depends on the location of the screw on the carb. (looking at the center of the carb) If the screw is in between the cylinder and the carb body , it's a FUEL SCREW, turn it OUT to get more fuel (richer) if the screw is in between the carb body and the air box, it's an AIR SCREW, turn IN to richen it. As far as I know this rule of thumb is correct.

dont forget to take notes as u go. right down the adjustment (1/8th turn out)ask yourself did it get better or worse and a what rpms.
put tape on the bar grip. mark off closed ,full then 1/2, 1/4 1/8th throttle . when marking the bottom openings dont get fooled by the throttle play. take up the slack in the throttle cable by twisting the grip till snug, then mark off the lower sections on the tape. u will be surprised how fast u can go in 5th gear at 1/4 throttle.
76 kZ, frame gusset work,1200CC.Ported by Larry Cavanaugh,This email address is being protected from spambots. You need JavaScript enabled to view it., 1.5mm.over intakes,.ZRX12 rear end,and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg,Ont.Can.

~ ~ ~_@
~ ~ _- \,
~ (k) / (z)

Please Log in or Create an account to join the conversation.

Jet needle improves acceleration. 10 Jul 2011 14:44 #462070

  • calvin17d
  • calvin17d's Avatar Topic Author
  • Offline
  • Member
  • Member
  • Posts: 187
  • Thank you received: 1
Just got back from the 1st gear test.

I started out making qtr turns at my first adjustment as my adjustment made for idle was rich and the bike surged through all rpm ranges. I then reached a point where I was about 2-1/4 turns out and the it started to backfire on deceleration. I began turning them back in over the course of 3 stops making adjustments of 1/8 a turn. I finally reached a spot where it is no longer popping and surging has faded. This is located at 1-5/8 to 1-3/4 on all screws. Unfortunately my acceleration is suffering.
1976 Kz900 A4

Please Log in or Create an account to join the conversation.

Jet needle improves acceleration. 10 Jul 2011 16:57 #462088

  • mark1122
  • mark1122's Avatar
  • Offline
  • Member
  • Member
  • Keep twisting it
  • Posts: 5350
  • Thank you received: 107

calvin17d wrote: Just got back from the 1st gear test.

I started out making qtr turns at my first adjustment as my adjustment made for idle was rich and the bike surged through all rpm ranges. I then reached a point where I was about 2-1/4 turns out and the it started to backfire on deceleration. I began turning them back in over the course of 3 stops making adjustments of 1/8 a turn. I finally reached a spot where it is no longer popping and surging has faded. This is located at 1-5/8 to 1-3/4 on all screws. Unfortunately my acceleration is suffering.


so as u turned them out it got leaner. are your pilot screws on the airbox side of the carbs?
ok. so, are u happy with the cruise . is it smooth there now? if so we will leave that and move on to the accell. they are 2 dif things.
describe the accell problem.
76 kZ, frame gusset work,1200CC.Ported by Larry Cavanaugh,This email address is being protected from spambots. You need JavaScript enabled to view it., 1.5mm.over intakes,.ZRX12 rear end,and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg,Ont.Can.

~ ~ ~_@
~ ~ _- \,
~ (k) / (z)

Please Log in or Create an account to join the conversation.

Jet needle improves acceleration. 10 Jul 2011 17:14 #462093

  • 78kzturbo
  • 78kzturbo's Avatar
  • Offline
  • Member
  • Member
  • Posts: 49
  • Thank you received: 6
i can help you with your carb problems.

Please Log in or Create an account to join the conversation.

Jet needle improves acceleration. 10 Jul 2011 17:42 #462097

  • calvin17d
  • calvin17d's Avatar Topic Author
  • Offline
  • Member
  • Member
  • Posts: 187
  • Thank you received: 1
Being unsatisfied with previous results. I brought it back to the shop to get a better tune on the pilot screws (located on the air cleaner side of carbs).
Watching the tach and listening I brought it back to optimum without load. Went for a test drive and after an acceleration that sounds of fluttering it took off smoothly and accel'd nicely up to 5 k with a silky transition. I hit the side streets to Start the 1st gear test again. All was smooth with the exception of a light yet noticeable surge at 3k. I made adjustments of 1/8 a turn on the screws in both directions and It got worse. After this I couldn't get it back to the silky smooth operation. My effort on the side of the road led to a rough running condition and again I think my plugs began to foul and the exhaust very smokey.

I am happy with the cruise when those screws are adjusted at idle for idle, but it seems to be fouling when left at idle. Am wonderin if the increased height in the needle is allowing premature entry of fuel. Sadly I attribute some gains in midrange to the new clip position. Am feeling like a smaller than stock pilot could help reduce the excess fuel at idle that has come at the hand of the raised needle.

The accel problem lasts about 2 seconds and occurs at take off and also during aggressive throttling at cruising speeds. I feel like this got better after I raised the needle.
1976 Kz900 A4

Please Log in or Create an account to join the conversation.

Jet needle improves acceleration. 10 Jul 2011 17:51 #462101

  • 78kzturbo
  • 78kzturbo's Avatar
  • Offline
  • Member
  • Member
  • Posts: 49
  • Thank you received: 6
this is not rocket science it is a matter of air fuel mixture screws set properly and correct jetting.dont worry about needle position right now.after your bike is jetted properly and you have the right fuel mixture fine tuning will be easy.my computer skills are not good but i've been building these bikes for 20 years now.if you like i can help you get it jetted properly.

Please Log in or Create an account to join the conversation.

Last edit: by 78kzturbo.

Jet needle improves acceleration. 10 Jul 2011 17:53 #462102

  • mark1122
  • mark1122's Avatar
  • Offline
  • Member
  • Member
  • Keep twisting it
  • Posts: 5350
  • Thank you received: 107

78kzturbo wrote: i can help you with your carb problems.


welcome 78kzturbo


please feel free to jump right in.
76 kZ, frame gusset work,1200CC.Ported by Larry Cavanaugh,This email address is being protected from spambots. You need JavaScript enabled to view it., 1.5mm.over intakes,.ZRX12 rear end,and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg,Ont.Can.

~ ~ ~_@
~ ~ _- \,
~ (k) / (z)

Please Log in or Create an account to join the conversation.

Jet needle improves acceleration. 10 Jul 2011 17:58 #462103

  • 78kzturbo
  • 78kzturbo's Avatar
  • Offline
  • Member
  • Member
  • Posts: 49
  • Thank you received: 6
what year is the bike and what size are the carbs?

Please Log in or Create an account to join the conversation.

Jet needle improves acceleration. 10 Jul 2011 17:59 #462104

  • mark1122
  • mark1122's Avatar
  • Offline
  • Member
  • Member
  • Keep twisting it
  • Posts: 5350
  • Thank you received: 107

calvin17d wrote: Being unsatisfied with previous results. I brought it back to the shop to get a better tune on the pilot screws (located on the air cleaner side of carbs).
Watching the tach and listening I brought it back to optimum without load. Went for a test drive and after an acceleration that sounds of fluttering it took off smoothly and accel'd nicely up to 5 k with a silky transition. I hit the side streets to Start the 1st gear test again. All was smooth with the exception of a light yet noticeable surge at 3k. I made adjustments of 1/8 a turn on the screws in both directions and It got worse. After this I couldn't get it back to the silky smooth operation. My effort on the side of the road led to a rough running condition and again I think my plugs began to foul and the exhaust very smokey.

I am happy with the cruise when those screws are adjusted at idle for idle, but it seems to be fouling when left at idle. Am wonderin if the increased height in the needle is allowing premature entry of fuel. Sadly I attribute some gains in midrange to the new clip position. Am feeling like a smaller than stock pilot could help reduce the excess fuel at idle that has come at the hand of the raised needle.

The accel problem lasts about 2 seconds and occurs at take off and also during aggressive throttling at cruising speeds. I feel like this got better after I raised the needle.


where are the screws set when u set them to highest idle ?
76 kZ, frame gusset work,1200CC.Ported by Larry Cavanaugh,This email address is being protected from spambots. You need JavaScript enabled to view it., 1.5mm.over intakes,.ZRX12 rear end,and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg,Ont.Can.

~ ~ ~_@
~ ~ _- \,
~ (k) / (z)

Please Log in or Create an account to join the conversation.

Last edit: by mark1122.

Jet needle improves acceleration. 10 Jul 2011 18:07 #462106

  • mark1122
  • mark1122's Avatar
  • Offline
  • Member
  • Member
  • Keep twisting it
  • Posts: 5350
  • Thank you received: 107

calvin17d wrote: 120 mains
Stock pilots
Pods
4 into 1
Timed
Clearances set.
Strong spark
Carbs cleaned twice
Float levels dialed

Have the bike running very smooth off idle and performing quite well at the top. Not shabby, but acceleration was a bit sluggish from take off and aggressive mid range throttle openings. I decided to raise the needle to the 4th notch.

Result:
Bike still running great with a very noticeable improvement in acceleration and smoother operation through higher rpm's. Unfortunately it seems that the high speed accelerations have tapered off?

Would you think that the top just seems more flat now that midrange has more snap, or is the new height of the needle allowing too much fuel through the 120s at the high end of midrange.

I am considering trying the 115s with this new needle position .......

Thoughts?


just for a refresher. this was your first post.


can u elaborate on this statement?

Result: after raining the needle:
Bike still running great with a very noticeable improvement in acceleration and smoother operation through higher rpm's. Unfortunately it seems that the high speed accelerations have tapered off?

seems to conterdict itself ?

what changes did u make to the bike in the first place, before u started adjusting the carbs?
76 kZ, frame gusset work,1200CC.Ported by Larry Cavanaugh,This email address is being protected from spambots. You need JavaScript enabled to view it., 1.5mm.over intakes,.ZRX12 rear end,and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg,Ont.Can.

~ ~ ~_@
~ ~ _- \,
~ (k) / (z)

Please Log in or Create an account to join the conversation.

Jet needle improves acceleration. 10 Jul 2011 18:10 #462110

  • 78kzturbo
  • 78kzturbo's Avatar
  • Offline
  • Member
  • Member
  • Posts: 49
  • Thank you received: 6
depending on the year of the bike and type of carbs your using will determine your jetting.set all your air fuel mixture screws at 1 1/2 then properly jet the bike.after it is jetted properly then you can fine tune your air/fuel mixture screws they should be set somewhere between 1 1/4 and 1 3/4.the 1 1/2 should get you real close.

Please Log in or Create an account to join the conversation.

Jet needle improves acceleration. 10 Jul 2011 18:32 #462119

  • 78kzturbo
  • 78kzturbo's Avatar
  • Offline
  • Member
  • Member
  • Posts: 49
  • Thank you received: 6
if your air/fuel mixture screws are not set properly you will start to foul plugs and will make it difficult to diagnose.the whole idea is to bring in as much air as possible.the more air you can bring in the more fuel you can burn.set your air screws at 1 1/2 and then jet your carbs until you get the results your looking for.then you can adjust each air screw to it's highest idle.when it is at highest idle you are pulling in as much air as possible through your air correction jets located on the back side of the carb going into the air box.

Please Log in or Create an account to join the conversation.

Powered by Kunena Forum