Help needed... over heat/super lean??
- Thread starter Clunk
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Clunk
Well-Known Member
Got the kick starter lever and had a quick play before tea.
I rang the mechanic friend as well and he decided to tell me he played with the ignition timing and air/fuel screw on the carby while i wasn't looking on sunday...
So i tried getting the ignition timing back to factory setting and screwed the air/fuel screw in all the way and then out 1 complete turn(360*).
Bike actually seems to run half decent but still coughing out the carb and stalling when off the throttle.
All this is while its under no load conditions in the garage.
I seem to think the air/fuel screw still needs some tweaking maybe as it only seems to cough when off the throttle and the motor is going down in rpm.
Exhaust is firmly sealed to the head, fitted new copper gasket ring.
Seems to start easily with full choke but will not idle with choke on no mater what.
So would i be right in guessing its down to carby settings now?
I rang the mechanic friend as well and he decided to tell me he played with the ignition timing and air/fuel screw on the carby while i wasn't looking on sunday...
So i tried getting the ignition timing back to factory setting and screwed the air/fuel screw in all the way and then out 1 complete turn(360*).
Bike actually seems to run half decent but still coughing out the carb and stalling when off the throttle.
All this is while its under no load conditions in the garage.
I seem to think the air/fuel screw still needs some tweaking maybe as it only seems to cough when off the throttle and the motor is going down in rpm.
Exhaust is firmly sealed to the head, fitted new copper gasket ring.
Seems to start easily with full choke but will not idle with choke on no mater what.
So would i be right in guessing its down to carby settings now?
DHZ_XR8cing
Master Spanner Spinner
1st thing you should do is get rid of ya mechanic. I think your doing a better job.
Maybe fiddle with the clip height on the needle again.
Maybe fiddle with the clip height on the needle again.
rotn50
Master Spanner Spinning Moderator
if you can adjust the mixture screw easily while running you need to turn the idle up so it does idle with choke off and start to screw the mixture screw anti clockwise and your waiting to hear the revs pick up and smooth out, but if you cant access the screw whilst running it will need to be done bit by bit about a quarter of a turn each time then reattach the carby.
Clunk
Well-Known Member
I agree 100% DHZ_XR8cing!!
At the moment its on the 2nd to bottom position.
Its a 30mm Mikuni.
At the moment its on the 2nd to bottom position.
Its a 30mm Mikuni.
DHZ_XR8cing
Master Spanner Spinner
just make sure you only do 1 adjustement at a time. Not only will it save you from chasing your tail but it will allso help you learn what each adjustment is doing
rotn50
Master Spanner Spinning Moderator
spot on mate, this is were the old oko comes in handy, damn the old 26 and 30mm mikunis, cant adjust while running is not handy at all.
Clunk
Well-Known Member
I tried maximum idle but would stay running so im guessing clip position needs adjusting but couldnt try it as the missus was calling for tea haha.
Because the air filter melted im doing this without a filter on, this shouldnt be an issue?
First thing to try tomoz afternoon is clip position and mixture tuning, the screw is easy enough to get to with the carby on.
You guys have restored my faith in my ol pitty, I appreciate your advice with this so much
Because the air filter melted im doing this without a filter on, this shouldnt be an issue?
First thing to try tomoz afternoon is clip position and mixture tuning, the screw is easy enough to get to with the carby on.
You guys have restored my faith in my ol pitty, I appreciate your advice with this so much
Clunk
Well-Known Member
ok after trying all different combinations the best i can get is idle (a very high idle) without choke but it seems to cough or splutter out the carb and stall.If i keep bliping the throttle i keep it running and it seems to sound fine and doesnt pop out the exhaust at all.
It seems to cough or splutter as soon as i let the throttle close by letting it return by itself.
The settings are as follows...
Idle screw(adjusts the amount the slide will go down) is turned all the way in...maximum idle adjustment.
Mixture screw 1 and 1/2 turns out from all the way in.
E clip 2nd from bottom increment.
So to start it a sure thing is to put choke on, give it one kick without touching the throttle
and then turn choke completely off and again without touching throttle 1 kick and it will start 90% of the time if it doesn't... choke on...1 kick..choke off...1 kick= idle.
When doing this if i adjust the idle screw down to a lower idle it will run fine for a while but then let a few coughs and then stall without touching anything.
It seems to cough or splutter as soon as i let the throttle close by letting it return by itself.
The settings are as follows...
Idle screw(adjusts the amount the slide will go down) is turned all the way in...maximum idle adjustment.
Mixture screw 1 and 1/2 turns out from all the way in.
E clip 2nd from bottom increment.
So to start it a sure thing is to put choke on, give it one kick without touching the throttle
and then turn choke completely off and again without touching throttle 1 kick and it will start 90% of the time if it doesn't... choke on...1 kick..choke off...1 kick= idle.
When doing this if i adjust the idle screw down to a lower idle it will run fine for a while but then let a few coughs and then stall without touching anything.
Clunk
Well-Known Member
Tried different ignition timing positions and have it on the best/least splutter spot.
Tried bottom increment but made it worse.
Im thinking another carb strip and clean as no matter how much i screw the mixture screw in and out it doesnt seem to change anything.
Tried bottom increment but made it worse.
Im thinking another carb strip and clean as no matter how much i screw the mixture screw in and out it doesnt seem to change anything.
rotn50
Master Spanner Spinning Moderator
sometimes adjusting the mixture screw is better done with some revs at one constant level as it can be really hard at idle to hear the changes, but yeah give it a bloody good clean with compressed air and whack a different plug in if ya can.
Clunk
Well-Known Member
Job for the weekend.
Am i right in thinking that it would be something to do with the 'idle' mixture as it seems to splutter and stall as soon as the throttle is released?
Am i right in thinking that it would be something to do with the 'idle' mixture as it seems to splutter and stall as soon as the throttle is released?
rotn50
Master Spanner Spinning Moderator
Idle mixture?? do you mean mixture screw or idle screw, it still sounds like it is the mixture screw(on the bottom of the carb), do your head to intake and intake to carb gaskets getting a good seal.
Clunk
Well-Known Member
gaskets are sealed with silicon to ensure this.
Mikuni carburetor operation and tuning
Just found this which has pointed out that what i thought was just an idle rpm adjustment (adjusts the height of the slide) actually is a mixture adjustment as well as the bottom screw which adjusts how much fuel.
So the bottom screw adjusts how much fuel at idle and the side screw adjusts how much air flow at idle.
So im thinking carby strip and clean.
Then adjusting so the bottom screw 1.5 turns out and then side srew as far out without stalling from too low idle then adjust bottom screw to finalise mixture
I think im starting to get my tech back... its been a while lol.
Mikuni carburetor operation and tuning
Just found this which has pointed out that what i thought was just an idle rpm adjustment (adjusts the height of the slide) actually is a mixture adjustment as well as the bottom screw which adjusts how much fuel.
So the bottom screw adjusts how much fuel at idle and the side screw adjusts how much air flow at idle.
So im thinking carby strip and clean.
Then adjusting so the bottom screw 1.5 turns out and then side srew as far out without stalling from too low idle then adjust bottom screw to finalise mixture
I think im starting to get my tech back... its been a while lol.
rotn50
Master Spanner Spinning Moderator
gaskets are sealed with silicon to ensure this.
Mikuni carburetor operation and tuning
Just found this which has pointed out that what i thought was just an idle rpm adjustment (adjusts the height of the slide) actually is a mixture adjustment as well as the bottom screw which adjusts how much fuel.
So the bottom screw adjusts how much fuel at idle and the side screw adjusts how much air flow at idle.
So im thinking carby strip and clean.
Then adjusting so the bottom screw 1.5 turns out and then side srew as far out without stalling from too low idle then adjust bottom screw to finalise mixture
I think im starting to get my tech back... its been a while lol.
From my understanding about the slide being richer and leaner, its talking about the cutaway on the slide(the angled section that the idle screw pushes on) and you can get different slides with higher or lower cutaways(but i have never seen this on china mikunis), so what your thinking is that by adjusting your slide height you are affecting the mixture, i dont read it thatway.(if im wrong someone please correct me
)So the idle screw is still just that an idle screw and it does not affect the mixture.
(were as a higher or lower angle on the slide changes mixtures)
Id still stick with getting the bike to a highish rev with the idle screw and start to very slowly turn the mixture screw(bottom one)until revs either pickup or smooth out.
This link maybe about the tuning of a genuine mikuni carb(as opposed to a china copy, with japan on the side) that you are able to get different slides for to modify mixture also.
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Clunk
Well-Known Member
iv got it to the point that it will idle and free rev fine with out pops and splutters.
SO then came the ride test...
1st gear take off fine but when you change up to second it bogs and dies if going up hill, even if you change up and its bogs then quickly try to get first and keep it going it struggles to get the revs back up.
Idle mixture screw doesnt seem to make a difference still but have it 2 1/4 turns out.
Stripped the carby and soaked in thinners and gave it a sweet clean but6 didnt change anything.
So then tried advancing and retarding the timing but didnt seem to make a difference to the bogging down when up changing gears.
SO then came the ride test...
1st gear take off fine but when you change up to second it bogs and dies if going up hill, even if you change up and its bogs then quickly try to get first and keep it going it struggles to get the revs back up.
Idle mixture screw doesnt seem to make a difference still but have it 2 1/4 turns out.
Stripped the carby and soaked in thinners and gave it a sweet clean but6 didnt change anything.
So then tried advancing and retarding the timing but didnt seem to make a difference to the bogging down when up changing gears.
