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Post by muttsnuts on Sept 20, 2017 17:12:31 GMT 1
get a new pair of 28mm mikunis from norbo ; put a new set on my 4LO ; its never ran so well Doddy, you got any jetting info on them as I have a pair to fit at some point |
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Post by lolly on Sept 20, 2017 18:42:46 GMT 1
forget all of the vm26 settings , there out the window.
I am running standard engine , standard airbox , JL stainless race pipes (not street) and boysen reeds , and pre-mix
I had to go up one on the emulsion tube (ran to weak on the one it came with)
I started on 280 main jets (two up on what I was running with the standard 26 mm carbs) , I am now down to 120 main jets with the clip second from top
it runs so sweet , no splutter , no lag , no bogging down .
its still a bit rich but I am reinstating the oil pump so that may bring it down
don't forget , you will have to cut a trim a bit of the outer cable
regards john
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Post by rapidgaz on Sept 21, 2017 14:52:47 GMT 1
Might try old carbs. Bidding on a pair of 4lo carb bodies at the moment. Look like they are in good clean condition. See what happens. If that don’t happen I will purchase some new ones.
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Post by rapidgaz on Oct 15, 2017 17:36:45 GMT 1
Hi folks.
Progress with my lc is as follows.
I have managed to sort out my starting issues so starts first kick now with choke.
Carbs set as follows.
310 mains
22.5 pilots.
Needles not sure. But new of yam bits. Middle setting.
Boyesen 2 stage reed new carb to reed boots.
Bike was pulling away quite nice but had the mid range splutter quite bad at aroun 4.5 to 5 thou revs. Air screws 1.5 turns.
So upped my needle one notch leaner.
Mid range splutter moved to about 5.5-6 thou. And cleared better, but made pullaway slightly worse. So put air screws to 1 3/4 turns out made it worse. Went to 1 1/4 turns made it better.
Tried needles on leanest notch which pretty much made it un ridable. Tried air screws in/out not much better either way but best was richer.
So went back to second notch down and settled for this for now. What should I try next to smooth out my mid range splutter. Pipes are lomas racing expansion chambers. Using pod filters not sure of state of tune of engine but it’s possibly ss stage 3.
Also new carb bodies now.
Cheers Gareth.
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Post by peter007 on Mar 7, 2018 22:14:53 GMT 1
I’ve had all the usual symptoms everyone gets poor starting , poor pull away , mid range stutter at 4.5 -5thou revs I’ve tried everything . Finally bought my own ultrasonic cleaner and used white spirit at 50 defrees heat , put carb bodies in right way up and also upside down an hour each way and all jets too . Rebuilt them with 220 mains and 22.5 pilots . Floats set at 21mm and also clear tube so spot on .all good at 1 1/2 turns on air screw pulls away sweet as but stutter still there .
Next step was to fit banshee coils made my own loom properly , still another improvement starts much better ,picks up much crisper off the throttle but still that bloody mid range stutter .
Next step I fitted CHAO stage 1 carbon reeds improved the stutter a little
Next and final step fitted 6mm reed block spacers on barrel side of reed block and bingo ! Stutter completely GONE !
I hope this long winded list helps you guys , I’m a happy bunny now yeeehah !! Anyone wanna chat about what I’ve done just pm me ok cheers
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Post by dono on Mar 8, 2018 0:40:25 GMT 1
Gaz has had his motor go pop now on the motorway, so he needs to get it re built.. cheers Dono
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Post by Tobyjugs on Mar 8, 2018 8:47:44 GMT 1
From my experience if its standard carbs with pod filters you need to be 400+ for main jets. I even ended going up to 400 for the 250 when the cold weather turned up.
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Post by andrel on Aug 9, 2018 13:51:46 GMT 1
nah, that carb is done, the locating pin hole has gone which keeps the needle jet in the correct position, scrap I am afraid Cannot remove my main jet as my needle jet just spins which means, i suppose, that the pin is no longer holding it in position. Pin still sits neatly in its hole when viewed from the outside. Drill it out and replace with something seems to be the answer, but has anyone done so and can help with a bit of advice? |
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Post by chrisg on Jan 12, 2020 17:47:22 GMT 1
get a new pair of 28mm mikunis from norbo ; put a new set on my 4LO ; its never ran so well Doddy, you got any jetting info on them as I have a pair to fit at some point Air cooled 250/400's run 28mm carbs. Would they be a better upgrade than the 350 carb fix? Im thinking of better flow rates? I understand that Yamaha only went down to 26mm carbs due to emission laws. |
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