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Post by Nicky on Dec 15, 2018 0:21:01 GMT 1
I've got standard 4L1 Mikunis running off cone filters and had them apart - Left one was pissing fuel when not running but with the tap on. Ultrasound cleaned every part as well as using brushes, wire wool, and pipe cleaners. They are perfect. The floats were correct height and the float needles seemed OK, they popped in and out in a nice firm manner and seemed to close when float tang made contact. The valve O Ring on one looked possibly thinner (certainly wasn't worn even under my mag glass). Re-assembled and took it out for a run. Open carbs (will not do this perm, waiting for new cones). Before I cranked it the left one was still pissing fuel but once running not. Once properly hot, it ran beautifully at the power band but the usual Elsie reluctance and coughing was present lower down in all gears. Also once pulled up / stopped at lights etc, it wouldn't idle. I've got 170 Main jets and pilot jets I really carefully cleaned/cleared. Needle clip is on 4th notch, I've got throttle stop screw set to just keep sliders open a hint of a crack at zero throttle. Air screw is approx 1¼ out (thought as running open carbs should be a little leaner?). Both carbs synced. What should I start with? The idle or rough running lower down rev range? I realise I have to have the cones on and also that an airbox is preferrable, but that's the way I want to go.  Also I know I should change one thing at a time. For the no idle - 1. Open air screw a tad? 2. Open throttle stop screw out a tad? 3. Replace pilot jets? For the pissing carb - replace float valve? THANK YOU!!!  |
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Post by dusty350 on Dec 15, 2018 9:55:51 GMT 1
Hi
Im no carb expert but 170 mains with cone filters sounds very small to me ?? Are the filters K &n style with metal end caps ? If so those arent great - if you keep individual filters go with foam pods, or better still, a standard airbox. Leak will be float valve or where it seats i would imagine.
Dusty
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Post by Nicky on Dec 15, 2018 12:26:50 GMT 1
Cheers Dusty.
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Post by stusco on Dec 15, 2018 12:45:47 GMT 1
Have you had the emulsion tubes out to make sure they are clean.
Have you removed the brass ball to clean the air circuit
These can’t be cleaned with just a ultrasonic cleaner
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Post by Nicky on Dec 15, 2018 13:34:37 GMT 1
emulsion tubes have little holes? Right? I didn't see these when I dismantled. Where are they? Brass ball? Never 'eard of that one Boss!! Please advise / point me!
Thanks
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Post by stusco on Dec 15, 2018 15:44:48 GMT 1
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Post by Nicky on Dec 16, 2018 13:07:47 GMT 1
Stusco - you're a hero! Cheers. I'm assuming all this is still valid for 4L1s? Mine's a 250. Enough info there to explain all. I'll let you know how I get on. I always wondered what those brass balls were doing there.
BTW, I need to replace the cone filters - yes - I know I should use an airbox but I like the cones. Any ideas where to find? I have had two sets from Az which have both gone back due to not correctly fitting then them breaking. I've got 42mm ID on the air side bell mouths.
Thanks once again.
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Post by Nicky on Dec 16, 2018 13:09:10 GMT 1
Stusco forgot to ask, where are the emulsion tubes? Beneath the pilot jet?
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Post by dusty350 on Dec 16, 2018 14:22:31 GMT 1
These are your emulsion tubes;  DSCN3702 by David Miller, on Flickr The main jet screws into the bottom end of it - the needle on the carb slide goes in and out with throttle actuation at the top end of the tube;  20181216_125258 by David Miller, on Flickr Best (safest) way I get them out is to push them out although you can tap them out but being brass I don't like hitting them. Unscrew your main jet and remove the washer, or better still fit an old main jet (no washer) and don't screw it all the way in. I then use a Large "G" on the main jet and tighten - it pushes the emulsion tube upwards towards the main body of the carb;  DSCN3703 by David Miller, on Flickr  DSCN3704 by David Miller, on Flickr Stick them in your ultrasonic and they should be nice and clear afterwards. Brass balls - religiously cleaned my last set of carbs in an ultrasonic, and when I removed the balls the area behind was still blocked with crap;  20170603_121535_zpsapquetka[1] by David Miller, on Flickr You can buy the balls in packs of 10 on ebay. Dusty |
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Post by dusty350 on Dec 16, 2018 14:27:15 GMT 1
Forgot to add, Norbo sells foam pods - about a tenner each I think. Fitting pod filters usually requires a jump in main jet size as you've increased the air flow, potentially weakening you mixture. Get some advice on jetting from the carb gurus on here before you proceed - weak mixture can lead to an expensive seizure.
Dusty
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Post by Nicky on Dec 16, 2018 20:45:26 GMT 1
Dusty, great photos and insructions, thank you! I will increase main jet to a 200 or 215, I don't want it running lean!
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Post by dusty350 on Dec 16, 2018 23:02:53 GMT 1
I would ask for recommendations from others as to what size jets to try. Are you running standard pipes ?
Dusty
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Post by bazzer5115 on Dec 17, 2018 9:14:17 GMT 1
Start big and work down with main jets.
Bigger changes rather than small changes at first just to let you know you are going in right direction.
Jetting can be done pretty good with riding if you know what you doing.
You will “feel” by the sound and characteristics of what is fuelling right or wrong.
If you not certain,then a Dyno is the way to go.
My tuned ypvs,with pipes and pod filters on 35mm carbs is running 390 mains.
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Post by Nicky on Dec 17, 2018 11:56:51 GMT 1
Wow! I'm sure I won't need to go so high. I think they're standard pipes? Can you advise?  |
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Also I know I should change one thing at a time. For the no idle - 1. Open air screw a tad? 2. Open throttle stop screw out a tad? 3. Replace pilot jets? For the pissing carb - replace float valve?
