benny
Scoot Member
Posts: 50
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Post by benny on Apr 29, 2015 5:58:05 GMT -5
Now back to 85 with clip at bottom. 70kmh top speed. Doing wot check on plug comes up a bit of a white tinge. So went to 90 main jet. wot check comes up with nice slight brown on plug. So left that. But still 70kmh to speed. Next was 1/2 throttle check with 90 and clip at bottom spot. Brown with bit of oil on plug. So Probly one notch rich but that's all for today. The 70kmh top has me a bit concerned that I've done some damage with the soft cease. As it used to run up to 75 / 80.
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Post by 90GTVert on Apr 29, 2015 6:06:43 GMT -5
It's safest to keep the mid/low throttle on the rich side. Tune the main jet for max power and a good plug read, though you should be looking at the mixture ring for a plug read on the main jet, and keep the rest of the tune rich so there's some sputtering even at low throttle. If I don't have any sputtering at low-mid throttle while riding I raise the needle. The richer settings are good for keeping the engine cool cruising around and also useful if you happen to get a hill or tail wind or some advantage that allows you to cruise around at lower throttle positions at high RPM.
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Post by fe53series3 on Apr 29, 2015 7:43:00 GMT -5
Now back to 85 with clip at bottom. 70kmh top speed. Doing wot check on plug comes up a bit of a white tinge. So went to 90 main jet. wot check comes up with nice slight brown on plug. So left that. But still 70kmh to speed. Next was 1/2 throttle check with 90 and clip at bottom spot. Brown with bit of oil on plug. So Probly one notch rich but that's all for today. The 70kmh top has me a bit concerned that I've done some damage with the soft cease. As it used to run up to 75 / 80. The white tinge tells you that you are definitely lean...... you should never run a mix like that. This presumably is the cause of your seizure. 95 looks to be safe. Check again the graph I made for you. While this is not your needle........ you can see that on N1 (needle measurements are taken from the bottom), @ idle it is delivering a huge amount of fuel. This could easily create plug fouling conditions. To run on N1 invariably means reducing the pilot jet size, to balance the fuel coming past the taper. The objective is to get your idle circuit correct, whilst matching the taper to the throttle opening. Looking at the graph, and drawing a line up from any throttle position...... you'll see that different quantities of fuel are delivered for that air flow....... only one fuel flow is correct. It is adjustable by both the needle and the main jet Main JetFrom your earlier post, you said "it seems the needle effects 1/4 right up to just beyond 3/4 throttle" This is misinformation that is repeated time and again, and anyway everything depends upon the carb design. The Dellorto PH series has the needle in the atomiser at all times....... the main jet never fully takes over. Similarly..... the main jet is the primary fuel aperture, feeding fuel to the atomiser. While the influence of the main jet grows as the throttle opens....... it affects everything above the idle circuit. Hence why achieving the perfect tune can be difficult/time consuming.You've already said you have little time, so how to do itProcedureFind a main jet that is happy at WOT...... say 98.Start with the needle on N3 (does it have 5 notches?), tune the idle circuit with the air/fuel screw, and then test performance at low to mid throttle. Take notes on how happy the engine is at max revs in gears 3, 4, 5.
Put the needle on N4, and repeat the above........ is it better or worse...... if worse, go to N2 and repeat the above.
This sounds laborious (and it is)........ but it's a defined procedure that will quickly lead you to Nirvana (there is no quicker method than this, as you will not be messing around in a fog of despair)
Note:If you have damaged your top end...... all the above will tell you very little. Your loss of power is a strong indicator, particularly after a seizure. You may need to bite the bullet, and strip the top end - taking all of about 20 minutes. Tidy the piston with fine carborundum paper, removing hot spots, and blow past carbon deposits. Clean the ring grooves. Break the cylinder glaze. Wash off Oil up, and assemble. It might just be almost as good as new
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benny
Scoot Member
Posts: 50
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Post by benny on Apr 29, 2015 8:12:10 GMT -5
Lost me at carbonundrum. Lol. Wet and dry work?. and yes the needle has 5 notches.
Looks like I'll pull the top end off and clean + inspect on the weekend.
That tuning procedure seems straight forward. At the moment with a 90 in and at the richest notch on the needle or has a very slight splutter from 0 to 1/8 throttle. So seems a bit rich. with the 95 it spluttered heaps at low throttle. Even stalled at under 1/8 throttle.
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Post by fe53series3 on Apr 29, 2015 9:58:59 GMT -5
Lost me at carbonundrum. Lol. Wet and dry work?. and yes the needle has 5 notches. Looks like I'll pull the top end off and clean + inspect on the weekend. That tuning procedure seems straight forward. At the moment with a 90 in and at the richest notch on the needle or has a very slight splutter from 0 to 1/8 throttle. So seems a bit rich. with the 95 it spluttered heaps at low throttle. Even stalled at under 1/8 throttle. Yes very fine wet and dry, used with a very light oil like paraffin/kerosene. I've re-done the graph for you with just N1 and N5, as this will simplify it and hopefully aid your understanding: Note how N1 at idle (doing no work) is feeding the same amount of fuel as N5 at 30% throttle opening! Imagine how fast you might be going at 30% throttle, and how much fuel you'd be using....... yet that's what N1 is delivering at idle..... and it could be even more than that. N3 is between these two extremes, so it is the best place to start.
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benny
Scoot Member
Posts: 50
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Post by benny on Apr 29, 2015 19:07:45 GMT -5
So with this. I think I'm at or very close to correct main jet. my second soft cease was with this main (90) and the needle at middle notch (3).
I think middle notch may be a tad lean but my experience may be incorrect as i already had 1 soft cease beforehand. Which as mentioned before may have made a tight spot.
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Post by oldgeek on Mar 7, 2020 6:40:01 GMT -5
Hi guys, know this is an old!0post. Been having almost the same issue. Got an old 70cc stage6 cylinder set up on my chinarelli. I was experiencing hanging idles and changed to a new carb and almost solved the issue. Now what i’m dealing with is when i ran the scooter, it was idling fine ran for the first 30secs to a minute then cuts off the power on the engine all of a sudden like turning the cut off switch. No bogs whatsoever. It starts fine and idles fine after then cuts me off again. Starts fine everytime but will just cut me off after a few seconds. Poor me as power cut off going up a hill haha. Is it soft seizing or am i just not getting enough fuel from the carb as it empties the bowl so fast when revving. Running lean? Or is my sports cdi busted? Currently using 95 main jet as the 102 main jet also had the same issues and cut me off but it also ran poorly with that size jet and bogs badly. I got better response with the 95 main jet and really thought i fixed the issue until i got cut off lol. Anyone had the same issues or expertise?thanks Please continue with the thread you started, It will be easier for everyone to assist you if we work through your issues in one place.
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neogie
Scoot Enthusiast
Posts: 142
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Post by neogie on Mar 7, 2020 7:40:02 GMT -5
Noted
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