benny
Scoot Member
Posts: 50
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Post by benny on Apr 28, 2015 5:02:08 GMT -5
So some may know i put a bbk sport exhaust and took the snorkle out of standard air box. was running a 90 main jet but had what i believe is a soft cease today heading home from work. As i was cruising at 70 it just cut out dead. I slipped off to the side of the road and hit the starter and it fired up straight away but I've noticed a bit of discolouration on my exhaust. Seeming like it has gotten hot.
Now i used to get 80km/h with the 90. i put a 95 main jet in when i got home and put the needle to the top clip but it still has a slight hesitation as i take off and my top speed has gone down to 75 km/h.
Is it running too rich and maybe a 92 or 93 main jet bring my speed back up to 80? or have i just done damage and killed my top speed a bit?
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Post by 90GTVert on Apr 28, 2015 6:17:23 GMT -5
That sounds like a soft seize. Moving the needle clip up leans the mixture. Not sure if that was what you were going for or trying to correct a rich condition from the 95 that way. If it's seizing with a 90, the 95 is prob a safer jet to be using but you may get more power back with a 92-93 with added risk if the weather gets cooler or more dry it could be back to seizing temps easier.
If you can't get the power back, check your piston. The crown can start to collapse a bit if it runs really hot and it lowers compression. A lot of times you don't get that and you get a hole in the crown straight away (not in your case since it wouldn't start if so).
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benny
Scoot Member
Posts: 50
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Post by benny on Apr 28, 2015 7:24:40 GMT -5
Yea moved the clip up to help off the line as I'm sure it's rich with the 95.
Now here's a nice noobe question.
Is there that much of a difference between 92 and 95 main jet?. and does running rich main bring to speed down?
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Post by humanshield on Apr 28, 2015 7:55:01 GMT -5
Yea moved the clip up to help off the line as I'm sure it's rich with the 95. Now here's a nice noobe question. Is there that much of a difference between 92 and 95 main jet?. and does running rich main bring to speed down? If your engine is on the brink of lean or rich then yes it CAN make that much difference. Yes running rich CAN reduce top speed. Anything other than "optimal" mixture causes a loss of power, thereby reducing performance
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Post by katastroff on Apr 28, 2015 8:45:26 GMT -5
Yea moved the clip up to help off the line as I'm sure it's rich with the 95. Now here's a nice noobe question. Is there that much of a difference between 92 and 95 main jet?. and does running rich main bring to speed down? If your engine is on the brink of lean or rich then yes it CAN make that much difference. Yes running rich CAN reduce top speed. Anything other than "optimal" mixture causes a loss of power, thereby reducing performance Just want to add that you would be better off on the rich side then on the poor side if you dont have the main jet yet to go optimal.
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benny
Scoot Member
Posts: 50
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Post by benny on Apr 28, 2015 8:48:36 GMT -5
Thanks guys. Yea ill be keeping the 95 in and have ordered a 92 and 94.
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Post by humanshield on Apr 28, 2015 10:50:28 GMT -5
Just want to add that you would be better off on the rich side then on the poor side if you dont have the main jet yet to go optimal. "Poor side" lol
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benny
Scoot Member
Posts: 50
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Post by benny on Apr 28, 2015 18:32:04 GMT -5
now the scoot hesitates off the line like its being choked. im assuming its too rich even tho i have the clip at the top.
and somwere between 3/4 and full throttle it also hesitates and dies abit before powering out.
also noticed my exhaust continues to go a darker purple sort of colour despite now being on a 95 main jet.... just at the header and where the bend is going up to the silencer. but it is a leo vince pipe unpainted with just clear coat over it? so maybe its normal?
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Post by niz76 on Apr 28, 2015 18:42:07 GMT -5
If you have the clip set to the top of the needle, then u have it set to it's leanest setting...
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Post by 2TDave on Apr 28, 2015 18:45:13 GMT -5
I've always tuned my main first with the needle in the middle or a notch rich.
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benny
Scoot Member
Posts: 50
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Post by benny on Apr 28, 2015 19:34:38 GMT -5
Yea. My jets go up in increments of 5. so i have a 80 85 90 95 100 105 110.
When i first put the bbk on i put the 100 in and it choked and bogged down and after removing the carb i noticed there was a fair bit of fuel in the intake which is why i guessed it's so rich that it's over fuelling. so i went down to a 85 which it felt really wild and would just take off like a rocket. After a few kms of riding it soft ceased and had some light purple on the header. Which points to running lean. So i went to a 90. That toned the acceleration down a tiny bit but was still usable.
Now on the way home from work it soft ceased again. With a now darker purple on the header. now I'm at a 95 with stuttering off the line and lower top speed to try and keep the scooter from combusting. :/. and this is why the needle is at its leanest to compensate for the rich jet from take off.
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Post by moofus02 on Apr 28, 2015 19:55:31 GMT -5
Be careful with a lean needle setting. More 2t's burn up from a lean mid throttle spot than anything.
Sent from my SPH-L720 using proboards
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Post by fe53series3 on Apr 28, 2015 20:16:28 GMT -5
i put a bbk sport exhaust and took the snorkle out of standard air box. was running a 90 main jet but had what i believe is a soft cease today heading home from work. As i was cruising at 70 it just cut out dead. Seeming like it has gotten hot. Now i used to get 80km/h with the 90. i put a 95 main jet in when i got home and put the needle to the top clip but it still has a slight hesitation as i take off and my top speed has gone down to 75 km/h. Now the scoot hesitates off the line like its being choked. im assuming its too rich even tho i have the clip at the top. and somewhere between 3/4 and full throttle it also hesitates and dies abit before powering out. also noticed my exhaust continues to go a darker purple sort of colour despite now being on a 95 main jet.... just at the header There are potentially a few issues here. First off, I'd agree with 90GTVert..... it sounds like a soft seize. BUT...... this could mean that the damage is done....... and everything you do afterwards is tainted by this. The motor could be overheating because you've now got a tight spot...... changing the jets, won't change that...... it could be too late. Looking at your evidence....... under normal conditions..... if you were lean on 90 (but running sort of okay), then a jump to 95 should have put you safe. Yet you are suffering overheating still. You really need to check your plug colour, as it will indicate if you are running rich or not. The first thing you need to know.... is that you are running a touch rich. Once you know this, then you can drop the main jet a size. However.... putting the needle on the top notch is not a good idea, unless you know what your doing (and have examined the needle specs). Raising the needle will have a huge effect at 'take off' as the taper is pushed further into the throttle opening (air stream)........ hence why you are stuttering at take off. Have a look at this graph of a typical PHBN needle at its different notches: You can see that when the needle is at its top notch (N5) it is still only getting the same fuel as at idle...... when the throttle is 20% open! Also note how much less fuel it is getting throughout the throttle opening, all the way to 100%. Every needle is different.... but it is critical to understand what needle you are using, and it's dimensions. I would put the needle back to the middle notch...... and check the plug colour.If you can get it darkish...... and you still have problems...... then it's a top end strip. Don't panic, if this is the case...... a bit of tickling, and it can be saved..... ..... with a bit of luck
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benny
Scoot Member
Posts: 50
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Post by benny on Apr 28, 2015 21:16:46 GMT -5
hmm.. so both of my soft ceases happened at about 3/4 throttle is it possible that maybe i had the right jet at 85 or 90 but lean needle setting causing the overheat? its hard having work all day then the mrs and kids after work. there isnt much test n tune time .
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benny
Scoot Member
Posts: 50
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Post by benny on Apr 28, 2015 23:50:20 GMT -5
after more reading it seems the needle effects 1/4 right up to just beyond 3/4 throttle.
so it seems i may have been at the correct main jet with either 85 / 90 but i should have richened up the needle position. as thats where the soft ceases happened.
it keeps rattleing in my head when i had my 85 in it took off like a bullet. and as has been said the best mix will give the best power. now it seems overheating if leaning out at 3/4 throttle..
time to go back to 90 with clip up. maybe rich as i can and see what happens.
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