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Post by flqu06 on Apr 13, 2014 20:01:48 GMT -5
Since new my scoot has a burble. I call a burble a situation where Im riding and let off the throttle and coast a bit then roll back on the throttle and get a sputter (burble) then it will go. Sometimes from a standing stop Ill get the burble when taking off. I hate it most when going into a turn then getting back on the throttle and get it. I will list everything that i have done to eliminate the problem and Im hoping someone can figure it out.
All fuel lines and filter have been replaced twice since putting on 3000 miles.
I have tried 3 different carbs in both 18mm and 19mm. One without an acellerator pump
I have eliminated the choke
I have tried many NKG irridiums due to jetting.
I have tried several AF settings from perfect high idle to rediculous rich and lean settings
I have tried larger and smaller pilots and mains but the 1/8 to 1/4 throttle does not point to a main jet problem
I have repalced air filter
I have tried 2 orange coils
I have tried various CDIs
I have searched for vac leaks and found none.
I have tuned the variator which shouldnt effect it and i know its not a slip.
Im stumped at this point. I have even taken a carb off of another perfectly running stock 50 and git the same result. The idle is perfect and all seems to be just fine...except for this one issue. It does seem mor pronounced when scoot is warm and it regardless of having a choke or no choke.
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Post by usmcdoc on Apr 13, 2014 20:15:24 GMT -5
Im stumped at this point. I have even taken a carb off of another perfectly running stock 50 and git the same result. The idle is perfect and all seems to be just fine...except for this one issue. It does seem mor pronounced when scoot is warm and it regardless of having a choke or no choke. With all the above..plus the line above..where you even get the same with a new or different carb..what would you guess to be a potential problem?.. A hint..'It's more pronounced when warm..choke or not'... If you guessed a bent..burned or improperly set valves...I would say you are now looking in the right direction.. @ weeks a go I had a guy I did some roofing for..give me a scoot with 275 miles on it. No matter what he did it would not run right. I would gurgle and bog when warm and trying to re-accelerate especially. 2 things I found wrong with it.. 1 A burnt and slightly bent intake valve and 2. The timing wheel was stamped about 18 degrees off just as the one 90GTVert found on an old Sunl he owned. Timing being off most likely is what bent the valve..then the leak made it burn. Doubtful yours is off time with an incorrectly marked timing mark. But if a vales is bent..burned..poorly seating or out of adjustment..you will get what you are getting..since you ruled out carb..carb jetting and air leaks already.. So that is what I would look into..since you covered all the other bases..  |
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Post by Upgrayedd on Apr 13, 2014 20:17:03 GMT -5
you've tried changing the clip setting on your jet needle i figure, ya?
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Post by flqu06 on Apr 13, 2014 20:26:44 GMT -5
That list was so long I did forget to mention that ive checked the valves a few times and the needle raised all the way and lowered all the way as well.
The timing should effect top speed? I can hit 44 on the flat. Another thing is i notice my mileage is low, somewhere around 50 mpg. Other tha this roll on burble this thing runs great!
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Post by usmcdoc on Apr 13, 2014 20:33:40 GMT -5
That list was so long I did forget to mention that ive checked the valves a few times and the needle raised all the way and lowered all the way as well. The timing should effect top speed? I can hit 44 on the flat. Another thing is i notice my mileage is low, somewhere around 50 mpg Ok..I see. Also what jet size and what type of air filter? I tend to get troublesome 'burps n gurgles' mid range when I use a free flow air filter..no matter what size jet I use or needle clip position...it just seems some customers scoots do NOT like a free flow air filter.Put the stock box back on and they run without as much as one tiny hiccup.. Do you know why that is??.. Neither do I...I just know they are like that..the old "some do..some don't..some will some won't"  But I can tune them to run just as strong and fast with a stock airbox anyway.. once you remove the restricter in the snorkel that some of them have.. |
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Post by flqu06 on Apr 13, 2014 20:40:25 GMT -5
Im running a stock air box. Fully sealed with RTV to make sure theres no leaks.
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Post by usmcdoc on Apr 13, 2014 20:58:08 GMT -5
Have you done a compression check with a gauge??.. Here is why that is important..a piston/ring leak or valve leak on the up-stroke is a compression leak and if present..on the down-stroke it will become an internal vacuum leak. Make any sense?.. Compression and vacuum go hand in hand..the only difference is the pistons direction of travel.. So I would check that as well..I would find out what that is first as many only think of a vacuum leak as an external thing..  |
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Post by flqu06 on Apr 13, 2014 21:04:09 GMT -5
Wont a tester only show the highest compression regardless of the stroke?
It doesnt use a drop of oil either.
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Post by Upgrayedd on Apr 13, 2014 21:13:36 GMT -5
Hey flu/doc.. that PAIR system on the valve cover... any chance that could be malfunctioning and causing issue? *edit* flqu .. not flu. sorry about that  |
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Post by Upgrayedd on Apr 13, 2014 21:17:00 GMT -5
50mpg seems pretty low for a 50 to me, idk how much they vary for fuel consumption but i'm all up in the hills and i get on it and still pulling about 70mpg (actual mileage via gps)
*and im running the 47mm/72cc bbk
u sure ur not running real rich?
dang ole maybe usmc on to something with valves there.
dunno. that 50mpg really seems off to me tho.
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Post by usmcdoc on Apr 13, 2014 21:18:54 GMT -5
Wont a tester only show the highest compression regardless of the stroke? It doesnt use a drop of oil either. Yes..and if your compression is low on the pistons travel up...vacuum will also be low on its way down. Remember an engine is nothing more than an air compressor right? Think of your vacuum cleaner..when it won't suck up a few pieces of your dogs or cats hair...or dust...you feel little suction...but also you notice the vent the air blows out of is weak too.. correct?.. See how compression and vacuum go hand in hand now? "For every action..there is an equal and opposite reaction" <-- Remember that from School? Thought like Algebra you'd never use that theory?.. Well you are now.. Sir..  |
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Post by flqu06 on Apr 13, 2014 21:38:57 GMT -5
One thing i havent checked is the fuel tank venting. I may remove the cap to see if that helps then go from there. I have one of those locking caps and no idea if thers a vent hole on it.
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Post by flqu06 on Apr 14, 2014 14:32:29 GMT -5
So I got another carb today from Monsterscooterparts and its a 19mm CVK. Made in Japan. Put it on and no sputter. Drove a few miles still no sputter. BUT it was a little flat on the top end so i opened it up and could barely read the second number after the 7 so it was 71 maybe? So I popped in a 79 and still no better. Tried an 80 same. Popped in an 85 and that was the magic number. So far all the carbs on my stock 50 that i have used need big jets! Anyway it runs great and that sputter is gone.
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