KymcoForum.com
Scooters - 50cc => Agility 50 => Topic started by: Geos on August 29, 2012, 06:30:29 PM
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I upgraded my scooter to a motofine 72cc BBK. It was an easy install and it ran great for about 70miles. Then it started to bog down when i try to get past 20 mph. If i keep gasing it it will get past the bogging some times, but it takes a lot of work to get it there. I had a 85 jet in it, so i tried putting in a 90 and there was no different. I have the stock air box still on it.
Could I have lots some compression? I am using the head that came with the kit. Should i try putting the stock head back on?
I am grateful for any help.
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try a plug chop to see if running lean or rich. this will show if the jetting right but would think you will need to change to open filter to get more air into the cylinder you will also have to up jet the fuel as well prob 100- 110 jet when after market filter.
soundes like you need more air and fuel.
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I know that i will need to upgrade the amount of air and gas. but the part that i can't figure out is why it ran fine before. I can't really do a plug chop if it can't get it up to wide open. I could understand if it was to lean befor the new jet, but with the new jet and the same amount of air, wouldn't it be richer?
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richer mix yes but not enough oxygen. you need the correct balence.befor the ballence was prob about right but to lean. now you up jetted to 95 still low oxygen so you need to rase the air intake. most on hear run 90 -100 jet just on after market filter. so with your bbk kit you will need a higher jetting still.
the reason it prob ran befor is the fuel and air mix was balanced but way to lean. now you up jetted to much fuel to air.
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i didn't upgrade the jet til afte i had problems. I will try giving it more air
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Im still 50cc's and run a 92 jet with an open filter.
Could be you were running lean and now you got compression issues from that but you'd need to do a test to check it.
If compression is ok it prob is too small a jet or too little air or both. The bbk will need more of both to run im sure. It does sound like its maybe not getting enough air in to me, had to tell tho without seeing it. You can take a drill to the air box of you want to keep that instead of going to an open filter. I did that a while ago and drilled about 10-12 1/4" holes in mine on the front cover which did let in more air, had to upjet with that so it def worked. Just need to watch that water doesnt get in.
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I tryed a differnt air filter (less resistance) and tryed it with no air filter in the box. It acted the same.
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My 72cc ran fine with the stock airbox and an 86 jet for a long time...
It's only with a 85cc that I found the stock airbox too restrictive to get a reliable jetting, although even then it would run all the way to it's top speed, and even with an 85cc it proved to be sufficient to just open up the narrowest passages in the airbox and run it with a 92 jet....
I think your problem is not the size of the main jet since it it was running fine before, have you tried cleaning the carb and checking for air leaks, like a cracked manifold ?
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Also check the main jet isnt blocked or dirty.
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but it takes a lot of work to get it there. I had a 85 jet in it, so i tried putting in a 90 and there was no different
..do you mean that your scoot is revving relly high? or very low...
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..i would think a 72cc needs more air than a oem airbox can deliver...
..aaannnd closer to a 100 jet should definately be in order....
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I agree. Probably a little lean. I was running a 90mj in mine..with an open air filter
Where are you located?
Are you still using the oem exhaust?
Did you check for air leaks?....re-torque after the 1st heat cycle?
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I changed the gas and cleaned the carb. I did a plug check after i babied it up to wide open, the plug was light tan. we also recheck the valve clearance. it seems to be a little better, but it still runs ruff. My friend that has been helping thinks it sounds more like it isn't firing and there for bogs down. When it is running ruff it seems louder. As it got cooler tonight it was very hard to start.
I do still have stock exhaust. And I live in southern michigan. I am not sure how to check for air leak other than i sprayed some starter fluid are round the carb while it is running and saw no change. I have not tryed re-torqeing it. I will try that tomorrow.
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Maybe your CDI is on its way out ?
Does the engine rev up all the way when you put the scoot on the center stand, or does it bog down at a certain rpm as well then ?
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It revs up all the way on the stand. there doesn't seem like a problem on the stand
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Strange that it seems louder while bogging down or running rough.....
Since the symptoms seem to depend on speed rather than rpm, have you checked your CVT lately ?
Can the rear pulley be opened all the way, are the rollers still round, and does everything move like it should without stickyness or scraping ?
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I took apart the CVT and found that there are 2 cracks in the back plate of the varator . there are 2 good sized cracks that made the varator move unevenly untill it got up to speed. I was going to take it apart today and when Mono posted to check made me want to do it more. I hope this is the cure. But I will drive it more to see. Thanks Mono, and everyone else for your help. I will keep you all updated.
Geos
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..cool, geos..
..can you post pics of this??
..i would like to see this, because i've never seen oem cvt parts fail prematurely...
..wanna see what this looks like...
:o
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I wanna see...I wanna see....I wanna see.........
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it is not oem. It is a KOSO, it came with the new varator.
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...wowww...that's ugly....
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Ouch, that is ugly..
Koso does have some good products but I believe I'd be weary of the vars now.......
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Man, ive never seen that before ???
I ended up using my stock ramp-plate with my race variator last year just cos it fit better and seemed to slide nicer than the one that came with the new variator sl If you still got the oem stock one just use that plate instead. You may need to swap the plastic guides over tho.
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hello...on the subject of the scoot bogging down..i did try my scoot with the original airbox and had the same problem. i tried going down jet sizes but ran out of lower numbers and decided to sling the polini back on with a #96 jet.
i also have a 72cc kit on my kymmi but its a naraku i also run it with a 50cc naraku head, apparently with a big valve head you loose alot of compression almost to the point you may just as well keep the engine stock lol...with the 50cc head my engine is pumping some serious compression, the only thing you need to be aware of is if you do use the stock 50cc head is to check the clearance between the piston and the valves and base of the head otherwise you will smash the piston and kill the scoot in the process.
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Geos, where at in south michigan are you? I live in southwest mich, and could help you if needed. I just helped my buddy tune in a 100cc kit on a jonway scooter
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I live in Adrian.
After replaced the varator part and it ran pretty good for about 2 miles. Then when ever I gave it any gas it would bog down and die. Which ment i got to baby it to my dad's, about 3 miles, only going about 5 m.p.h. >:(
and then baby it back to my friends today to work on it. He milled .001 off the head and cleaned up the valves. we also took the carb apart, again, and cleaned it. We put it all back together and it started right up but was loud. the exhaust gasket was missing. we put it back on and had a hard time starting it. Once we did it had better pick up then it ever has. It started to rain so we didn't ride it to much. Turned it off let it sit for five minutes and it started up. I rode it 3 miles to my dad and left it for the night.
I will try riding after work tomorrow thru out the week. hopefully it is fixed. Next is cab work on the carb and air setup. I don't really want to use the little K&N type, because they are so loud.
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Another update:
My buddy took apart the new head and found that the intake valve was warp as well as the seat. I only had 75 miles put on the head, before it happened. The fuel mix was good and everything else is good. I will drive more to see if it is good to go for awhile. I am going to email motofine to see what they say about it.
Geos
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thats strange man?!?! i wonder what happened for that to occur?? my scoot is still running fine with a smaller head, running on 99 octane "unicorn piss" (the engine runs rough with normal unleaded fuel) still need to do a compression test ::)
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I upgraded my scooter to a motofine 72cc BBK. It was an easy install and it ran great for about 70miles. Then it started to bog down when i try to get past 20 mph. If i keep gasing it it will get past the bogging some times, but it takes a lot of work to get it there. I had a 85 jet in it, so i tried putting in a 90 and there was no different. I have the stock air box still on it.
Could I have lots some compression? I am using the head that came with the kit. Should i try putting the stock head back on?
I am grateful for any help.
Hello, I know this topic is old, but I came to the same issue. Upgraded to BBK 72cc and changed the main jet to #85. It ran fine for 500km, but then, suddently, the power was gone and it ran very slowly. My serviceman found that the carburetor had bad seal (sucking more air) AND the plug was black. This is a contradiction to me. Anyway, the machine runs much better now but still not as good as before. It is unclear what had happened.