KymcoForum.com
Scooters - 50cc => Agility 50 => Topic started by: Deejays50 on October 09, 2013, 10:41:29 PM
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Hey guys,
I recently put the stock head back on my BBK (exhaust studs snapped, figured it was easier to swap the old head) and went for a ride.
I went fast down a hill and shortly after the engine was blown (very high heat).
I'm not sure the actual size of this BBK (I didnt install it, some moron did), i measured the cylinder wall inner diameter with a caliper and it measured 49mm. Can you help?
I want to do an 80cc kit. I currently have a MRP exhaust, open cone air filter, and I believe a 90 main jet. Do I need to go bigger with the main jet?
Also, where is the most trusted place to buy BBK's from with quality in mind? I want to do the large head as well.
Thank you guys in advance
PICS
1) http://i41.tinypic.com/28mfva9.jpg (http://i41.tinypic.com/28mfva9.jpg)
2) http://i40.tinypic.com/2yorbx3.jpg (http://i40.tinypic.com/2yorbx3.jpg)
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Better to go with a new motor maybe a 125.
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Better to go with a new motor maybe a 125.
Why a new motor? Just needs top end.
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Yup...
BTW... Nice piston dude... DAMN! ;D ;)
We all learn the hard(expensive) way sometimes. Now you can build it stronger, build it faster.
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Better to go with a new motor maybe a 125.
Blue, what 125 motor is a bottom mount motor that could be swapped in?
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Other opinions (http://itistheride.boards.net/post/50774/thread).
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Reported to moderator
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Lol I take it linking to another forum isn't allowed.. take that link down!
Blue, what 125 motor is a bottom mount motor that could be swapped in?
Yes, exactly. otherwise I would have done this already.
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To me it looks alot like premature combustion. :)
If your piston is 49mm in diameter, your displacement is a little over 75cc. :)
Given that the original engine has a compression ratio of 11 and a displacement of 50cc, it is found that the combustion chamber is 5cc, but it might be a little bigger because of your piston design. Anyway, if we think that your piston has not changed the combustion chamber size, your compression ratio is now at 15, but since these engines are often only around 80% efficient at filling the combustion chamber at the best rpm, your final compression value is most likely 12 (compression ratio x pressure in cylinder at end of intake). It is usually recommended to use 100+ octane when having a final compression value of above 11, according to Elsberg Tuning (http://www.elsberg-tuning.dk/supercharging.html). :)
Premature combustion is when the highest pressure comes too early and is caused by the mixture either being ignited too early or that the mixture temperature is too high due to exessive compresion. Because of the way gases behave, the temperature rises even further when this happens and the problem becomes worse. :)
It is usually handled by having the right mixture and either decreasing the compression ratio or using higher octane fuel, both along with adjustments of the ignition timing, which is 28 degrees before TDC (above 4000 rpm) with the original ignition. :D
Another kind of controversal way of dealing with it is to cool the piston with an oil squirter, so that the temperature of the mixture wont raise too much. :D
But hey! It could also be as simple as some dirt getting into your engine through your air filter and wedging between the piston and cylinder, breaking the piston it seems and then the metal pieces has been thrown around in the combustion chamber. :p
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Awesome informative stuff there! Thank you!
I got a scrappydog kit put in (80cc) with the large head.
I tried to put the stock airbox back on but the scooter bogs and cracks so badly around 1/2 throttle. Here is a pocket cam video I recorded: Agility 50 1/2 throttle breakup (http://www.youtube.com/watch?v=tOsFBwkcQfs#)
I had a 95 main jet in there and the plug in the scooter was pretty white with no signs of color ---> http://i44.tinypic.com/68ab12.jpg (http://i44.tinypic.com/68ab12.jpg)
After that, I put in a 100 main jet! Just as bad if not worse. Still no color on plug.
I swapped the carb from a Roketa into my scooter that has a 80 or 85 main jet and the popping was less, but still does it on occasion, but the scooter has very little power.
What should I do?
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I dont have your bike (I have the Like50) but I can tell you that with the airbox restrictor out (Note even open cone!) my MJ was up to 105. Stock restricted is 78 MJ.
Dont know if that bit of info will help ya but good luck
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I dont have your bike (I have the Like50) but I can tell you that with the airbox restrictor out (Note even open cone!) my MJ was up to 105. Stock restricted is 78 MJ.
Dont know if that bit of info will help ya but good luck
Where is the restricter specifically?
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Its very very similar to the one in this thread
http://www.kymcoforum.com/index.php?topic=8060.0 (http://www.kymcoforum.com/index.php?topic=8060.0)
There is a rubber tube that goes to the airbox. At that connection, there is a removable piece of plastic on the airbox inlet that reduces the diameter of it.
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Thank you!
I'm going to look into this, but I think I may just leave my 100 jet and go back to uni-filter. Stock airbox is aggravating the hell out of me.
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I put the 100 main jet in, shimmed the needle with two washers, put the uni filter back on and the engine is alive again.
But, I did a 30% throttle run with little to no idling. Went for a long ride at 30% throttle cut the key off and came to a rolling stop.
Pulled the plug, and it still looks like this:
(http://i44.tinypic.com/2vbs9xc.jpg)
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Can't see the smoke ring. Look for the smoke ring on the white insulator.
Check this out:
http://www.rays-shop.com/2010/01/how-to-read-your-spark-plugs-they-are-telling-you-whats-going-on-in-there/ (http://www.rays-shop.com/2010/01/how-to-read-your-spark-plugs-they-are-telling-you-whats-going-on-in-there/)
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how did he get the porcelain out? Can't see squat looking down into the plug.
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He didn't "get it out". He cut the threads off. Hence the name plug chop. A hacksaw or cutting wheel can be used to remove the threaded outer ring.