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Post by colemanscoot on Oct 17, 2019 10:34:55 GMT -5
I just installed the Glixal 47mm Piston/Cylinder kit from Amazon which is cylinder and piston/rings only, I did also install an "upgraded" carburetor that is adjustable since mine had 0 adjustments on it at all (couldn't even adjust the idle). I will say it made a huge difference on bottom end and mid range. I only bought these 2 scooters to ride around campgrounds and needed a little more power for the hills and now I have it. I do have one issue though and I'm hoping someone can help. Since the install, when accelerating the engine sounds like it is running with no air filter at all on it. I am using the stock airbox/filter and tubing so I'm not sure what is going on. I have triple checked that everything is hooked up and nothing came apart, but for the life of me I cannot figure out why it sounds like it does. It sounds just as it did before at idle and just off idle, but under a more aggressive acceleration it makes this noise. Anyone experience anything like this after an install? Could it sound different because I'm re-using the stock head or because the PAIR system is still in use? Is it a jetting problem (I don't really think that it is). Just to be clear the timing is correct as well as valve lash setting at .004. Seems like it should be simple to figure out, but I just don't know what is going on and this is the first time I have ever big bored a scooter. Any help is appreciated.
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Post by scooterted on Oct 17, 2019 10:42:10 GMT -5
Fuel mixture can definatly make a difference in how an engine sounds. Youre 100% certain yoi have a proper main jet installed?
Is there a way you can get a recording of this sound?
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Post by colemanscoot on Oct 17, 2019 11:06:23 GMT -5
I can try to get a video at some point. As for the proper jet, I honeslty don't know what is in it right now. The carb was installed just before the big bore kit and it ran just fine, no hesitation or missing and no odd sound either. Then the next day I did the big bore. I don't know how to explain the sound other than saying if you take off your intake tube from the carb and rev ride the scooter, that's basically the way it sounds now. It's the weirdest damn thing ever.
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Post by scooterted on Oct 17, 2019 11:59:21 GMT -5
That is your problem. You MUST retune. Get a bigger main jet asap. Edit: With my 47mm setup (stock head, intake, exhaust and an a9 cam) i wound up with a 92 main jet. I started at a 98. Roughly 300-400 ft above sea level. To reiterate, you're probably too lean. Get a jet kit asap. I wouldnt even ride it until i got a richer jet installed. Here is an excellent write up on carb tuning. www.49ccscoot.com/faq/carbtune.html |
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Post by colemanscoot on Oct 17, 2019 13:08:48 GMT -5
Thanks for the info, I will get a jet kit ordered and start the process. My elevation is about 1050 feet, so I will check out that article you sent and see if I can get it figured out.
I do appreciate your response.
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Post by scooterted on Oct 17, 2019 13:34:14 GMT -5
Good luck.
I forgot when i mentioned what jet i settled with. That 92 main jet was with a larger "20mm" carb, it had a larger venturi than stock, thus needing a larger jet.
Iirc i was at 88 with the stock carb.
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Post by colemanscoot on Oct 17, 2019 18:32:51 GMT -5
Ordered a jet kit (hopefully they are the correct size and pitch). I did pull the plug when I got home and yes it is definitely running lean.  |
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Post by colemanscoot on Oct 17, 2019 18:34:14 GMT -5
Just out of curiosity, does the A9 cam make much difference? I will be leaving the stock intake and exhaust on because of only using it at campgrounds so I am wondering if I should even bother changing out the cam at some point based on that?
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Post by 90GTVert on Oct 17, 2019 18:39:45 GMT -5
It could pep up the high RPM performance a bit.
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Post by GrumpyUnk on Oct 17, 2019 19:11:05 GMT -5
When installing the 'boot' that connects the air filter housing to the inlet side of the carb, it is easy to miss getting the lower edge of the boot over the lip of the intake bell. That could cause some noise. Additionally, you are drawing more air per stroke through the carb, at lower rpms than before. I expect the carb to sound a bit 'rorty'. That being the sound of a carb that is working. One thing I did on a GMW/Wolf was to remove the tiny ribbed air tube on the inlet side of the airbox. Take off the air cleaner cover, and you may see a small tube on the left end of the airbox, just inside the tube that allows air in. About 2" or 5cm long, and about 1/2" in diameter, with an angled mount flat. Dunno if it made any difference, but it just looked very restricting.
A 47mm bore will make a good change in the carb sound. Almost as if it actually has some horsepower. You should notice the increased acceleration more than anything. An A9 cam as I understand, should increase power at the higher rpms. Vague, I know. But you can read all about the other 'performance' versions, with different numbers after the "A".
tom
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Post by ozziephil on Nov 19, 2019 22:28:54 GMT -5
It's probably pinging from using the stock head especially if you used the thin head gasket. It sounds like a rattle that gets worse on acceleration.
The small combustion chamber with your bigger piston and bore gives huge compression with a stock head.
Either get another head or get your dremmel out and grind it out bigger. Also use high octane fuel.
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Post by jackrides on Nov 20, 2019 13:40:48 GMT -5
GrumpyUnk, yes it makes a big difference. The inner snorkel acts as a intake silencer and restricts airflow. If the total open area of the outer snorkel doesn't exceed the open carb (venturi) area by at least a little that is also a restriction (in my opinion). Both of these changes will lean the mixture. 'Rorty' increases power more than stickers!
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