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Post by scooterted on Oct 31, 2019 8:41:54 GMT -5
Spare room smelt like a warm summer breeze and I'm now banned from the air freshener Lol
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Post by scooterted on Oct 28, 2019 14:27:38 GMT -5
I did ride it with the domed piston and the stock head. Without detonation.
I did decide to go with the larger combustion chamber though. Im currently waiting on parts.
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Post by scooterted on Oct 28, 2019 14:23:25 GMT -5
Cool stuff.
Would be cool to have a temp job like that.
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Post by scooterted on Oct 28, 2019 7:45:46 GMT -5
You didnt really say what you had done.
By 100cc i assume you mean a 50mm bbk, which is actually around 80cc. You could move up to a 52mm bbk which will put you around 90cc. Then a stroker crank will give you another 5cc-ish.
Gears might get you what you want.
Or you can engine swap. Go crazy, gy6 qmi/qmj with a 67mm bbk, nos and turbo.
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Post by scooterted on Oct 28, 2019 6:56:38 GMT -5
Try calling the vendor? Some are superhelpful. Some.
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Post by scooterted on Oct 26, 2019 10:35:52 GMT -5
FWIW, I have looked at '80cc heads' on the web. They sure look like standard heads with a relief around the circumference. The relief being a circle of some depth apparently at the 47mm diameter of the cylinder. It appears it would allow a bit more combustion chamber volume, but I don't know how much it would matter. If you look, you may be able to see the relief come very close to the outermost spot on the valve seat. IOW, they start grinding(I assume) a regular 39mm head just outside the edge of the valve seat(in the head), and grind for some distance, I expect to 47mm, which in theory would match the edge of the head gasket fire ring. tom That is exactly what they do. I would have compression test* data to prove a lower ratio right now, if i didnt screw up thinking i had 64 mm valves when i actually had 69mm. Oh well. I can wait. *im well aware that one cannot extrapolate compression ratio from psi, bit it is real world evidence.
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Post by scooterted on Oct 23, 2019 19:04:32 GMT -5
Racers are definatly clever. Those stories were interesting. Thanks for sharing.
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Post by scooterted on Oct 19, 2019 19:48:38 GMT -5
You may just need to adjust idle mixture.
Probably worth pulling the carb amd cleaning it. Probably also worth replacing the fuel filter and completely replacing the gas with new.
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Post by scooterted on Oct 18, 2019 8:11:49 GMT -5
On a 139qmb, The enricher uses a 12v heating element to expand the plunger and plug up the enrichment passageway. If you unplug it, it will always be in enrichment mode.
It doesnt immediatly cool off and restart the enriching process completely over again. I didnt time it, but i think it was long enough to pull the bucket, flip the carb over, pull the bowl, swap jets and reassemble. I still allow a few moments of warmup time and a minute or two of riding before making a tuning run, im not sure how neccessary that is.
If you were that worried about it, you could wire up a switch or somthing to the enricher circuit so it maintains 12v while swapping jets.
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stocks
Oct 18, 2019 6:29:47 GMT -5
via mobile
Post by scooterted on Oct 18, 2019 6:29:47 GMT -5
Sure. I stick with mutual funds though, rather than individual stocks.
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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 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 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 scooterted on Oct 16, 2019 19:03:29 GMT -5
I installed my new 50mm airsal bbk setup on my 139qmb today. Wont start it until this weekend probably.
For curiosity, I did a preliminary comprssion test, 215psi. Pretty high, and thats while cold, WITHOUT ring breakin, im interested to see how it changes after breakin.
For comparison, With the 47mm bbk (and the same stock head) i had 205psi warm, after breakin.
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Post by scooterted on Oct 16, 2019 11:33:20 GMT -5
I have a 50cc Taotao with a BBK. 50mm piston, big valve head, A9 cam, no rev CDI, performance exhaust and 40/17 final and a 20mm CVK carb.The CVT is banging around. It was hitting 50mph now it struggles to do 40mph. It's starting very hard so I did a valve adjustment and still starting hard. Could my timing chain have jumped a tooth? Carburetor problem? I installed the 49/17 last season? They are pre pressed finals? Youll have better luck starting a new thread in the 49cc 4 stroke troubleshooting forum. As for as your issues. Since the cvt is clunking, open it up and have a look. Hard starting, i would spray the passages out in the carb, have a look at your idle mixture and do a compression test. Also, the performance cdis advamce timing so much it can be hard to start.
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