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Old 06-06-2011, 10:42 AM
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mapbike mapbike is offline
Motorized Bicycle Elite Member
Join Date: Mar 2010
Location: Central Texas
Posts: 5,379
Default Re: I really can not figure out which motor to buy please give suggestions!!

I have 2 good running BGF 66cc's right now that will both hit well over 30MPH and with a 36T sprocket like biknut mentioned you can expect 30-32MPH cruise speed if you do some other mods like SBP expansion chamber, better plug and better plug wire with a very well tuned carb. if you are in the 205# or less weight class, I weight about 203# at last weight in and I can cruise all day at 30-32 with my 36T sprocketed Karaoke bike and it tops out @ 41MPH on the flat with NO! (zero) head wind, the manic ported intake is a great addition also.

I have anothe BGF 66cc that will hit 35-36mph on the flat ground with NO! head wind and it is also completely stock except for the NGK plug, it's on a mountain bike that has a 41T sprocket and it cruises nice @ 26-28mph, it would do a nice 30MPH cruise also but this engine just has too much vibration for it to be comfortable at that speed with the 41T sprocket, this engine also has over 1,200 miles on it now and still runs like a champ.

these engine as you will find by doing some reading are a crap shoot no matter where you buy them and every one of them needs some mods to be at all dependable, including better mounting studs, better carb gasket, better spark plug ( NGK B6HS ) take the head nuts off and add a extra flat washer and then retorque head, and for sure the best speed and torque increase you can do right off the bat is a better exhaust, the cat-mufflers that come with most of these kits are so restrictive that they dont pull good at all above about 25-27MPH from my experience, and just an exhaust change and a good tune on the carb. after about 150miles of breaking time will have you in the 35 MPH range easy with a 41T or 44T sprocket, but RPM's will be way high so I suggest the 36T if you aren't in an area that has loads of steep hills you have to climb all the time.

Plenty of us guys on here that will jump in and help you out with all the info. you need to get your engine going good if you have the mechanical ability to do the mods and the tools to do them, if not I would suggest you stay awauy from the China Girls (HT's ) and consider a EZ motrobike set up or a simple friction drive set up from Thats Dax or something down those lines.

These China Girls are great fun if you have the ability too & like to tinker on them, because that is a never ending part of this HT engine my experience.

I do have great success so far with the mountain bike and have not had to put a wrench on that bike in months......but I dont ride it everyday either and if I did I'm sure I would have to piddle with it a bit more.

If you do go with the China Girl engine kit just remember to mount it correctly and upgrede the rear studs..........with a higher grade and DON"Tuse any rubber or anything under the mounts, get them mounted solid and secure to the bike frame or you will have trouble, especially the rear mount, it takes a beating and must be very secure, and then on the front it needs to just be solid so it cant slip or move side to side and the bike you use will determine what route you will need to go with he front mount, different frames require different mounting mods for the front so be aware of this also.

Best wishes on whatever you do.......and stay tuned in here for all the help & advice you will need to know on what you should do in the questionable areas you may face on the mounting issue and the tuning.

I dont always ride WOT, but when I do..I do my best to keep the rubber side down..Ride safely my friends!

Last edited by mapbike; 06-06-2011 at 10:48 AM.
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