Engine Options?

Wild Bill said:

Im not sure about Oregon but most states you have to have a drivers license to ride motorized bicycles. As far as engines, at 280 lbs I would go for a Harbor Freight 4 stroke because they have more torque that a typical 2 stroke.

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Im 6'5" 305 lbs and my 66cc 2 stroka pull me up hills no problem as long as you break it in proper it will do just fine I may suggest the NT speed carb it is a lot cheaper than the cns and just as good if not better without all the hassle If you ride in a congested city grid with lots of stops and short blocks, a 44 tooth (stock size) or larger sprocket may be best. On the other hand, if you're in a rural area and have long stretches of road to travel, try a 40 tooth. he will still have to pedal to get going but once he is rolling he will be all set .. unless of course you do not mind spending the extra o get he 4 thumper

vonericson said:

Awesome and thanks for all the great feedback! I think I'll give the 80 a shot, swapping out the OEM carbs right away same with plugs, air filters and finally rounding off with a nice little tune pipe and gearing down with a smaller sprocket for a bottom end boost then I guess I'll just have to keep my fingers crossed and hope they will stay upright pulling hills! If nothing else it should be a fun learning (slightly expensive) experience for myself and my brother in law.

Quick side note, I got my hands on a wrecked Yamaha 750 (totaled front end) for dirt cheap and I've got my eyes out for a used trike bike that I have some insane plans in the near future for and possibly a laydown recumbent racer concept I'm working up in AutoCAD I'll keep posted as I update these!

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I would recommend keeping the NT carb and tuning it by a jet size reduction, plug wire and boot is good to chnage up front and a sbp expansion exhaust is a good choice.

You mentioned a smaller sprocket to " boost the bottom end" a smaller sprocket actually reduces lower end pull and increases top cruise speed, get the engine broke in and learn more about it by tuning NT carb which is a perfect little low maintenance carb for these engines, I have a bike with the 66cc/80 china girl that cruises at 42mph and it still has the NT carb.

Do what you want to do to it by all means, but most of us who have been tinkering with these for a while will likey recommend it a good idea to just keep the NT carb at first and get the engine set up to be as reliable as possible before a carb upgrade.

Best wishes with the build.

Map

i got a motor a few weeks ago my 7th in all and I noticed the inside diameter on the stock NT intake manifold was a lot smaller inside than that of the same on all of my other stock manifolds .

I Didn't notice this at first, however it was the lack of speed that got me investigating it, At first I though I may of had an NT speed carb. on my daily rider so I took it off started investigating put my pinky finger in one manifold "dont ask me why"... then when I went to do the same pinky plug on the other one I couldn't even get the tip of my pinky in the manifold, So I swapped the intake sout using the same carb and presto I was back up to speed so to speak.

So keep an eye out on these manifolds I think it may be a 49 CC manifold IDK all I know is it is a lot smaller and it affected take off, the mid range and top speed immensely He is right get a bigger rear sprocket to get more "off the line vpower " A smaller sprocket means more pedalling to get going but better top end once you do get going Id suggest a "as big as you can get " sprocket!

vonericson said:

Ok, yeah my mistake I always got gearing ass backwards and thanks for the tip on the carbs even with all the research I've done so far on these I haven't come across anything about break ins, since it's a 2 stroke it makes sense though isn't the formula 8oz oil per gallon of fuel normally just double the oil to 16oz for break in?

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No, 16:1 is way to much oil, if you use a good quality dyno oil I would do 32:1 some say 25:1 which is ok if thats what someone wants to do, I run Opti2 and start my engines on what I plan to run with no problems I run 100:1 and just take it easy for the first 10-15 miles after that I just cruise like I plan to ride it.

Dont try a 100:1 mix with qn oil not designed for it but if you go with Opti2 you can if you feel comfortable with t like myself and several other here who run it, some add an oz of high quality castor oil to each gal of 100:1 mix also that makes a real good mx, castor is great stuff for high heat aplications.

Map

vonericson said:

Good lord my head hurts trying to break down that ratio into a usable fraction lol

My only real 2 stroke experience is Nitro based R/C trucks and I only buy premix so the fuel ratio thing is a mystery to me.

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Lol........!

If you plan to run a standard type 2stroke oil you can go to most and auto parts store or home depot or lowes or most hardware stores and buy bottles or packets of oil specified for a particular mix ratio per one gallon of fuel, unless someone else beats me to it I will post a link to a oil/fuel ratio calculator here on this thread when I get off work at 6am in the morning and am at home with access to my PC, on my GalaxyIII right now and dont remember the link addy.

I think 25:1 is aroumd 5.2oz of oil per gallon of gas or at least real close to that, I know others here on the forum have thenlink ane maybe someone will see this post and list it .

Just take 128oz which is one gallon and divide it by the ratio you want to run and it will give you the amount of oil in ounces that you need to use per gallon of gasoline.

Example: 128 ÷ 40= 3.2oz which will be 40:1

Hope this helps.
Map

vonericson said:

Awesome thanks again Map greatly appreciated!

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You're very welcome vonericson,

Hope you have a great build

Map

SD Stinger Engine

Hello,
I'am new to this Forum. I just purchased a SD Stinger Engine kit from bikemotorkit.com. I also have a Schwinn Del Mar (Walmart) bike. I was wondering, and hoping that this will be compatible. Does anybody have any suggestions?
Thanks,
~Logan

If you go to the album I just uploaded called "from barry's shop", look at "Raven" it's a 79 Preditor and I bought all the drivetrain stuff from: http://gokartsusa.com/. The engine mount is home built from 1/4" steel plate and muffler clamps. This is not really too great an idea for your first build but, I'm here to talk you through it if you need me.