79cc 7 speed mongoose threshold

xXNightRiderXx

xXNightRiderXx

Active Member
Hey guys, so considering this is 3 hp, and is above the 49cc limit before motorcycle classification, how can I get this up to 50 mph? It currently cruises at around 25.4 - 28.7mph. I've already bypassed my governor, and am being careful with it until I get new springs. I need to keep my current muffler seen in the pics, because it keeps the engine quiet enough to ride after 10 pm. I have a CVT on the way, with a bushing to reduce the driver bore.

I'm also planning on GEETing this bike, as a test. If I get any impressive, or at the very least positive, results, I will post my findings, from maximum range on one tank, to emissions produced.
 
Last edited:
Heres the pics of my bike:
 

Attachments

My current final drive ratios are as follows, for each gear:

1st:15.514

2nd:13.297

3rd:11.635

4th:9.973repeated

5th:8.311repeated

6th:7.202

7th:6.094

my chainrings are 44 and 30, my cassette is 28-11, and my other sprockets are as follows starting at the clutch:11, 22, 10, 17, 9. how can i modify this gearing to optimize my ratio?
 
Just got my CVT installed today. I tested the CVT without a load, and it works precisely the way it's supposed to. I am buying a new wheelset and fork for my bike, because I need some suspension, and my rear tire is cracked halfway through. I'm also buying some screw in carbide tipped studs for my tires, because it is likely that I will be facing snow and ice this winter.
 
Last edited:
Ok, so I have an issue I have to face after ignoring it all this time. My front wheel is a qr wheel, but the skewerr is bent at the end, preventing the but from loosening, which means I can't take it off. How can I fix this while salvaging the skewer?
 
not sure why, but it seems hardly anyone is interested in this shifter. No matter, ill just continue working towards 6HP out of this little thing, and hopefully get 60MPH.

I currently have in my purchase queue a 40W rear running light with turn signals, a spring actuated brake light switch, a 2.5 inch V-groove pulley, a permanent magnet alternator rated at 12V 14A@600RPM alternator speed, a rectifier for a small tractor, and a linked V-belt. This will allow me to ride somewhat legally (because brake lights) as I don't yet have a plate, or even a license at the moment.

upload_2017-12-11_3-5-45.jpeg

This is what the brake light is supposed to look like. we'll see.

upload_2017-12-11_3-7-21.jpeg

I will likely need help figuring out a mount for this. shouldn't be too hard.
 
Mount it like a car alternator, may need a pulley on the flywheel. Your pictures it is hard to see were one chain goes and the other ends up. Are you crossing over to use the shifting cassette ? Think if you take a look at small 50cc four stroke it has a 80 or 100 tooth sprcket before it croses over the the shifting chain............Curt
 
i was planning on mounting it on the clutch side, because its already an open system, and there are mounting holes readily available.

I recently installed a torque converter, so i've got a belt instead of a chain on the clutch now. the output chain is going down to the jackshaft, and i have a 44t-30t chainring set. my cassette is an 11-28, which im planning on replacing with a 14-28 cassette.

pics:
Inked20171211_180020_LI.jpg

would this be a good location for the alternator? i can't mount it on the front of the case with the crankshaft pulley like i originally planned

20171211_180057.jpg

replacing that cassette for a one with a higher average ratio.
20171211_180012.jpg
this is a 1/2 inch belt, correct?

20171211_180040.jpg

my tensioner will go behind the driver pulley
 
Last edited:
Think the cvt belt is to wide for the alternator, and the cvt belt goes up and down with speed. You would have to mount it so it pivoted, to move with the belt. Get rid of the U bolt and find a flat strap to work on the engine mount, or at least a flat strap behind it. I would say to try the gearing and see what it does.............Curt
 
the alternator does require a half inch v belt. perhaps i could design something with a spring so the alternator maintains contact with the belt. i should be able to use the cover as an anchor for the spring.

that is an interesting idea, to use a strap on the rear mount.

i couldn't use two of the brackets that were provided with the u bolts cause the frame is about an inch too short.

i think the 28-11 set is a bit too low for me to properly utilize, so im getting a 28-14 set. that will maintain first, second, and third gear ratios, but the ones below those will have a higher gear ratio. I will also be getting a new chain to go along with that cassette.

thanks for the ideas curt. do you know anybody who can make a mount for the alt? I'd like the mount to bolt in behind the driver pulley to make it look cleaner. the mount would need a rail on the lower half, to allow the alternator to pivot.

what is the best way to shave .026" off the head? im at a current compression ratio of 8.5:1, and i used a milling calculator to determine the amount to shave to achieve a 10:1 c-ratio

Im thinking this is to scale, and this may be the best way to mount it. it shows the back of the alt because i couldn't get a face on shot of the front. i edited to more accurately show how it would sit when installed.
alternator placement.jpg
 
Last edited:
Looks to be the same alternator. Im gonna have to make a few adjustments with my modeling, if that is in fact a tav 2 equivalent. Is that engine 50, 80, or 100cc's? Also, it seems like I may have to mount the alternator somewhat sideways to allow a fit.
 
Last edited:
That last picture seems to be the "cleanest" looking mount, as long as you have a voltage regulator and battery, it will keep a battery charged to run lights etc..
 
ok, then I certainly have to make a few adjustments to my original mounting plan. also, my torque converter has reduced my top speed to 21 MPH from the 31 that my centrifugal clutch allowed. what could be the cause of this? belt drag? do i need more power to use the CVT? It is a 30 series asymmetrical.
 
Scorpion1 said:
Maybe lose that 40 lb battery for more speed, kinda overkill
Click to expand...
Its only 20lbs and it was the cheapest walmart had. I can't get rid of it because I can't afford a smaller battery and it is powering my headlights and my brake lights. I probably won't get rid of it until I have the lights running off engine power.
But even with that battery, I still get 30mph with the centrifigual clutch. I'm just wondering why the torque converter reduces my top speed so much.
 
Last edited:
Nothin like a good rumblin and growlin to end your day. Just took a ride into meridian today, to Harley Davidson. Got a free breakfast for it too!
 
Hey guys, its been a while. Heres an update on my bike:
image:2538.jpg

I added a bbr tuning monarch fork, a set of 26" balloon fenders, installed hinges and clasps on my box, replaced that 20lb battery with a 10lb gel battery with an lcd display, and put a light and horn control unit on my bars. My lights are mounted currently on the front fender using the two strut screws, however, that will soon be replaced with a 5 3/4" bucket mounted headlight.

Ive just recently gotten this bike to 40mph on a slight downgrade and with a soft tailwind. No chain issues anymore, now that ive upgraded the clutch and jackshaft chains. I will be heading to the closest small engine repair shop to inquire about a head milling in return for some labor.

Has anyone done some experimenting with various springs to find some that would work in the 79? If not, then ill do some research and give some springs a look see.
 
You must log in or register to reply here.
Back
Top