big tires vs small tires for mini bike

[tundrabeagle3]

I got some bigger tires that came with the frame i got and am debating whether or not to put them on. They are about 19 in and thinner than the ones i have now, which are 16 in and are wider in the back. I do plan on offroading it and hill climbing it but i only have a clutch with a 6:1 ratio and 6.5 hp motor. I don't have funds for a torque converter.

 

[Bluethunder3320]

i wouldnt, if youre off roading you want all the torque you can get

hill climbing with that ratio will be hard to do even with the small tires

 

[kendelrk]

torque converters are really what you want, i absolutely love mine even tho it gives me minor issues. the wider ones will help on trails because they're wider and have more tread. but at the same time is that a 5hp briggs? if you do a governor delete, exhaust and intake and tune the carb perfectly. it will make more than a clone with the same config. on the same bike with the same gear ratio. i loved my 5hp dearly. a 3/4 by 11" or longer peice of tubing from your local home depo will work fine for an exhaust, plus you have the option of elbows and such to make cool exhausts. air filter adapters and filters are cheap for it and its got a fully adjustable carb to handle it all.

 

[tundrabeagle3]

yea i have a 5 hp briggs with the with a uni filter, straight exhaust with muffler, governor removed but i could not get it to start after i changed the crankshaft. so i got a predator 212 and i was surprised that i felt weaker than the briggs. but i love how the predator starts alot easier, and i want to do the same mods i did to the briggs later down the road. i guess im going to keep the smaller 16 inch tire in the back. right now i am deciding what tire i want in front, the 15 inch or 19 inch one .

 

[tundrabeagle3]

im going to leave the 19 in tire in the front because it raised my footpegs so i can do better turns

 

[kendelrk]

did you make completley sure your timing is lined up? the two dots on cam and crank must line up in perfect order, just check on that. but you may just need a carb going through and a good tuning. do you have a VENTED gas cap? if you dont it wont run. theres a second part to the tank above the first. the engine gives a small vaccum to pull fuel from the bottom of the tank to the top and uses the top vented gas to run the motor.

 

[tundrabeagle3]

yea i matched the timing marks, drilled an extra little hole in the gas cap, the only thing i can of think is the carb which im going to try cleaning with lemon juice later today. also is it possible to install the rod backwards on a 5 hp briggs ?

 

[kendelrk]

no. because the clutch should be on the left of the motor with a straight crank. and flywheel goes on the tapered side by the magneto. looks correct in the picture. but before you pull it off and go through that. you know which is the adjusting screw right? turn it ALL the way in. now BACK it out 1 1/4 turns and it may take a couple of pulls (mine took 6 ) and it should fire. if it does even for not very long you need to work on tuning it. the more you back it out the more gas it gets and the more you turn it in the less it gets. also does it seem to leak gas from around the mounting area? if so make sure all bolts are TIGHT and it should fire. i got mine for 40$ because it wouldnt stay running because 1 bolt was a little loose
EDIT: heres a video of mine running before its sale. it has an 11" straight pipe out the back so it sounds like bubbles a little. disregard that. now it wasnt tuned perfectly but it was tuned well enough for me to ride and it to stay running oh and the zip tie is a kill switch http://www.youtube.com/watch?v=kJreTg21jx8

 

[Socal_machinist]

Dang I have almost the exact same ratio, lemme know what kind of take off your getting.

 

[tundrabeagle3]

i tried the lemon juice cleaning on my carb and got it to start but again the rpms were not that high even at wot and i had my carb screw almost all the way out. i also sanded the head down, shaved the intake eyebrow a bit, and ported the intake a little. could it be possible that i dont have enough gas going into the motor to get to high rpms, so i need to re jet the main?


"Dang I have almost the exact same ratio, lemme know what kind of take off your getting" (quote)

It depends what size tire do u have and how much hp is your motor?

 

[Socal_machinist]

Well I have a 6hp tecumseh, Im planning on ordering a 72 tooth rear sprocket, and a 11-12 tooth clutch I'm running a 20" rear wheel

 

[tundrabeagle3]

i have great acceleration but my tire is only 16 inch in the back with predator 6.5 hp.

i dont really know how it would be for you since u have a bigger tire diameter im guessing its for your motorized bike which is lighter than my mini baja type bike.

maybe someone with motorized bike experience will chime in.

 

[tundrabeagle3]

i tried the lemon juice cleaning on my carb and got it to start but again the rpms were not that high even at wot and i had my carb screw almost all the way out. i also sanded the head down, shaved the intake eyebrow a bit, and ported the intake a little. could it be possible that i dont have enough gas going into the motor to get to high rpms, so i need to re jet the main?

is this a jetting problem? how big should my jet be for the performance mods?