project build with rear springs

delray

delray

Well-Known Member
#1
#1
ok guys i was planning on finishing my build off project for my nephew. things have change? he's just to big for a hardtail 3hp briggs and at almost 15yrs old and 140 or so pounds:doah:. he as been riding atv's and has over 35 acres of farm land and trails to ride on. so i think i will try to build him something that he can ride on farm path roads and trails. i pick up a large baja minibike couple years ago with out a motor for $100. couple things i would like to do to it . build a rear suspension and install a flathead 5hp briggs and a torque converter.
here are some mock-up pictures on how i would like it to look like.

this part of the frame i will be cutting off for the rear springs:hack:

also on the engine mount there is a small plate in the rear that will need to cut off:hack:

to make a rear suspension out of the original frame i will need to cut a small peice out of the lower frame behind the engine mount and install some bushings and then become a lower swing arm.

engine i am using is just for mock-up only. i have another low hours snow blower 5hp briggs that i will be using and is ready to go:thumbsup:

the only thing i will have to do to make the engine fit good is to slot the engine mount holes 1/4 inch forward so the rear gas tank won't be so close to the frame rail.

:scooter:.................:weld::grind::hack:
 
delray

delray

Well-Known Member
#2
#2
first thing i did, i tac up some angle iron so the frame would not move around when i go to cut it up :hack: bushings and tubing i will be installing will look like this and i will be adding a grease insert. bolts are grade 8 so they should hold up:thumbsup:

after everything was square up, i went ahead and tac it in place and also welded the nuts in side the tubing. tubing looks to be about 14g(thick):weld:


after finishing that i went ahead cut the rear frame tubing for the springs.


also tac a piece of metal on top of the rear frender to keep it in place.

i well be reusing part of the fender bracket and will have to make a new bracket to hold it in place
 
delray

delray

Well-Known Member
#5
#5
i fab up some small plates with two adjustable holes for mounting the shock. this give me some adjustment for ride height, if needed.

before welding them in place i made sure that the mounting holes from top to bottom on both sides where the same measurements.
 
smallbikes88

smallbikes88

Active Member
#6
#6
Looks good! I have the same bikeand now might have to do the same thing! I also noticed how the swing arm was bolted to the frame looks like how i made my monster honda. Also you might want to think about a chain tentioner becuase when the swing arm comes up it might loosen the chain
 
delray

delray

Well-Known Member
#7
#7
yes greg, i plan on installing a Tensioner on the bike:thumbsup: i machine out a roller skate wheel with a grove in it to help keep the chain in place and they also keep the chain noise down more then a roller sprocket. i have had one on a bike for 2yrs and has been working very good with no wear.
i also wanted to ad little more strength to the lower control arms from moving back and forth or i should say side to side. so i welded a cross tubing from one side to the other.peice of tubing came from part of the frame i cut off earlier for the springs(recycle metal):weld:


:scooter:..................................................
 
F

FootScoot

New Member
#8
#8
It's amazing how much stress pressure is in a mini bike frame. I cut the rear tubes off of mine so I can widen it. When I made the first cuts on the top tubes it popped out almost an inch, they must have been welded that way.

Looks like your project is coming right along. Should be cool with shocks on it.:thumbsup:
 
delray

delray

Well-Known Member
#9
#9
finish up with the shocks and fender mount. i wanted to use a grade 8 bolt for the shocks and i needed a 1 3/4 for the bottom and 2 1/4 for the top. well i got lucky,at the hardware store i could only get the grade 8's with a flange head in 1/4 lengths.the grade 8 gold zinc bolts only came in 1/2 length,for example 1 1/2,2,2 1/2inch...etc....
black flange head bolts where ok with me:smile:


fender mount bracket support was just made out of a long bolt that i just cut the head and threads off:hack: also while mounting the fender i desided to move the fender up little and also square it off more with the tire,so it would not look so off-set or crooked. (kept the curve of the fender the same as the tire:smile:)
 
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delray

delray

Well-Known Member
#10
#10
also finish up welding some support plates on top of the tubing. tubing is very thick(14g),but i thought i make sure it was extra strong for the upper shock mounting area.
 
Randy

Randy

#11
#11
That looks really good. Seems like a high quality shock. All I seem to fine is the cheep china/pressed steel type shocks. I like the milled ends on them, just seem like a high grade shock. I must be looking in the wrong place?
Randy
 
delray

delray

Well-Known Member
#13
#13
when i was fabing the extra support for the upper shocks i made sure the seat would still fit correct and it did,but then i notes the front rubber grommets(yellow box) where not even touching anything and the front center of the seat where it clips on to was supporting everthing. the rear grommets(green box) where resting on top of the tubing ok. must of been a after thought when the chinese built this bike:doah: so i just fab up some small plates for the front grommets to rest on and take the load off the front center of the seat(blue box) or in time the front plastic clip and seat would of crack:doah:mmmmm..something wong:chinese:

 
minibikedude

minibikedude

Active Member
#14
#14
I like it! delray, Great Idea and it looks original! Are you going to turn the gas tank into a working gas tank. I wish when Baja made these they would of done that way. I seems a waste that they used the tank on the engine when they went to the trouble of stamping the top half of a tank to put on the bikes.
 
delray

delray

Well-Known Member
#15
#15
minibikedude,if i was building it for me i would of like to had a 6 or 7hp H model big block tecumseh with a lighted coil for lights and made the fake tank into a real tank:thumbsup:
bike is being built for my nephew and i got to make easy for him to start and have least amount of problems with it and the flathead 5hp briggs is going to be a good engine for him to use. i first try to install a complete 5hp tecumseh with a front mount tank and the with the standard carb and air cleaner. no luck with that:doah:. air cleaner hit the frame tubing going up to the seat and the tecumseh tank was right under the fake tank,so you could not fill it:doah: also kind of in a rush to get it done for his birthday this summer:happybday:
 
delray

delray

Well-Known Member
#18
#18
roller tensioner
i needed to make a chain tensioner now that i modified the rear suspension. chain will become loose when the rear suspension travels up and down. so i wanted to make something that would pivot up and down with the chain and i also wanted to use a modified roller skate with a grove machine out in the center to hold the chain in place(side to side). couple nice things about the roller wheel it comes with a high speed bearing and the plastic wheel is very hard and will not where down. i been using the same type of wheel on another minibike for 2yrs and have not had any where yet. also with using the roller wheels they are alot less noiser then a sprocket tensioner. i first made a L type bracket and then drill some holes for it to pivot and mount the wheel to it. the pivot point is a 3/8 bolt that go's through a 16g tube that will be welded to the frame and also will have grease insert fab on to the side of the tube to keep everything lube up. 3/8 bolt will be welded to the bracket so the tensioner will stay square with the chain. also drill some small holes(spring adjustment holes) in the bracket for the spring to hook on to and made a small bracket and welded it to the frame for the other end of the spring to hook on to.

 
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