Posts Tagged 'yz80'

gettin dirty – yz80 suspension on dirty general PT4; THE CONCLUSION

last post i kinda showed you my solution to tieing the linked suspension into the general’s frame; a tubesteel loop that mounts to the outside of the swingarm as well as anchors the lower links.

once tieing the lower part of the loop (made from handlebar u-bends and a bit of tube steel i had laying about) into the flat steel swingarm mounts, i needed to figure out a way to mount the lower link to it. after digging around the shop forever i found a pair of generic vespa scooter mirror mounts that did the job well.

after cutting them up a bit they totally worked out perfect.


after welding them on, i cut some more u-bends and tied everything to the frame.

i filled in all the gaps between the handlebar u-bends and the metal plates on the lower half of the loop, and will do the top half later, because i plan to grind everything smooth and make the loop kinda blend into the swingarm mounts. those square plates will get shaped too. it’ll all be smooth and pretty when done.

so the suspension is fully mounted now! that’s exciting.

now to work on getting the engine and transmission all fitted up and worked out.

this is roughly how the hobbit final drive transmission will be mounted in the frame.

i have a brake plate that i shaved all brake related bits and nubs from, though it’s in a box somewhere. for now i’m mocking up with this other brake plate.
as you can see, i have the brake plate inside out from how it would be on a hobbit. i did this because with the brake plate bolted flush to the outside of the frame, it puts the final drive unit right where i want it. i think.


this is one of my ideas, anyway. i have another one kicking around that would put the final drive much more inboard on the frame, but i gotta mess with things some more before i know for sure.
also, i’m waiting on the sprocket adapter i made and sent up to naz in seattle to be shipped back before i can get too serious and start welding up brackets and things.

in the meantime i still need to figure out a steering stop to keep the yz80 forks from smashing the tank and a subframe to support my butt.
hopefully i’ll be able to bust that stuff out in the coming weeks and have this thing ready to roll by 2014! yeah!


gettin dirty – yz80 suspension on dirty general PT3

last post i had a little animated gif with the rear of dirty on in one frame, then chopped off in the next with the yz shock stuffed in there, like so –

since then i’ve set about to get the dumb shock mounted in there proper. i just happened to have some flat steel left over from the dirtbag virago laying around that was exactly what i needed.

i really need a drill press –

after some drilling and chopping and welding, i got the upper mount all sorted. it’s not the prettiest thing i’ve ever made, but then again this bike isn’t really meant to be pretty.

the shock is offset on the swingarm by about 1cm to make room for the drive chain, which put the upper mount flush on one side of the frame.

next, and what i’m still working on, is fabbing up a mounting point for the lower link. you can see it just hanging out here –

i explored many different options of doing this, but what i decided on was to build a loop that supports the outside of the swing arm, simular to the way the yz frame would have, and also ties in the lower link.

i chopped up some bars and some random tubing to make the lower loop. yeah, it’s ugly, but that’s alright.

i cut a couple chunks off my flat stock and drilled the centers for the swingarm pivot bolt. i had measured the width of the swingarm before building the loop, so i knew how wide to make it. i’ll notch the loop so that the flat stock rectangles will slide into them, and then weld the three pieces together. it’ll sit like so –

then i’ll use more handlebar u-bends to tie the tops of those rectangle plates into the frame, and more flat stock to tie the lower link into the lower part of the loop.

later on, when i’m mounting my pedal shaft, i’ll probably tie the lower part of the loop into the engine mounts i’ve yet to fabricate. we’ll see how all that goes when i get there.

so here’s dirty sitting pretty much where it’ll be sitting stance wise –


i haven’t had more than maybe two hours a week to work on it lately, so it’s been kinda slow going. i hope to get the swingarm loop done next week, as well as gussetting the frame up near the head tube and fabbing up some kind of steering stop so that the tank doesn’t get beat to death by the fork.

oh yeah! speaking of the tank, i’ve been kinda thinking about what i’m going to do about the gas cap. the stock one is there, but the lock/latch is missing. it’s totally not that important during this part of the build, but it’s something that will need addressing eventually.
last week i bought a box of sachs parts from swoops will d, and he loaded it up with all kinds of random awesomeness, including this! –
the latch/lock for a general gas tank! best part is that it uses the same key as my other general tank. one key for both bikes! that’s awesome.

and that’s it for now. this thing’s a ton of fun to work on, even without access to tools and machines that would make life so much easier. it’s showing me that all i REALLY need to build fun stuff is a welder, a cut off wheel, drill and some c-clamps.

gettin dirty – yz80 suspension on dirty general PT2

my headset reamer/facer showed up and i was finally able to get busy getting my fork on.

i can totally see why bike shops charge so much to do this, IT SUCKS. then again, it’s probably not very often bike shops are cutting the cup seats into fresh tubing, they are more typically just cleaning everything up on an existing cup seat. anyway, yeah. even with a generous amount of tap oil, this probably took me a good 45min to do.

the finished product looks a little rough, but it’s actually quite smooth and the cup presses in nicely.


i then attempted to assemble the fork and realized i didn’t cut the head tube short enough still and had to take another centimeter or so off, then re-ream/face the dumb thing. GAH.

i also discovered the steering stem where the bottom race presses on on the yz80 tripple tree is of a much smaller diameter than any moped fork. it’s the same size/thread at the top for the threaded race/nut, but the bottom race is too small. such a stupid oversight.

so i was left doing a lot of measuring with calipers on 100 different fork, texting back and forth with david at treats about different races they had in stock and getting distracted on the internet when i was trying to research different size bearing races, i decided i was being stupid and ordered a shim bearing from
i found one that once pressed on would allow a race that treats had in stock to press on over it. the whole process took me wailing on my park race installation tool with a 16oz hammer, a copious amount of fire and wanging my left hand with that hammer i mentioned just a second ago before everything was seated nice and tight on the fork. then i had to trim off the excess shim so that it wouldn’t hang on the lower cup and it all went together awesomely. almost.

a little bit ago i said i didn’t trim enough off the head tube on the frame and so i had to cut more off, well as it turns out i cut off about 1mm too much. all of the threaded upper bearing races i had would bottom out on the threaded part of the steering stem before getting tight on the bearing. in the end i used another lower race that fit tightly over the steering stem, locked down with a lock nut. it’s the same way the stock yz80 headset works, and once the upper triple was on with the head tube bolt installed and tightened, the thing was together nice and tight and smooth as butter. smooth butter.


here’s most of the bike roughly laid out where everything will go when it’s together.

erm. something like that. and here it is again, but up on two wheels.

next up, that pesky rear suspension. this is gunna be gooooood.


gettin dirty – yz80 suspension on dirty general

i’ve been putting off posting about this until i got further along, but it’s taking longer than i thought it would due to me having to buy a couple tools to get the job done, so whatever.

firstly, to mount the swingarm to the frame, i needed to ream out the 10mm tube steel to 12mm for the swing arm bolt. the tube steel was thick enough that i would still have plenty of meat, so i wasn’t too worried about it.
i bought a 12mm ream, but there was no way i was going to be able to ream the thing with a hand drill, so i went down to my buddies machine shop to see if i could get him to work it out for me. i left him the frame and the reamer and later that day he called me to tell me he totally goofed and thought i wanted it at 13mm, so he made me a whole new sleeve and tig welded it in for me.
after sanding the weld down on both sides, the swingarm went right on. the suspension link ran into the frame where the kickstand mounts were, as i knew it would, but that’s gunna go anyway.

so i sliced the bottom of the frame off under the swing arm. i will be welding in a mount for the lower link, but before i do that i have to figure where the front will sit, as the lower link mount will dictate the height of the rear of the bike.


i mean, this might look like a mess
but i’ve done more with less in the past.

as you can see, the rear shock is going to want to go right through the rear of the frame there. the plan at the moment is to chop that curved square steel out of the altogether and replace it with two tube steel pieces on either side of the shock, like your typical motorcycle subframe.
that will come later. first i gotta get the fork on this thing.

the problem with the yz80 fork is that the steer tube is too short for the general frame. originally i was planning on pressing the steer tube out of the lower fork triple and press in a longer bicycle steer tube, both the yz80 and the general frame use a steer tube the same diameter as your typical 1″ bicycle headset.
i decided this was more work than it was worth.
the head tube on the general frame is super long, however there is a large gusset supporting most of it. i figured i could cut the gusset off, shorten the head tube and modify the gusset and weld it back in. it should look pretty stock except, perhaps, with nicer welds than the boogery stock welds. hopefully. that’s on me, though.
so yeah, off with that gusset!


then i put the fork triple trees together with the general’s headset cups on the steer tube, measured about how long the head tube needed to be, scored an even line around the bottom of the head tube and then chopped that sucker off.

the only issue with this is that the inside of both ends of the head tube are machined for the bearing cups. except it’s not on the bottom, not any more.
this is the part that makes or breaks this whole project. not only is it super tricky (nearly impossible) to cut a steer tube perfectly parallel with the fancy machines currently at my disposal (pipe cutter, hacksaw and a cut off disk on an air drill), but i have nothing to machine the inside of the tube for the bearing cup.

knowing some bicycle shops have head tube facing/reaming tools that will make sure the head tube is flat on both sides and reams a nice little machined surface inside for your bearing cup, i called around to a half dozen shops here in the city to get some quotes. of the seven shops i called, only four had the tool, and only one of the four had the bits to do 1″ head tubes as 1 1/8″ is the “standard” for most bikes these days.
the one shop that had the tool quoted me $75.
that might be fair but the tool can be had for around $300, and i have at least two other general frames that will be getting this same front end once i’ve worked out the kinks, so i decided it would be worthwhile to just buy the dumb thing.

so that’s where i’m at. once the tool shows up, i’ll ream/face the head tube, trim up the gusset and weld it back on, install the fork with the general’s stock headset, figure out where the swing arm’s lower link is going to go and build a bracket for it. then i get to build a subframe for the thing! yay!
and once all THAT is done, it’s finally time to start figuring out how i’m going to put my engine on this dumb thing.

rally torn down + dirty’s dirty shock

not too exciting i suppose, but that rally from the last post is just about ready to go to paint. gotta stuff the cables and wires into the frame, remove a few more little things and it’s off.



also, the yamaha yz80 rear shock finally showed up. it was $10 shipped, though i’m wishing i had spent a bit more and got a nicer one.

the seller said it was in good shape and ready to bolt on and go, but i’m not so sure. i can’t compress it at all with just my weight. not sure if i should be able to or not, but i fell like i should be able to.

i guess i’ll just clean it up and see how it works? i won’t be too bummed about tossing $10 if it ends up being trash.

that’s pretty much the last piece of the suspension puzzle, now to get to cutting and welding!
erm, once the welder arrives, that is. haaa

you guys, this is going to be awesome.

swing arm showed up, shock should be here any day.
IMG_20130214_175526seriously. i’ve never been this excited about a moped build.

dirty fork and a couple small things for the sr

i’ve not posted much lately because i’ve been mostly tweaking my ninja. i don’t know if anyone really cares about me and my 09 er6f, so i haven’t really bothered. if you DO want to hear about it, let me know!

anyway, i picked up this all-in-one handle bar switch thing for the sr. it’s got everything but a start button on it. if the bike were mine, i probably wouldn’t bother with half of the electrical stuff, but it’s gunna be L’s and so i say it needs it all.
i’m was a little bummed that it doesn’t have a start button on it as i didn’t plan on having any other buttons or switches on the bike, other than the ignition switch.
so why not a keyed ignition with a start position? it works like one you would find in a car, you turn the key to start and it’ll crank the bike over. you let go when it fires up and the key springs back to the on position. why don’t motorcycles use this style of ignition anyway? the only thing i can think of is they want you to be able to start the bike with both hands on the bars. there’s no other reason i can think of.
the fit and finish of both of these parts are kinda meh, but they are robust enough to hold up, i think. besides, i’m on a $1000 budget for the whole build.

oh, and my fork bits for the dirty moped showed up!
i’m totally taking this build in a different direction than i started with, and i’m super excited about it.
i also have a yz80 front wheel of the same vintage on the way. one good thing about using old little dirt bike parts is that this whole front end, including front wheel and caliper (assuming i can get one at a decent price), is shaping up to cost me a lot less than a set of hydraulic ebr moped forks, and these are much better quality.

i might be getting fancy with the rear end of the bike. i’m still sourcing parts and trying to make sure my ideas will work out on paper before i commit to spending paper. i’ll fill you in on all that later on though, once i’ve made some decisions.

so yeah. how’s life?

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