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.
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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.
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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.
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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.
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i mean, this might look like a mess
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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.
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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!
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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.
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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.
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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.

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