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4704
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8/25/2015
Location
Taylorsville, GA
US
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2342nd
Edited Date/Time
4/25/2016 6:45pm
I'm making this post as both a build thread and a looking for help thread. So please, any advice, insight, suggestions, what have you... I could use it. This is my first vintage bike and my first Yamaha. My first bike was a 2003, so this thing is foreign to me.
Onto the bike. I picked up a 1979 Yamaha MX175, not running but mostly everything's there. Got it for a whole $200. Turning the engine over by hand, I could hear metal scraping (ouch) so needless to say the piston and cylinder are heavily scored. The crankshaft doesn't spin freely, and the con rod is nearly frozen. Transmission seems to go into each gear though. Someone spray painted the plastics and tank, I'll be interested to see what's underneath. Front brake isn't grabbing, I think the cable just needs adjusting though.
My goal is to turn the little Yamaha into a good putt putt bike for my mom and anyone else that wants to tag along to the trails. So I'll probably gear it down a tooth or 2 and maybe do some mild porting, but nothing extreme. Gotta keep some bottom end.
Budget is $400 not including anything fancy pancy I feel like doing lol
Onto the bike. I picked up a 1979 Yamaha MX175, not running but mostly everything's there. Got it for a whole $200. Turning the engine over by hand, I could hear metal scraping (ouch) so needless to say the piston and cylinder are heavily scored. The crankshaft doesn't spin freely, and the con rod is nearly frozen. Transmission seems to go into each gear though. Someone spray painted the plastics and tank, I'll be interested to see what's underneath. Front brake isn't grabbing, I think the cable just needs adjusting though.
My goal is to turn the little Yamaha into a good putt putt bike for my mom and anyone else that wants to tag along to the trails. So I'll probably gear it down a tooth or 2 and maybe do some mild porting, but nothing extreme. Gotta keep some bottom end.
Budget is $400 not including anything fancy pancy I feel like doing lol
http://www.cookseycrank.com/#!crank-rebuild/cfvg
Boring? I have found that no one locally chamfers ports or relieves exhaust bridges when they bore a cylinder so you have to go in and finish the job for them. I would call Millenium Technologies and ask about their boring process on iron bore cylinders. They have done many chrome lined cylinders for me and they have always been perfectly relieved and chamfered.
They also do cranks.
http://www.mt-llc.com/dirtbike.php
The Shop
Thanks for the suggestions! I'll be giving them a call
This is a forum member that was doing some cylinders and cranks. Might be worth a look if you are inclined.
http://www.vitalmx.com/forums/Old-School-Moto,22/crank-rebuilding-and-c…
And thanks for the link. I was gonna send him a message about doing my crankshaft, but I saw my dad at my little brothers soccer game last night so I talked to him about the bike. Turns out he can do crankshafts! So shout out to my dad for saving me some cash. He's a great mechanic but I was unaware he had the tools at home for that.
I got the frame painted today, and polished the fork lowers. Neither look beautiful but I'm happy. Also tried to attack the wheels... but I can't get the damn tire off. Ripped the tube trying, so I'm not sure what I'm gonna do there. Might hit the tire with a torch first lol
a mod i did on mine was to free flow the air box and enlarge the ports on the piston to match the cylinder .....and just about double the size on the carb jets......doubled the torque on that spunky engine !
Found a piston/rings for $25... awesome except I remembered I don't know how much of an overbore the bike will need. The deepest gouge seems to be about .2mm deep, so a .5mm overbore SHOULD be enough. I'd hate to order the +.5 piston and need .75, or order the +.75 and remove more material than necessary. I did get the cylinder/head painted and came out pretty good. I think I'm gonna go port it right now.
Finally got around to painting the muffler today, and figured I'd check the packing. I'd say it needs to be repacked
Also, I should add. Ordered the .5 piston and received it. Looks good for being as cheap as it is. Also order the connecting rod, but no clue when I'll get it. $30 but it's coming from India
Finally got around to splitting the cases. Wasn't expecting any suprises so I wasn't in a hurry... shouldve been. There's a tooth missing off 1st gear. So pissed I done kicked all the parts all over the garage. Hopefully I can figure out how this all goes back together since I just have a pile of parts now. What I get for throwing a temper tantrum I reckon. On a side note, any links to cheap gears for an old yami? Just the output gear, everything else looks good in the transmission.
The reason I ask is I ran across a DIRT CHEAP '78 Kawasaki KL250 that I'm thinking about bringing home. It needs some work, but can be repaired at a decent price. Just wondering if parts are obsolete for these older bikes are if it is definitely a do-able project for me.
Thanks.
I'd guess a Kawasaki 250 is relatively easy to find parts for. I mean there's guys restoring bikes I've never even heard of.
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