Vintage trash collection 1980 Yamaha IT175G Vintage cross country racer

Discussion in 'Some Assembly Required' started by SFDemo, Jul 17, 2020.

  1. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
    I’ve been a vintage rider and racer for years, and it’s been a while since I’ve had a vintage off-road bike.

    I’ve built a few Pentons, trials bikes and others, but I decided I wanted something with decent travel, because I’m getting the race itch again, and 4” of suspension isn’t for me anymore.

    I’ve tried a few purchases, but got beat out.

    A few weeks ago I found a desirable bike on Facebook marketplace. It was in Cleveland, a couple hours away, so I got my brother to pick it up.







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    Here it is in all it’s glory, $350 later.

    I know the kickstarter shaft is broken, it shifts and is pretty complete.

    I’ll be finally getting it to Cbus in a couple weeks.

    I’ve already sourced a gasket kit, Kickstarter and shaft, chain and sprockets and a manual.

    I also found a factory parts list pdf, factory bulletin for performance mods and period tests from Dirt Bike and Cycle.

    I’m going to do as many of them as I can on the upgrades after I get it running properly.
    #1
  2. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
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    Here are some of my prior builds
    #2
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  3. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
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    #3
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  4. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
    The biggest picture regrets I have is winning the Florida Ahrma National in 2001 and getting my trophy from Brad Lackey on the Yamaha MX250 in the pictures.

    It was wild build of a bike, I built it in Ohio and took it to Georgia with me for work training.

    I broke the frame at a Florida VMX event three weeks before the race, ordered a frame from eBay and rebuilt it in my dorm room. It turns out the 40 year old welds on the modified frame bike, took my new shocks (Works Performance) with it.

    I only had 3 days once the frame came in and no testing time.

    It looked like a yard sale in the Open Age class first Moto, stuff falling off everywhere, and spent every second between motos putting it back together.

    I went 1-1 in 250 class.

    The bike was stupid fast, ported, PVL ignition, Circle F pipe, period correct fork mods from the kit that replaced parts and WP shocks.

    It was my first serious dabble in VMX.

    That picture was taken on the back stretch by the professional during that race
    #4
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  5. greasyfatman

    greasyfatman Long timer

    Joined:
    Oct 18, 2014
    Oddometer:
    3,674
    I am starting to play with air cooled 80cc two strokes.

    Did the hopped up mx250 run ok on pump gas?
    Interested to see if you will do any porting or head shaping.
    Hate to say it but also interested in oil choices and ratio.
    #5
  6. r60man

    r60man Long timer

    Joined:
    Mar 14, 2013
    Oddometer:
    2,123
    Location:
    Centralish PA
    When I was a lad my Dad worked at a Harley/Yamaha shop in Philadelphia. The IT series were my dream bikes. Can not wait to follow along.
    #6
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  7. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
    I'm primarily a Golden Spectro user, at 50:1. I plan to keep it reasonable enough to run 93 pump gas just for simplicity's sake, especially since I want to run a couple of the vintage dual sport runs.

    The tech bulletin for 1981 had some minor porting and a recommendation for head milling. I will probably due the head for sure, and it will be determined about the cylinder once I see if I need to get it bored right away.

    I don't plan to do the boost bottle (Yamaha EAIS) or whatever it is called. Too much chance of causing an air leak or something to break during a cross country race versus minimal gain. I can do better with a carb upgrade, and I am looking a PWK type upgrade, due to price and availability. For whatever reason, they went from a 34mm in 79 to a 32mm in 80/81. I am also replacing the stock steel reeds with Boyesen petals. I've always upgraded the reeds, going back to RZ350 in '86.

    The 250 ran fine on whatever I fed it, but best (of course) on 93 or race gas. The only real "problem" with the PVL was flywheel weight. I was only beat the first turns a few times, either by a big bore or because I was sleeping, it would hit the pipe and rev and run like the proverbial raped ape. It handled okay with the upgraded forks and WP shocks, but still wasn't in the class of an Elsinore or YZ due to weight and handling. It was more like a modern bike in power delivery versus a vintage bike. It ran well down low, just no engine braking and no flywheel effect if you are a short shifter. As I recall, I had a set of huge Mossberger reeds/cages in it, too.
    #7
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  8. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
    I finally got the bike to my shop, and have been tearing into it. First discovery, a huge mouse house in the airbox. Nasty, but gone.

    Overall, looks better than it is, and it turns out the cylinder is rusted to the rings. It has been soaking for 24 hours with PB Blaster.

    The carb is a crusted mess, too. I've never had a slide fused to the body.

    The good thing is that it is a 2 cycle engine with many parts available. I have the gaskets already, and plan to have a new rod installed, new main bearings and seals and obviously a top end.

    I hope to refinish the fuel tank, got a new rear fender and side panels. The headlight shroud and front fender look to be salvageable but need refinished.

    I used bolt cutters to cut the clutch and throttle cables to ease the process.

    Pictures to follow, I got tired and disgusted yesterday after taking it apart and have tools spread everywhere
    #8
  9. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
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    I started work on it. Water on the piston, I’ve never seen one this stuck. Wood and hammer have gotten it down somewhat, but still stuck and lube and heat haven’t worked. I’m going to use a puller in reverse to push the piston down to where I can remove the pin.

    I did get the ATMX completed and running, only 6 years! It’s pretty much a replica of my first bike, CT cylinder with ACK high compression head.

    There is also a part of the clutch basket broken off. It never ends. The next problem will be the swing arm pivot removal.

    I did score a good cylinder and piston that are ready for paint and a light honing.

    I plan to have a new rod and big end done and will replace the main bearings and seals while I’m in there
    #9
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  10. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
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    Engine is out, and crank looks worse than expected, and I expected bad. Good news is that seals kept water in crankcase and out of clutch and transmission.

    The swing arm pivot actually was fairly easy.

    The flywheel is next to take care of, then remove everything to prep for case splitting. Luckily, I have most pullers needed for vintage bikes. The clutch basket is junk, with broken parts. One was by me, too much hammer.

    I have the top end ready to go back on, with a used cylinder with a fresh hone and Wiseco piston kit, Boyesen reeds and new intake boot.
    #10
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  11. Pressingonward

    Pressingonward Looking forward to what is ahead

    Joined:
    May 29, 2015
    Oddometer:
    166
    Location:
    SW Washington State
    That is ugly...if you were in Florida I'd say you should watch out for baby alligators when you split the cases and drain that swamp :photog
    #11
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  12. Foxed101

    Foxed101 Monkeywrench

    Joined:
    Aug 1, 2015
    Oddometer:
    508
    Location:
    Holland
    That is quite some journey you have ahead of you! But you sure sound up for the task.

    Godspeed
    (Never used that word before, but seems appropriate:D)
    #12
  13. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
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    The top end is ready to go, fresh Boyesens reeds, gaskets and honed.

    I got all the screws out of the cases and everything removed so the next step is splitting the cases.

    I did find the magnets in the rotor looked horrible and unusable and cleaned up the backing plate. That looks okay.

    Off to Speed and Sport for a few more parts. I managed to find a NOS front fender here for $37.02, cheaper than replacement from DC Plastics.

    A buddy owns a business and sent me their products to try, so I’ll report back

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    It’s supposed to work on paint with pigment at the molecular level, whatever that means.
    #13
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  14. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
    Swamp crank or crank from black lagoon IMG_0707.jpg
    #14
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  15. CA-Cincinnatus

    CA-Cincinnatus Semi-retired GI-Bill student, husband, GSD-host Supporter

    Joined:
    Feb 28, 2013
    Oddometer:
    509
    Location:
    San Leandro, CA
    Good lord almighty... Well, we know where you're going to be for the next couple of months... :D

    Have fun, don't break too many new parts, keep us up to date with pics!
    #15
  16. Pressingonward

    Pressingonward Looking forward to what is ahead

    Joined:
    May 29, 2015
    Oddometer:
    166
    Location:
    SW Washington State
    Nice progress. Swamp crank looks better than I expected - there must be some oil mixed in with that sludge :)

    Odd request for you if you happen to have a scale handy - could you weigh the engine once you get it back together? I'm compiling engine weights for ~200cc 2 strokes to see which is the best candidate for the ultralight woods bike I want to build someday. Weight without the shifter or kicker would be ideal (apples to apples with the other weights I have). No worries if you don't have an accurate scale, but thought I'd ask :beer
    #16
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  17. SFDemo

    SFDemo Been here awhile

    Joined:
    May 5, 2008
    Oddometer:
    533
    Location:
    Shawnee Hills OH
    Sure, I'll weigh it for you. It is significantly lighter and smaller than the engine from the ATMX/CT1 I recently did. It really is compact, this is the first of this family of engines I have worked on. Basically the 1980 YZ125, 80-83 IT175 and 82-83 YZ100 share the common architecture and interchange some parts. The 1981 YZ125 also interchanges some parts, but gained weight and complexity with watercooling.

    I've been soaking replacement crank #1 overnight in rust remover, as it had a few nasty spots. A little side to side play, no up and down. I'm more worried about the bluing near the big end pin
    #17
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  18. Roadracer_Al

    Roadracer_Al louder, louder, louder!

    Joined:
    Aug 5, 2007
    Oddometer:
    2,504
    Location:
    Oakland, CA
    You're a better man than me! If I saw that sludge in the crank, I'd have dusted off my hands and walked away.
    #18
  19. tjzondrz

    tjzondrz Non-Nefarious

    Joined:
    Sep 20, 2012
    Oddometer:
    9,058
    Location:
    Macungie,PA.
    The IT 175 is a blast of a bike to ride. I have a 1980 & a 1981. Good luck with the build.
    BTW
    Boysen Reed Co. is about 15 miles from my place. I need to take a tour through the place.
    #19
  20. Highliner

    Highliner Been here awhile

    Joined:
    Jun 27, 2009
    Oddometer:
    209
    Location:
    West by Gawd
    Saw that bike on FB, Really wanted that bike ITs complete are hard to find especially the 175 and 200s.

    I may have dodged a bullit. I don’t have all the pullers necessary to tear that down without breaking stuff.
    #20
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