Hello all. 

I hardly get lucky, but was buying a honda parts quad locally. When I showed up they said, "you can have this dirt bike too if you want it" I couldn't get it on the truck fast enough! Its missing a few things and locked up, but for me its a score! I have put a few top ends on and gotten a few things to run over the years...but im pretty much a noob thats learning. This thing has such a cool look, I have to see it ride again. I believe it to be a 74 or 1975.

Few questions:
Is there a top end kit out there for this?  Or a common swap?
Is there a more common gas cap that works? Found an OEM $100!
Anyone know of a more common part number for the rubber gas tank bushings on the side? (im missing 1)
Shift foot lever is super sloppy in the hole. Does anyone know a part number for the bushing/seal?

Im not looking to restore to showroom, I want to use this bike for fun!
Looking forward to learning alot from here and working on it. Ill probably have 1000 more questions! Any help or info is greatly appreciated!

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The 175MX cylinders advertised on eBay, are for later 6 bolt head motors. DT175 twinshock cylinder will fit, but the porting is not the same as 175MX.

Yamaha still sells the gas cap new.  Don't be fooled into buying "NOS" parts for crazy prices when they are still available. www.partzilla.com/product/yamaha/322-24611-02-00

There are also aftermarket options like this one: yambits.co.uk/yz125-fuel-cap-1974-1976-p-17001.html

You might need to buy a gasket separately...  not sure if caps come with them...  also available though. 

Also, you simply need to take off the top end and hopefully it can be reconditioned by a shop like Bill Bune. They bore the cylinder oversize to fit a slightly oversized new piston.

I have a fix for play in the gear change, but cant seem to attach pics to comments? You will need a new gear selector cover though, which should still be available?

Yamfan, the pics issue has been going an for a while.  Site is overloaded again...  too big.  Owner is working on it.  Should be a yellow-ish banner at top of some pages that talks about it.

For now you need to use a 3rd party host like imgur and link pics here. 

My way of repairing the gearchange might not help the OP much, as it needs a part making to fit in the gear selector cover, and the crankcase boring out to take a bush? Not difficult for anyone with a lathe and a mill though. 

You guys are awesome.

Yamfan, make me one while yer at it!

Which number is the part I need seen here on pzilla?
www.partzilla.com/catalog/yamaha/motorcy.../mx175a/kick-starter

I was hoping to get an off the shelf kit for a quick fix....but pricing on boring doesnt seem too bad.

Any info or advice looking forward is greatly appreciated. Maybe in regards to what piston size is optimal and such forth.

Ill post pic inside the motor soon.

If it still has the MX175 cylinder, the porting is more extreme than any of the other 4 bolt (early) 175 motors. Message me your email address, if you know anyone with a lathe and mill, and I will send some images and info on how to repair the gearchange.