I have a 1979 DT175, my idler gear was loose and I found the Circlip in the bottom of the crank case, I put it back on and put everything together and the Kickstarter worked great for like 20 kicks and then i think the Circlip fell off again, making the idler gear loose, what do I need to do so that circlip won’t keep falling off?! Thanks guys!

The circlip may be spread and/or lost its tension. Suggest a new one.

www.partzilla.com/catalog/yamaha/motorcy.../dt175f/transmission gear 26 & associated parts. looks like there's a washer either side between circlips & gear bur anyway, corlips have a flat side & a slightly beveled side generaly, So the flat sharp cornered side should go 'away' from the gear & gives it less chance of getting ramped out of the groove , but the question must be asked is there severe wear in the gear center or the shaft causing odd movement which forced the clip off. Think the gear or the kick gear has a bit of a lead in to stop it getting smacked sideways or that's the theory. Make sure that clip is engaged too--number 10 in the second link www.partzilla.com/catalog/yamaha/motorcycle/1979/dt175f/starter, the little sticky up bit has to find the groove to slide in. Maybe i'm repeating myself sorry, or was another post but anyway if it lasted 20 kicks then the friction clip 10 must be in place & not relevant to the idler gear letting go.

Yes, what RT325 says is exactly right... thin washer on each side of kick idler and sharp edge of circlip faces "out" away from gear.

Plus as he said I've seen a used "core" engine I bought cheap where the idler gear and shaft had a really sloppy loose fit... guessing happened when someone ran the trans low on oil. First gear bushing was ruined on that one too.

Or of course as 1971DT250 said, bent or damaged clip could be it too... hopefully it's just that or needs sharp edge of circlip facing out.

Thanks guys! I’m not sure exactly about the “sharp” side of the circlip. I will have to check it out again.

Also is there any secret to taking off the flywheel? I have been hesitant becuase I don’t want to ruin any thing, any suggestions?! Thanks!

Yeh use the correct puller, there for sale on ebay,, cheap too.