Use of a POWER impact tool is not recommended. The Grainger tool linked above is NOT a power tool. You stick the bit into the screw head and hold it tight with enough twist to keep it solid, then whack the end with the aforementioned 16 ounce hammer. If you're lucky, you'll get a sixteenth of a turn - just enough to knock it loose where it can be turned with a screwdriver or by hand with the impact tool. A power impact does the same thing, but it does it dozens of times a second when most of the time you only need two or three whacks - if the first doesn't work.

Hard to break or strip when there's almost no movement. The power tool has lots of movement, the manual tool has almost nothing.

Here's what 'can happen' if you're not careful, so be gentle but firm no matter how you go about it [if that works] A new impact tip on a T handle 'should' free it without climbing out of the screw head. Impact tips are good, & don't lose their sharp edge easily. Pic isn't yamaha but is a typical pic of what can happen .

Maybe invest in some of these tools from Vessel.

www.vesseltools.com/handtools/screwdrivers/screwdriversets

That reminds me that on ebay you can often find the "gold standard" Vessel #2500 Impact driver sets for decent prices... the old original ones that came in the blue or green metal box with proper JIS bits.

Back when I was a kid, the Vessel bits were the only ones that fit the Yamaha screws correctly... all the "Phillips" screwdrivers you could get would slip and strip the heads. The kit in the little metal box was a must have. I still have mine. I think it cost $3.95 new back then... which was a lot when you could buy a 100 pc Craftsman tool set with box for like $30 or $40.

(And like I think RT325 said, make sure you use the right bit... #3 fits the case screws better than #2... )

You can still buy the bits new from Vessel or look for a used kit that's complete... Vessel also sells a new model with a rubber grip.

I know I have an impact that came in a blue metal case. Have to see if I can find... Is this the one you mean Mark?

www.ebay.com/i/124186216098?chn=ps&norov...bS7ozuIaAj-kEALw_wcB

That one is a little rough with no bits, but yes... a few months ago I bought a nice complete one to keep at my other place for under $20 shipped.

Thanks for all the tips guys. Impact screwdriver with correct size bit did the job nicely. So now I have the clutch plates out I need help please. A few things concern me. First when I removed the pressure plate the lock nut underneath looks like it’s been beaten on a number of times in the past.....



Next the friction plates look to be in decent condition but I’m not sure what I should look for with these - are there specs they should be within in terms of thickness etc (I cant find a workshop manual)? Then the clutch plates have a bit of a weird shape - seem to be worn more on the outside on one side but then each seemed to be same way in slightly varying degrees. - is this normal (see 12 o’clock position in pic)?



What thickness should these be?

Finally after removing all of the plates and rubber rings the back of the basket that hold all of these plates (Boss, clutch in the parts manual I have) there is evidence of some metal that has been removed from this just in one edge section which I’ve tried to show below.



Is this a serious issue and any idea what may have caused it? I haven’t taken it apart any further until hopefully someone can give me a few pointers on what I need to concentrate on in terms of measuring and potentially replacing.

Here are all plates out in order.

Reading DT175 service manual gives the following spec

Friction plates new should be 3mm thick and replace at 2.7mm - mine are measuring 3.8mm so I am wondering if the AG model had thicker plates?

Springs are supposed to 36.4mm new and replace at 35.4mm - mine are 33.6 which is rather well under spec or this is accounting for thicker friction plates?

Any advice on this guys?

Do you know what sort of fluid was in the transmission? I'm not familiar with your bike and it's specs, but the plates look to me like they are rather well worn. I can't really tell with the friction (fiber) plates themselves. First thing to try would be to clean the fiber plates with brake cleaner and then re-assemble the whole thing. Then put in a transmission fluid that is rated for wet motorcycle clutches. Search that here, and you'll find some listed, I'm sure.

Thanks - I believe the oil I used was rated ok for clutches as I was aware of this potential issue. I’ll have to check when home next.

Searching the part number of the friction plates it seems these may be 4mm thick new so looks like I have a bit of wear if that is the case. I think I will order new OEM ones and then I know I have that sorted. The old ones are smooth and seem a bit glazed but I have nothing to compare to. Not sure what I need to look for in relation to the steel plates - they seem like there is some wear but condition seems good.