Im sure this info is here somewhere but I have not run across it yet. While riding my newly restored 1975 dt250 I noticed an obvious rear wheel balance problem. New tires were put on and the rim locks were left in place. It takes about 6 ounces of weight to get the wheel to not settle with the rim locks at the 4 and 8 o'clock position. I would like to remove them hoping that nothing will be negatively effected. I only plan on riding on the street during the summer months.
So,
1 - is it acceptable to remove them completely?
2 - what is the best way to cover the holes in the rim to protect the tube?
3 - did all factory bikes share this problem when riding on the street over 45 mph?
  Thanks to all, Scott

They keep the tire from slipping on the rim.... and the tire on the rim if you have a flat on the trail and need to limp home.

If you keep tires aired up, you probably will be ok. One old trick is to never run the nut on the valve stem down against the rim. That way if the rim does slip, you'll see the valve stem start to angle from straight up so you can fix it. The nut will keep the valve stem nice and straight... but if tires slips it will rip the tube off the stem... better to have stem be able to move.

Anyway, your dilemma is not unique. My solution is to remove the "cast iron" rimlocks and replace them with Motion Pro LiteLocs... They weigh a fraction of the originals and then it generally doesn't take much weight to balance the wheel.

www.motionpro.com/product/11-0059

You can generally find them cheaper on ebay or Amazon or someplace else online. Make sure you buy the correct size for your rim width if you go this route. I use them on almost all my bikes. I think your bike has a 1.60 on the front and a 1.85 on the rear. (Link above is for the 1.85 width).

Another option is to check at your Yamaha dealer for rim locks from a modern dirt bike... something smaller like a YZ85 might have the same rim widths. Modern factory rim locks are a lot lighter than yours... and while they won't be as light as the Motion Pro, they might be cheaper.

Thanks for the reply.
I understand how rim locks function and how they keep the tire in place in case of a flat if trail riding aggressively etc. Were these bikes all delivered from the factory with the wheels so out of balance that riding at speeds above 50 mph resulted in wheel hop? I spent a great deal of time restoring this bike and have zero intention of taking it off road, its too clean. I will only be taking short trips in and around this tiny village I live in. This bike does not have the so called cast iron rim locks but hard rubber/plastic ones in place. Again, 6 plus ounces of weights just to get it close seems excessive. So my question remains, what are my options to eliminate the rim locks to get closer to a neutral balance.
thanks again, Scott

When I said "cast iron", it was an exaggerated reference to their weight, they aren't actually made of cast iron, they are just heavy.. 

Just take the rim locks out and throw them away if you want to.  Not sure what's best to do about the holes...  you could manufacture a lightweight bolt to keep the look of a rimlock or find something else mechanical like a rubber plug or plastic plug which is what I would do. Piece of aluminum tape? Or do nothing.  The holes really won't hurt anything the way you plan to ride. 

And no, these bikes weren't that bad then and aren't now.  I balance my wheels because it does make for a slightly smoother ride.  I don't recall the factory balancing the wheels at all and they rode fine, even with the rim locks.

If you actually have "wheel hop" at 50 mph, you likely have out-of-round wheels or bad tire(s). It's not uncommon to have or end up with an egg-shaped. wobbly, or off-center wheel.  It doesn't take much to create a bad vibration.  Wheel truing specs are fairly precise.  Anything more than 2 mm runout will definitely be felt...  and 2 mm off center won't be seen without a pointer or dial indicator. 

New tires can be bad, I've had to return one or two... and certainly old ones can vibrate like hell from sitting too long in one position and developing a "flat spot" that is impossible to see by eye.  It can also be tricky to get some tires on the rim properly...  especially with 2 rim locks.  Can be very hard to get the bead to seat evenly around the rim.  I've almost tossed rim locks for that reason. 



 

The only time I've experienced a near wheel hop condition was when my tire bead wasn't seated properly in the rim.
   

Thanks for the quick response. I am on my way to an old school motorcycle shop to have them give it a try.
- Scott