The internet seems to agree that the eye to eye length of the DT100’s rear shocks is 320mm, but my bike has 285mm (approx) shocks. 

Can anyone with a DT100 measure their rear shocks eye to eye to verify the stock size? 

Alternately, can anyone think of anything dire that would affect the bike going up about 40mm in shock length? I know it’ll change the geometry of the bike but I feel like it’s not a huge change. 

The chain top rail might contact the swinging arm around the pivot point ,

Shock length of my US market 1977 DT00D is 280mm centre to centre.

I specify US market because here in the UK we kept the physically larger 1976 model right through to 1983, albeit with minor paint and graphics changes.  Model was discontinued in 83.

We never had the smaller 77 onwards DT100.

I expect the 320mm shocks are from the pre 77 models.

As for fitting the bigger shocks, it will certainly tighten up the steering, but since the 77 onwards DT100 has rubber compliance bushes instead of conventional swingarm bushes, they may not enjoy the longer travel of bigger shocks and may start to spin between the axle and frame tube.  This leads to loose bushes and eventually an egg shaped frame swingarm axle tube if not caught early.

RT100s were notorious for wearing out the axle tubes if not checked daily, admittedly the ones I was in charge of, used commercially, were submitted to extremely harsh conditions and hours of usage.far, far more than the norm.


UK spec DT100 1976 till 1983.  Full size bike.


US spec 1977 DT100.  Kids minibike. The size difference is very evident just in the gap between the cyl.head and the bottom of the tank.  A hoot to ride though, absolutely bonkers.  I love it.  The missus says I look like a circus clown perched on top of it.

It is a pure fun bike.  You are not going to get much more than a 50 mile range from a full tank of fuel ( 1 imp gallon to the brim) and probably much less off road on the more technical trails.