1979 RM125 Restoration Complete

[monaro308]

Thanks Rod,the 100 seems to be the forgotten child for donor parts to its big brother....especially those important tranny bits.
Now...because i'm an impatient prick and keen to answer the question on this subject.

Here is My cooking lesson for the year.....Master chef has nothing on me 

First you take an RM100X left side case....
Place it on the concrete (next to the shed in my case) is fine.




Turn the Melbourne weather control to 43 deg C (slightly o/cast is ok )

Cook for only 10 minutes on said concrete....




Remove crank bearing from the freezer which was placed in for only 2 minutes
and slide into LH case...no force is needed,just drop it in.




Now place that RM125T crank assembly into the RM100X case and take photos and dimensions for future reference for the OZVMX public.





This RM125T crank webbing measures @94.34mm
This RM100X case measures @ 96.25mm

Looks like we have a YES on both engines being interchangeable as long as you have the crank,barrel and head from either engines.

PS....Sorry Spicydave if i highjacked your post...thought i'd keep it with the RM100/125 theme.

Cheers....Master Mario 

[Marc.com]

Mario,
The biggest issue that I found is locating a barrel that wasn’t completely rooted.
Rod

Thats where the Japanese parts are good, my engine arrived with good compression and standard bore 

[spicydave]

PS....Sorry Spicydave if i highjacked your post...thought i'd keep it with the RM100/125 theme.

+

No worries,

I like to see that there is more little RM's from that era that gets reborn 


Cheers,
SD

[caps 999]

my 125t is almost ready now that been a project and a half

[oldfart]

Why was idle bearing not replaced

[lukeb1961]

Why was idle bearing not replaced

My bet is - a bugger to get out of you don't have any tools.   

[monaro308]

Why was idle bearing not replaced

Oldfart were you refering to my crank and case pics?
If you were....this was just a mock up to answer our own question of 100/125 compatability.
That 125T crank will eventually get a rod kit and go back into the bike to bring it back to a 125.

If it wasn't....just ignore my post 

[Loydee]

"Looks like we have a YES on both engines being interchangeable as long as you have the crank,barrel and head from either engines."

Monaro, nice one for clarifying the 100/125 interchanges, really useful. Was just wondering ,especially as people wanna have STD 125 bores to work from -can ya not just bore out an RM100 barrel to 54mm? Maybe it's too short (compression issues/ ports won't line up??) 
Currently doing an RM100X with 125 forks,wheel and swingarm/shocks by the way

[rocketfrog]

RM 100 Barrel is shorter by 4mm, but a spacer under the barrel and possibly longer studs may make the switch possible. There looks like enough meat in the liner to bore to 54mm.
Also check out TF 100 and 125 for interchangeability, Lozza mentioned that customising the ports on a TF100 may be just the way to go if you want to build up hot 100 donk. Although I have not looked into it myself, it might be worth looking at if you have a TF engine to compare the two. I would be interested to hear from anyone who has looked at the possibilities.

The idler bearing can be removed with a split collet extractor and slide hammer readily enough, but using the "old pack with grease and drive out hydrauically trick" did not work for me.

[DR]

RM100/125B/C parts interchange with the TF100/125 models not RM100/125N/T or 100X

[rocketfrog]

Cheers Doc, I have never seen a TF in the flesh, they are an Ag bike are they not?

[Lozza]

can ya not just bore out an RM100 barrel to 54mm? Maybe it's too short (compression issues/ ports won't line up??) 

You could probably bore the 100 cylinder to 56mm(makes a 125) if you want to and the barrel spigot is willing.You have to reprofile the ports again but that's no real drama. The TF cylinder will allow you to run more modern ports(which give more and a better spread of power) and having a cheap endless supply of cylinders.

[monaro308]

Cheers Lozza thats good to know about the TF cylinder.
I assume they are of the same era to the RM or did the TF cylinder continue on to the late 70's and beyond with that same cylinder config? (i haven't seen one).

As for the idler bearing removal.....i throw mine in the oven (or wait for that Melbourne summers day )
and lay a sheet of masonite on the ground and slam the case flat....it falls straight out.

[DR]

The TF100/125 is basically an identical engine to the TS100ER and TS125ER built from about 1978 onwards...

[Marc.com]

The TF100/125 is basically an identical engine to the TS100ER and TS125ER built from about 1978 onwards...

Yes it was marketed as the Mudbug .... or slug take your pick, against the mighty Yamaha AG range.

Ask TMBill he is a worlds authority on them. You could get 125 and 185 versions from memory. Came with all the comforts of home like long range tank and carrier for your bovine companion. Highlighted technology has to be the lockable clutch, saved selecting neutral.