Hi Everyone, Can anyone tell me what the difference is between a FZC-1A1L rotor & stator which is fitted to the 1970  RT1 and the FZA-1B1L rotor & stator which is fitted to the RT2 & DT2. Can i use the FZA rotor & stator on the RT1, if not why not.  Is the taper different, mounting holes etc. The reason i ask is i have been given a rt1 engine with no rotor or stator, and i can get the FZA parts . Any help will be gratefully received, many thanks  Alan.

The RT1 Rotor has a mechanical advance mechanism , and RT2 rotor has a fixed cam .
Looking in from the back , the RT1 rotor has an obvious plate and spring .
The RT1 and RT2 stator plates are different , as the RT1 points are located in a slightly
different position , due to the different rotor , so you have to have a matched pair .
The RT1 setup is designed to have the timing retarded for startup .
They have a fairly evil reputation for kickback .
The 71 RT1 B has a decompressor valve on the cylinder , whereas the 70 doesn't .
You might get away with fitting an RT2 ignition to a 71 c/w decompressor , especially if you
retarded the ignition timing slightly , but you'd be a very brave man to attempt to fit it to a 70 RT1 .
Every time I had to start it , I'd hear Clint Eastwood saying  " Do you feel lucky punk " .
( just my opinion , others may disagree )
 

Swoop56 is 'onto it'. I had a decomp on mine so i must've had a "71 cylinder fitted but also had the retard thingy so i could damn near start it by hand. Also the points are different between the two plates due to the fat cam & sitting further out on he plate. Swoop could advise on that i hope, incase i'm wrong. Miss my RT1 motor, or top end at least.

Just to clarify . The points are identical in each case , but on the  RT1 ,
due to the advance mech , they are positioned further outwards on the stator plate ,
hence the different stator to match with the advance type Rotor .
 

Do I take it that by fitting the RT2 stator  & rotor to the RT 1 with a decompressor which is fitted into the cylinder head, I would be giving myself a bike that would be a sod to start, or am I miss reading your message. If this is the case I need to find a RT1 rotor & stator . Thanks  Alan.

Fitting the RT2 components to an RT1 B , would probably put you on par with a RT2
regarding starting . Kickback was still an issue with RT2 .
It has been suggested in previous posts , that retarding the ignition timing slightly ,
reduces that tendency , without any great effect on performance .
From memory , stock timing is 2.9 mm BTDC , and the suggestion is to knock it back
to 2.5 mm BTDC .
I don't know for certain , but that may be comparable to 70 RT1 in full retard setting .
Check the operation of the manual decompressor . They can get clogged up with carbon ,
and become ineffective  .

Some additional info and questions.

Does your RT1 cylinder have the decomp valve in front? The early '70 RT1 did not have it. The later ones may have had the cylinder replaced back in the day with a '71 RT1B cylinder as customers complained about hard starting and kickback. As mentioned the hole can get plugged with carbon.

Retarding the ignition timing can cause the engine to run hotter.

The compression release like this one that goes in the extra spark plug hole is for engine braking to help slow down the bike. It is not really an effective aid for starting.

 

This is what I use on my riders in the extra spark plug hole. Works well but must be manually depressed before each kick.

 






 

Ok, on my RT2 i had a cdi mag of a late DT250. Ok i made it up out of bits n pieces but rode it for years & never kicked back & no decomp fitted [blanked off as was my vmx bike]. Parts were equal to say a "79 DT250 or DT400 with the simple pulser not the two stage big one. Anyway--total fix. But the one i ran recently on my mix n match 360 in an R5 frame was a super simple DT360A stator plate & charge coil with a suzy RG50 cdi box with plug coil combined. One wire from source to box/coil & starts easily & runs well. Don't let me confuse you haha.
Also-- Swoop--i initially thought the points part numbers were different & i know they sit out further with fat cam etc, but every version on partzilla fails to show the advance flywheel which is bloody annoying haha. I thought the points had a shorter arm or something--i dunno,-- or i'm proving i dunno lol.

Gotta keep changing this as for some reason it fails to add a sentence with [ ] around it

Morley , I'm working with original parts books , which tend to give a bit more detail
when covering more than one model . The digitised versions on Partzilla and the like
fail to differentiate which parts fit which model . especially so when the pertinent parts are obsolete .

Cool Swoop thanks. Wish i had access to original books. If only we could see this far ahead when these bikes were current. The advance flywheel is different to look at externally on the front face & steps out a little.