Jays100
Veteran Member
I wrote this and posted it on another site. They're being annoying just now so am bringing that post over here. I believe everyone can benefit from this information. I learned it the hard way. Please feel free to post your experience(s) too.
Part 1 (of 2)
There are three ignition advancers from different manufacturers used on the 450/500Ts, their markings are CB450 (65-72) TEC292 (71-74) and TEC375 (75-76).
The manufacturer (Kokusan or Nippon Denso) determined how the points cam is mounted on the advancer mechanism.
They all mount and identically on the engine but the ignition advance curve varies with the year.
They’re quite simple with typically two fail mechanisms, there are more but primarily two. Btw, depending on your year 450, there are three suppliers of advance mechanism. Their parts do not interchange generally, However, they do interchange on engine.
Failure modes
1. Advancer stuck/points cam results in non-advance and low power output
2. Cam moves but idle hangs, results non-return to idle rpm
Tools needed
Scotchbrite pad, small (1/8” across blade max) flat blade screwdriver, can of brake-clean aerosol cleaner, 3 in1 oil, shop towels/rags, patience and a well lighted workspace, solvent/soap cleaner of choice.
Both failure modes require disassembly to solve.
-Take a before condition pic, both sides. This may be optional to some but future you will thank current you if a piece is lost or you forget how it all goes together.
-Spread the centrifugal weights and remove the cam. If rusted, you’re hosed as they require heat a Herculean effort to remove without damage. If solidified/aged grease, the cams can generally be separated and once they start to move they’re easy. Aside.
-With the small screwdriver, remove the E-clips from the weights pivot post, remove springs, shims (flat and wavy). Keep the shims in order but it’s flat on the bottom and wavy top.
-Remove all grease, clean thoroughly. This is the critical step
Note I’ve found the best tool to remove accumulated, mung, grut, spooge rust and other nastiness (and you’ll find it all) is new Scotchbrite. With adroit treatment of all sliding surfaces, base plate armature, cam inside diameter and the outside too, remove all nastiness encountered. Don’t be shy, it’s hard steel and scratches are no harm (they retain oil). Next, do the pivot posts, get into the corners, bucko, as well as the weight pivot holes.
-Spray brake clean (or use soap and water with an old toothbrush) all parts, do it twice and check if naughty or nice, redoing missed or questionable areas.
-Wash your hands and clean the area, not losing anything. Laying out the dry parts on a clean towel helps inventory, quality inspection and is the gold star of good work practice.
Reassembly in Part 2.
Part 1 (of 2)
There are three ignition advancers from different manufacturers used on the 450/500Ts, their markings are CB450 (65-72) TEC292 (71-74) and TEC375 (75-76).
The manufacturer (Kokusan or Nippon Denso) determined how the points cam is mounted on the advancer mechanism.
They all mount and identically on the engine but the ignition advance curve varies with the year.
They’re quite simple with typically two fail mechanisms, there are more but primarily two. Btw, depending on your year 450, there are three suppliers of advance mechanism. Their parts do not interchange generally, However, they do interchange on engine.
Failure modes
1. Advancer stuck/points cam results in non-advance and low power output
2. Cam moves but idle hangs, results non-return to idle rpm
Tools needed
Scotchbrite pad, small (1/8” across blade max) flat blade screwdriver, can of brake-clean aerosol cleaner, 3 in1 oil, shop towels/rags, patience and a well lighted workspace, solvent/soap cleaner of choice.
Both failure modes require disassembly to solve.
-Take a before condition pic, both sides. This may be optional to some but future you will thank current you if a piece is lost or you forget how it all goes together.
-Spread the centrifugal weights and remove the cam. If rusted, you’re hosed as they require heat a Herculean effort to remove without damage. If solidified/aged grease, the cams can generally be separated and once they start to move they’re easy. Aside.
-With the small screwdriver, remove the E-clips from the weights pivot post, remove springs, shims (flat and wavy). Keep the shims in order but it’s flat on the bottom and wavy top.
-Remove all grease, clean thoroughly. This is the critical step
Note I’ve found the best tool to remove accumulated, mung, grut, spooge rust and other nastiness (and you’ll find it all) is new Scotchbrite. With adroit treatment of all sliding surfaces, base plate armature, cam inside diameter and the outside too, remove all nastiness encountered. Don’t be shy, it’s hard steel and scratches are no harm (they retain oil). Next, do the pivot posts, get into the corners, bucko, as well as the weight pivot holes.
-Spray brake clean (or use soap and water with an old toothbrush) all parts, do it twice and check if naughty or nice, redoing missed or questionable areas.
-Wash your hands and clean the area, not losing anything. Laying out the dry parts on a clean towel helps inventory, quality inspection and is the gold star of good work practice.
Reassembly in Part 2.