Topic: Shifting timing & Spark advancer issues

[edwardrytas]

Hi All,

I'm relatively new to the forum - at least I haven't posted much but I read a lot! I am fixing up a CB550 and also have a 500 in pieces. Been working on the CB550 for the summer (in Australia) and have done a lot of updates to the bike. Including carb clean/rebuild, new Lithium battery and connection clean up; and a general 'service' (new sparks, valve clearance, new points, cam chain tension, oil change...)

Currently, my issue is that the timing seems to 'slip'. I set it up (point gaps, then 1-4, then 2-3) all good. I run the bike and all 4 cylinders fire. After a few seconds/minutes one cylinder stops firing (currently #4, but it has also been #2 - and #1). I check the timing and it is out. So I do it again, same thing. I've tried a number of different things - carbs, new sparks, check valve clearance) I've got new points in too. It is now consistently #4 that stops firing (cold exhaust pipe).

I think it's the Spark advancer (it's a 323 model). There is some play in the action where it joins the engine/crank (about 2-4 mm, sorry I'm metric!). From my research, this is a common issue due to the hole in the crank/engine that the pin on the advancer fits into being worn (and oval shaped).

Some posts here suggest and a shim and drilling out the cranck a little (my pin in 3mm - I've seen suggestions of finding some thin-wall brass tubing with a 3mm ID and a 4mm OD (Scottly from forum post http://forums.sohc4.net/index.php/topic,113338.25.html p. 2). Hondaman also suggests adding some thin brass shim.

Soooo... Can anyone provide more detail on this procedure? Has anyone done it? Does anyone else have a 'shifting timing' issue?

Thanks and happy dayz - Ed (Melbourne, Austalia)

[Deltarider]

Can't advise you on what you ask. Never had that problem. I'd start with the easiest: verify all washers and springwashers are present. Even in Honda documents pics do not always show all of them. The pic below does. When springwashers are missing, owners tend to overtighten the screws. It doesn't take much to damage the threads...

[edwardrytas]

Hi Deltarider - thanks for the response.

All washers including spring washers accounted for - it's not the plate that is moving but the advancer which is 'sloppy' in its mount to the engine.

I have added a small copper shim to the mounting hole that the advancer sits it. This seems to have restircted the amount of free play on the advancer and means my timing is more reliable and doesn't shift.

Happy dayz

[Deltarider]

Thanks for reporting. We learn everyday.

[bryanj]

The cause is owners using a big spanner on the advancer to turn the engine with plugs in when servicing. If you can shim the peg and get the advancer tight you should have no further problem unless you rotate the engine with the advancer.

[PeWe]

1. No problem with the advancer play if you set it right. Max counterclockwise position and tighten the small nut, This is how I have done on 2 Cranks+ advancers that I have used in same engine, now 2 engines. Check with piston stop + degree wheel, measure pistons tops with head off. This to ensure correct TDC where T should align with case mark. When this is correct F (ignition will be correct too.

2. Next is the advancer springs that most likely are too soft causing too early ignition.

3. The Ignition Base plate sit loose, it has 3 machined  surfaces on cases where it should sit tight. It doe miósst likely not do that and will change position making points to change when you adjust 1:4 setting turning the plate. This will make it difficult to ever set the ignition correct.

I have described this several times since I found out with help of this forum where this has been up. Hondaman described cutting the springs, another about how the base plate must be properly centered. I found  good description about ignition setting on hondachopper site.

I described this yesterday with links
http://forums.sohc4.net/index.php/topic,176642.msg2053918.html#msg2053918

Note! Floats (Fuel level too high) in carbs are another detail that will make an old bike to run crap causing sooty plugs at idle. It cannot be too low either, it will then run lean at higher speeds. Typical if all carbs are set equal but 1 or 2 runs leaner.

[BenelliSEI]

Read the suggestion that the shim or bushing should be a “piece of small tubing” or shim wrapped around the original pin. Don’t just jam a strip of shim  in there...... just a very small, permanent offset in the advancer pin centre will change all your future timing settings. Since the TDC, idle advance and total advance marks are stamped on the advancer, a very small offset will change your actual settings. To confirm, pull the spark plugs and get a dial guage (or a Screwdriver) on #4 piston. Make sure that TDC mark is really lining up correctly. I’ve seen errors of 3-5 degrees.