adjustable ignition timing

[Richardg]

Well, I have been told on many occasions that my late RDo7 @ has fixed ignition timing, and that there is no adjustment (but I am the kind of guy that won’t take no for an answer.
Well last week I was having a few niggles with the bike running a bit ‘lumpy’ at low RPM, not the kind of fault that you could say the bike needed to go into the shop for, but still not quite right. I checked all the normal things but no luck, carbs were all OK, TPS (throttle position sensor) OK, plugs OK, valve clearance OK etc etc. Finally I opened the timing inspection plug and stuck my ignition timing light in, and guess what? Yes the ignition timing was about 4 degrees out (retarded or late). Problem!!! The @ manual says that if you find the timing out then you have to start replacing ignition components. My problem is that the ignition system all seems to be working fine, no misfires, no poor starting and on runs out it has been fine, the only issue was the slightly lumpy running at low revs (tick-over to 4Kish. Anyway, I decided to take the plunge and try and alter the timing (bad lad) so if you ever have the same problem then you might like to have a go.
The way I did this is as follows (not for the fainthearted). Take off the IPG cover (Ignition Pulse generator, by the way this is not a ‘sensor’ as some people think, it is a small generator that sends a voltage up the ignition box as the flywheel spins) (three bolts), inside you will see the IPG bolted to the engine case (a black box with two wires soldered on), rotate the engine until one of the flywheel magnets directly aligns with the centre of the IPG. Use a feeler gauge to take the gap between the end of the centre of the IPG and note it on a piece of paper (this is very important). Then remove the two bolts securing the IPG (careful you don’t lose them into the engine BIG $$$$$£££££), Looking at the metal backing plate to the IPG you will see that Honda have stamped out two dowels that fit into machined wholes in the engine case to lock it in one place. In order to change the ignition timing I had to re mount the IPG in a new position, this is only possible by filing off both dowels from the backing plate (be careful not to damage the IPG, plus opening out the bolt wholes in one direction in order to allow the IPG to move up or down. Now as the engine rotates anti clockwise (as you look at the left side of the engine), in order to advance the ignition timing I had to move the IPG clockwise (or up). This required the bolt wholes slotting up by about 3mm on both bolt wholes. I then re fitted the IPG and when I had repositioned it (bolts slightly lose) use the feeler gauge I re set the IPG gap to the same as it was before I started. This is very important as it determines the amount of ignition advance as the engine revs increase (very complex so I won’t go into it now). With the gap re set, all that is needed is to tighten down the IPG so it won’t move, hand turn the engine to check nothing catches and re check the timing (with a good timing light). I had to try a couple of times to get it bang on the mark so be patent.

Total cost £0 and timing sorted

Engine runs fine now, I am not sure why the timing should slip over the years but it has. One possibility is that the flywheel magnets lose some of their flux and are not quite as strong as when they were new, this would cause the ignition timing to retard slightly as the voltage ‘trigger’ point for the ignition would be slightly later (flywheel rotation wise). By the way, before anyone asks I did check to see if the flywheel was lose before butchering the IPG.

Few, that’s a technical one.

[TanisWolfbane]

Wow, that what I like to see. People not taking no for an answer. There are way to many people afraid to make mistakes and learn by them.

D

[Richardg]

Thanks D,

[GSPD750]

Way cool. Good job. I just may have to check my timing for sh!ts & giggles.