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A A A A Author Topic: Rough Running over 5000rpm - Ignition Timing or?  (Read 232 times)

Barocca

Rough Running over 5000rpm - Ignition Timing or?
« Started on: 18-Aug-19, 14:51 »
Finally got the CX500 back on the road after trip-bypass, Raesan Hall-effect ignition, and CXPhreak carb rebuild.  The bike started OK and pulled OK at low revs as I nursed it around the suburb and got it up to temperature.  Then I took it for a brief lope (about 5km) up the freeway and back.  It would pull cleanly up to 4500-500rpm and then start to lose power (and miss?). 
If asked, I would say that I was fastidious about correctly setting the ignition timing with the new Raesan unit, however.......  I checked the timing with a strobe light with plugs out and batteries (car battery in parallel) spinning the engine.  It appears that both left and right coils are firing about 8-10mm retarded as viewed on the flywheel. 
Is this a valid test?
How many degrees retarded is this?
Could this be the source of my problem?
Are there any other tests that I should do before reluctantly dropping the engine?

CX PHREAK

You didn't perhaps time the Raesan on the T mark, rather than the F mark?

How many degrees that is depends on the circumference of the flywheel. I'll run a tape measure around one later. but it is roughly the distance between T and f marks.

Barocca

Thanks Mark, I think that the bike is firing about 1/3 of the way between "F" and "T". 

CX PHREAK

You will need to retime. The green LED should go out at the F mark for each cylinder. There is about a degree of straddle side to side so one just prior, one just after..

You want to be rotating the motor counter clockwise when looking from the back or rotating the hall sensor plate clockwise.

Barocca

Thanks Mark,
if flywheel is 8-9 inches in diameter (guess), then 10mm on circumference represents 5-6 degrees.  Is this enough to cause the symptoms observed?  BTW, I agree I'll have to retime anyways (perhaps try to do it by removing swing-arm rather than complete engine removal?). 

Barocca

I have verified that the timing was retarded by 8mm on the flywheel, so about 5 degrees of crank rotation (sloppy work from me).  I've dropped the engine and carefully re-set the timing.  However, I'm not sure that my 5 degree error can account for the symptoms observed.  I'm ready to re-assemble, but before I embark on this I wonder if there is a way to check the advance circuit on the Rae-san ignition without firing up the engine.  I imagine not, but I'd hate to complete re-assembly and then find that there was a simple check that I could have done.  I've sent a pm to Rayman seeking advice. 
Whilst doing this work I've re-torqued the cylinder heads and re-set tappet clearances.  Strangely all tappets were running too big. 

Cass

Barocca,

I just installed the hall effect in my "81 and what I did might help you to check your timing. Set the flywheel mark (FR\FL) in the correct position with the marker then loosen the hall effect,
pull the corresponding plug out and earth the plug to the tappet cover lead on. Turn the ignition on and rotate the hall effect clockwise until you get a spark, you will hear it go crack then hand tighten one bolt and then do the other side and repeat 3 or 4 times. Once you happy that there both sparking on the marks hand tighten both the bolts and rotate the crank 17mm bolt at the front of the motor clockwise and check your timing marks as you hear the spark, helps if you can get a second person to turn the crank. One should be just before the timing mark and one just after.

Cass

Barocca

Thanks Cass, I'll give it a go.

Cass

PS. Barocca,
Try curve D ( Jumper A & B ) on, I have had the best response on this setting and also check air fuel too. Might need to look at carbie  syncro as well. Checked Mine today with  a timing light and spot on, took it for quick fang and went to 9.5 k in top gear with no ignition break down. happy0158 happy0158

Cass

Cass

Another P.S. Barocca,

I've had to advance my timing a few degrees ie: between the fr\fl mark and the double lines which are the high speed advance marks, the bike is so much more responsive.
Note the same method as mention in previous post, you can do this with the motor in just got to get the overflow bottle out and it will come out from the left.
Get an 8mm ratchet spanner makes the job so much easer and you might need to grind the top and side off a little to fit the timing cover, bugger of a job but beats dropping the motor!

Cass

 


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