Topic: Dyna s ignition. Set between Advance marks won't idle

[winkster2005]

Hello everyone,

I installed a dyna s ignition on my 1976 cb750 with stock coils. I adjusted it to full advance with a test light and then checked it with a strobe. When it is set this way the timing marks at idle are way off. The  problem is that when I stop the bike stalls when it is set like this. I set the bike up with the lines for idle and it runs fine but I am getting some popping while riding around. Do i just need to find a happy medium between the Advance and idle marks or is there something I'm missing?

[540nova]

You could try adjusting your idle speed higher. If that doesn't work, like you said, a happy medium between the fire and full advance marks.


1974 CB450, 2006 CBR1000RR

[madmtnmotors]

Something's not right. Weak advancer springs, advancer mechanism "sticky", poor wiring connections, fouled plugs, high resistance in one or more spark plug boots, etc...

"Popping" can sometimes be caused by carb issues.

I've set up half a dozen Dyna ignitions and have never had any issues.

Why did you install the Dyna? How was it running on points?

[mj1176]

I can't tell if you did this by the way you worded your post, but the dyna is supposed to be timed statically to the advance mark with the rotor in the advance position. So you have to line it up such that you get spark when you turn the rotor all the way by hand, not just by turning the crank until you get spark. Make sense? I did mine statically and never even needed to time it running with a strobe.

[winkster2005]

Ok so I timed it to the Advance marks again and it was running good but now either cylinder 3 or 4 is popping pretty bad. I checked my plugs and they are all sooty.

[madmtnmotors]

Why did you install the Dyna? How was it running on points?

[calj737]

Ok so I timed it to the Advance marks again and it was running good but now either cylinder 3 or 4 is popping pretty bad. I checked my plugs and they are all sooty.

Too much fuel. Clear tube method check on your fuel level in the bowls. 

[winkster2005]

Yea I think I'm gonna go back to 110 main jets and throw a new set of d8ea plugs in

[madmtnmotors]

Why did you install the Dyna? How was it running on points?

Yea I think I'm gonna go back to 110 main jets and throw a new set of d8ea plugs in

So now you're saying you installed a Dyna ignition and bigger jets at the same time?

[winkster2005]

No I replaced the points with the dyna when I first got the bike and switched jets maybe 300 miles ago but I was running pods and went up a jet size because the plugs were a little white. I put the stick box back on because I was just having issues and didn't want to mess up the bike. The popping issue started after I bench synced the carbs. So I got a set of gauges and got them running good but the popping is still there

[flybox1]

Why did you install the Dyna? How was it running on points?

Yea I think I'm gonna go back to 110 main jets and throw a new set of d8ea plugs in

So now you're saying you installed a Dyna ignition and bigger jets at the same time?

...and then went back to the stock airbox 

Put the tools down, and back away from the bike, son. 

[madmtnmotors]

The popping issue started after I bench synced the carbs. So I got a set of gauges and got them running good but the popping is still there

>Popping on acceleration, deceleration, or all the time?
>How long since the valve lash was checked?

[winkster2005]

The popping issue started after I bench synced the carbs. So I got a set of gauges and got them running good but the popping is still there

>Popping on acceleration, deceleration, or all the time?
>How long since the valve lash was checked?

I checked the valves right before I did the sync on the carbs. It pops when decelerating or when idling. 

[winkster2005]

Why did you install the Dyna? How was it running on points?

Yea I think I'm gonna go back to 110 main jets and throw a new set of d8ea plugs in

So now you're saying you installed a Dyna ignition and bigger jets at the same time?

...and then went back to the stock airbox 

Put the tools down, and back away from the bike, son. 

I didnt see the question about installing the dyna... I went to the dyna s because the condenser Died on my points system. I tried replacing it and the new condenser was making the points arc. I had the dyna s sitting around because I was going to put it in my 71 cb 750 after I got it back together and knew it ran.

The reason I left the 115 mains in is because I read a post somewhere online about how the later cb 750s ran lean to begin with and the bike came with Mac 4 into 2 pipes when I got it. I figured I could adjust the air fuel, maybe even adjust the slides to make the air fuel mixture right...

[flybox1]

youve caused your own tuning issues, wink.
too many changes at once when they arent proven to be needed.
points arcing after new condensors?  did you get the wires and spacers in the correct stack and not touching anything else so they wouldnt arc?
thrown on the dyna to fix it (probably not needed)...white plugs, then sooty plugs.  pods then airbox, 110's or 115's.
slow down, bud...figure out what the real problem is before you throw another part on it 


List for us your current setup:
main jet brand and #
Pilot jet brand and #
Needle in the stock clip position:
float height setting? and verified w clear tube test?
air screw setting?
plug caps on the dyna good?
pods or stock airbox?  what type of filter?
exhaust  type/brand/baffled?

with all of this....what is your symptom, and what do a new set of plugs look like after an idle plug chop?

[PeWe]

No poblem to set ignition "F" mark at idle 1200 rpm. Increase throttle and see full advance at around 2600-2700 rpm.
My bike had sloppy adv springs, F at idle OK, but full adv way too early. I cut both springs 1/2 wound and reshaped them with a plier looking good. Worked good after that, same behaviour with Pamco, Dyna-S and now std points with Hondaman ign module.

[madmtnmotors]

I checked the valves right before I did the sync on the carbs. It pops when decelerating or when idling. 

Popping on deceleration usually indicates a lean condition, or an exhaust valve not closing fully, which can be caused by a number of factors:

>Carb to head rubber boots old/hard/cracked/leaking. This cannot be overlooked and must be checked thoroughly.
>Float level too low
>Idle mixture screws set too lean (although not so much effect from this on deceleration)
>Main jets too small (least likely)
>Exhaust valve lash set too tight (exhaust valve not closing) or exhaust valve burnt and leaking
>Timing too far advanced (not very likely based on previous posts)

How difficult was it to achieve a vacuum sync of the carbs?

[winkster2005]

youve caused your own tuning issues, wink.
too many changes at once when they arent proven to be needed.
points arcing after new condensors?  did you get the wires and spacers in the correct stack and not touching anything else so they wouldnt arc?
thrown on the dyna to fix it (probably not needed)...white plugs, then sooty plugs.  pods then airbox, 110's or 115's.
slow down, bud...figure out what the real problem is before you throw another part on it 


List for us your current setup:
main jet brand and #
Pilot jet brand and #
Needle in the stock clip position:
float height setting? and verified w clear tube test?
air screw setting?
plug caps on the dyna good?
pods or stock airbox?  what type of filter?
exhaust  type/brand/baffled?

with all of this....what is your symptom, and what do a new set of plugs look like after an idle plug chop?

I agree... even though most of these changes had a good but of miles between them I still probably rushed them.  I was kind of in a panic because my girlfriend was actually interested in riding it to a festival this weekend and I wanted to get it ready. We aren't going now so I'm gonna try and straighten this out. Since I have the stock air box on I'm going to return to the stock jetting. This means the only engine modification is the mac 4 into 2 exhaust. I put 2" baffles in it because I had to wear ear plugs to ride it. 

The valves are all in spec, Timing chain tightened, carbs synced (they were all fairly close to begin with) idle screws set to 1.5 turns out, the carb to head boots look good,  I didn't set the carb floats but when I dropped the bowls last time they all looked pretty good (I know that's probably not the best way to judge it)

  I am pretty sure the 110s and idles are oem. The plug caps do kind of worry me. The coils wires and caps all look original and I got a little zap when I pulled #4 wire off to see if the popping at idle would go away. I can't remember needle position from when I cleaned carbs.

[madmtnmotors]

I checked the valves right before I did the sync on the carbs. It pops when decelerating or when idling. 

Popping on deceleration usually indicates a lean condition, or an exhaust valve not closing fully, which can be caused by a number of factors:

>Carb to head rubber boots old/hard/cracked/leaking. This cannot be overlooked and must be checked thoroughly.
>Float level too low
>Idle mixture screws set too lean (although not so much effect from this on deceleration)
>Main jets too small (least likely)
>Exhaust valve lash set too tight (exhaust valve not closing) or exhaust valve burnt and leaking
>Timing too far advanced (not very likely based on previous posts)

How difficult was it to achieve a vacuum sync of the carbs?

I forgot one, popping can be a result of an exhaust leak as well.

[flybox1]

The things we do for women  

The valves are all in spec, Timing chain tightened, carbs synced (they were all fairly close to begin with) idle screws set to 1.5 turns out, the carb to head boots look good Look good or are good?  Cracks can hide near the edges of the clamps I didn't set the carb floats but when I dropped the bowls last time they all looked pretty good (I know that's probably not the best way to judge it)  No, its not.  Clear tube test your fuel level to be sure

  I am pretty sure the 110s and idles are oem. Make sure.  They should be stamped 'K' near the size stamp The plug caps do kind of worry me. Measure their resistance, and change them if above 8k ohms.  If they are good, cut back the old wires to good copper and reinstall The coils wires and caps all look original and I got a little zap when I pulled #4 wire off to see if the popping at idle would go away. I can't remember needle position from when I cleaned carbs.  I'd check what slot the clip is in.  The PO might have changed it for the pods

[winkster2005]

I forgot one, popping can be a result of an exhaust leak as well.
[/quote]

I just checked and number 3 is leaking between the header and where it collects into the large pipe. What would be the best way to seal this?

[winkster2005]

The things we do for women  


Yea lol and 95% of the time when we do it  we still don't do it right

[calj737]

I forgot one, popping can be a result of an exhaust leak as well.

I just checked and number 3 is leaking between the header and where it collects into the large pipe. What would be the best way to seal this?
[/quote]
Remove the pipes and install 4 new crush gaskets on all pipes. Make sure to extract the existing ones first.

[madmtnmotors]

I just checked and number 3 is leaking between the header and where it collects into the large pipe. What would be the best way to seal this?

Remove the pipes and install 4 new crush gaskets on all pipes. Make sure to extract the existing ones first.

The description refers to where the pipes join the 4-into-1 collector, not at the head. Since we don't have any pictures of the pipes in question, any suggestions made would be a shot in the dark. Leaks at the collector are far less likely to cause popping than leaks right at the head, unless it happens to be leaking profusely at the collector...

[winkster2005]

I'll try to get it out of the garage and take a picture today