Topic: Symptoms of weak advancer springs?

[tfrasca]

I currently don't have access to a timing strobe, which would be the easy way to test the timing advance on my '76 CB550. I installed a Dyna S and timed it with a static light, and refurbished the advance while I was there. It's very smooth, and almost feels like there's not enough resistance in the old springs. What would the symptoms be of worn springs causing the advancer to fully advance just off idle, instead of around 2500 RPM?

Just trying to chase down this slight sputter off idle. It was really bad when the carbs were over rich, but now they're running stoic, if not a little lean and the sputter is still there, ever-so-slightly. Just thinking that maybe the bike needs retarded timing around 1500, and maybe it's advancing too early. Or would that not manifest as a slight stutter?

Thanks,

TF

[HondaMan]

I currently don't have access to a timing strobe, which would be the easy way to test the timing advance on my '76 CB550. I installed a Dyna S and timed it with a static light, and refurbished the advance while I was there. It's very smooth, and almost feels like there's not enough resistance in the old springs. What would the symptoms be of worn springs causing the advancer to fully advance just off idle, instead of around 2500 RPM?

Just trying to chase down this slight sputter off idle. It was really bad when the carbs were over rich, but now they're running stoic, if not a little lean and the sputter is still there, ever-so-slightly. Just thinking that maybe the bike needs retarded timing around 1500, and maybe it's advancing too early. Or would that not manifest as a slight stutter?

Thanks,

TF

100% of the 500/550 bikes I have worked on that have more than 8000 miles on them have annealed, too-soft spark advance springs. (The same is true for the other Fours, but the worst is the 500/550.) It allows them to hit full advance in some cases by 1500 RPM. I solve it by cutting off usually 1/2 turn from each spring, which helps to delay it to about 2500 RPM. If you go to 3000 or even 3500 RPM, the midrange torque usually improves as it stops spitting back into the intake tract during overlap so much then. That's what causes that 'stumble'.

You can 'sneak up' on it by cutting one spring at a time: then it is like an old Ford automotive distributor, where one spring was strong and the other weak: it lets 2 different advance curves be tailored into one contiguous sweep. Often, the old Ford springs would have a "free loop" on the stronger spring that let the weaker one reach some advance point quickly (usually about 30 MPH) to improve throttle response, then the heavier spring began to slow things down. My old 1967 LTD has exactly this: the first spring let it advance to 28 BTDC by 1400 RPM where it stayed until 1600 RPM, the heavier one then let it advance to 45 degrees by 2200 RPM. The Police Interceptor distributor I later bought (because it allowed use of lesser octane fuels when Colorado banned "real" premium gas in 1988) made the 'lower' RPM spring rate advance to 32 degrees by 1600 RPM, then at a slower rate to 40 degrees by 1800 RPM.

Of course, considering 1800 RPM in top gear was 88 MPH, it seldom reached full advance with the latter distributor aboard...

[dave500]

get hold of a timing light before you try and modify anything.

[tfrasca]

Good to know- thanks Hondaman. It's interesting how precise they were able to get those Ford ignition curves with such simple methods!

Regarding our 550's, can you think of a reason that the stutter would only show up when the engine is warm?

[PeWe]

I had too soft springs too. CB750. Full advance at ~ 1500 rpm, not possible to adjust. Read Hondamans recommendation in an old thread. Timing light is cheap and a must to confirm ignition with. I cut both springs.
http://forums.sohc4.net/index.php?topic=131339.msg1464986#msg1464986

[tfrasca]

I'll get a timing light before cutting anything. Just trying to chase down this sputter, and wishing it was the timing. But I really think it's the jetting and/or something in the carbs. Frustrating.

[HondaMan]

Good to know- thanks Hondaman. It's interesting how precise they were able to get those Ford ignition curves with such simple methods!

Regarding our 550's, can you think of a reason that the stutter would only show up when the engine is warm?

Yep, it's worse when warm. Reason: these bikes use a waste-spark system, firing the unused cylinder of each coil's pair during overlap. When the engine is cold, the fuel mixture does not ignite well (or at all) during overlap, so it does not spit back into the carb throats. When the engine heats up, and especially if the timing is too early, the mix DOES partially ignite, and this spits into the carb throats, disturbing the next incoming charge. As soon as the engine speeds up past this point, this ignited burn is pushed out the exhaust valve with more force and it can't burn its way up in toward the carbs.

Honda tried to mitigate this in the post-1975 engines by delaying the intake valve opening to 0 degrees TDC instead of 5-7 BDTC. The later engines had to have lean-burn mixtures (due to EPA and DOT interference with Honda in those days), which ignited easier during overlap. This also led to the later engines having stronger spark advancer springs, for this same reason. It causes a loss of low-end torque to delay the cam, but this is the same phenomenon as having the charge spit back into the carbs: both produce less fuel in the next intake stroke. It is perceived as a stumble when the throttle is first 'cracked' open at low speeds.

[dave500]

if your running retarded youll have a flat soggy spot off idle,if you crank the throttle hard you can get a cough or induction fart,time the engine to the max advance marks by using the strobe,slowly increase the rpm watching the advance marks move toward full advance,once they stop advancing with more rpm input set the timing there at the full advance mark,ignore where the timing ends up at idle and forget about the "F"mark for timing,think of the advance unit as a retard unit,it retards the ignition to let you start the engine easy,full advance is all in by 2500-3000,this is the lowest rpm you should be riding in,anything less is lugging the engine,these run happy around town in 4th gear at 35mph/60klm phr,when your riding the bike the engine is always at full advance,the curve itself isn't as critical as you might think,once your riding don't baby or try to cruise the engine too much.

[Maurice]

But Dave, won't the engine idle like crap if advanced too much? It's going to be fighting itself, no? Sure you can make up for it with richer settings, but still.

I always try to both static and dynamic time and get it as close as possible in both areas, and like you said advance curve is not critical.

[Vinhead1957]

It will not idle down smoothly.

[dave500]

itll be ok unless your advancer is that worn it allows an excessive advance at idle,its mostly out a couple of degrees,your best of gaining the advance for power and economy than giving a #$%* about your idle,you shouldn't be letting these idle for long anyway,some people get too fussy with the f mark timing,the fact is unless you've dialled the advancer on to the crank it can be a few degrees off either way,the locating pin doesent always locate exactly there is some movement like this one.


some are worse some are better some are perfect.

[Maurice]

I don't know, I do give a #$%* about my idle, I don't like to stall at red lights or stop signs it's embarrassing

But you're probably right that much difference is likely negligible.

[dave500]

why will you stall at stop lights?adjust your idle speed?its more likely to stall being retarded than advanced unless its stupidly over advanced,you can set these past the second advance mark by quite a few degrees so long as your fuel is good,youll gain mileage and power,too bad they don't have a vacuum advance system.

[Deltarider]

I remember that the first two years I owned my bike I had all the maintenance done by the Honda dealer. Soon I became curious and step by step I tried to make myself acquainted with tuning my bike. After all it was all there in the Owner's manual. I had noticed that when I checked the ignition after the bike had been at the dealers, ignition always had a few degrees extra advance. At first I was proud to discover this and correct the timing to exacly the marks, Honda had put there, only to discover my bike was not as lively as before. Also a friends 550 always returned with a few extra degrees advance. When I corrected this for him, proud to use my new dwellmeter and strobe and met him later on, he told me he had not been happy with the result and had the dealer set the timing like before. Later I found out more mechanics (some of them had owned a 500/550 or still owned one) had the experience of a better result with a few degrees extra advance,
Why was Honda on the conservative side with its marks? I don't know. What I do know is that the CB500 was exported to all kinds of countries including markets with low quality gas. I remember having seen CB500 policepatrolmotors in southern Africa. The quality of gasoline there was very poor indeed.
I don't know how the situation has developped in the USA, but during my holiday in 1989 riding a Goldwing I came to the same conclusion as many Europeans before me: gas equalled third world quality. On why this was so, I can only speculate but I have a suspicion. Nothing wrong with the Goldwing btw.
I'm with Dave, as long as your gas is good, there's no harm in having a few extra degrees advance. Optimum depends not only on octane, but also gas quality and the condition in the combustion chambers. It's for you to find out.
 

[PeWe]

My advancer has a rather large play (backlash) that affect the timing. It's correct at max counterclockwise position.TDC and T vs case index mark.
I have done one extra case index mark I can use if the advancer is turned max clockwise. It differ around 3-4mm on the case.
I made mark when pistons were at TDC, checked both ends of the lash.

About ignition timing. I learned many years (old cars) to advance the timing until pinging was heard on high gear driving in low speed giving the throttle. (possible to retard a litlle here until to less or no pinging)
I had pinging on my bike earlier this year when driving on 5:th gear in 100-140km/h increase throttle. This was caused by too lean carbs. Retard ignition did not help. Engine ran really hot too.

[dave500]

car motors are a bit different,they have a longer stroke and run at much lower rpm,im talking older distributor type engines here now,the advance on them is mostly run from idle to around 3/4 of the rpm band,say idle to 3500 on an engine that peaks at 5000?the curve is more important on these engines as they spend most of their time ranging from idle to say perhaps 3000?so the curve is always in use,they also run a vacuum advance system that comes into play at light throttle loadings like cruising on flat roads at highway speeds,the advance in this case is way higher than the engine could tolerate at any load like going up a hill or powering away from a stop light,in that instance the vacuum is low and the vacuum system stops working retarding it to the mech advance only,if you can run as much advance as you can on your Honda without pinging your sort of making up somewhat for not having a vacuum advance if you will,a lot of retards disconnected the vacuum advance on street cars thinking it was a hinderance to other hi po mods they made,they would've lost power and economy and tractability all at once,#$%*ing retards.

[Deltarider]

#$%*ing retards

IMO you are the guy that could put Putin in his place.

[dave500]

I don't get political delta,i leave that up to the professional retards!

[tfrasca]

Interesting read, thanks Dave. I thought it was in my head, but I would swear that my bike pulled harder before I ever touched the timing. Either the PO had advanced it a bit, or he had no idea what he was doing, but when I set the timing to stock spec, it was definitely slower. Thanks for the insight.

[Maurice]

Reminds me of this.