G5 Spark advance springs

[wirespokes]

1979 G5. Stock engine with gilardonis. It's been a project sorting this bike and getting it running right.

It's running pretty well right now, but not quite 100%. It doesn't feel quite right at low RPMs and am pretty sure it's due to advance springs.

I'm thinking of getting both the low performance and high performance springs and trying them out to see which work best. I know Mark at MG Classics installs the high performance in everything. I've studied the graphs and write-up in Guzziology and can't decide which is the better choice. Should I go with the low performance springs and set the timing at six or seven BTDC or the high performance and static time at 8*.

If I set the timing at seven or eight with the low performance springs I could be getting way too much advance, where as, running the high performance gives less advance. More advance = more power and better economy. Of course, the end goal is 33* full advance at 4K or 4500 RPM.

I'm thinking the low performance springs are the way to go and setting static higher than the 2* stock. Like at six or seven or eight BTDC.

I've also considered making a slightly stiffer low-rpm spring to give a little less advance with the low performance springs after raising the static setting.

What worked for you?

[guzzisteve]

My Cal 2 has the stock low performance springs and is set at 6* and I have had no ill effects from it in 90,000mi since the mod. I did this same time I put a heavy V700 flywheel in it for sidecar use. I also put on 32mm carbs which helped to get past the gearing wall around 70- 80mph.
I did buy the LeMans springs just in case but they are still in an envelope, no issues yet.

[Antietam Classic Cycle]

I've never used anything other than the "low performance" springs, timing set to stock specs.

[PeteS]

I am not familiar with the G5 specs but if it has the same cam as a T3 and 850 LeMans you won’t be making much power below 4k. Try the LeMans springs. You don’t have anything to loose. For better low end, higher compression and a cam with less overlap (higher effective CR) will do more good.

Pete

[wirespokes]

I've never used anything other than the "low performance" springs, timing set to stock specs.

Thanks, Charlie. What economy do you get with the Liter engines?

I am not familiar with the G5 specs but if it has the same cam as a T3 and 850 LeMans you won’t be making much power below 4k. Try the LeMans springs. You don’t have anything to loose. For better low end, higher compression and a cam with less overlap (higher effective CR) will do more good.

The G5 is essentially a Convert with a standard transmission - low compression, not the high performance package. The story I heard is that G5 is short for GEARS 5. Makes sense to me.

The high performance springs retard timing, which hurts power and economy. Retarded timing is the solution for pre-ignition, which shouldn't be a problem in low performance applications.

My Cal 2 has the stock low performance springs and is set at 6* and I have had no ill effects from it in 90,000mi since the mod. I did this same time I put a heavy V700 flywheel in it for sidecar use. I also put on 32mm carbs which helped to get past the gearing wall around 70- 80mph.
I did buy the LeMans springs just in case but they are still in an envelope, no issues yet.

Steve - I'd imagine if you had pinging with the advanced timing you'd know it hauling a car. I think you convinced me to get the low performance springs. As for economy, miles/gallon tend to be low with side cars, but still, I'm interested in what you're getting.

[Antietam Classic Cycle]

Thanks, Charlie. What economy do you get with the Liter engines?


My Convert averages 40 mpg, the Cal III FF averaged 50 mpg on the cross-country trip.

[guzzisteve]

Steve - I'd imagine if you had pinging with the advanced timing you'd know it hauling a car. I think you convinced me to get the low performance springs. As for economy, miles/gallon tend to be low with side cars, but still, I'm interested in what you're getting.

Never had any pinging on that bike before or after changing timing. Running Dyna3 and Dyna green coils. Bike pulls the car over 100 and can cruise at 80. The carbs @ 32mm made a big difference. I would have liked 34's but had a new set of 32's.

[PeteS]

You can have performance along with fuel economy. A friend with a built LMIII, >1000cc with a stroker crank and 992 kit would typically get 46-48mpg while I was only getting around 40 on my 850 LeMans while riding together. Same with my EV with Power Commander. Around 45 mph and much more low end compared with the stock 40 and all its flat spots.

Pete

[wirespokes]

That's been my experience too - power and economy can go hand in hand. I've got bikes that run very strong and get 50 or better - 850 mostly. Seems like the 1,000s top out somewhere 45-50mpg.

[theoneandonlymin]

How about one of each spring or is that where madness lies ?

[spmoto]

The key to the effectiveness of the heavier (performance) springs used in the Le Mans models is that they also have totally different distributors. I had a T3 a while back that ran like a dog below 4500-5000 rpm. I spent a long time trying to get it sorted and nothing I tried made a difference until I popped in a pair of the light springs and the bike was transformed. Turns out that the T3, G5 etc. distributor doesn't spin fast enough to overcome the stiff springs until the engine RPM's are way up.
Steve M

[wirespokes]

The key to the effectiveness of the heavier (performance) springs used in the Le Mans models is that they also have totally different distributors. I had a T3 a while back that ran like a dog below 4500-5000 rpm. I spent a long time trying to get it sorted and nothing I tried made a difference until I popped in a pair of the light springs and the bike was transformed. Turns out that the T3, G5 etc. distributor doesn't spin fast enough to overcome the stiff springs until the engine RPM's are way up.
Steve M

The high performance distributor has a different part number than the low performance counterpart, so it's logical they're significantly different. However, Dave Richardson (Guzziology) compared each in minute detail and found they were identical except for the advance springs. He even went so far as having them tested on a distributor tester and found they both gave 13 degrees of advance - which equals 26 degrees on the bike.

So I'm sorry to contradict, but it was the springs that made the difference, unless there was something wrong with the original distributor.

I have a second distributor, so I installed it. The bike now runs as it should. I'm very pleased! I'll be ordering some new springs - the low performance variety!