Has gas, compression, spark but no go

[Canuck750]

I am having a struggle getting my 750S to fire up. I rebuilt this bike at least five years ago, never got it on the road, too many other projects, finally planning to get it on the road.
This bike’s motor has been completely rebuilt, and has Dyna III ignition, it’s a gear driven cam, stock carbs.
I have good compression on both sides (bike has never been fired up yet), the spark on both sides is strong, the carbs are spotless and stock.
It won’t fire at all, nothing!
I pulled the front engine cover off and once again dialed in the cam timing and confirmed TDC on both sides and marked the flywheel accordingly, the marks on the flywheel were off 1 tooth for right hand cylinder TDC. I had a very experienced motorcycle mechanic go through the cam
Timing with me as well and we are sure we have it correct.
I have gone through the Dyna ignition installation and I believe I have it all connected properly.

I am wondering if I have the distributor installed incorrectly but after reviewing Guzziology instructions for installing a twin point distributor it looks to be installed correct. I got the odd slight backfire pop but it won’t t fire.

I am at a loss on what to look at next, anyone have any ideas?

[nc43bsa]

My first impression from your symptoms is that the ignition is firing on the exhaust stroke.

[Huzo]

My first impression from your symptoms is that the ignition is firing on the exhaust stroke.

This

[cliffrod]

If it’s not firing, it can’t misfire.  I agree Timing is off, probably with distributor installation.

[faffi]

Been there, done that. Not on a Guzzi, but on a KZ650, where you could fit the points cam 180 degrees off on the advancer. The odd bang is the result of residue gas in the combustion chamber or, more likely, in the exhaust system.

[Huzo]

If the bike has points, put a globe on the left hand points set and bring the left cylinder up to TDC on the compression stroke.
You’ll then see if the spark is occurring at the right time.

[Don G]

How fresh is the fuel? One of my Eldos would not start after sitting a couple of weeks, checked for spark first thing, had good spark, changed out the fuel and it fired right up!   DonG

[Stretch]

I might try a squirt of starting fluid.

If it fires, you have a fueling problem of some sort.
If not, you have a valve or ignition timing problem.

You say you've been over the valve timing 6 ways from Sunday,
so let's look at ignition.

Swap spark plug leads.

Next,  let's use Huzo's advice: Try setting the static timing for #1 cylinder
ACCORDING TO THE MANUAL. (Make sure you and the manual agree
on what the #1 cylinder is!    )

This should hopefully get you closer to the root cause of the trouble.

Keep us all posted!

                                                    -Stretch

[Huzo]

Yes.
 Mentioned TDC but that was for testing purposes only. Naturally the points would need to open @ the correct time for full ignition retard.

[Canuck750]

Well another day on the 750S,

The bike is fitted with Dyna III Electronic ignition, never had an issue with these before.

I consulted Guzziology on the Dyna setup and I am ashamed to have to admit I had the right Dyna rotating part setup for the right hand cylinder aligned to the wrong pickup, the Dyna instructions are a bit confusing but Richardson is clear the right hand cylinder is set by aligning the mark on the rotating part to the upper pickup. That said I got the bike to fire on the Left Hand cylinder only.

I tested each side grounding the plugs to the block and cranking over the motor, spark is strong on both sides but it only runs on the Left.

I swapped out plugs, I swapped out the coils and still only runs on left side. This leads me to believe the black box is faulty or the right side pickup is faulty.

I pulled the distributor at least a half dozen times and carefully followed Guzziology, set right hand piston to static timing mark, about 5 teeth before TDC, insert distributor with notch at 9:00 and as the distributor drops in the notch rotates to about 11:00 o’clock.

 I removed the Dyna ignition plate and made sure the underside was clean (again as per Guzziology).
I finally gave up at the end of the day and dug out a good set of original points, condensers and the points plate I had kept when I got the bike.

Tomorrow I will see if the bike will run on points.
I don’t think it’s a cam timing issue as I spent a day getting the aluminum timing gears and crank pin in the right spot for the right hand cylinder valve opening specs and it’s actually the left cylinder that is running.

I checked compression again, brand new Giladorni kits, 120 psi per side, about what I usually get with a brand new motor.

[RinkRat II]

     Thanks for the update, Jim. Hopefully the points will confirm your suspicions on the electronics.

     Paul B

[Muzz]

If it has you stumped Jim I don't think anything I could say will be of any benefit.

[faffi]

A cheap timing strobe light will tell you if the timing is a) happening at all under compression, and b) if it take place at the correct time.

[chuck peterson]

Tried running it in a dark garage while looking for misplaced sparks?

Frame grounds hidden by fresh paint?

Bad brand new condenser?

Danced in circles around a fire while burning $100 bills?

Zotsprkzzzponk…”Moto Guzzi, making electricians out of motorcycle riders since 1929…”

Good luck

[Chuck in Indiana]

but it only runs on the Left.

Classic Dyna failure..

[Canuck750]

Classic Dyna failure..

Good to know that what I described is a common Dyna failure, thanks Chuck.

Now to figure out how the points system goes back together, somewhere there has to be a picture of what goes where and the wire connections, I seem to recall it’s pretty simple but I’m pretty simple as well😳

If anyone has a good photo of their dual point Guzzi distributor with the cap off you might save this old fart a lot of grief!
Thanks in advance.

[Antietam Classic Cycle]

Good to know that what I described is a common Dyna failure, thanks Chuck.

Now to figure out how the points system goes back together, somewhere there has to be a picture of what goes where and the wire connections, I seem to recall it’s pretty simple but I’m pretty simple as well😳

If anyone has a good photo of their dual point Guzzi distributor with the cap off you might save this old fart a lot of grief!
Thanks in advance.

There's a good photo in the factory manual, that I go by when I forget how it all goes. Here's one from my Cal III FF refurb.

[SIR REAL ED]

If anyone has a good photo of their dual point Guzzi distributor with the cap off you might save this old fart a lot of grief!
Thanks in advance.

I agree with Chuck in Indiana.  Partial failure of electronics seems plausible.

If it is any comfort Jim, your grief is our entertainment & education.  I learn a lot from your trials and experience.

Not to mention, most of the great stories I have heard from Old Timers in my life have had more to do with troubles than successes!

Especially when the Old Timers start to "One up" each other with tales of woe!

[wirespokes]

Been through this over the last few months. Got a G5 project that ran, but not well. In the process it's possible I blew out one side of the dyna3. Rather than replace the dyna I went back to points and now, a couple months later, I've just about got it sorted out. It's simple stuff but sure can be confusing at first.

[guzzisteve]

If you have spark on both cyls how would it be a dyna failure?
180 out, wires from dyna should come out the back, facing rear of bike.

[Canuck750]

Original points and condensers back in, bike fired right up!

My timing light is on the Fritz, so it’s off to the auto parts store to buy a new one, timing by  feel and ear’ is basically ok but I need to set it at full advance.

It appears the Dyna just would not trigger the right hand cylinder at the correct time, there was a spark with the plugs pulled and grounded but it just would not run on the Dyna on the right cylinder, strange. Something to be said for good old points.

[Frenchfrog]

I'd never trust a dyna from what I've been consistently been reading for many years.
I used a Piranha /newtronic for many miles ...then upgraded to a sachse.Both have been very easy to set up and time, zero problems in use either.

[Antietam Classic Cycle]

Original points and condensers back in, bike fired right up!

My timing light is on the Fritz, so it’s off to the auto parts store to buy a new one, timing by  feel and ear’ is basically ok but I need to set it at full advance.

It appears the Dyna just would not trigger the right hand cylinder at the correct time, there was a spark with the plugs pulled and grounded but it just would not run on the Dyna on the right cylinder, strange. Something to be said for good old points.

30k miles since I set the points on my Convert, still the same gap, timing hasn't moved at all. A little dab of Bosch Distributor Grease is key to this. 

[faffi]

30k miles since I set the points on my Convert, still the same gap, timing hasn't moved at all. A little dab of Bosch Distributor Grease is key to this.

That IS impressive. Anything with points I have had, have required adjustments somewhere between 3 and 6k miles and replacement at 12,000 at the very latest, unless fitted with electronic "condenser".

[Antietam Classic Cycle]

That IS impressive. Anything with points I have had, have required adjustments somewhere between 3 and 6k miles and replacement at 12,000 at the very latest, unless fitted with electronic "condenser".

Just checked the points on my Cal III FF - I set those 9k miles ago and they're still exactly where I set them. Original Marelli points in both bikes. I won't even go into how long the o.e. points last in my Loopframe Guzzis (virtually "forever").

[Canuck750]

Thanks Charlie for posting the picture of the points and reminding me the V7 Sport Owners Manual has a great picture of the setup, that really helped me out!

A friend brought over his Snap-On strobe light and I was surprised to find I had both sets of points set just about bang on by ear, the full advance marks were within 1/2 a tooth at 4500 rpm.





I am taking the 750S out to the interior of southern British Columbia for the 1st week of September, the Kootney region has some of the best motorcycle roads anywhere, and the summer traffic is usually gone by the beginning of September.

[Stretch]

Glad you got it sorted!

Nice bike, by the way!   

                        -Stretch

[Mike Tashjian]

Condensers are key to long life for the point sets.  Cratering is going to tell you if your condenser is not quite right. Transfer of material to positive side you need a condenser with higher capacity or shorten condenser lead.  Transfer to the negative side you need a lower capacity condenser or lengthen condenser lead.  Sounds like Charlie has it right. 

[Huzo]

Condensers are key to long life for the point sets.  Cratering is going to tell you if your condenser is not quite right. Transfer of material to positive side you need a condenser with higher capacity or shorten condenser lead.  Transfer to the negative side you need a lower capacity condenser or lengthen condenser lead.  Sounds like Charlie has it right.

I did not know that the condenser rating had a bearing on which side of the points the material migrated to.
Not that it matters much now I guess, but interesting none the less…

[John A]

I’m glad you fixed it at home, rather than on the side of the road 80 KM south of East Jesus at night in the cold rain! I always tried to bring along spares in case something in the Dyna system croaked.