77 Le Mans a non starter

[canuck750]

I am at a complete loss as to why I can not get my rebuilt 1977 Le Mans 850 to fire up, this is what I do know so far,

The engine is fully rebuilt to stock, new rings, honed iron cylinders, new valves, guides and springs etc... compression is 150 +/- per side, checked and rechecked.

Valves adjusted to proper clearance. I have spark on each side, a Newtronic electronic ignition was fitted, spark looked good but just to see if there was any change I installed a DYNA III electronic ignition I had and swapped the distributor while I was at it, installing the distributor as per Guzziology, installed at right hand cylinder static timing mark (not the full advance line above), rotor set at 9"00 o'clock goin in rotates to 11:00 o'clock like the book says.

The stock Dllorto 36mm pumper carbs have been fully rebuilt with new slides, atomizer, jets,  needle, fuel valve and pump diaphragms, new choke valves, cables etc. Float height set at 23.5mm, checked and rechecked.

I installed a new battery, and I swapped in a new lighter starter motor just to ease the starting.

I removed the old kill switch and just joined the two white kill switch wores so that onbly the key will turn the motor off for now, the spark is bright on each side.

The bike merrily cranks over, it sparks, there is strong suctioon at the carb bellmouths.

Once in a while it backfires a little, not too often though. I have tried rotating the distributor a few degrees either way, no differemce. The plug wires, caps and coils are new.

There is no hint it wants to start.

I have had the carbs apart a half dozen times, I am missing something painfully obvious but I shipped the carbs off this afternoon to Wolfgang Haerter in British Columbia to look at, he sorted out my Laverd SF1 Dellorto 36mm carbs last year and they now run fine.

Seems really strange that I have good compression and spark, and I can only assume the carbs are the culprit.

Anyone have an idea on what the heck is wrong????

[pehayes]

Please reference what instructions you used for the distributor install.  I believe all of the installations start with TDC on the LEFT SIDE cylinder.  You used the right side.  Have you used a strobe timing light in the inspection hole to verify that the spark is happening when the correct cylinder is on the correct stroke?  If you fully restored the motor, you must have removed the flywheel.  Since it carries the timing marks it has to be re-installed properly.  Source of error?

Patrick Hayes
Fremont CA

[rodekyll]

What Pat says.  Also, are you on the correct phase of TDC?  Backfiring sounds like either you set the distributor at tdc of the exhaust stroke instead of the intake, you set to "D" when it should be at "S", or the plug wires are mixed up.

Just for troubleshooting -- have you eliminated fuel as the culprit by squirting starter fluid in the intakes as you crank it?

[Chuck in Indiana]

Like RK sez.. what Patrick sez.  Carburation problems are almost always ignition..

[canuck750]

I knew it was something obviously stupid on my part

Thanks guys, pays to read Guzziology rather than try to go by a fading memory!

I am heading off on a couple weeks vacation tomorrow so I will tackle it witrh a fresh brain when I return.

When I removed the flywheel I painted the marks to get it back on properly plus I used a degree wheel, piston stop to conmfirm TDC and then checked the marks to be sure it was correct so I feel pretty certain the flywheel and the markings are corrretc. 'D' - right hand cylinder is indicating correctly for TDC compression stroke. It's probably as simple as I have the damn distributor installed on D rather than S.

Thanks again guys

[harrytief]

Yup. Sounds earily familiar...

[pressureangle]

Yup. Sounds earily familiar...

Let me count the ways.

Honda
Suzuki
Moto Guzzi
Ducati 450
Bultaco (if you count timing a 2-stroke ATDC instead of BTDC)
Chevrolet small block (ten? a dozen times?)
Chevrolet big block (at least a handful)
Chrysler small block (bastards set the distributor with #6 TDC)
Chrysler big block (a couple)
Ford small block (why am I working on a Ford?

I think the only engine I owned and didn't get wrong at least once was my MGB.

Not just familiar, but comfortably familiar. I don't even get mad anymore.

[Dukedesmo]

Whilst repairing my LM2 (after a piston/valve interface) I removed the camshaft to check the spec. I put it back in correctly but totally overlooked the fact that the distributor was driven by a gear on the rear end of the camshaft. 


Of course when I tried to start it, it would just pop & fart with the odd backfire because the ignition was out of time... 

[Kiwi_Roy]

Whilst repairing my LM2 (after a piston/valve interface) I removed the camshaft to check the spec. I put it back in correctly but totally overlooked the fact that the distributor was driven by a gear on the rear end of the camshaft. 


Of course when I tried to start it, it would just pop & fart with the odd backfire because the ignition was out of time...

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[lrutt]

pull the spark plugs so it spins quickly and hit it with a timing light. Just to make sure it's sparking when you expect.

[Kiwi_Roy]

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I put the heads on the wrong side, does that count?


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[canuck750]

Thanks fellas, good to know I am not the only one who misses something so simple

[Don G]

At least you didn't burn your hair off or the Garage to the ground, and you got to learn something as well.    DonG

[canuck750]

At least you didn't burn your hair off or the Garage to the ground, and you got to learn something as well.    DonG

I ain't got no hair!

[twhitaker]

Dis side and Snot Dis side.

[canuck750]

After three great weeks in California and Arizona riding some great roads and just relaxing its back to the cold north, more snow expected Monday!

I opened up Guzziology to page 6-16 - Tonti-frame big twins with Marelli points distributor.

"to install the distributor, begin by bringing the right-hand piston to its static timing mark (second line above the D on the flywheel) at the end of the compression stroke (both valves closed).
.. position the upper notch in the distributor's central shaft at 9:00. Install the distributor, noting that the shaft will turn clockwise because of the curve of its drive teeth. The notch in the distributor's central shaft should turn to 11:00 when the distributor is fully seated in its receptacle."

So I think I had it installed right all along, Right Hand (D) as sitting on the bike.

The carburetors should come back from Wolfgang this week and then I can test it again.

I tried to check the static timing with plugs in the engine (loose) and no carbs, the engine turns over pretty slow and its real hard to match the flashes to read the timing marks, I am guessing I may have the red and green wires from the coils crossed, in effect the high tension leads are firing opposite as they should.

What side is the right hand (D) cylinder fired, red or green wires (coils)?

Second question, can someone confirm how many teeth on the flywheel is the static timing mark before TDC? My LeMans flywheel static timing mark is 9 teeth before TDC (a gear driven V7 Sport by comparison is 4 teeth and another 8 teeth past static to full advance.).

Thanks

Jim

[Chuck in Indiana]

From memory, Guzzi is backward from nautical and aeronautical practice, therefor green would be port and red starboard. 
Shirley  it's on the schematic?

[guzzisteve]

Remember the letters  Red=Right, Green = other side for point wires, flywheel comes UP in hole is direction of travel, dizzy can be put in off a few gear teeth as long as you can rotate it to be correct w/o outer body hitting cyl. The wires should come out at about 8 oclock.  MOST importantly I DO NOT read any Guzziology, only service manuals.

[jacksonracingcomau]

From memory, Guzzi is backward from nautical and aeronautical practice, therefor green would be port and red starboard. 
Shirley  it's on the schematic?

World std nautical, except for USA, one of those confusing things for RTW sailors

Red is right easy to remeber

[canuck750]

Remember the letters  Red=Right, Green = other side for point wires, flywheel comes UP in hole is direction of travel, dizzy can be put in off a few gear teeth as long as you can rotate it to be correct w/o outer body hitting cyl.  MOST importantly I DO NOT read any Guzziology, only service manuals.

Service manuals do not explain how to install a Tonti distributor, other than stating to strike a mark in the distributor base and the block to match the position the distributor upon reassembly. I have installed at least a half dozen Guzzi Tonti distributors according to Guzziology and never had an issue before. I have fitted a Dyna III and the wires are red and black coming out of the dist plate, the pick up modules are all black wires so its not as simple as following the stock wire diagram. Not that this is a big issue, at worst I have to flip the green and red coil leads around.

I found a diagram on Greg Benders site, Red to 'Cylinder Des' and Green to 'Cylinder Sin'

[guzzisteve]

It's just common Guzzi knowledge to set up #1/LH cyl to TDC and drop it in where LH point is opening. I did same stuff w/Accel duel point on my 289 Mustang. Same thing different motor.

[oldbike54]

 My heroes aren't infallible ??? I am crushed 

 Dusty

[canuck750]

It's just common Guzzi knowledge to set up #1/LH cyl to TDC and drop it in where LH point is opening. I did same stuff w/Accel duel point on my 289 Mustang. Same thing different motor.

If I were to install the distributor with the left hand distributor / LH points about to open, should I not be installing the distributor with the flywheel timing mark for the LH (S) cylinder to at the LH static timing mark and not the LH TDC mark?

[guzzisteve]

Close enough to turn & make it  correct, Dyna 3 instructions say TDC.

Edit: Sorry, shouldn't be posting & drinking. Don't worry bout bike, it'll be fine.

[mtiberio]

Remember the letters  Red=Right, Green = other side for point wires, flywheel comes UP in hole is direction of travel, dizzy can be put in off a few gear teeth as long as you can rotate it to be correct w/o outer body hitting cyl. The wires should come out at about 8 oclock.  MOST importantly I DO NOT read any Guzziology, only service manuals.

Red = Right is correct...

Lower (set of points or sensor) = Left

there is your mnemonic...