68 Ambassador WILL NOT START. I've tried everything...

[gittbox]

Hello All,

I built my bike from the ground up, feel I know it pretty well, and am a competent amateur mechanic, so am puzzled at where I presently find myself... Totally mystified! I've timed the valves twice, set the static timing multiple times, removed and reinstalled the distributor, installed new points, cap and rotor, condenser, you name it and I bet I've done it. The generator pulley is a replacement (the original was missing) but according to Guzziology the TDC and static timing marks on it are correct for the Ambassador. I've got spark, compression, fuel, air, but the engine will not fire, just builds compression and sprays a mist of fuel out of the carbs.  The point gap is correct, the plug gap is correct, the engine is behaving as though it is off time, but I have no idea how that can be possible! I'm missing something really obvious or really obscure. I've taken my time and gone very carefully through the valve timing and static timing procedures. Everything seems to check out, the valves open and close when they're supposed to, the distributor is in the right position, but NO JOY. Any suggestions anyone might offer would be most welcome. Besides wanting my bike to run, I am extremely curious about what could be keeping it from running, because as far as I can tell it ought to fire right up. Thanks for reading.

[acogoff]

     Thumb in sparkplug hole while bringing crank up to top dead center will make sure crank is on the compression stroke while timing. Only thing that comes to mind.

[EldoMike]

Sounds like cam is out of time...did you have the timing gears off?

[fotoguzzi]

    make sure crank is on the compression stroke while timing. 

[Rich A]

The first thing I do is run a simple test to see if the problem is fuel or spark (assuming you have decent compression). To do this, I shoot some starting fluid on the air filter (or directly into the cylinder thru a spark plug hole, obviously then replacing the plug). If the engine won't run that way, the problem is electrical--and that includes timing.

Rich A

[Idontwantapickle]

and sprays a mist of fuel out of the carbs.

There's the clue. This should not be happening. Does it pop or burn the fuel at all?
If it is blowing back through the carbs then most likely the cam timing is wrong as Mike stated.
Hunter

[Waltr]

Sounds like cam is out of time...did you have the timing gears off?

Did this bike run before rebuild?  To blow fuel out of the carburetor the the intake is not closing on the compression stroke.  I know that is overstating the obvious.

[John A]

Which side is number one? It is numbered fore to aft, not left to right

[rodekyll]

Did you try the other tdc?

[Kiwi_Roy]

It's something really simple,
Crossed plug leads
Firing on wrong stroke, I assume you are getting a nice fat spark, if not lack of condenser perhaps

[Tom H]

Fuel spitting, most likely the cam timing I would guess. But before tearing the engine apart.....

When you put the marked pulley on the crank, did you set the TDC mark with the LH cylinder at TDC with the valves closed? or did you do it with the RH cylinder? LH is the correct one to use.

Also, might want to check the distributor to make sure the narrow lobe is opening the points on the fire stroke as well as the wires to the correct side.

Good luck!!
Tom

[gittbox]

Thanks for all the replies. The bike probably hasn't run since the eighties, I found it in pieces in a garage. The timing gears have been out, flywheel has been off, crank has been out, etc. on one occasion I got a little pop from the engine, while I was cranking the starter and advancing the distributor. I've set the timing on the compression stroke, LH cylinder, a few times now. The narrow lobe on the distributor is opening the points for the left cylinder. I'm thinking the cam timing is off, and I have to go in and set it again, but I've already done it twice, with no positive result. I used the procedure outlined on ThisOldTractor. I'll try it again and see how it goes.

[Tom H]

You say the spark, timing and fuel are good and have triple checked the timing.

Just a shot in the dark, but.. Is the battery fully charged? Also, could it be flooding? With the air filters off, turn on the fuel valves and see if fuel is flooding the carbs. If you are trying to start with the choke/enrichener lever on, try it without. My old bikes have never needed the choke. The only one that does is the BMW when cold.

Let us know more as you go!

Good luck,
Tom

[Mike Tashjian]

Being mystified is not going to help an engine run.  If you have installed all the parts correctly there should at least be something on fire by now.  I like to check compression to insure valves are closing. I like to ignite some fresh raw fuel on the plugs to prove ignition. I like to use a straw in the sparkplug hole to prove the TDC marking I am using for the timing.  With compression, ignition and fuel something will happen even if things are not quite right.  Mike

[John A]

Check your exhaust valves, if you have rolled it over with the heads on while checking/ changing valve timing. The piston chases them and will bend very easily if the cam timing is out and they kiss the piston. It won't start with bent exhaust valves, don't ask me how I know about that mistake

[Kiwi_Roy]

An easy way to check valve timing, they will rock at TDC on the exhaust strobe, that is the exhaust is still closing while the inlet is starting to open at TDC

[AJ Huff]

Somewhere in my foggy memory I remember someone on the old Loop list having a similar problem. Turned out they were looking that the left cylinder from the front wheel not left cylinder as sitting on the bike. Often times the hardest problems have the simplest solutions. hope yours is.

-AJ

[Kiwi_Roy]

Good Point

[Antietam Classic Cycle]

Somewhere in my foggy memory I remember someone on the old Loop list having a similar problem. Turned out they were looking that the left cylinder from the front wheel not left cylinder as sitting on the bike. Often times the hardest problems have the simplest solutions. hope yours is.

-AJ

Easy way to remember: Destra (right) = driveshaft, Sinestra (left) = starter.

[twhitaker]

Or.... D is Dis side and S is 'Snot Dis side. Distributor is on Dis side

[Tom]

You could loosen the bolt holding the distributor and move it to see if you can fire the engine.  If it happens then it'll confirm that your timing is off.  Very short increments.

[gittbox]

Hello All,

     I remember when I figured out that right on a motorcycle is the same as starboard on a boat; I had some work to do over at that point. I think I'm in the clear as far as mixing up left and right is concerned... However!!! It is entirely possible that while initially (and, incorrectly, on account of mixing up port and starboard) setting the valve timing I bent my exhaust valves. I for certain remember contact occurring between the piston crowns and the valves.  The carbs could be flooding as well... My friend who sold me the bike never uses the choke, and his Eldo starts right up, I've seen it in person. I'm running 29mm VHB carbs, I think the originals were SS1s. What would be causing the flooding? I haven't been able to find any really good explanation online of how to set the mixture screws for the initial startup of a rebuilt Guzzi engine, I set them three full turns out from the bottom on the advice of a BMW-owning pal. Maybe this is a factor... Of course, there is also still the possibility of the timing being off somehow. I'm going to spend a chunk of Independence Day thinking and wrenching, I'll let you all know how it goes.

[wymple]

If you bent valves you won't have sh*t for compression.

[gittbox]

What's an acceptable reading on the compression gauge for a 68 Ambassador?

[twhitaker]

It's doubtful both exhaust valves kissed if you were running it over by hand. Look for a difference in pressures. 150 psi is nominal. If you have new rings expect lower pressures. Add a bit of oil to cylinders to rule out the rings.

[Mike Tashjian]

I think you must start over checking each system.  Empty the carbs and leave them dry. Check Compression on both barrels. Throttle open ignition off.  Check that your spark is at the right time and will burn fuel. I like to turn the engine by hand with a finger in the spark plug hole until air pushes, then use a straw to find TDC. Move that piston to the timing mark.  Check timing marks and then check distributor. Rotate the distibutor and you should have a spark as you move it back and forth. Once that is proven, then add a bit of fuel with squirt bottle and make it fire off. Then add fuel to the carbs and if they are the problem at least you know the rest is good.  By proving each system you should either find your problem or have a running bike.  Mike

[Antietam Classic Cycle]

The carbs could be flooding as well... My friend who sold me the bike never uses the choke, and his Eldo starts right up, I've seen it in person. I'm running 29mm VHB carbs, I think the originals were SS1s. What would be causing the flooding? I haven't been able to find any really good explanation online of how to set the mixture screws for the initial startup of a rebuilt Guzzi engine, I set them three full turns out from the bottom on the advice of a BMW-owning pal. Maybe this is a factor... Of course, there is also still the possibility of the timing being off somehow. I'm going to spend a chunk of Independence Day thinking and wrenching, I'll let you all know how it goes.

If the carbs were flooding, you'd know it. Gas would be dripping out somewhere. For initial mixture screw setting, I use 2 turns out for the left and 2 1/4 turns out for the right.

Plug wires: easy to get these wrong because what looks correct isn't. This photo illustrates the correct installation. Upper socket of the cap goes to the right cylinder, lower goes to the left - the plug wires should cross.



More information on VHB carbs here: http://www.thisoldtractor.com/moto_guzzi_loopframe_carburetor_rebuild_-__vhb.html

[Tom]

Do like Mike says. Luckily it's a non-electronic bike.  Still has points?  That should be easy to sort out.

[gittbox]

So, I'm sitting on a plastic bucket, looking at my bike, which is without its mufflers, headers, and heads. It's the fourth of july, my neighbor is firing his sks, epic explosions are echoing across mystery bay, the barn swallows are dive-bombing me and crapping on my Guzzi, and I'm thinking maybe it's time to call a mechanic. I decide to put a 10 degree advance mark on the pulley, even though I'm not sure the stock mark is wrong, and try to re-time the spark. The exhaust valves aren't bent, compression is good in both cylinders, the engine won't fire with the carbs drained and fuel dripped in the spark plug holes, I'm just about at a stand. I get out the degree wheel and for some reason I stop and really study it, and my brain finally remembers what I learned in school many years ago! There are 360 degrees in a circle. The degree wheel is divided into four quadrants of 90 degrees apiece. I had been reading it like a metric scale, assuming a value of one hundred units per quadrant. I reinvented the wheel, which I have a tendency to do... I had to laugh man, all those hours of wrenching on account of having forgotten elementary geometry. I don't have a lot of spare time, but with any luck at all I'll be able to actually start her up on thursday. Thanks to everybody for their suggestions, chewing them over and working them through has, I believe, put me in the right state of mind to realize my mistake. I'm going to get a geometry textbook...

[Huzo]

You've never learned anything by doing it right. That'll feel great when it fires! (And it will)