69 ambassador 750 troubleshooting and general questions

[tacolibre]

Hello everyone first time posting here. I have a 69 ambassador 750 as you could see from the title of the post but I am going through the bike to get it so that it is back on the road. for now to keep cost down the goal is to just get it running to the point that it can be ridden occasionally to work. So starting with compression, since I think it is very low based on the chilton's manual download that I have here what I measured:

compression on left cylinder ~100psi

right cyl. ~95psi (this is after I sprayed fogging oil in the cylinder)

is this enough cylinder pressure to make the bike run? This is the average of 3 tests with less than 5psi variance between each test and the bike turning over under starter power with no carbs attached to the bike.

If it is the case that the engine comes out what are some recommended "upgrades"? oil system adding a filter? Also, for engine, machine work who is reputable?
(Located in Eastern Washington state)
 

[rodekyll]

Welcome, Taco.

You don't have a nickel-and-dime runner there.  You have a project bike.  The engine is a grenade at that age and compression.  I would not run it until I've popped the sump and heads for inspection.  Plan on rebuilding the heads and probably replacing the pistons and jugs.

Oil filter is an option.  I'd suggest adding one from an 1100cc cali -- complete with the rest of the engine.  A good used 1100 +mods for fit will cost about the same as the 750 rebuild, but you get 40% more of everything when you're done.

$0.02

[tacolibre]

rodekyll, thanks for that. I fully understand that I have a

could you go a little more in depth to what you are referring to for the cali 1100? I am not familiar with that bike or most motoguzzi's for that matter. I think you are telling me to install the engine from that bike into the ambassador. That being said, does this require significant retrofit from a fabrication or parts standpoint? I am unfamiliar with the parts interchangeability.

[Antietam Classic Cycle]

Most likely what has happen is the original bores have flaked to the point that there's a ridge at the top of the cylinder and that has cracked the top rings. This is exactly what happened to my '69 Ambasador at 54k miles. You will need new cylinder and piston sets. This is the best way to go:
http://www.mgcycle.com/index.php?main_page=product_info&cPath=68_129&products_id=2127

There is no easy way to add a "full flow" oil filter to the early Ambassadors. Unlike the late Ambassador and Eldorado engine case, there's no provision for retrofitting the later "Tonti" Guzzi oil filter sump. Escher sells a kit to add a "bypass" type oil filter system (only filter oil to the rear main bearing). Some information here: http://www.thisoldtractor.com/moto_guzzi_loopframe_oil_filter_addition_-_escher_kit.html

The best "upgrades" will be the Gilardoni cylinder kits and heads rebuilt with new valves and guides.

If you haven't already found it, one of the best sources of information on the 'net, is Greg Bender's website: http://www.thisoldtractor.com/moto_guzzi_loopframe.html

You're also welcome to join the rest of us "Loopers" over on the Loopframe Guzzi Yahoo Group:
https://groups.yahoo.com/neo/groups/Loopframe_Guzzi/info

[tacolibre]

thanks Antietam classic cycles, what do you know about the "cali 1000" engine and buying a used version and installing it in the place of the ambo engine? is that realistic or worth while?

[oldbike54]

thanks Antietam classic cycles, what do you know about the "cali 1000" engine and buying a used version and installing it in the place of the ambo engine? is that realistic or worth while?

 The engine in question came in the California series Moto Guzzis , 1000 CC and 1100 CC versions . Commonly known as "big blocks " , based on the same basic architecture as the 750 CC engine in your bike as opposed to the "small block" 750 CC engines . The conversion can be done , although it will involve some work . Do a search here on WG .

  Dusty

[JoeW]

thanks Antietam classic cycles, what do you know about the "cali 1000" engine and buying a used version and installing it in the place of the ambo engine? is that realistic or worth while?

I would fix what you have. This comes from a guy that rides a 71 Ambo, with a 950 motor and five speed. There is something about an "original" Ambo that you lose when you upgrade to a later motor. Maybe the chrome has flaked or, is ready to.  I don't think your compression is too low to run but, I agree with pulling the cylinders and upgrading the bores. I would drop the oil pan first, and check for chrome and/or babbit flakes. If there is no metallic particles in the pan, I would be confident that the bottom end is sound. You can buy new cylinder kits or have the original cylinders updated to nikasil bores.  Keep it stock, post some pictures!

[Antietam Classic Cycle]

thanks Antietam classic cycles, what do you know about the "cali 1000" engine and buying a used version and installing it in the place of the ambo engine? is that realistic or worth while?

I've put later engines into Loopframes., working on a Cal II conversion right now actually. Here's a general outline of what will be required:

1. You need to decide whether to a) retain the crank mounted alternator of the donor engine or b) go with the generator mounted in the "V" as original to the chassis. I've always went with b), so will cover that way only. I'm not going to get into all of the variations and work required for anything past the Convert/G5/SP/CX100 949 cc unit - that might require pages and hours to cover.

2. The timing cover will need to be changed to one from a late Eldorado (with chain driven camshaft) or one from V700 or Ambassador with some minor machining to "ribs" inside to make clearance for the donor engine's timing chain.

3. A crankshaft adapter will need to be sourced. "guzzi-renew" on eBay sells them (Mark @ Moto Guzzi Classics).

4. On top of the engine case, three holes for the generator bracket and generator locating pin will need to be drilled and two of them tapped.

5. Ignition system decision time: retain the single point distributor or go with the donor engine's system? I have had good success with the single point distributor - it will require an Eldorado lower distributor mount and the gear off swapped over from the dual-point timer of the donor engine.

6. Header pipes: Loopframe header pipes attach different than later ones. An adapter ring can be made to center the Loop header in the later exhaust port, but it's sometimes hard to get a good seal and prevent leaks. I prefer to have the Loop header pipes modified - the flange cut off the Loop pipe and the later type flange welded on.

In the end, it becomes quite involved, if not difficult. I agree with Joe W. - fix what you have. 

[tpeever]

I've put later engines into Loopframes., working on a Cal II conversion right now actually. Here's a general outline of what will be required:

1. You need to decide whether to a) retain the crank mounted alternator of the donor engine or b) go with the generator mounted in the "V" as original to the chassis. I've always went with b), so will cover that way only. I'm not going to get into all of the variations and work required for anything past the Convert/G5/SP/CX100 949 cc unit - that might require pages and hours to cover.

2. The timing cover will need to be changed to one from a late Eldorado (with chain driven camshaft) or one from V700 or Ambassador with some minor machining to "ribs" inside to make clearance for the donor engine's timing chain.

3. A crankshaft adapter will need to be sourced. "guzzi-renew" on eBay sells them (Mark @ Moto Guzzi Classics).

4. On top of the engine case, three holes for the generator bracket and generator locating pin will need to be drilled and two of them tapped.

5. Ignition system decision time: retain the single point distributor or go with the donor engine's system? I have had good success with the single point distributor - it will require an Eldorado lower distributor mount and the gear off swapped over from the dual-point timer of the donor engine.

6. Header pipes: Loopframe header pipes attach different than later ones. An adapter ring can be made to center the Loop header in the later exhaust port, but it's sometimes hard to get a good seal and prevent leaks. I prefer to have the Loop header pipes modified - the flange cut off the Loop pipe and the later type flange welded on.

In the end, it becomes quite involved, if not difficult. I agree with Joe W. - fix what you have.

I agree with Charlie and Joe W. Keep it original except for replacing original chrome plated cylinders with new Gillardoni cylinders and piston kit. Also renew the top end with new valve seats, valves and guides and you will be good to go.

Where are you in eastern WA? I am in Pullman and am happy to discuss and show you my newly restored V700 if you are in the neighborhood!

Tobin

[canuck750]

I suggest you pull the crank out, clean the sludge trap at a minimum and take the crank and main bearings, along with the con rods to a reputable machine shop and have them measure the crankshaft journals and bearings. Hopefully the chrome flakes have not gotten into the bearings and worn the crank journals beyond spec. If the crank journals are scored or the main bearings worn you may need to have the crank ground and oversize bearings fitted.

I don't want to be the bearer of bad news but I have pulled apart three of the non-filter Loop frame / V7 Sport motors and the damn chrome flakes had already buggered the bearings and the crank shaft. Added about $700.00 to the rebuilds for grinding and new bearings.

This is what came out of the sludge trap of my Eldorado, lots of nice shiny chrome flakes embedded in the sludge



Weigh out the cost of rebuilding a motor carefully, not opening up the bottom end may be only tackling half the job. Once you factor in the Giladorni kits, rebuilt heads, gaskets, seals, and you may as well replace the clutch if it is original, the total will be close to $2500.00 minimum.

If you can source a good motor from a newer Guzzi it may be the less costly and you would have more power.

[John A]

If you are very very lucky the reason for low compression could be a big bore kit installed that was actually for an 850 but would work in a 750. The deck height of the pistons is lower on the 850 so in a 750 it's really low compression. Like you have been advised, you'll be money ahead to yard that thing apart. They are good machines and will take you across the country many times before you have to overhaul it again if you do it right the first time.