1980 Le Mans CX100 looking for info about mods by prior owner

[Frenchfrog]

Lots of interesting modifications done there....quite intriguing !

[chuck peterson]

Aerospace engineering eh?

[Alfetta]

bike looks good next to that x9..  i think you should sell that air head, and slide a non running Alfa in its place.  then you entire garage will be beautifully annoying !   

[rocker59]

Whats with the push-pull rod going from the frame to the rear caliper mounting bracket??!!  So, the bracket moves/pivots on the axle in
unison with the rear frame??  I wonder how well that works as compared to the caliper bracket remaining stationary and moving in unision with the swing arm?  Oh well, interesting complex project for 1st time Guzzista, good luck!

Art

The floating rear brake caliper is a common modification.  The force gets routed through the frame rather than through the swingarm and improves rear suspension performance.  Common on race bikes.

[rocker59]

Hi All.  Just picked up this neglected Le Mans CX100 and the prior owner was an engineer who loved to mod his bikes.  He passed away around 15 years ago so I can't ask the original owner anymore so I am looking for information about the modifications done.  Most interesting are the wheels and brakes.  I have never seen a setup like this.  The wheels are wider than the originals, forks stanchions measure the same as stock but the lowers are custom or had the brake caliper bosses shaved off and replaced by a mounting setup that consists of a plate that floats free of the lower fork leg and is anchored by the strut mounted to a bracket below the triple clamp.  The rear swing arm is chrome plated so may also be non-stock?  Other pictures show the solex carb mod, not sure if this was ever hooked up, and the oil cooler.  So where these common modifications or something fabricated by the prior owner?  Spot anything else odd?  I am sure as I go through this bike other things will pop up.  I think I have almost all the parts for the bike.  From the condition of the fuel tank it looks like the prior owner was in the middle of shaving the emblems off the bike when the project stopped along with the carb install.

Also this is my first Guzzi.  Luckily included with the bike is a pile of shop manuals so I have some guidance to follow.  Where are the good parts sources for these older Guzzi's?

Thanks for the help.

The front floating brake setup is for anti-dive.  This may have been a race bike, or at least a racer who was performing '80s/'90s racer mods to his streetbike

[Turin]

That might be a modified BUB sump.
information here - https://wildguzzi.com/forum/index.php?topic=93470.0

[spiggs]

That might be a modified BUB sump.
information here - https://wildguzzi.com/forum/index.php?topic=93470.0

That sure looks like it.  Those rubber hoses and barb fittings in that sump terrify me.  Of course seeing as how the one on my bike was modified I won't know what is inside until I drop the sump.

[spiggs]

Just looked at the frame and engine numbers.  Frame matches the pink but the engine does not.  Engine serial is VG206927.  What is that engine from?  A web search seems to point to a SP1000?  Any idea what year and what differences would it have compared to the original engine?

[faffi]

The CX100 came with the same engine as the SP IIRC. It was down to emissions, I believe, that preventet Guzzi from using the Le Mans engine. And/or it had to do with homologation, that it was too costly to have the Le Mans engine approved compared to how many units they could expect to sell.

[Frenchfrog]

Not sure if that version is quite right as the LM 2 engine is exactly the same as the LM 1 which was homologated. So it would have been importable as an 850 cc  just like the Euro bikes. But the US market wanted a 1000cc machine and to satiate that they simply put the G5/SP lump into a LM2 frame and called it the CX.

[rocker59]

Just looked at the frame and engine numbers.  Frame matches the pink but the engine does not.  Engine serial is VG206927.  What is that engine from?  A web search seems to point to a SP1000?  Any idea what year and what differences would it have compared to the original engine?

SP 1000 engine numbers were VG 18781 - VG 25693

According to Greg Bender's site, CX 100 began with  "VU 111383 - ........"

On your frame and title, do you have "VU" after "ZGU" ??

[guzziart]

The floating rear brake caliper is a common modification.  The force gets routed through the frame rather than through the swingarm and improves rear suspension performance.  Common on race bikes.

Oh, interesting!   I get the floating caliper part but was unaware of expressing that force up to the frame. 
Zero track time here,
Art

[rocker59]

Oh, interesting!   I get the floating caliper part but was unaware of expressing that force up to the frame. 
Zero track time here,
Art

Most of the time, they used to run the rod forward to the lower frame rail, as on the Daytona and 900ss pictured below.  On the subject bike, the link runs upward, apparently trying to counter rear end rise under braking.

[spiggs]

SP 1000 engine numbers were VG 18781 - VG 25693

According to Greg Bender's site, CX 100 began with  "VU 111383 - ........"

On your frame and title, do you have "VU" after "ZGU" ??

The frame and title are assigned VU 111449, original engine was T51461 according to the title.

[faffi]

Not sure if that version is quite right as the LM 2 engine is exactly the same as the LM 1 which was homologated. So it would have been importable as an 850 cc  just like the Euro bikes. But the US market wanted a 1000cc machine and to satiate that they simply put the G5/SP lump into a LM2 frame and called it the CX.

I can only reiterate what I have read, specifically in Cycle magazine, since I do not have any first hand knowledge. Below are exempts from their July, 1980, edition:

...the 850 was replaced by a one-liter version, called the Le Mans CX100. A couple of reasons prompted the displacement increase... For starters, the EPA was writing ever-tighter rules for motorcycle exhaust emissions. (This) would make the 850 too slow..... Second, the...US importer found themselves faced with ushering...three engines through the EPA tests. The V50...the 850s and 1000s...the Le Mans was booted upstairs to enjoy life with new 475cc cylinders. This year's LM shares with the 1979 edition all but its 80 mph speedometer... 1980s LM shares the same powerplant as the 1000SP: both engines have 948.8cc...compressi on ratio is 9.2;1, significantly lower than the 10.2:1 ratio used in the 850 Le Mans...(CX100) drag-strip showing: 13.50 s @ 98.46 mph...the old 850 Le Mans: 13.08 s @ 103.21 mph...(The CX100) got between 35.1 and 51.1 mpg, 41.9 mpg average

[Antietam Classic Cycle]

The frame and title are assigned VU 111449, original engine was T51461 according to the title.

T51461 sounds like the transmission number to me.

[spiggs]

T51461 sounds like the transmission number to me.

And so it is.  Thanks.  Looks like when the bike was titled they used the transmission number instead of the engine number.  Which means the engine is most likely original.  I need to have someone come out and verify the serial numbers to the pink slip and sign off before I can transfer the title since the bike is not in the system anymore.  Guess I'll just point confidently to the transmission number when they ask where the engine's serial number is.

[spiggs]

...
Check those wheels.
...

Checked the wheels and they are magnesium.  Oh well I guess they will make good conversation pieces.  I am hoping the brake hardware fits the stock wheels as well.

[Turin]

I meant for you to check the wheels for cracks / damage. Not everyone will agree with me, but I wouldn't hang them on the wall just yet.

Back in the day there were cases of magnesium wheels failing on new bikes. The debate was Fatigue vs. Road conditions vs. abuse vs. build quality.
 
Not all magnesium wheels are created equally. I'd try contacting EPM first. See what they were using, and see what they recommend.   

I'd perform my due diligence and if I decided to run them, keep a close eye on them for damage.

If you plan on riding through pothole city or Australia, then by all means swap back to the stock rims.

my 2 cents

http://www.magni.it/epm_6_razze.htm

[John A]

Corrosion was the reason we scrapped many aircraft magnesium wheels. Mostly in the bead toe area if irc.
The scrap wheels are great party additions for a campfire if you have a small one. Stress corrosion cracking and intergranular exfoliation comes to mind

[faffi]

You can strip the paint and have them x-rayed for hairline cracks, and inspected for corrosion. If good, you could reseal with the proper paint.

[spiggs]

I meant for you to check the wheels for cracks / damage. Not everyone will agree with me, but I wouldn't hang them on the wall just yet.

Back in the day there were cases of magnesium wheels failing on new bikes. The debate was Fatigue vs. Road conditions vs. abuse vs. build quality.
 
Not all magnesium wheels are created equally. I'd try contacting EPM first. See what they were using, and see what they recommend.   

I'd perform my due diligence and if I decided to run them, keep a close eye on them for damage.

If you plan on riding through pothole city or Australia, then by all means swap back to the stock rims.

my 2 cents

http://www.magni.it/epm_6_razze.htm

Thanks for the link and advice.  I will reach out to the company and see what they say and go from there.  Would be great if I can use them.

Anyone recognize the brake rotors?  They are not magnetic and have a dull finish to them.  They do not look like iron or steel.

Also found a set of rear sets and the missing intake manifold pieces in a box.

[Moparnut72]

In the airplane shop we dealt with magnesium engine cases from time to time. They were almost always structurally sound but usually looked a bit rough. We didn't xray but checked them carefully for cracks etc with Zyglo and black light. The boss always said magnesium is always trying to return to earth.
kk

[Turin]

I'm not familiar with those rear sets. They look the business. I'm not sure what intake pieces those are? for the Solex?

[spiggs]

I'm not familiar with those rear sets. They look the business. I'm not sure what intake pieces those are? for the Solex?

Yes for the Solex carb.  Custom aluminum pipes to connect between the rubber manifolds at the head and carbs.  An interesting setup since they are unequal length.

I had a chance to wash the bike and take a closer look at everything this weekend.  I am now pretty sure this bike was a track bike or intended for the track or a masochistic owner.  Looking at the way the battery was wired into the system there is no way it would carry enough current to support an electric starter and the starter is removed.  So it was setup for using a starting roller or bump start only.

[John A]

Single carb manifolds for Guzzi’s have differences between left and right runners that I don’t understand. If you look at a single manifold from Sonny Angel the difference between the runners is obvious. The diameter and length are not symmetrical but I don’t remember what is the reason exactly, I expect part of it is the direction of airflow in combination with the degrees of rotation between power pulses. I won a Sonny Angel single carb setup complete with Mikuni carb at Ken’s Italy, TX rally . I never used it and donated to the Oklahoma rally . It ended up at Atlas Cycle, OK and don’t know if it was ever installed . I was told they were great for torque

[Moparnut72]

I don't know if it has ever been done on a motorcycle but different length manifolds can affect torque. For many, many years I thought the intake manifolds on the Chrysler Slant Sixes were a design merely to save costs. Not so as I found out not so long ago. The unequal length runners were designed to provide maximum torque at low rpm, long ones, and maximum horsepower at higher rpm, short ones, with a balance in the middle. I doubt a motorcycle manufacturer would bother doing something like this. though.
kk

[John A]

I don't know if it has ever been done on a motorcycle but different length manifolds can affect torque. For many, many years I thought the intake manifolds on the Chrysler Slant Sixes were a design merely to save costs. Not so as I found out not so long ago. The unequal length runners were designed to provide maximum torque at low rpm, long ones, and maximum horsepower at higher rpm, short ones, with a balance in the middle. I doubt a motorcycle manufacturer would bother doing something like this. though.
kk

The Scientific Design and Tuning of Intake and Exhaust Systems goes through that in detail with most of the testing done on a single 500 cc cylinder. Get a copy if it’s still in print - you won’t regret it

[spiggs]

Single carb manifolds for Guzzi’s have differences between left and right runners that I don’t understand. If you look at a single manifold from Sonny Angel the difference between the runners is obvious. The diameter and length are not symmetrical but I don’t remember what is the reason exactly, I expect part of it is the direction of airflow in combination with the degrees of rotation between power pulses. I won a Sonny Angel single carb setup complete with Mikuni carb at Ken’s Italy, TX rally . I never used it and donated to the Oklahoma rally . It ended up at Atlas Cycle, OK and don’t know if it was ever installed . I was told they were great for torque

With the way the intake on this bike was designed each barrel of the Solex feeds one cylinder so it acts the same as having 2 one barrel carbs.  The differing lengths just seem to be because of packaging.  Perhaps there was some thought on how long to make it so each runner would benefit the power curve in a usable range but to me it looks like packaging took precedence over optimal intake length.

The Scientific Design and Tuning of Intake and Exhaust Systems goes through that in detail with most of the testing done on a single 500 cc cylinder. Get a copy if it’s still in print - you won’t regret it

That does look like a good read.

[spiggs]

I measured the lift of the cam at the top of the intake rocker adjuster.  The setup was quick and dirty but I measured .255" so I think this is close enough to tell me it has the stock cam in it (stock is .259" I think?)  I also looked at the flywheel as best I could through the starter motor opening and did not note any machining.  So stock cam, stock flywheel, stock size intake ports is telling me the engine is stock internally.