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

[Moparnut72]

Looks like something I should read. I read We Were The Ramchargers twice. Very interesting and educational read. These guys were Chrysler engineers who were interested in and participated in drag racing. They did a lot of tuning with intake and exhaust tuning through math and physics rather than just throwing stuff at an engine. They were very successful and shared everything with anyone racing the brand to make Chrysler successful on the drag strip. The win on Sunday sell on Monday thing. They did this on their own time with minimal support from the factory. They got a body in white once in awhile and maybe a long block from time to time. One of their early experiments, the High and Mighty. It set the record the 2nd time out I think. Rules were written to ban it on pressure from Ford and GM.
kk



 

[Turin]

The plot thickens!

[spiggs]

Looks like something I should read. I read We Were The Ramchargers twice. Very interesting and educational read. These guys were Chrysler engineers who were interested in and participated in drag racing. They did a lot of tuning with intake and exhaust tuning through math and physics rather than just throwing stuff at an engine. They were very successful and shared everything with anyone racing the brand to make Chrysler successful on the drag strip. The win on Sunday sell on Monday thing. They did this on their own time with minimal support from the factory. They got a body in white once in awhile and maybe a long block from time to time. One of their early experiments, the High and Mighty. It set the record the 2nd time out I think. Rules were written to ban it on pressure from Ford and GM.
kk



 

I have read about their exploits before, the science works.  Now if I wanted to go full Ramcharger with the Solex setup on this Guzzi I could redesign the intake length based on calculated values for peak torque then run it up and over the fuel tank.. The High and Mighty Guzzi intake!

[spiggs]

The plot thickens!

Yes it does.  So this may seem silly but up until now I have not looked at the odometer.  I haven't even thought about it and the gauges had a thick layer of dust that obscured the numbers.  I gave the bike a quick wash over the weekend but didn't want to spray the gauges down with water so left them.  Finally I took a cloth and some detail spray and gave them a quick wipe down.  The odometer reads 25 miles, I felt a bit dumbfounded.





So I can think of a number of scenarios.

The bike has 100,025 miles

The previous owner disconnected the odometer and rode/raced the bike that way from new

The gauge cluster is new or the odometer was reset

The bike was purchased to be a track bike but the prep was never completed and so it sat with 25 miles on it

Another piece of the puzzle.  The tires on the original wheels have full tread, a date code of 150 which could mean the 15th week of 1980, and are the type that would have come on the bike originally.  I think it is safe to say these were taken off early in this Guzzi's life.  The tires on the EPM wheels are Michelin M45's with a date code of 519 with full tread.  So they could have been manufactured on the 51st week of 1979, 1989. 1999 and are not the kind of tire you would put on the track.

Obviously I think it's highly unlikely this 43 year old bike has 25 miles on it.  I wish the original pink slip had the engine number on it so I knew for sure if this is the original engine.  I will also note that among the boxes is a stack of old head and cylinder base gaskets.  All I can say is this was a project in progress, where in the process I don't know.

[John A]

Most likely is the speedo was replaced and the mileage is what was on the guage

[Turin]

85mph speedometer. those we for model years 1981 and 1982 I believe. maybe 1980. Doubful for a bike built in 1979. If it was a replacement, it was probably cheap. The owner really was a guzzi guy!

[Tusayan]

79 CX100s didn’t have the 85 mph speedo.  I have one.

Compare the fluorescent orange needle tips on the speedo and tach, it may give you an idea of how new the speedo is in relation to the rest of the bike. The tips fade pretty fast in sunlight.

I’m not sure motorcycle tires had date codes in 1980.

[spiggs]

85mph speedometer. those we for model years 1981 and 1982 I believe. maybe 1980. Doubful for a bike built in 1979. If it was a replacement, it was probably cheap. The owner really was a guzzi guy!

The title says the bike is a 1980, the data plate on the bike lists mfg date? as 07/1980 and model year 1981 so I would think technically an early 81?

79 CX100s didn’t have the 85 mph speedo.  I have one.

Compare the fluorescent orange needle tips on the speedo and tach, it may give you an idea of how new the speedo is in relation to the rest of the bike. The tips fade pretty fast in sunlight.

I’m not sure motorcycle tires had date codes in 1980.

Needle tips look relatively the same





I did a search on how to read date codes and came up with the information that prior to year 2000 they were 3 digits and the last digit represented decade.  It seems to follow the format that would say this is a date code but of course this is just based on internet search information.  If it is a date code it could be 1980 or 1990 based on the last digit being decade.  I was guessing 1980 because I found a contemporary review of the bike that listed the original spec tires as Pirelli Super Sport Gordon.  Don't know if this was still a current model tire in 1990.





 

[Turin]

Those are some old tires! Don't throw them out, someone may want them for a display bike / museum piece. I bet they are as hard as rocks!

I checked and it looks like the M18 Gordons came out in 1975. (thank you facebook). Your guess of 1980 is probably correct.

[Tusayan]

The title says the bike is a 1980, the data plate on the bike lists mfg date? as 07/1980 and model year 1981 so I would think technically an early 81?

CX100s were built in two batches, 1979 and (I believe) 1980 models.  I think there was maybe a year or a bit more between them.  Yours looks to be from the second batch.  There were some very minor differences between the two batches: other than the speedo one that comes to mind (from memory) is the method of manufacture of the fairings:  the early ones were chopper gun fiberglass, rough on the inside. The later ones were smooth on the inside, and had slightly different lower brackets. 

I would guess that your bike was run without the speedo for a while and then it was remounted on the bike.  I bet it doesn’t have a lot of miles on it regardless, because anything you do with a bike minus speedo isn’t going to involve riding a lot of miles. The same might be true for the entire instrument cluster.

The Pirelli Gordon tires are original, the original wheels have probably never had another set of tires on them.

[spiggs]

I very much get the impression that this bike was a project early in it's life that never made it back on the road.  How early I don't know.  Like you said it may have been run without the gauges for a time, the previous owner did add an oil pressure gauge where I think the original clock would be.  Maybe he even swapped the gauges at that time I will never know.  There are just so many things partially complete.  The brakes are decoupled but the back brake is not hooked up and the front master cylinder is still the stock 12mm unit.  The Moto Guzzi badges are removed from the fuel tank and the mounting holes welded up and ground back but not painted, a Bosch blue ignition coil is mounted to the fairing but there is no wires to it, the carb conversion did not have a throttle cable hooked up nor a fuel line fabricated with it.  Among the paperwork is a hand drawn wiring schematic and on the bike there are some wires that do not go anywhere.  Just a bunch of stuff.

Well my goal will be to get this LeMans back on the road as a solid runner.  Hopefully keeping some of it's uniqueness with the EPM wheels and anti dive front  It's going to be a puzzle though.

[Turin]

Do you have the original carbs? what do the intake manifolds look like? what throttle do you have, tomasselli 2C?

If the current solex carb was never run, then I suggest going back to something more conventional.

You could probably get decent $ for those Solex carbs. That would offset some of the costs.

[spiggs]

Do you have the original carbs? what do the intake manifolds look like? what throttle do you have, tomasselli 2C?

If the current solex carb was never run, then I suggest going back to something more conventional.

You could probably get decent $ for those Solex carbs. That would offset some of the costs.

I was thinking the same thing.  I do have the original carbs and yes the throttle looks like the Tomasselli 2C.  Attached is a pic of the intakes currently bolted to the heads.  Don't know how much the Solex carbs are worth, hard to find any info about applications.  There is probably someone who would pay reasonable money because of a specific application, just need to find that person.





On another note I think the brake discs I have are aluminum coated with iron from Harry Hunt.  They got good reviews but I found some people mentioning that the iron coating can separate if moisture gets under it so I'll have to give them a good once over.

On the mechanical anti dive I have found references to the Preston Petty no-dive setup for off road bikes although some of the articles about his system mention his setup was used on some road race bikes as well.  I also found info about Udo Gietl and his championship winning BMW AMA superbike which used a very similar setup.  Aprillia has also filed a recent patent that takes this concept a little further by adding a variable ratio link in the mix to change the amount of anti dive based on how far the suspension is compressed.  Interesting stuff.

[Turin]

Manifolds look like the factory set up. Carb cables are cheap.

I'd bet there's some JDM car guys that would be interested in those mikuni's .
found these-
https://www.wolfcreekracing.com/index.php?option=com_content&view=article&id=69%3Amikuni-carburetor-id-guide&catid=30&Itemid=51

https://rmcarburetors.net/

[spiggs]

Manifolds look like the factory set up. Carb cables are cheap.

I'd bet there's some JDM car guys that would be interested in those mikuni's .
found these-
https://www.wolfcreekracing.com/index.php?option=com_content&view=article&id=69%3Amikuni-carburetor-id-guide&catid=30&Itemid=51

https://rmcarburetors.net/

Thanks.  Looking at those sites they feature the PHH 40/44 carbs.  The PHH 36 is a physically smaller carb than the more popular 40/44 that was a drop in to the Weber DCOE.  It looks like the PHH 36 was a Mikuni development based on the Solex PHH 35 carb found on the Lancia Fulvia and other such cars.  The original Solex PHH 35 carbs go for good money, perhaps there would be some interest in the updated Mikuni version but I have a feeling prime dollars go to the originals for factory correct parts.  I also found some info about a kit being offers for Honda 750 SOHC engines that used twin PHH 36s.  I will clean up the one taken off the bike and see what kind of market there is for a pair.

Inspected the brake rotors and found pitting and some separation.  Too bad, would have been cool to be able to use them.  Anyone know what the stock bolt circle is front and back?  Perhaps I can just get new steel rotors to bolt on.

[Turin]

If you are looking for custom discs, I highly recommend ISR. Acke mad me a set of custom carriers for 300mm discs (this wheel was not meant for a guzzi) The cost was comparable to what EBC charges and the quality is top notch. He will make you pretty much anything. He may even take your existing carries and install new discs.

https://www.isrbrakes.se/

https://www.isrbrakes.se/order/isr_discorderingform.pdf

[spiggs]

I will keep them in mind.  First though I need to see if the magnesium wheels are usable.  I sent an email to Magni asking for any advice on reconditioning an older set of EPM magnesium wheels but have not got a response.  I wrote them in english so perhaps it was automatically ignored.  First step will be removing tires, bead blasting, then testing.  All this I will need to figure out still.  If the EPM wheels end up being wall art then back to stock I think and then figuring out if the brake setup will work with stock wheels.

What does the stock rear brake mounting look like?  The swing arm on my bike is chromed and I am wondering if/how much it was modified.

[Turin]

There should be a small tab on the inside of the swing arm for the factory brake bracket.

[spiggs]

No small tab on my swing arm.  I think the prior owner shaved it off and chromed the swing arm.  It seems like this was something he liked to do as the final drive and valve covers are missing the little ribs/fins/logos that I see cast in the stock parts and are chromed as well.

[Turin]

You won't be able to run the stock swing arm brake/spacer plate without that tab. The tab keeps it from moving around. It also looks like the disc brake tabs have been shaved off of the front forks.

[John A]

On EV’s the rear brake nub is a special bolt with the threads at the head end but not at the other end which is run through a threaded hole in the swingarm to intersect with the slot in the caliper mount. I don’t know if that would be a repair option or not.

[spiggs]

What I am thinking now is that if the EPM wheels end up being usable I will run a anchor rod from the rear brake that is on the bike now to some point on the frame below where the swing arm mounts and only keep the front anti dive setup.  This will also probably mean keeping the brakes de-linked as well.  If the EPM wheels are not usable then back to a stock setup for wheels and rear brake and put it back to a linked setup as Moto Guzzi intended. The front anti dive might need to go as well depending on how much effort it is to use it with the stock wheels, my preference though would be to keep it so the bike retains some of it's personality.

[Turin]

you may have to replace the fork lower legs as well, as the tabs look like they've been shaved off. (hope not)

The rear drive rod looks odd being attached to the upper frame. You might be able to rotate it 270 degrees clockwise so it's underslung and weld on an attach point to the swing arm or lower frame.



I hope the wheels are good, as it would be the path of least resistance.

[spiggs]

No caliper mounts on the fork lowers so I would need to find some new ones if I went back to the stock setup. 

This bike will be a project for sure, the prior owner really changed a lot of things.  Looking  at the wiring harness there are a number of extra switches wired in along with an aftermarket regulator branded as Voltpak.  Buried in the parts is a hand drawn electrical schematic.  Don't think I will bother figuring out what was changed and just go back to stock.

[Turin]

Wiring isn't a big deal. Greg Bender sells harnesses. https://www.thisoldtractor.com/moto_guzzi.html Good guy and his stuff is top notch.

I think the brake set up and wheel set up is pretty cool. If it's not your thing, fork legs and parts show up on E-bay. You may also want to contact Mark Etheridge at Moto Guzzi Classics.

[blackcat]

Do you plan on bringing this bike back to CX stock condition? Do you have the stock upper fairing as I didn't see that in the box of parts. 

[spiggs]

Do you plan on bringing this bike back to CX stock condition? Do you have the stock upper fairing as I didn't see that in the box of parts.

I do have the stock upper fairing along with 2 windshields.  Not sure yet if I will use it, depends on if the EPM wheels and the anti dive brake setup are usable.  If they are I think I will use something different for the fairing like on the MK1 Lemans or a period style frame mounted fairing to keep more with the modified 80s track bike back on the street vibe.  If those parts are not usable then I think I will go mostly stock and put the original fairing back on.

[blackcat]

I do have the stock upper fairing along with 2 windshields.  Not sure yet if I will use it, depends on if the EPM wheels and the anti dive brake setup are usable.  If they are I think I will use something different for the fairing like on the MK1 Lemans or a period style frame mounted fairing to keep more with the modified 80s track bike back on the street vibe.  If those parts are not usable then I think I will go mostly stock and put the original fairing back on.

Do you have an H shaped piece in the pile of parts? You will need that part to attach the stock front fairing and if you do have one it would be wise to weld up a new stronger piece because mine would break after a few years of use. And if you do go with LM I front fairing you will need to open up the cut outs for the wider forks on the CX. I’ve never got the fairing to sit the same way as a the one on my Lemans I but when I can locate the LM I left headlight bracket it might solve the problem.

My CX:

[faffi]

My CX:

That is one beautiful bike 

[blackcat]

That is one beautiful bike 

Thanks but it looks better in the photo than in person. I recently had the frame powder coated and a new wiring harness installed but the tank,fenders and side panels all need new paint as it’s been at least 15-20 years since they have been painted and it was used as a commuter for many years.