The little Ducati Featherweight

teazer said:
Now it is getting really interesting. Lots of pictures please...
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Absolutely! I plan on getting all the info from Tom that I can while I am there. He know's things about these motors that really is quite fantastic. I mentioned how this now has me wanting a 450 desmo, to which he laughed. Apparently the holy grail status of a desmo head is greatly misunderstood. Either way, as info on these engines is not the easiest to come by, i'll be taking notes ;D.

I took the top end apart last night, and damn that was easy. I'm used to fighting with a mess of JIS screws that want to strip, 4 pistons worth of moving parts, and a cam chain. Nope! 4 bolts and yank! Not even 1 stuck gasket. Oh, and no head gasket! The way the head is machined there's no need for one, it's nuts!

I gotta say, after inspecting the internals first hand, I'll like to see these motors re engineered slightly with today's knowledge, and put back into production. There are a few things I even noticed immediately such as the shape of the valves that could easily be improved. I see no reason why a nice reliable 500cc example couldn't be a real gem back in the ducati line up. So Damn pretty too! Anyhow I digress. I'll have a major update after Tom's today.
 
Going to see Tom was, interesting. I wasn't sure what I expected, but if I wanted a crash course in 60's era Ducatis the way they did it in the 60's, well I got it.

Let me start by saying, I haven't been around a lot of professionally trained mechanics. Other than working by myself, my experience is more or less nil. When I work on a motor, I'm usually working on a very clean, if not sterile work surface, all the proper tools I need laid out (i'm big on the right tool for the job), and I generally work very carefully; the whole scene probably looks like a surgeon in an operating room. It's important I lay this out or my experience won't make sense. So when I watched a steel rod get jammed into a cam, and then get bludgeoned by a claw hammer to remove a cover, I was a little shocked.

That scene kind of set the tone for the way I witnessed a 160 head being worked on, Like a bull in a China shop comes to mind. That being said, I was able to learn a bit about the motors. I opted to take the milled barrel, an old VHB carb, but I felt the condition of my head was better, and I will port out the intake myself.

Tom didn't have much input on the 12 conversion or the cdi instead of points. He seemed to feel neither really needed, was in favor of just running it total loss, and charging up the battery, not really my style.

All in all my main takeaways were, A) I know a lot more about motors than I thought, and B) even though these motors are referred to as being complex and a pain to work on, they really aren't bad compared to a Honda 4. In fact, I think they are easier to work on.
 
I converted an XL175 motor to 12v. It's a super easy swap with a CB350 stator and alternator. The only gain was lighting and even for that using 12v regulators or a step up converter would've been simpler. There really is no performance gain when it comes to the motor.
 
irk miller said:
I converted an XL175 motor to 12v. It's a super easy swap with a CB350 stator and alternator. The only gain was lighting and even for that using 12v regulators or a step up converter would've been simpler. There really is no performance gain when it comes to the motor.
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This seems to be equally as easy, other than sourcing the parts which was hard. In this case, I think there is performance to be had, albeit only a modest amount. The shape of the combustion chamber, and angle of the valve, is less than ideal. A better coil, and stronger spark, should be a little helpful. And if I go to 2 plugs, it's been proven to be very helpful on the singles.
 
Converting to 12v isn't going to get you better spark. Bosch makes a 6v coil that produces 50k volts just like most high performance 12v coils. It's all about resistance and the amount of secondary windings for whatever input voltage to the coil.
 
irk miller said:
Converting to 12v isn't going to get you better spark. Bosch makes a 6v coil that produces 50k volts just like most high performance 12v coils. It's all about resistance and the amount of secondary windings for whatever input voltage to the coil.
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I'll rephrase, the 6v stock system is good for all of 28w at speed. Running a headlight and keeping a coil fed is not easy with that.
 
jag767 said:
Going to see Tom was, interesting. I wasn't sure what I expected, but if I wanted a crash course in 60's era Ducatis the way they did it in the 60's, well I got it.

Let me start by saying, I haven't been around a lot of professionally trained mechanics. Other than working by myself, my experience is more or less nil. When I work on a motor, I'm usually working on a very clean, if not sterile work surface, all the proper tools I need laid out (i'm big on the right tool for the job), and I generally work very carefully; the whole scene probably looks like a surgeon in an operating room. It's important I lay this out or my experience won't make sense. So when I watched a steel rod get jammed into a cam, and then get bludgeoned by a claw hammer to remove a cover, I was a little shocked.

That scene kind of set the tone for the way I witnessed a 160 head being worked on, Like a bull in a China shop comes to mind. That being said, I was able to learn a bit about the motors. I opted to take the milled barrel, an old VHB carb, but I felt the condition of my head was better, and I will port out the intake myself.

Tom didn't have much input on the 12 conversion or the cdi instead of points. He seemed to feel neither really needed, was in favor of just running it total loss, and charging up the battery, not really my style.

All in all my main takeaways were, A) I know a lot more about motors than I thought, and B) even though these motors are referred to as being complex and a pain to work on, they really aren't bad compared to a Honda 4. In fact, I think they are easier to work on.
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Sounds like you like anal and the "mechanic" likes to eat. ;D
 
Tune-A-Fish© said:
Sounds like you like anal and the "mechanic" likes to eat. ;D
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Lol. Everytime i haven't set myself up right and been a little nutty doing motor work, it hasn't gone well. And i walk into this guy whackin shit with a claw hammer, mating surfaces all smacked up, oh and not to mention a few missed blows with the hammer hitting the bevel gears, allegedly never has issues. I was practically slack jawed.
 
I wipe my tools down going back in the box (rare occasion) and do my best not to add any additional dirt to my motors but as for doing any surgery (on humans) in my shop... You might need a good dose of antibiotics ???

Clean as a whistle ;D
 

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Tune-A-Fish© said:
I wipe my tools down going back in the box (rare occasion) and do my best not to add any additional dirt to my motors but as for doing any surgery (on humans) in my shop... You might need a good dose of antibiotics ???

Clean as a whistle ;D
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Im exaggerating slightly. I also usually do motor assembly in my house not in my shop, that is not a clean place! Yea, we're on the same page based on your photo.
 
Kitchen tables were designed to rebuild engines on.
As a child we shared supper for a while next to a V8 my father was rebuilding :)
 
Erskine said:
Kitchen tables were designed to rebuild engines on.
As a child we shared supper for a while next to a V8 my father was rebuilding :)
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Thats fantastic!

I've used granite dining room table a few times if I think Ican get it done before my wife gets home. FYI I don't always get it done before she gets home. LOL
 
As I wrote that I realized I have the 2 barrels heating in the oven to swap the sleeves. Hope she doesn't wake from her nap!
 
Sleeve swap was uneventful, other than smoking the oily film on 1 sleeve, which stunk. I'm trying to gather what my new compression ratio will be with 1.5mm removed from the bottom of the barrel. Common sense tells me if factory is 8.2, and removing 3mm yields 11, then I am around 9.6. That being said, I have no idea if charting the data like that will work, since I do not know if it's a linear change or not. If my guess is correct, by itself that's only around a 7-8% power improvement. It's times like this I wish I have more spare parts. This motor is so simple to take the top end off on that I'd like to have some dyno time and try all this out. Unfortunately, that isn't an option, so once on a dyno I will be trying a 26 and 28mm carb, 2 different length exhausts, and jet adjustments for all of it based on my air fuel readings.

I found some old paperwork listing improved exhaust length for a 250, which does not necessarily translate to this motor, since they are more cousins than siblings. Also, it turns out I have an 'unidentified' cam in the motor. The ends are of a different design than any photo documentation I can find, and since I am not removing it right now, I won't be measuring the lobes. Fingers crossed this winds up being a good thing.
 
Lots of boring things to report. Ordered new gaskets and orings from across the pond, and still waiting for parts from Australia. In the mean time, I had my machinist verify the cylinder was good to go, and there was no ridge from where the rings stopped travelling. The whole thing has a 1 thousandth v taper to it, but still all round, and will work just fine. Put it on and spun the motor around several times. I was happy to see the sleeve is clearing the con rod fine.

I spent some time on the bevel drive, trimmed 1.5mm out of each half shaft, and 1.5mm out of the housing. For those of you just checking out the build, this was to accomodate the 1.5mm removed from the base of the cylinder to bump up compression. At that point I removed the points side cover, verified the timing, and spun her over a bunch of times. Valves cleared just fine, as I was told they would. Now i'm down to boring stuff, removing 50 year old gaskets and the sort. Once the new gaskets get here I will get them on asap. I know I've said it several times, but I love how simple this motor is to work on.

I will get a bunch of photos up soon, I know I've been lacking.
 
Slight change of plans. With gaskets getting here Tuesday, ignition some time this week, and carb jets coming as well, rather than create more work, I'm going to start getting items checked off. This means for now the head will not be ported. It'll kind of wind up being a good thing, because now I will get to dyno it as a before and after. Stage 1 will be a mikuni 22mm carb, compression bumped up to 9.6 from 8.2, and free blowing exhaust. Stage 2 will be the ported head, and a 26 or 28mm carb.

For Stage 1, the Mikuni 22mm will start with a 100 main jet and 35 pilot. Best I can tell, that's about 1 jet size richer on the pilot, and 2 sizes larger for the main. I'll know quickly with the air fuel gauge how far off I am. My guess is with this setup, the motor will run quite well with nice lower end grunt, but the top end won't be impressive. Based on the riding I will be doing, sounds like a good place to start.
 
stroker crazy said:
with small capacity bikes that is a more satisfactory combination than the other way round!

Crazy
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Yeah I have a feeling if I port the hell out of it and put a giant carb on the top end I'm sure will be fantastic, but the lower end characteristics may go to shit. This will never be a race bike, so I may get a second head for testing. I figure the compression bump, having it being able to breathe in and out a little better, and a nice reliable ignition should make putting around town fun.
 
Regarding ignition, I kept mine stock so I wouldn't need a battery to run it. The lights were run off a 6 volt alarm battery hidden in a fake battery case. IIRC I rarely ran it with the headlight turned on anyway. Never had an ignition problem with it but did forget to turn the power on once so had no brakelight either.
 
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