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Thanks Brian. I think that 1 carb per cylinder is a worthwhile improvement, given the quirks of the Vee-twin. On my Motorcycle engine, I still re-tune the carbs for idle every year, then tweak them for Spring, Summer and Autumnal use as the town idle temperatures change! For anything where I am at more than 1/4 throttle, the carburation is "sufficiently within limits" that I never change it, but after Spring riding, with stable tick-over, the bike goes off noticeably when the temperature gets over about 17deg.C, so gets re-set for Summer, then come September it needs tuning again, when the air cools, as otherwise it simply won't idle securely. And that's how it has been for the last 25 years of ownership! Also, I knew the same model of bike in the late 1980s that a work colleague owned. I spent a whole year, re-setting the idle for him almost weekly, as the weather changed! So it wasn't just my bike. And it was an 1/8th of a screw on one or other carb just to stop it from stalling, apparently at random. Then it would be fine for a week or 2 until a dramatic weather change...
Everyone else seems to manage by just setting a fast idle - that causes popping and banging on over-run. I even here it today with carburetted Harley Davisons... Their riders appear to have no mechanical sympathy for bad tuning? Of course, super electronic controlled fuel injection has countermeasures for all that...!

Have fun!
More than a few motorcyclists probably like the popping and banging on the overrun because it sounds 'tough.' Similar to people who own souped up Honda Civics and adjust their fuel injection to get the same effect...
Maybe I am too fussy, or have owned too many properly running Japanese bikes...
The second one I had popped and banged one day, then blew the silencer apart. The condenser had failed on one cylinder, causing a mis-fire so after fixing everything I have always tried to fix mis-firing. It almost always means something is wrong.
Just so you know---I have saved all my drawing files for this engine as .pdf files, and they are now for sale for $25 Canadian funds. I sold the first set today and will be happy to see someone else build this beautiful engine. I have been very busy with "other stuff" since Christmas. This engine runs, and if I can get my tired old arse in gear I hope to do some more fine tuning on it. If you are interested in purchasing a complete set of detail drawings and assembly drawings and material specs, contact me at [email protected]
Hi Brian,
Well done on completion of this one.
I have dropped some comments about the Quirks of my Moto Guzzi V-twin motorcycle onto this thread.
Well here's another Quirk!
Last time I ran it (November? - Because there was fuel in the tank and I like to move the oil around!) it idled perfectly, when well warmed-up.
Well, this time it was a poor starter! - I blame the fuel being old, as often happens after more than 3 months in the tank. But after cranking for 15 seconds or so, 3 or 4 times, it coughed, spluttered, and a few more goes had it running on one cylinder, and popping on the other, while the choke was ON. It stopped as soon as I dropped the choke off. So I swapped the spark plugs, the warm one in the cool cylinder, and vice-versa. One was clean and wet, the other sooty and dry, as you may expect?
So next crank it started on Both. - I have been here and done this before... And after just a few seconds I was able to drop the choke off and keep it going above 1500rpm on the throttle. When warm (5 mins or so?) and it had settled to an idle around 1100~1200rpm, with one side running smoothly, and the other running for a second or 2 then stopping for a second or 2. Not right. I knew the one with intermittent running would foul the plug and cease altogether. Yes, I have done this before... So I did the usual trick of screwing the air screw in a 1/4 turn, then back to the start point, then out a quarter turn, then a half turn. And as I expected, the idle settled to both sides running smoothly when I was 1/4 turn out from the previous setting. So I fiddled a bit more on both carbs, but this was the optimum setting - For that run! Outside temperature just a few degrees above freezing, with roads too salty to take it for a ride, so a quick dusting and back in the garage awaiting the next nice day - when I guess it will want more tweaks to the carbs! V-Twins! Who would have them? (I love them).
I hope yours runs more consistently. After 20 years mine is just a variable as ever! - Like a good Woman, they like to be treated with care and attention every time. (Note, I did not say "Understanding"!).
I read a while back that toda's pump gas ( ethanol ) has @ 1 30-40 day life before it starts to degrade . Certain gas stations make my truck run bad . Problem is you don't know their gas affects your vehicle till its in your tank .
I read a while back that toda's pump gas ( ethanol ) has @ 1 30-40 day life before it starts to degrade . Certain gas stations make my truck run bad . Problem is you don't know their gas affects your vehicle till its in your tank .
I think it depends how the fuel is stored. The EtOH makes the fuel hygroscopic so if the container isn't sealed it will absorb humidity from the air, not enough to stop it from burning but it can cause corrosion or make gummy deposits in the fuel system. Small engines tend to fare worse because their tiny carb jets block up easier.

In Australia our main fuel is 91 RON ethanol free, it lasts pretty well generally. E10 is usually a few cents per liter cheaper and the added ethanol boosts the RON to 94, which is high enough for some engines that want premium assuming their fuel systems can handle it. But nobody puts E10 in small engines or stores it a long time, so we don't have issues with it.
Thanks , I can get Ethanol free gas but it's 100+ miles round trip . I live off grid so up until I recently got a generator that runs off propane I always kept 25-30 gallons of gas in tanks . WHen your snowed in for a week ya need the reserves . The jury is still out on the propane unit , it seems that it will only run on my tanks til their at a certain level & they it shut's off . If I have time tomorrow I'll take a tank in & see wht tht level is . Our regular gas with E in it will destroy a carb on a snowblower in a season if you don't run it dry after each use & the carb still looks crusty t the end of the season .
I learned (as a lad) about "degraded fuel, when after spending a whole day trying to get a long-stored motorcycle running, my Dad said "try some fresh petrol". Blow me, it started first time! The "old" petrol, - actually only 2 or 3 years old - had a different smell.
For a couple of decades (Since I rotted a few new replacement exhausts, etc., and spent ages polishing greyed aluminium cases) I have been winter storing bikes while the Council dump huge amounts of salt onto the roads, to add to the salt that blows from the North Sea, just a mile away. So for 4 to 6 months, starting the bike roughly monthly, I have noticed how starting gets much worse after Christmas, when the fuel is more than 3 months old. Usually by April, I am draining half a tank or more out and replacing with some fresh, then burning the old with new through the season. A chemist told me it is natural degradation in petrol and always has been!
But he advised Diesel is worse, as there is a "splash" of something that helps "instant starting" in DERV (~25% naphthalenes and alkylbenzenes?), but the very volatile light fractions can leach through plastic storage bottles, and when it is gone the DERV isn't really DERV any more, just oil-fuel. - And that makes it harder for the first ignition to happen. Whatever makes "old" fuel a poor starter is probably not a bad thing really, as I like to crank an engine until the oil warning lamp goes out before letting it fire-up, after it has been standing for a month or more. Usually I do this before turning-ON the fuel tap, or while waiting for the float bowls to fill.
I keep carbs dry-ish by running with fuel off until the engine dies, before storing.
Not experienced Ethanol problems yet, as I use the lowest available ethanol, highest octane, plus valve lube and octane booster, as it it 5 years or more since the leaded stuff dried up in N.E. England.
But not a problem for models, just long-term storage of petrol for the models! I use a very old (WW2) brass container, with lead screw top, and cork gasket. - It has not rotted - yet.
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100LL (avgas) is another good option for winter storage or for machines that sit for years. Yes, it will lead foul plugs after sustained use, but you can drain or mix in the spring. A bit pricey.
I have avoided using E10 on machines I bought new and have so far had no trouble in the spring. Nothing but grief for all the machines that didn't.
For our model engines I recommend alkylate petrol (gasoline). In Europe it comes under the Aspen brand name, and is designed for power tools such as brush cutters and chainsaws. The exhaust in your face is much cleaner, it has a much longer shelf life, and contains no ethanol. Some folk confuse this stuff with Coleman fuel, but they are completely different: alkylate has an octane rating of 95, Coleman fuel about 55.
I keep carbs dry-ish by running with fuel off until the engine dies, before storing.
For any of my gasoline-powered tools (generator, weed whacker, lawn mower, etc.), I always run the bowl dry before storing. On the two strokes, I empty the gas tank and run it dry. This has seemed to avoid gummed-up carb problems over the past umpteen years. But I also do one other thing - I always add fuel stabilizer to any gas that I buy for these tools. It seems to really help - as suggested above, some of the 4-stroke tools may have some gas sitting in the tank (not as easy to drain as a chainsaw or weed whacker) for some time between seasons, but with the stabilizer I've never had any problems.
This is the v-twin configured engine that I built last year. I was never totally happy with the way it ran, but ill health and work for money has kept me from spending much time on it. I decided that since this engine was basically two separate engines running on a common crankshaft that I would remove one cylinder, piston, and con rod and tune one engine to run satisfactorily, then set up the other engine. I had made the cylinder heads from brass, which was very pretty, but almost immediately pulled the threads out of the sparkplug holes.--Lesson learned--Make heads from mild steel or aluminum in future!!! You can not buy a 5/16" threaded sparkplug, so this meant that I had to make two sparkplugs of my own with 5/16" threads and re-tap the cylinder heads for the next larger thread, which was 5/16". Today I finally got around this morning to running this engine as a single cylinder, and I am quite pleased with the results. Next step will be to reinstall the cylinder, piston, and con rod for the other half of the engine and get the engine running as a twin.---Brian
After you get the other cylinder to work, then you will need to get them to talk to each other. Great going getting this engine to run, you will get there.
Its been a long ride, but great to follow.
How about using a steel insert in the brass heads for the spark plugs to thread into ? I don't know if I missed something in reading this thread , how did you solve the blue smoke issue ?
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Animal--you could probably do that, it is just easier to make the entire head from one solid piece of metal. The blue smoke was never an issue. When an engine first starts up it always runs blue smoke for a bit until the oils and greases used during assembly burn off.---Brian
After a half days work, I have the second cylinder firing consistently. The engine is very stiff, and I haven't been able to get the engine to run on only the second cylinder alone, but it is very close. Keep in mind, I haven't changed anything from the original design except for the spark and cam timing. I think that this is the point where I oil everything up really well and drive the engine with an electric motor on my work-bench out in the main garage until all the "stiff spots" are worn in and the engine doesn't have to fight with internal friction.
YESS!!!--I just ran the other side cylinder on it's own!! Haven't got it down to a fine idle yet, but it really wails at mid throttle. I'm having issues getting a funky exhaust valve cam set in exactly the right spot, but this is very heartening.
Keep on Bryan. This is basically the same process that I have been using for a decade or 3 to get my Guzzi V-twin motorcycle sweetly tuned. Bought a new carb to try on one cylinder, not yet fitted, but the threat has frightened th bike to running sweetly for the first time in my 25 years of ownership...