XLCH/XLR Hybrid build

Classic short-frame models

Re: XLCH/XLR Hybrid build

Postby xlh59 » Sat Jan 15, 2022 4:06 pm

Thanks for all the feedback -- I hope I can also share some experiances sometime.

My main "problem" is actually, that the bike/engine needs miles on it to be understood. I have my XLH since 1992 and by now I understood most of that specific bike. I had many different carburetors on it (the stock 900) -- a Bendix (came with it), the DC-11, the DC-6, CV, Mikuni VM, Dellorto 38 and 40 and the CV. From all carbs I loved the CV the most for the ease of use and good power (at least for my "butt" :D) -- I liked the icredible "drama" on the Dellorto 40 in high rpms, and I almost went crazy in trying to set the DC-11.

When I drive on of my bikes or a car (whatever), I like to go fast and check the handling, but I am not crazy -- I have a family and kids and I am actually happy to live. On the track I like the "kick" of competition, but drifting on dirt without a front brake in between others is quite definately scary. Saying that, the bikes performance is propably way byond my willingness for risk. On the street, even a modern bike is somewhat dangerous and Germany is plastered with speed limits and the respective radar stations. So the realistic street operation is between 45 and 75 mph on (hopefully) curvy roads. On the track I would ride "vintage gold", hence with modified WLs, Ironheads, K-models, KRs -- even if I would be one of the better riders (which I am not), a 77cui XLR is propably overkill. Hence I rather make sure the bike works flawless and has a smooth power distribution -- adding a preferred riding position with reliebale brakes, frame and suspension and I have what I was looking for. I think I have a good basis for that.

Actually I would need to go on the street now for breaking in the engine -- how on earth did racers do that? Just having a few heat cycles and "on the track"? -- As riding on the street is very restrictive in Germany, I will use the next two months to add the stuff needed to be street legal. Eventually you will like my electric system, but its not ready yet :)

I still have the carbs mentioned above, so once I ride on the street, I will find out the correct carb diameter for a smooth power band and decent top end. I have read that the Tillotson has been bored out back in the late 60s? Maybe a 42mm Tillotson would be a good choice?

Lets see .. Cheers, Ralf
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Re: XLCH/XLR Hybrid build

Postby xlh59 » Sat Jan 15, 2022 4:29 pm

Actually the "riding feel" is the reason why I hate the solo seats -- I just don´t feel safe "in" them ... I prefer to sit "on" the seat and be able to move around. I love the 59-on buddy seat, but the early K-model buddy seat seems to be the perfect match. I extended a seat pan, widened it in the front and narowed it in the back to get closer to the buddy seat shape. Just now I am carving the seat foam to get a decent design for my butt feeling :D -- I hope it turns out well.
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Re: XLCH/XLR Hybrid build

Postby chuckthebeatertruck » Sun Jan 16, 2022 8:48 am

45-75 mph riding on hilly roads is exactly what this bike will love.

The nice part about the bike you’ve built is the flexibility. As you dial in the carburetor, the bike will ride very nicely at low speeds and accelerate without fuss. You can swap around your final gearing to suit how up you ride. It will surprise you with how you can ride it softly in town and roll off the throttle to keep the noise down, then just crush the throttle and have fun outside of town.

It takes me ten minutes to get to open roads in my town. That’s how long it takes to get some heat in the oil. And it is damn fun to roll the throttle on and surprise the living daylights out of yourself. In this regard, my sincere advice is to replace your drive chain yearly if you like beating on the bike. Much cheaper than the damage from a broken chain.

I have thought about totally removing the generator and doing up a led total loss system. I’ll be curious your solution.
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Re: XLCH/XLR Hybrid build

Postby xlh59 » Sun Jan 16, 2022 3:32 pm

I equipped my XLH with a 12V - 2,5Ah LiFePo Battery, build into an old coil, so pretty small. You can also get at least 5Ah into the frame backbone, so plenty of places to hide the battery. Still, the LED headlight should have a minimum of 20W, lets say (for the easy of calculating) you need a total of 28W @ 14V, hence 2A -- so a 2,5Ah would be good for 1hour (total loss). With a regular light system it would be roughly 1/2 hour. From my perspective I would like to be able to ride at least 3hours befor recharging, so a total loss system is not really on option (and eventually not legal in germany).

I always liked the modern brushless RC motors, as you can also use them as a alternator -- my first prototype was a small brushless motor with an "intermediate" adapter between engine an front magneto. But the solution was not practicable from many perspectives. I later on experimented with large diameter flat motors (like in gimbal systems), but did´t find a good solution either.
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The easiest way is to put the brushless in place of the distributor. Enough room, enough air and somewhat "stock" looking. The most challenging part was to find the correct version (kv=rpm/volt) for the use as alternator. Pure calculation is not really answering this question, as the motor behaves different if run as an alternator. The range of the voltage somewhat reflects the range of engine rpm, meaning the generated output is from e.g. 10V to 70V -- you can imagine that this would have been a killer criteria 20 years back. But not today: You can use a buck/boost converter, that has an input range like 3V to 30V, hence enogh range to cover the whole rpm band ... I tested different brushless motors and came up with a 50mm brushless.
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Yes really! That small thing is big enough :o -- I tested it on my drill press with 1000rpm (2000rpm engine speed), so basically the highest Amp load for the motor. As the motor generates a higher voltage at higher rpms, the amps drop thanks to the buck/boost converter. After 30min with a 55W bulb the brushless motor had not heated up dramatically. So I am positive. Actually you can get these motors with hall sensors -- would be interesting if you could use them for an electronic ignition. For bigger loads you could still go bigger in diameter and lenght.
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Re: XLCH/XLR Hybrid build

Postby xlh59 » Sun Jan 16, 2022 3:35 pm

BTW -- I really hate the generator noise of the stock system. You only experiance the difference when you run a plate in place of the generator. I assume, that the noise created by an alternator conversion is similar, so I thought I give that solution at least a try.
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Re: XLCH/XLR Hybrid build

Postby chuckthebeatertruck » Mon Jan 17, 2022 9:26 am

Thanks for this, and I do get what you are doing. For several years, I built high intensity LED dive lights before the industry caught up and made them in expensive.

In this regard, I can build LED arrays that arent street legal, but will light the night like dawn, and draw relatively little amperage. I figured out that with a pilot lamp to meet the minimum laws I would draw 2 watts. By using a 2-18v stabilizer I could pack 12ah in a hollow generator body with alloy end caps. Ultimately I decided the weight savings were negated by the pita.

But, adapting a small brushless to a front mount could be an interesting experiment.

Thanks for sharing this. I appreciate the thinking.
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Re: XLCH/XLR Hybrid build

Postby dr dick » Mon Jan 17, 2022 10:50 am

transmissions:
we should attempt to have different terms for the close ratio trans versus the c ratio trans, as they are as different as night and day.
all the different gear boxes are laid out in the kr competition racer instruction manual or the xr parts book.
in my circle we would differentiate them by hds terms :"close ratio" for the hd standard close ratio or 'c box' for the c ratio.

the close ratio trans:
used in c class racing (dirt track).
this trans was the standard 58> trans with a 20/25 clutch gear/countershaft ratio instead of the road going 17/27.
this made the gear spreads very close. way to close for any asphalt track or road use.
reason they were favored in c class is shifting wasnt allowed after the 1st corner.
in c class the start/finish line was midway down the straight section of the track.
so getting quickly to high gear was a seriously big deal.
the variables getting there included all of these the combinations;
track hardness, track moisture at start, bike weight, rider weight, track length (remember 1/2 way to corner) torque curve, and the and the 2 biggest variables of all: the pilot and the weather.
hd made different alternate 1st, 2nd and 3rd gear sets that could be used. plus or minus tooth on any 1-3 grear sets. these were used to tune the close ratio lower gear spreads between the start line and the first corner.)

now the "c" ratio
isnt the above.
instead it fits to every day fun on your road bike.
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Re: XLCH/XLR Hybrid build

Postby xlh59 » Mon Jan 17, 2022 12:49 pm

Very good point dr.dick -- in my case we are talking HD "c box" with a 18/26 clutch gear/countershaft.
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