Twin Carb Knuckle Bobber

[Flathead Jedd]

I know he won't mention it, but I will. Chopper Dave's twin carb knuckle bobber is in the latest edition of "The Horse." Wow what a bike! Traditional bobber with a crazy dual carb set up. He gives some good tech info on building it using to front cylinders. The bike features many parts he made himself through Chopper Dave's Casting Co. If it sounds like he's my friend, he is. Check out the bike it should stir up some good tech discussions. I personally think he should have stroked it, but what do I know.

[AdminGuy]

Great - could you post some pictures of the head intake ports? pictures of the completed bike? Sounded like it was fun project with lots of headaches.

[c.o.]

Chopperdave did a helluva job with that knuck. There are definitely some features on that machine that show his craftsmanship capabilities....... I could be wrong, but maybe part of not stroking it had to do with keeping it period correct.......

[Flathead Jedd]

I pretty sure Knuckles were being stroked using 80 ULH flywheels during this time period. I'm just razzing him. Maybe he'll post a reply as to why not. Maybe he was just scared. I'm posting one pic I have. The magazine article has better ones. Dave post some good pics of the engine.

[Flathead Jedd]

The pics not coming up. Second try

[c.o.]

I sit corrected Jedd.....your right about the flathead flywheel swap........

[Chopperdave]

thanx for the compliments on it

well, if ihad had some stroker wheels i might have used em, but not told anybody... until someone saw the stroker plates...

i actually wanted to use 61" wheels in it, but again i didnt have any, i have some now, but im not takin it apart

ill post some pix of the bike tomorrow and pix of the motor...

jedd, there is a huge hole in your cylinder head now....

HUGE

[Flathead Jedd]

Dave, can't you use the 80" ulh wheels, 74" knuckle cylinders and shave a little off the pistons? I know this is probly the old (and wrong) way to do it, but wouldn't eliminate the plates and create a true sleeper? Food for thought for when you blow the motor up. And you know you will.

[Chopperdave]

ill blow the tranny up first!

[Lonnie]

coupla questions, Dave:
1 - Why use the Burman trans when a std. H-D 4-speed is more than adequate? (I know, correct answer is 'because I could", but any other reason?).
2 - Is the Burman up to Smoke-out style abuse?
3 - Re the stroker, are there not stroker pistons available that could have been used?
Thanks in advance,
Lonne

[Chopperdave]

1. well, coz my whole plan was to build a 51-52 style bike, yes the foot shift trans was available in 52 and yes i have a b&h shifter in my shop, but i wanted a period british foot shift...
and i had never seen one behind a big twin, only 45's, when i break the case, i might even make a whole new one that is much heavier, but until then i like it.

also, when making left turns the first thing that hits (on a stock clutch), after the kickstand, is the clutch basket and this one doesnt even come close, i can ride this thing like a road race bike and it clears everything.
and once i got the clutch dialed in it works great

this drivetrain is so narrow its stupid... it rules.

2. well, honestly other than jumpng it at the smokeout which was fun, thats really the hardest i have been on it, i have some more issues with the carbs, i think i have a new intake leak somewhere..

and yes cotton, i have a test block to test it with, i just havent had a few hours to **** with it lately, and i am waiting for some swedish bombsites that are coming my way...

i ride it around some, but i havent put any "real heavy" miles on it, i hate my seat assembly so i am remaking the whole thing...

and to answer your question, probably not, but we will see what happens...

3.
as far as stroking it, oh yeah it would have been easy, you can get most of the parts to do it period style or with offset piston pin pistons....
i just was on a limited budget and had a set of 74" wheels and my main focus was makin the top end work.


i just really wanted to build something period and different, not just different.

and it was fun at the smoke out in the dirt too, i'd fire it up and get into the center of the fairgrounds in a slight left and nail it and the back end would come out perfectly, easy to control slides...

those tires rule on the dirt,and i always get people tellin me that you cant run them on the pavement.

those people have never run them on the street
they are the best tires i have ever run on the street, ever!
yes they dont last as long, but they are cheap as you can order em from the harley dealer as they even have a HD part number.

but then again i am building a bike with a 117 in motor that will have one on the back and i will probably go through them kinda fast...

actually, if you aren't hard on em they last fine, when i rode to sturgis in 01 i was runnin them front and real and i still ran them for at least another 2 years after that


any of that make any sense?

[Lonnie]

Yes. it all does make sense and the bike is both "period" and different, using components that were available in that timeframe.

Re the transmission, I have a shortened by 1" oil tank that I plan to use at some point, most likely with a '47 knuck motor. This would let me raise the trans 1" of course. I just hate to modify the seat post (raise tank bracket 1", etc.) on an original frame. But this would alleviate, I think, the clutch basket grinding. (If I got to the point the clutch basket hit with this set-up I'm a goner anyway.

At issue is how to keep it 6 volts since this set-up would be TT-style which usually ran a Wico (?) horizontal mag. Of course I could use a Morris-style mag but I don't want to grind on the original knuck cylinders. Plus, mags now have gotten real pricey.

Suggestions?

Lonnie

[Chopperdave]

well, thank you!

and

my old panhead frame is now the chassis for an evo flattrack bike i built a few years ago and am now finally putting back together, the trans in that is raised .850 and its a world of difference in ground clearance...

you could always cheat and run 1" spacers on the front mount of the tank... i do it out of one piece tho, or link em together somehow to eliminate possible movement...

why dont you just run a hunt mag and a generator?

that would probably be the easiest way to go...

the wicos are crazy expensive these days especially the horizontal mount ones...

i am assuming that you wantit 6 volt to run lights?

[Lonnie]

Yeah, gotta have good lights here in the woods - the deer here are everywhere at night! So, need the generator.

Is it possible to run a retardable magneto without grinding on the knuck fins? Most I've seen have ground fins, but I can't remember if that was on pans or knucks!

Thanks, Lonnie.

[Chopperdave]

well, i didnt grind any...
but i did cut my relay boss off!

but i believe that if you use a .200" spacer underr your mag, you can run it without cutting anything off, and still have enough gear contact

the only problem i have is mag to pushrod tube clearance issues...

if you really need lights, run a 12v generator...

im not runnin a battery and with the capacitor i am running the lights are nice and bright!