Author Topic: home built adjustable cam sprocket (Read 5829 times)

bucky katt · « **on:** December 12, 2009, 02:44:47 AM »

what kind of bit would i use in the drill press (i built a rotary table a while back) to open up the bolt holes on the cam sprocket for my cb750? i have a bunch of sprockets so if i screw one up i wont be too upset about it.

dave500 · « **Reply #1 on:** December 12, 2009, 02:59:21 AM »

i think the standard spocket is cast iron,so a high speed drill bit should do it,if its hardened a more expensive carbide bit is the go,if you can file the sprocket a high speed steel bit will do it.

bucky katt · « **Reply #2 on:** December 12, 2009, 03:06:25 AM »

cool, thanks for the info. when i pull the valve cover to re-torque head bolts i'll put one in. next question is, with a stock cam, where do i start, advancing or retarding the cam.

Whaleman · « **Reply #3 on:** December 12, 2009, 05:44:44 AM »

Buck, Do you think you can improve on the original Honda engineering? Do you think that 1 or 2 degrees on a stock cam would be worth the trouble? Thanks, Dan

bucky katt · « **Reply #4 on:** December 12, 2009, 05:57:18 AM »

well, from what i've read in books as well as on the web (this one included) yes i DO think an improvement can be made, especially is i have the cam i'm trying to find, in hand when i have to take the camcover and cam/holders out to retorque the head.

Whaleman · « **Reply #5 on:** December 12, 2009, 06:14:38 AM »

Are you trying to tune for low end torque or high RPM roadracing?

bucky katt · « **Reply #6 on:** December 12, 2009, 06:57:33 AM »

i'm looking for a little less on the bottom end, not so much that it's hard to launch but i'd like to have more power up top.

Whaleman · « **Reply #7 on:** December 12, 2009, 11:35:11 AM »

Do you actually spend that much time at the top of the RPM range that you are willing to give up the lower end? Do you race?

Gordon · « **Reply #8 on:** December 12, 2009, 11:43:51 AM »

You don't have to race to make good use of more high end torque. These bikes were made to be good all-around riders. If you do mostly stop-and-go riding, then you may want more low end torque. If you do mostly highway riding, then wanting more high end power is perfectly reasonable.

754 · « **Reply #9 on:** December 12, 2009, 11:46:26 AM »

Stock was built to suit most riders, also higher cost on indexable sprocket.. so.. do it..

Steve_K · « **Reply #10 on:** December 13, 2009, 06:15:38 AM »

If you are trying to keep the same diameter hole and make a slot in the sprocket I would use an end mill. You said that you are using a drill press to machine it. A drill chuck can not hold an end mill safely as the chuck can NOT say tight on the end mill. Also, drill presses have a taper shank to hold the chuck on. Vibration will loosen the taper and fall out. I would use a mill (Bridgeport or similar) to do that job. The rotary table will work on a mill and you will like the result.
Steve

bucky katt · « **Reply #11 on:** December 13, 2009, 06:23:58 AM »

Quote from: Steve_K on December 13, 2009, 06:15:38 AM

If you are trying to keep the same diameter hole and make a slot in the sprocket I would use an end mill. You said that you are using a drill press to machine it. A drill chuck can not hold an end mill safely as the chuck can NOT say tight on the end mill. Also, drill presses have a taper shank to hold the chuck on. Vibration will loosen the taper and fall out. I would use a mill (Bridgeport or similar) to do that job. The rotary table will work on a mill and you will like the result.
Steve

if i had access to a mill i'd do it in a heartbeat. i guess i'll try it with a hand file and see what happens. i'm a cheap bastid and i dont (and cant) want to spend the money on one already done.

Bodi · « **Reply #12 on:** December 13, 2009, 06:40:21 AM »

I've used an end mill in a drill press with no problems.
Not all drill presses mount the chuck with a taper shaft, and there's no certainty a taper that's been locked together for years will come loose... milling steel will cause quite a bit of vibration though and the chuck may drop. Big deal, it drops down and stops turning, no disaster.
The side of a drill isn't going to work. It only has two flutes (and thus cutting edges) and the vibration will be terrible, plus the edges are not really very good. You need a proper milling tool, designed to cut with the side flutes. More flutes is better but naturally more expensive.

HondaMan · « **Reply #13 on:** December 13, 2009, 08:28:38 AM »

I've had decent results with a 1/4" (6mm) end mill in a drill press (about $6-$7). You can make a "rotary table" for slotting sprockets with a piece of wood or metal dowel, the same size as the shoulder on the cam where the sprocket sits, mounting it into the center of a piece of 2x4 wood about 6" long. Clamp this to the drill table on the dowel, so you can spin the sprocket around it with the hole(s) right under the mill bit.

You'll want to slot it about 5 degress if using a K0-K6 cam, 8 degrees if using an "F" or K7-8 cam. Essentially, Honda dialed back the "K" cam 4 degrees to get the "F" engine, but it was done more to pass the EPA test than for power. They started with the dialed-back sprocket, at the time. When the F2 came out (or thereabouts) the sprocket changed and so did the cam, again, to fit it: the lobes were made steeper to open the valves faster, which ultimately ended up wearing the valve guides faster, too (part of the the F2-onward "valve problems").

Moving a "K" cam back about 4 degrees will add a little extra HP at 8500 RPM: how much HP depends on a lot of other things in the engine. Moving it forward about 3 degrees adds a real nice low-end surge that's useful in city traffic at the cost of a HP or maybe 2 at 8500 RPM. I've found through experimentation that many "F" riders prefer the cam moved forward, probably because that's where they "live" most of the time with the bike. Most riders don't spend a lot of time at 8500 RPM.

754 · « **Reply #14 on:** December 13, 2009, 10:28:11 AM »

Guys he said he had a rotary table, therefore, he can index off original location , rotate, and put in a fresh drilled hole.

Someone shoulda told me I cant plunge with a short stub drill, ground flat.

, I just hate finding out it aint possible after I have done it..so many times..

Hondaman 1/4 inch endmill is about 16 thou bigger than 6mm and bolt generaly has clearance.. My take on it tho, is the sprocket is held concentric by the shoulder on the cam so it should not matter.. except that bigger hole allows a bit of movement, probably only a few minutes..

On an unrelated note, ever tyry a 4 flute 1/4 inch endmill in a die grinder on aluminum..

HondaMan · « **Reply #15 on:** December 13, 2009, 08:22:18 PM »

Quote from: 754 on December 13, 2009, 10:28:11 AM

On an unrelated note, ever tyry a 4 flute 1/4 inch endmill in a die grinder on aluminum..

Just once. I couldn't find the end of the endmill after it broke off and zinged across the shop, though. I'm really glad it went THAT way and not THIS way.

754 · « **Reply #16 on:** December 13, 2009, 08:28:59 PM »

I use em once in a while, grabby, but cut fast & clog less. End mills usualy wear the end first and sides are still crisp...

turboguzzi · « **Reply #17 on:** December 13, 2009, 09:03:43 PM »

sprocket is pretty soft, a common HS drill will be fine

did it with a simple 35$ press drill and then a hand file, it's been working like a dream for three seasons of all out racing at 12,000 RPM, never had a problem.

just make sure to clean the bolts and threads with some thinner and then apply quite a few drops of blue loctite

that said.... I am not really sure that you'll feel much change with the stock cam which is pretty short duration to begin with.

also, in order to be a little scientific, you'd want to make a full process of cam indexing, starting with stock setup as a baseline and for that you'd have to invest in a dial gauge, there's no other way to do it right.

bucky katt · « **Reply #18 on:** December 13, 2009, 10:42:09 PM »

i wont bother with using the adjustable gear until i can find a 77 or 78 750f cam in usable condition

lordmoonpie · « **Reply #19 on:** December 14, 2009, 05:00:33 AM »

Go for it Bucky - it's worth the trouble on any engine to dial the cam in. The sprockets like T said are quite soft - I think they have surface hardening treatment but not full on hardened material so cut up quite nicely.

bucky katt · « **Reply #20 on:** December 14, 2009, 05:07:00 AM »

as soon as it warms up a little more i'll head out to the shop. no propane for the heater so i dont go into the shop until it's at least 50 out there

Jerry Rxman Griffin aka MuthaF'er · « **Reply #21 on:** December 14, 2009, 09:12:18 AM »

I believe I used a rat tail hand file on mine.

HondaMan · « **Reply #22 on:** December 16, 2009, 07:26:15 PM »

Quote from: Jerry Rxman Griffin on December 14, 2009, 09:12:18 AM

I believe I used a rat tail hand file on mine.

I've done that, too! Ugly, but effective.

Big Jay · « **Reply #23 on:** December 16, 2009, 10:37:31 PM »

Sounds like a lot of work to save $35.00

http://cbrzone.com/sohc.html

Yoshi823 · « **Reply #24 on:** December 17, 2009, 03:44:13 AM »

Quote from: turboguzzi on December 13, 2009, 09:03:43 PM

sprocket is pretty soft, a common HS drill will be fine

did it with a simple 35$ press drill and then a hand file, it's been working like a dream for three seasons of all out racing at 12,000 RPM, never had a problem.

just make sure to clean the bolts and threads with some thinner and then apply quite a few drops of blue loctite

that said.... I am not really sure that you'll feel much change with the stock cam which is pretty short duration to begin with.

also, in order to be a little scientific, you'd want to make a full process of cam indexing, starting with stock setup as a baseline and for that you'd have to invest in a dial gauge, there's no other way to do it right.

A kit like this would be ideal...
http://www.holeshot.com/tools/cam_degreeing_kit.html

I made up my own bits and pieces and plotted a graph of lift against crankshaft rotation. Unfortunately the graph itself did not reproduce too well when I went to put it on to photobucket so I can't show you what I mean. I'll try another way.
Needless to say it was a lot easier to see which way to adjust if I had got that far.But the graph showed that the lobe centre for #1 intake was at about 118 degrees ATDC, with 290 degrees duration and 0.315" lift...about 8mm. This was on my standard F2 cam that was reprofiled for me by a so called cam specialist.

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Author Topic: home built adjustable cam sprocket (Read 5829 times)