Topic: Web Cam #41 in a hi-comp 849cc, advantages?

[banzaibob]

I've decided to lower the compression on my Cycle X hi-compression 849cc motor by putting the .040" base gasket on it.  Since it is not a race motor and is going to live a fair portion of its life in the 3000-4000rpm range there were some spark knock issues so I've decided to play it safe. 

The cam that is in it now is an R8, decent performance, etc.  However I was thinking that since the engine is now apart is there a cam out there on the market that will give me a good bump in mid range (4000rpm) performance.  I mentioned the Web cam #41 since it seems to be the most readily available and also appears to be a drop in component.  Do you think it will give me $200 in added performance? 

I also have an assortment of SOHC cams, 2 of which are cams from an F2.  What about using an F2 cam?  Would I sacrifice mid range performance? 

[Don R]

 My seat of the pants feeling on the F2 in an 836 is favorable. It seemed to be torquey compared to a k cam. I noticed it didn't require as much rpm before a shift. I have no dyno results to back up my pants though.

[HondaMan]

The F2 cam is a good one, in general. It opens at 0 BTC, and if you're looking for more midrange response instead of high-end HP, you can advance it about 5 degrees for easier starting and idling, especially with the big-bore engine. Or, you can obtain a Megacycle 125-00 (or their reweld version, the 125-04) and have a well-behaved engine with more power through most of the RPM band, although it does not get strong until past 4000 RPM.

The Webcam 41 (or 41a) cams have a lot of overlap. This reduces compression ratio, increases spitback into the carb throats, and puts the power band up to about 6500 RPM starting point. At 3000-4000 RPM, all it will do for you is foul sparkplugs.

The F2 cam, stock (0 BTC opening), begins powerband around 5000 RPM. If advanced 5 degrees, this becomes about 4400 RPM. This one would be pretty happy at 3000-4000 RPM ranges. Advancing it 5 degrees will also reduce your compression a couple of tenths of a number, and reduce spark knock tendencies by cooling off the combustion temps a bit. This is because the exhaust will open a little sooner than, say, a K0-K6 type cam (5 degrees sooner), which will let some of the unburned fuel exit the head above 3000 RPM.

The Megacycle 125-00 is a near-exact copy of the "85 HP" Yoshimura cam (slightly optimistic number) of the 1970s that ran in Dick Mann's famous Daytona win. It has strong power beginning at 5000 RPM, to 9000 RPM peak, and is well-behaved on the street. I've probably done more of these than any other performance cam, and can advise on the tuning if you care.

[Rookster]

Hi Mark

Where might one find a Megacycle 125-00 for sale?  I checked the usuals, Ape, Dynoman, Cycle X, but I only come across Webcam or DP cams.

Thanks
Scott

[Bodi]

Get the catalog at http://www.megacyclecams.com/. I bought direct from them, I can't remember if they require a cam to rework or sell cams without exchange with a core refund if you have one.
Megacycle does hardwelding to build up the lobes rather than regrinding a stock cam to have a reduced base circle. Most reputable cam suppliers now hardweld or use new cam blanks to avoid this regrind problem, I would avoid using those regrinds where the base circle is seriously reduced - a mild cam regrind is OK but for much added lift or duration the base circle gets very small and the valvegear geometry is compromised..

[banzaibob]

The only web presence that Mega-cycle appears to have is a .PDF price list and info page from 2012.  http://www.megacyclecams.com/

I had some earlier threads last year about that rattley spark knock that this engine had below 4000 rpm under heavy load and throttle.  I was able to get rid of 85% of it by drilling out my pilot jets to the equivalent of about a #48.  I also shaved about .007" off the back/bottom of the slides.  By the time I got it all sorted out it was fall and ambient temps were less than 65º.  My fear is that 100º heat would wear this engine hard and fast.  My plugs were always reading rich also. 

For the type of riding I intend on doing I can't imagine ever floating the valves or getting much above 7000rpm. 

I assume that to use the F2 cam advanced 5º I would have to slot the cam sprocket and get a degree wheel.  I have never done this type of operation but it is not outside my skill level.  I have access to a vertical mill but would it be simpler to just use a die grinder?  My best guess is that the whole operation would basically be making the two mounting holes oblong as to accommodate the movement, right?  Is there already a predetermined size/template that one could use? 

I would think that there would already be a cam on the market for low/mid power aimed specifically at people who want a good fast touring bike? 

[PeWe]

Ported head will match your pistons!
I've used Action Fours SS-1 cam which was a very nice cam in my engine.  No idle problems. I used it mostly on long tourings. With ported head, 836cc and mostly OEM carbs when my Smoothbores had problem with carb boots (now sorted)

Numbers similar to WebCam 41

Lift           0.360"
Duration   270 degrees     
IN   28/62
EX  62/28
"Ok with stock valve springs, smooth and  tractable as a stock machine. The cam for those who are worried about "hot" cams."

I have replaced it with Cycle X  CX-7 which is a little bit hotter when I want new fun experience after not using the bike since 1990,  out on the road again spring 2014.

WebCam 41 is rather common in this forum. You'll hopefully get reply from others using it.

[Jerry Rxman Griffin aka MuthaF'er]

You say high compression. You're talking 12.5:1 right? Or are you talking about the slight bump most kits give to 10.25 or 10.5:1 where you can run normal pump gas?

As far as slotted sprockets if you have the equipment to do one yourself go for it. Even a rat tail file will work if you have time and patience. They are readly available and not too expensive.

R8 is not a cam model, that's just a forging identifier. Is your present cam stock? The F2 would help over a stock cam as would a F0/F1 or a K0 however you're not going to be able to reliably identify one unless you know for a fact the engine they came from is a stock unopened engine.

The cam Hondaman speaks of would be considered the Daytona Special and is NOT a mid-range cam but it does start to come on strong around 5000. Their mid-range is the Road Special and it would be better but you're not going to find one. I can dig up the specs on all the Yoshimura cams if you need any to use as a comparison for another currently available cam.

[banzaibob]

I went over to my storage unit and retrieved the cam from the F2.  I checked the numbers on the engine and it is indeed an F2.  I got out the measuring thingy and measured the maximum lobe height on both cams; stock cam (R8 marking) #1 in. 1.401", ex. 1.388"   #2 in. 1.403" ex. 1.3875"  #3 in. 1.403" ex. 1.3885"   #4 in1.4015" ex. 1.388.

The F2 cam (R1 marking) read; #1 in. 1.419" ex. 1.402"  #2 in. 1.422" ex. 1.4035"  #3 in. 1.4195" ex. 1.405"  #4 in. 1.4225 ex 1.409 

Everything appears to be within specs.  Would it be advisable to also retrieve the springs from the F2 head also?  Any other parts?  I've located the tools, etc. to degree this cam.  However I'm a big fan of keeping things simple and doing less work.....just how much more mojo would I get from dropping in the F2 cam and not messing with advancing it 5º?  It appears that the stock (R8) cam intake opens at 5º btdc and closes at 30º bbdc, exhaust opens at 35º bbdc and closes at 5º atdc.  Does anybody know what those specs are for the F2 (R1) cam are? 

[Jerry Rxman Griffin aka MuthaF'er]

K8, F2, F3 all had stronger springs. That will provide some protection against valve float at high rpms if say you miss a nasty 1-2 shift with wide open throttle. The keepers and retainers are specific to K8, F2, F3 valves

5 BTDC
40 ATDC
40 BBDC
5 ATDC

Keeping it simple then just line up the cam markings with the cam tower. The extra cam may give you what you're looking for without going to 7,000 - 10,000 but you'll notice the difference when you do go there.

[banzaibob]

I'm still not against spending $200-$300 on the "cam of my dreams"  if someone knows of one that will work well with the CycleX 849 kit to give it more low end and mid range punch. 

[rlvitt]

I just finished dropping a Web Cam 41a into my K0. I also replaced the #1 and #2 cam tower because the oil supply had become blocked and burned the bearings. I went with it over the Megacycle 125 cam because their cam would have run me $425 which was a little too expensive for me at the time. Upon start up I found the cam ran very rich. Hondaman advised me to drop my needles to the top notch and put in #38 pilot jets .  I set the float bowls at 25mm. I also put 110 main jets to further leaning the mixture. I set the air screws to 1 turn out and synchronized the carbs. I read about 6lbs of vacuum across the carbs. It should normally read about 8lbs. Hondaman told me that the duration of the 41a would reduce the vacuum though. I installed a Dyna ignition and coils for spark. My timing light won't pick up the spark signal at idle but does start to read out when the engine is above 2500 rpm. It shows the spark at the advance marks as normally it would. Got to sort out why the timing light won't read out at idle though.

It's still running a little rich and I haven't taken it out on the road yet  As I'm finishing up rebuilding the master cylinder as part of a general overhaul of the bikes front discs. However, the throttle response seems good and there is no lag or choking when I throw the throttle WFO. That's probably due to the rich fuel mixture.

That has been my experience so far with the 41a grind. If anyone has input or comment to it it is always welcome. I'm plotting and planning to do a build on my other K0 and dropping in a big bore kit as part of it. Any ideas, recommendations  or warnings would be appreciated.

BTW, I picked up Hondaman's book and I would recommend it for most guys working on their CB750's.

[Nic]

You really need to ride the bike to get the big picture on how the cam feels. I'm, sure you know that so I dunno why I said it lol.
 I've just gone the other way, just come back from riding. I had the #41 webcam in since I did my rebuild, I finished it 6 months ago and have had the 41 in there from the start. I did a check n bodgy job of seeing when the cam was opening 1n4 intake valves. Turns out it was 16° BTDC, I just wanted to get that figure n didn't bother with anything else until I put in the stock cam, the stock cam was in the engine when I got it but it was a wreckers cam n so I didn't know what it was so I checked the intakes again n it came in at 0° BTDC so I figure F cam. So I advanced it 8°. Might be a bit much but that's what I did.
The 41 cam didn't seem to do jack until 8 grand on the tach and I'd been getting more n more underwhelmed with the performance so today I put in  the stocker and after first ride feel very happy with it, the bike is a lot more fun to ride, 5th gear at 4 grand just goes when you hit the throttle, before I would have downed it to 4th. The engine has rebore to 1st over, some mild port work, heavier springs and new valves and guides. I won't be putting the 41 cam back in. I will need to address the carbs again but for now the bike to me goes better with the stock cam at least up to 8K or so. From 4 to 6 it just rockets. In a couple of months I'm gonna pull it all down n put in the flat top 836 kit so I reckon that'll do me. See pic of home made degree wheel printed off from the net, cost, $0000.00

[rlvitt]

Got a lot done in a days work sound like, Nic. I installed the 41a set at TDC on the cam end marks. I didn't degree it or anything, though I installed an adjustable can gear. The 41a is somewhat different that the 41 and is supposed to be for mid-range and top end HP boost. I'm wondering if I should also advance it a bit since the timing is set at stock settings. Maybe that would get a more complete burn and finally eliminate the black puff when I roll on the gas.

[Nic]

Our man Hondaman is the dude to ask I reckon. I don't like advancing early cams myself, you're valves will be gettin pretty friendly with them there pistons. Esp with the extra lift and your high top pistons but wadoeyeno?

[HondaMan]

The only web presence that Mega-cycle appears to have is a .PDF price list and info page from 2012.  http://www.megacyclecams.com/

I had some earlier threads last year about that rattley spark knock that this engine had below 4000 rpm under heavy load and throttle.  I was able to get rid of 85% of it by drilling out my pilot jets to the equivalent of about a #48.  I also shaved about .007" off the back/bottom of the slides.  By the time I got it all sorted out it was fall and ambient temps were less than 65º.  My fear is that 100º heat would wear this engine hard and fast.  My plugs were always reading rich also. 

For the type of riding I intend on doing I can't imagine ever floating the valves or getting much above 7000rpm. 

I assume that to use the F2 cam advanced 5º I would have to slot the cam sprocket and get a degree wheel.  I have never done this type of operation but it is not outside my skill level.  I have access to a vertical mill but would it be simpler to just use a die grinder?  My best guess is that the whole operation would basically be making the two mounting holes oblong as to accommodate the movement, right?  Is there already a predetermined size/template that one could use? 

I would think that there would already be a cam on the market for low/mid power aimed specifically at people who want a good fast touring bike? 

You can get a slotted sprocket from DynoMan or APE. I have found that their zinc coating must be sanded off inside the center hole (I use a Dremel with sander drum, low speed) to fit onto the cam shoulders, but otherwise they work great, and are lightened. I think even CycleX sells these?

Or, if you have a Proto-Trak type mill or a rotary table, you can slot out the existing holes on a mill. I've even done them with a rat-tail file when I was younger (and got over 130k miles from one of them, just changed it out last year). About 1/4" is enough.

For a rough installation, you can time the cam to the "F" mark on the spark advancer, which is also 5 degrees.   Shade-tree wrench stuff...

To help with that spark knock, maybe consider cutting the spark advancer springs back a coil? This will stiffen them up and delay the advance for a while. I do it to almost all the rebuilds I do these days, a the springs are sacked from their constant heat-treating/annealing for 40 years.

[PeWe]

More about the old Action Fours SS-1 cam that woke up at around 6500rpm with a wonderful sound! Rpm estimated, no tacho back in those days. I remember that I geared from 3:rd to 4:th gear at ~160km/h (100mph). Gearing 17/48 (front one tooth less than std)

I checked the timing before installing the new cam.
(forgot to mesure the lift, should be 9,14mm)
@ 0.04" (1mm) lift, 0 valve lash
IN: 22/55    duration  257
EX: 56/24    duration  260

Cam sprocket was probably a modified F sprocket with plenty of holes. 2 holes for screws grinded oval by my local tuner. This sprocket is much lighter than APE that I also needed to grind to make it possible to fit on the cam.

I have bought a new Falicon sprocket almost as light as the old F sprocket.

[banzaibob]

My performance benchmark is high speed interstate cruising; passing trucks on two lane uphills in 100º heat with a 20mph headwind (and still go for another 400 miles to my destination).  My reasons for low and mid range performance is because I want the engine to live an under-stressed life.  So far it is beginning to sound as if I used the WebCam 41 I would want to advance its timing to give better mid range.  Since I have the F2 cam in hand.........

I tried different spring rates on the advance, no improvement in spark knock and abrupt performance at full advance (4000rpm). 

[HondaMan]

My performance benchmark is high speed interstate cruising; passing trucks on two lane uphills in 100º heat with a 20mph headwind (and still go for another 400 miles to my destination).  My reasons for low and mid range performance is because I want the engine to live an under-stressed life.  So far it is beginning to sound as if I used the WebCam 41 I would want to advance its timing to give better mid range.  Since I have the F2 cam in hand.........

I tried different spring rates on the advance, no improvement in spark knock and abrupt performance at full advance (4000rpm). 

yep, the Webcam makes the bottom end pretty rich. It's all that spitback that is going on, makes the intake tract real wet.

[PeWe]

...................
yep, the Webcam makes the bottom end pretty rich. It's all that spitback that is going on, makes the intake tract real wet.

I found that to be common in tuned car forums when searching about idle tuning with my current cam.
Next timing session will have the closing of inlet valve as first prio to reduce the reversed airflow thru carbs on low rpm. Advance the cam ~4 degrees if valve to piston clearance allow it.  Exhaust will open erlier too, lets see what will happen...
Mod the frame for access to the cam will make it easier to change the timing and cam.

[banzaibob]

I went to the Cycle X site to price the frame splice kits and crap, they're out of stock.  Who else makes/has them? 

I have all of the CB750 stuff in the mail to me right now and I'd like to get it all done by the end of next week.  I forgot to mention that I have some other complicated projects in the pipe.  1) BMW R90/6 Seibenrock big bore 1050cc kit 2) '72 Triumph T100 Daytona restoration and 3) '76 Goldwing diesel conversion. 

[Nic]

I went to the Cycle X site to price the frame splice kits and crap, they're out of stock.  Who else makes/has them? 

I have all of the CB750 stuff in the mail to me right now and I'd like to get it all done by the end of next week.  I forgot to mention that I have some other complicated projects in the pipe.  1) BMW R90/6 Seibenrock big bore 1050cc kit 2) '72 Triumph T100 Daytona restoration and 3) '76 Goldwing diesel conversion.

http://forums.sohc4.net/index.php?topic=62832.msg1503327#new

[Garage_guy_chris]

i emailed cyclex last week about a few things they said the frame kits should be in stock again by the end of the month

[HondaMan]

I went to the Cycle X site to price the frame splice kits and crap, they're out of stock.  Who else makes/has them? 

I have all of the CB750 stuff in the mail to me right now and I'd like to get it all done by the end of next week.  I forgot to mention that I have some other complicated projects in the pipe.  1) BMW R90/6 Seibenrock big bore 1050cc kit 2) '72 Triumph T100 Daytona restoration and 3) '76 Goldwing diesel conversion. 

I nominate Ilbikes: Gordon's are real nice conversion kits.

[HondaMan]

...................
yep, the Webcam makes the bottom end pretty rich. It's all that spitback that is going on, makes the intake tract real wet.

I found that to be common in tuned car forums when searching about idle tuning with my current cam.
Next timing session will have the closing of inlet valve as first prio to reduce the reversed airflow thru carbs on low rpm. Advance the cam ~4 degrees if valve to piston clearance allow it.  Exhaust will open erlier too, lets see what will happen...
Mod the frame for access to the cam will make it easier to change the timing and cam.

Yeah, Honda's solution was to retard the intake cam and make DOHC engines, by 1980. This lets the intake tract not spit back so much, but also pushes the RPM power band higher for the tradeoff.

On the SOHC4 bikes, I have sometimes used leaner idle jets (#38) with these cams, and set the air screws at 7/8 turn or so. This requires the float levels be raised slightly, or cold starting is hard because the intake tract won't wet enough at first. So, I combine the #38 jet with the 25 or 25mm float depth.

Another control that Honda used is the #271301 jet needle. This uses the same needle jet in the carb body, so these can be swapped directly. This needle, found in the late K6 and F0-1 carbs, has a thicker low-end section and a slower taper to midrange. This makes it lean out the bottom end while the cam is busy spitting back, but gives back the fuel when the cam should be getting busy again. This is how the tractability of the F0-1 engines came out to be so "in-town-able" for commuting service. Increasing the mainjet beyond the meager #105 size Honda used to meet EPA emission test of those days will improve the flat spot at 4000-5000 RPM with the more early-opening cams, too.

So, this leans out the bottom end while richening up the mid-to-upper end, perfect feed for a hungry cam.