Topic: Advancing the 41a, in 836,for more bottom?

[1976cb750f836]

76,F1,stock carbs,pods,4 into 1,electronic ign,836 Wisco kit, and a 341a
WebCAm

Valve Lift: .335/.335
Duration: 275° / 275°
Duration @ 0.050":242° / 239°
Bike is flat below 4k,rich needle,lean needle,doesn't matter ,it's Sluggish!
4k to 6.5 k it's OK, will lug most riding done Hear!
At 6.5k she comes on hard,still pulling at 9.5k when I Shift!
I'm older now and don't really care bout the best ET?
Would advancing the cam a bit help?
And how much?
I have to replace those leaky pucks under the cam anyway,so why not advance it a bit while I'm in their?
Someone done th is with good results?
Any ideas welcome?

[PeWe]

Did you try richer needles?
The other thread about needle setting where you wrote "I went up again to 132s, removed needle shim,now in 4th from bottom."

132 might be OK, needle 4:th from bottom definitely not since that is 2:nd from top which is 1 step leaner than stock (middle) using air box that work as a choke.
Change needles to 4:th from top as the pic show. Notice the difference

Below clip at stock position, arrows where you should try on yours and feel that the force will be with you

Check this
http://www.hondachopper.com/garage/carb_info/tuning101/carb_tips.html

When carbs OK you might reconsider your cam timing hopefully done before with an adjusted cam sprocket and equal lobe centers (IN vs EX) as often recommended on these bikes.

[MRieck]

Did you time the cam with your build? That cam has pretty low lobe center #'s, and..as PEWE said...the cam is split equal.

[PeWe]

If timing cam is a new thing, lobe center method need an explanation.

Below from the must read site Satanic mechanic.
http://satanicmechanic.org/cams.shtml

CALCULATE THE LOBE CENTER
Assemble the top end but leave off the valve cover. Set up a dial indicator on a intake valve, set it to zero with the valve closed. Rotate the crank until the valve is .040" (1 mm) open. Note the reading from the degree wheel (OPEN). Further rotate the crank until it is 1mm from closing. Note the reading at the degree wheel as well (CLOSE). Lobe center for the intake is:

OPEN - CLOSE   +90
------------------------
             2

Do the same for the exhaust valve. Lobe center for the exhaust is:

CLOSE - OPEN   +90
-----------------------
            2
If these values differ from what the cam manufacturer says, adjust the cam sprocket until the LCs match the specs. If you do not have specs from the manufacturer, adjust the cam to be symmetric, i.e. identical lobe centers for intake and exhaust.

Overlap is also explained here and good to know what it is. Some cams have in and ex valves open at the same time during rather long time leaking compression. These cams need higher CR pistons to maintain the compression and power. There are cams that have relatively short overlap since the duration is shorter, but lift is higher so more fuel mix can be delivered.

[1976cb750f836]

When I built the 836, I just slid the cam in,did not degree it.
I understand how to I was just excited about riding the bike.
I've degreed v8 cams before.
I might be wrong on the cam number, I thought it was the 2nd up from Stock?
It was recomended by a bike shop?
I'll get the number off cam when I attack the pucks.
Before I tear down. I'll try your needle suggestion and go 2nd from bottom?
Bike has always benn lazy up to 4k, since cam Install?
132s might be OK? Should I go up More?
They were only slightly better than 130s?
Thanks
High Temps hear in East TN now in 40s.
Don't want to get it too rich, then do it all over again in spring?

[slikwilli420]

Doesn't matter what cam number, all should be and will benefit from, careful degreeing.

[PeWe]

Yes, verify needles before tearing it down. Set clip as the photo I attached earlier, no washer under clip on these CB750 stock carbs. setting
 If the problem is as I think based on your threads, you'll be much happier.
Main might be OK as is.
Cam timing can be done after carbs. It's a good idea to measure how it open and close, in as ex. Maybe you must have an adjustable sprocket if timing is off. Most likely.
Running lash will show the reality. You measure and time cam with the recommended valve lash. Maybe 0.004 / 0.005) (0.10mm IN/ 0.15mm EX).

Measure with 0 lash (tighten the valve adj screw until the dial indicator start  to move to overcome the play in rockers etc) is to verify the cam card.
With actual lash you can adjust better if the valve train has different play, in vs ex.
Important to double check afterwards if this is something new. Easy to make mistake and set chain one tooth wrong or have the slack on front side. Rotate without plugs and measure again after some crank rotations.

One more thing. The advancer unit has a play on the crank shaft. Youl'l see it before tighten the 10mm nut. I noticed on my engine that turning the advancer to left side of the play, opposite of crank rotation match with real TDC. I have done an alternative mark on case that match advancer set max to the right, same as crank rotation. About 2mm at the right of crank index mark. This for ignition too so all marks line up correctly. T, F and advance marks on 1:4/2:3. ( I verified TDC with screwdriver thru plug hole first time, dial indicator before assemble the head and finally a Piston stop (APE).
The upper dead center is in the middle of the flat area when piston does not move up-down, but crank does.

[turboguzzi]

back to your original question, there's nothing wrong in advancing the cam to try get more oomph. nothing holly about symmetrical lobe centerss, plenty of bikes run asymmetrical. after you time it to say 2-3 degs, make sure to check the inlet clearance as it will get closer to the piston now.

[1976cb750f836]

Thanks for the honda chopper Link!
Needles are set, I also jb welded the air screw holes as per Link!
Rear wheel painted and on.
Going to test ride before I change out the front wheel.
Hope to test tomorow,hope u r right bout needles?
And do I understand the jb welded screw correctly, it makes it richer?
Thanks all!

[1976cb750f836]

Starts and revs good in shop, snow hear today,  I might get to test ride tomorrow.

[PeWe]

Ride carefully on cold roads. I'm curious about the result even if I "know"

[1976cb750f836]

OK Mr, I know, u were right sir!
Kinda it is much improved ,above 3k.
3k to 4k still  doesn't pull hard? But way better than before.
And I know get a rich, dah,dah,dah, when backing off to just above idle while causing 4k to 6k.
Think I need to go back to 3rd. Clip?
And it's only 40 hear today,I let it idle bout 10 min, then only rode bout 5 mile,would probably get worse with longer ride, in higher Temps?
Thanks.

[PeWe]

Just above idle is not the needles. Your carbs are clean, pilot circuit, airjet not clogged? Choke devices opens completely?
Adjust the air screws. I should remove airscrews with springs and spray carb cleaner inside just for sure. Set them to 1/2 turn out from bottomed, then ride bike for a while so its really warm, bring a screwdriver with you and adjust air screws 1/8 steps out until it cannot be better that way.  Area 1/2- 1 1/2 turn out.
My CB750K6 with 836cc, cam, ported head, pods, 4-1 must have clip as I showed, 4:th grove from top.
 
I have had carbs that sounded like too lean but it was too rich with some bangs when closing the throttles while riding on lower speeds.

Next is to time the cam, it might be way too late.

[1976cb750f836]

Carbs are clean. Chokes open.
I just did the jb mod to the screws.
It idles well anywhere from 1/2 turn out to 1-1/2 Out?
Best at 1 turn out,where it is now.
So I need to go leaner on the Screw? To 1.5 out?
I might try to ride again today, sun is out should get to mid40s by 2.
Thanks.
And I wasn't really looking forward to changing the needles Again?
Hope the screws oestrogen it.

[1976cb750f836]

Christmas shopping done Yesterday!
And so it Begins?
Got the frame section out and cables and wires out of way.
Hope to check where my cam degree is today and find out which cam I Have?
I've benn reading honda man faq, and am considering some timing Mods?
I'll post cam Id when I get some numbers?
Hope I can find my degree wheel?

[1976cb750f836]

Cam marked. WF3
                12 03
What cam do I have?
Springs must be upgrade, I don't remember?
White paint on ENDS?

[MRieck]

The white paint made it fast to identify (when being manufactured) which end of the spring goes up.

[Jerry Rxman Griffin aka MuthaF'er]

OK, I'll bite - white up or down?

[1976cb750f836]

Found my old cam box, it's a 63a Web cam?
Their site has a card.
Mine was retarded.
So should I set it according to the card? Or advance 3-5 Degree?
I have a adjustable sprocket.
Since mine was retarded I. Tempted to set up as per card unless u all have some advice?
Thanks

[TurboD]

The 63a may not give that great of a bottom end, might try advancing it or go a little smaller.

[1976cb750f836]

How much can I safely advance?
It was on 19deg btdc intake open @.050
Now on 23deg btdc.
Should I go more?
Don't want to slap a valve?

[PeWe]

When does it close IN? It can depend how you measure and you'll get other numbers.
Best if you have all numbers of IN open vs close and EX open vs close. This will verify how the cam is set and your method measuring.

IN open and EX closing at similar numbers according to CycleX cam data of CX-3 (63A)
Same with IN close vs EX open.
Upon those possible to advance around 3 degrees.

[TurboD]

General rule of thumb is about 4 degrees, any more and you should look for a different cam.

When it comes to advancing a cam, in most cases you actually reduce the chance of slapping a valve.

[1976cb750f836]

Cycle x, opens intake. @ 27 degree.  Btdc. Vs Web  19 Degree?
Mine is set on 25btdc. It's going back together.
Why different ?
I probably needed a smaller cam?
It does really kick hard above 6500rpm.
I'll live with it  however it is.ant buying anot her cam.
It's pretty easy to advance, might play with that more this summer?
Just got a keep it mostly above 4k, and that really ant no problem.
Also going to mess with the advancers, according to honda man, with premium fuel I can add some
Total .
Thanks

[PeWe]

Numbers can differ due to different lift. Running lash or 0 lash another thing giving other numbers.
Thats why you need to  check both IN and EX.

[1976cb750f836]

I checked with zero lash,@.050,as per Web site instructions.

[classic bike tuner]

most cams are messured with   1mm lift  no lash  below the 41a from web  the 8,6mm is  total lift


# 41a van webcam  gemeten waardes
inlaat open 20 gr btdc
       close 42 abdc
lift 8,6mm
uitlaat open 42gr bbdc
          close 20gr atdc
lift 8,5 mm

[1976cb750f836]

Well she runs,after I got a pop or two first time I tried to start?
Some how I reversed the coil wires during assembly,after I switched them it started.
Now it's cold and snow and rain hear so no test ride till???
Now I made 3 new mods and can't ride yet, can't stand IT?
I've advanced the cam,I've bent the advance stops out a tad,and I've
Enlarged half the holes in my jet holders.
Might have to reread honda man and find some more mods I can Do?
It does seem to take gas better in the shop when reving the throttle,time will Tell?
Thanks to all and merry Christmas!

[1976cb750f836]

Sun came out,temp got up to 42, couldn't stand it any longer.
Decided to ride, at least in the yard,on the farm road.
Never got above 4k.
In dry grass and on gravel drive.
Feels much crisper than before, really responds to throttle better.
First day it hits 50, I'm hitting g the road?

[1976cb750f836]

20mile ride,Temps hit 64,so I hit the road.
Advancing the cam was the right move.
Starts pulling now Bout 3400rpm vs the 4k it was.
Is also crisper than before.
Mid 4.5k to 6.5 k is much stronger.
And I can't yet find any loss of top end,only bumped 9k once during ride?
I can live with this cam now.
Thanks.

[MRieck]

20mile ride,Temps hit 64,so I hit the road.
Advancing the cam was the right move.
Starts pulling now Bout 3400rpm vs the 4k it was.
Is also crisper than before.
Mid 4.5k to 6.5 k is much stronger.
And I can't yet find any loss of top end,only bumped 9k once during ride?
I can live with this cam now.
Thanks.

Moral of the story.....always time a cam. It is a good idea even with a stock cam.

[PeWe]

First time I timed a cam needed many turns on the crank to get it right.
I found that I had to tighten the valve adj screw until I saw the dial indicator needle to move to ensure 0 lash.
Then measure EX to ensure my methodto achieve correct balance if IN vs EX.
Later measured with running lash to see the reality and eventually adjust before lock the bolts with loctite medium or similar.

I got longer duration with a low mile set of cam holders with less play.

Most cams numbers are not absolutely true.

[MRieck]

 I recommend timing the cam with the running lash. Your opening and closing #'s will be a little smaller but  it is better to see what is happening with the lash in there. Plus....getting absolute 0 lash is a PITA....especially on shim/bucket arrangements.

[1976cb750f836]

I'll agree all cams should be degreed . But I'm sure I'm not the only one to just install and go,done this many times in cars and bikes. If I'm doing a  performance engine I do degree them. This one was degreed when I installed it years ago, it probably ran as it should,but my taste changed and ET isn't the most important part of a ride now. By advancing it is now a more friendly riding bike. Another way to tune to taste. I really should have used a smaller cam,but now this one will Do!  Last summer I did this to one of my classic cars, for the same reason, more bottom.
Thanks for all the post.
While I was in their I retorqued  the head, they all turned just a tad before click, I'm hoping to stop or slow oil Seapage?

[1976cb750f836]

A nice warm 62 degree day last week, I hit the road for test ride 2.
Still like it way better than before,bumped 9.5k several times,top might be down just a tad but not much, mid and bottom lot better.ready for summer.