Author Topic: Advancing the 41a, in 836,for more bottom?  (Read 6412 times)

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Offline 1976cb750f836

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Re: Advancing the 41a, in 836,for more bottom?
« Reply #25 on: December 24, 2017, 10:17:40 AM »
I checked with zero lash,@.050,as per Web site instructions.

Offline classic bike tuner

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Re: Advancing the 41a, in 836,for more bottom?
« Reply #26 on: December 25, 2017, 03:27:02 AM »
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

Offline 1976cb750f836

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Re: Advancing the 41a, in 836,for more bottom?
« Reply #27 on: December 25, 2017, 05:20:58 AM »
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!

Offline 1976cb750f836

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Re: Advancing the 41a, in 836,for more bottom?
« Reply #28 on: December 28, 2017, 05:46:14 AM »
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?

Offline 1976cb750f836

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Re: Advancing the 41a, in 836,for more bottom?
« Reply #29 on: January 11, 2018, 08:40:10 AM »
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.

Offline MRieck

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Re: Advancing the 41a, in 836,for more bottom?
« Reply #30 on: January 11, 2018, 03:53:53 PM »
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. ;)
Owner of the "Million Dollar CB"

Online PeWe

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Advancing the 41a, in 836,for more bottom?
« Reply #31 on: January 13, 2018, 04:01:58 AM »
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.
« Last Edit: January 13, 2018, 04:05:09 AM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline MRieck

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Re: Advancing the 41a, in 836,for more bottom?
« Reply #32 on: January 13, 2018, 06:54:20 AM »
 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.
Owner of the "Million Dollar CB"

Offline 1976cb750f836

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Re: Advancing the 41a, in 836,for more bottom?
« Reply #33 on: January 14, 2018, 05:58:29 AM »
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?

Offline 1976cb750f836

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Re: Advancing the 41a, in 836,for more bottom?
« Reply #34 on: January 24, 2018, 05:40:24 AM »
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.