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Discussion Starter · #1 ·
Did a serch and can't find anything on what would cause a miss-fire and spit back out the carb.
My guess was timing or valve adjustment or both.
So I double checked - valves and timing spot on. Oh, and the battery is fully charged - 12.3V.
Checked the advancer unit, looks good...
But I still get a sputtering out the left carb @ 3000rpm just before the advance kicks in.

I'm running a Dynatech with one magnet removed to eliminate the wasted spark, but this was hapening before that mod, It just seems to be getting worse... I'm at a loss... :?

And now I have oil & greese all over my keyboard... :lol:
 

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Sensei
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Did you check timing with a light (bulb) or a strobe light?.....
 

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l5cygx said:
Did a serch and can't find anything on what would cause a miss-fire and spit back out the carb.
My guess was timing or valve adjustment or both.
So I double checked - valves and timing spot on.
spot on to what spec.? the stock honda valve spec. is pretty tight and a tight intake will backfire thru the carb
 

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Sensei
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Reset valves to .002"..... Normal running can hammer them in after awhile and the original gap becomes too small (tight)......We're only talking of a .0005" difference, but it could allow the blow-back.... Bill said he sets the 450 valves at .002" regularly....
 

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Discussion Starter · #6 ·
Well after setting the valves to .002" And checking it three times, and messing with the timing for hours I gave up on trying to fix the cough out the left carb at 3000rpm.
I've been riding around like this for weeks now and have just gotten used to it... but it can’t be good for the poor girl and maybe I should just rip her apart again and do a hone and ring and top end and... bla, bla, bla.
Wish Bill or Steve or GB were my neighbors... :lol:
Can’t seem to find anyone that specializes in these old gems around here...
 

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Sensei
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Mat... random thought....You DID set the valve lash between the follower and CAM lobe, NOT between the follower tip and the valve stem....CORRECT?...

Just FYI, the advance is progressive (it doesn't "suddenly" kick-in @ 3000).....A loose/weak spring could allow it to be at full advance too quickly.... I have a spare you could "Borrow" to see IF that's the problem.....

I'm clutching at straws on this too......???????
 

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Discussion Starter · #8 ·
Thanks for giving this some more thought Steve.
Ya, i'm setting the valve clearance between the cam lobe and the rocker... (but thanks for asking. I wouldent put it past me.) :?
I'll try to get a couple new advance springs and see what that does. Are they still available at the big H?
Thanks...
 

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Springs never were available separately...You had to get the whole advance unit (currently about $50+ to $75 used ...IF you can find one)....Loaner still available for postage both ways.... e-mail me at [email protected] ...Steve
 

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Discussion Starter · #10 ·
Thanks to Steve I got a new advancer unit.... BUT...
The day before I was going to install it, I was one mile into my ride home from work when BANG, BACKFIRE, SPUTTER, BANG, SPUTTER, BACKFIRE, dead on the freeway.... :shock:
I thought it was the end. Got the bike home (a whole other story), and the first thing I looked at was the timing unit (Dyna S ignition) and the rotor containing the magnet was free spinning on the cam end.
The key pin that holds the whole timing unit from rotating on the cam shaft had gotten loose and worked itself completely out!
I slipped it back in but it had worn the hole in the cam shaft into more of a crater than a slot (which explains the erratic spark around 3000rpm) so I hit it with my mig welder in one spot and put it all back together with the new advance unit.... No go.... for some reason the new advancer put my timing about 45deg off and my modified plate won’t allow for that much adjustment.
SO... I put the old one back on after a good cleaning and it fit nice and solid/snug on the welded key pin. Went to set the timing and my timing light was all over the place (harbor freight junk) so i went and spent $50 on a new one and WOW what a difference!
Runs like a champ! No more backfire, no more hesitation, starts first (or second) kick, smiles all the way to fifth gear and 8000rpms :D
Thanks Steve (and all of you) for helping me out with this one. I never would have thought that little key pin could be such a problem, i would have never suspected it was the issue.
 

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Mat..... I don't quite understand about the advance unit...It's stock and from a 450...Are you saying it DIDN'T fit/work?...45 degrees on the point plate is 90 degrees out on the crankshaft, That doesn't make ANY sense to me.....??????????
 

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Discussion Starter · #13 ·
Ya Steve, I see that it even has 450 stamped into it...
I'm not sure about the 45deg, that was just an estimate. All I know is that when I put it on I had spark but it was way out of time... like on the exhaust stroke or somthing... and since I removed my wasted spark magnet it wont work. I even tried installing the magnet/rotar 180deg in the advance unit, no go.
At one point I switched plug wires/jugs and got it started on one jug... :roll:

?????the advance unit only goes on one way, and the magnetic rotor can only go on two ways, and the rest is plate adjustment, and I tried everything I could think of?????

The good thing is that the old one works fine now. Maybe I'll pull it back out and look closer to see if I can figure out what the differance is....
 

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SOME advance units do have enough of a cut on both sides that they CAN be installed backwards (180 out)... I don't remember if that particular one did, but between that and the "alterations" to the key pin, perhaps it WAS 180 off.....Pix of the camshaft end (bare, showing key pin) and the underside of both units could help prove/disprove this theorem....
This situation has definately made me curious.......
 

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Discussion Starter · #16 ·
Well this made my brain hurt so I'll just post the pics and let you decide...
The one stamped 292 is the one that was on the bike when I bought it, so my timing plate (Dyna eletronic) has been moded to work with it (292).

CB450 is the stock one from Steve, 292 came with the bike.
[attachment=2:1tuoo9qo]CIMG8946.JPG[/attachment:1tuoo9qo]

The vertical pencil line represents the oreientation of the key way.
[attachment=1:1tuoo9qo]CIMG8947.JPG[/attachment:1tuoo9qo]

My crapy weld holding the key/pin in place on the cam shaft end. (laugh all you want, it works.) ;)
[attachment=0:1tuoo9qo]CIMG8955.JPG[/attachment:1tuoo9qo]

I'm shocked the pin came out in the first place...
but now my advance unit sits snug and my timing is rock steady.
 

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Sensei
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They are products of different manufacturers..... Both could function properly as long as the breaker cam lobe is correctly oriented relative to the key pin slot..... The one stamped 292 is a "TEC" product.... The "CB 450" one is a Kokusan.....
Since you modified your ignition to "fit" the "TEC" design, you MUST now use a "TEC" advance bottom plate assembly........However, EITHER complete original assembly should work if you ever go back to points
...(Fat chance of that HUH?).... :lol:
 

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Discussion Starter · #18 ·
66Sprint said:
if you ever go back to points
...(Fat chance of that HUH?).... :lol:
LOL... I keep a set of points in the garage just in case, but ya, so far so good with the Dyna...

Thanks for taking the time to help me with this Steve...

Btw, have you ever heard of the key/pin (proper terminology, key or pin???) falling out?
 

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Yes, I have seen them come out before (interestingly, mostly on 450's)....
Honda calls them " PIN, knock, 3 x 5.2"....
So, they are the PIN (title) that "Keys" (discriptor) the advance unit on the camshaft

Interestingly, Honda also call the "tubes'" that locate the cylinders on the cases (over the studs) "knock pins"..... Probably something translational....:lol: :lol: :lol:
 

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Now that is great, subtle humor, nice one 66, and I will leep my fingers crossed that it never comes true on mine.
 
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