1982 CB750F...Better Devil

Nice, I hope to get at the GL this weekend. we can ride anytime the snow is gone, but we have enough that could be May. I should be going over to the states tomorrow, I think you sent me the receipts for your stuff. If I'm missing one I'll message you. As for the cam, there is a ton of things you can change with profile changes that effect power over all the rpms etc. Teazer would be the one here who can explain it all. The diff between the 900 and 750 if I remember is duration, lift and timing. So when the valves open, how long and how far and if the intake and exhaust overlap at all. What the difference between the 2 is, I don't remember but I read it once.
 
Nice one Mike, my man. Pretty sure I've sent you the invoices but I'll double back on my emails to be sure. Once I get my hands on those powdercoat samples one of two things will happen - I'll pick out one that I like and I'm off to the races, or I'll confuse the shit out of myself and end up going gloss black. A bit like when we painted our apartment. "Shit, let's just paint it white, keep things easy". Yeah, right. The missus came back from the paint shop with 500 different whites to choose from. So much for easy.

Hopefully Teazer will chip in with some more info, thanks for the input mate. If the cylinders need more than a hone then the same guy that hooked me up with the 900 cams also has the 900 cylinder block too, and pistons. It's a good job I have bottomless pockets filled with cash plucked fresh from the tree in the backyard that blossoms crisp hundreds every week. Not.
 
Higher performance cams, like the 900F ones you are installing usually have greater lift, this means that the valves open further, so like a water tap, the more "open" it is the great the flow, or in this case, air/fuel mixture. The other aspects are the timing and duration of the valves being open. Higher performance cams allow the valves to open and close for longer durations and both are open for greater overlaps. These changes allow the engine to breath better at higher rpms for more horsepower, the trade off being that the engine breaths less efficiently at lower rpms. If you put your cams side by side, you may see the difference between the 750 and 900 ones. A poor analogy might be comparing a person blowing air into a straw compared to blowing into a large pipe, the velocity of the movement in the straw will be much higher.
 
That makes sense Crabs, thanks for the explanation. Should I be adjusting anything else when I install these cams? Also, would I need to re-shim the valves, or would their spec remain the same as with 750 cams?

This just showed up -

VQ95SfK.jpg


Love it, just not sure it's yellow enough.
 
You're welcome. You have to make sure that there are no clearance issues between the valves and the pistons. You say the cams are a drop in, just make sure that they are. Sometimes you do have to change the valve clearances with cam changes, my Guzzi was like that.

That is a nice speedo, hope you are able to peg it :)

Brian
 
Oh shit you're right. Dammit. Note to self...buy things at 2am after a few beers - consequences.

I'm blaming it on beer anyway.

Doing the Ton will have to be measured in butt-clench instead.
 
Surely the speedo isn't a left-over from the early 80s? I'd check to see if the vendor will do a swap.
 
pidjones said:
Surely the speedo isn't a left-over from the early 80s? I'd check to see if the vendor will do a swap.
Click to expand...
The only thing vintage about this thing is the guy's brain that bought it.

Still, if they're take apart-able maybe I'll just write FASTER after 140...

Edit - google says no, not really take apart-able without trashing the bezel. Might etch the glass instead. Either way, at the rate this build is going, I've got plenty of time to figure something out ::)
 
pidjones said:
Surely the speedo isn't a left-over from the early 80s? I'd check to see if the vendor will do a swap.
Click to expand...

He is in Canada so kph is legal and if hes going faster than the 140 indicated in Quebec he'll lose his licence anyway LOL
 
Can anyone tell if this would work for me? I'm pretty sure I need a tach with a 1:4 ratio, but this is advertised as a 4:1 ratio (for old Triumphs) -

jtBdHu4.jpg


I think I know the answer already, but I really, really want to be wrong.
 
SOHC/4 FAQ says 4:1 for tachos.

That really weirds me out that the 10, 20, 90 , and 100 are flipped.

It looks like a knockoff VDO gauge from one of the VWs

s-l1600.jpg
 
Not sure man - the ratio for a 750 is 1:4 not 4:1. Where did you see that SOHC's tach ratios are 4:1? Not doubting you - in fact really hoping you're right!
 
The Jimbonaut said:
Not sure man - the ratio for a 750 is 1:4 not 4:1. Where did you see that SOHC's tach ratios are 4:1? Not doubting you - in fact really hoping you're right!
Click to expand...

http://forums.sohc4.net/index.php?topic=87443.0
 
Well, hello snazzy tach then.

Here's why I'm confused - DimeCity lists the tach suitable for a cb750 as 1:4. When I contacted the seller of the tach I showed in an earlier posting however, they told me it was not suitable for a CB750, as the tach was a 4:1 - they said that a 4:1 tach and a 1:4 is not the same thing.
 
Not sure the deal there, unless they went from 4:1 to 1:4 after 1978. The stock replacements, like was Vintagecb750 sells, is 4:1.
 

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