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What the deal with advancing or retarding the breaker points timing. I've been told that doing one or the other can improve performance especially if your running a non stock bike. On my cb750 i'm running pod filters and 4-1 pipes with a megaphone muffler and i've just installed new points, condensers and plate. She's running pretty true now but i think i can push her a little bit more...

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I hate to bust your bubble sonny, but megs and pods are not really a heavily modified bike. For all intensive purposes the internals on your bike are stock and will react like a stock bike to changes.

running advanced or retarded timing on a stock bike isn't going to really do anything for you. your stock timing is a balance of low end performance and top end. If you change the timing the bike will run slightly better at one end of the spectrum and really bad at the other.

If you had a radical cam and big bore kit this would be something you would be looking at, but for just pods (which aren't a performance mod BTW) and an exhaust I woudn't bother with it. You won;t get anything out of playing with the timing also because the biggest restriction in a cb750 is the head. Port some of those passages and maybe you can start to see an increase.

In the old days (the 90's...ha) I used to play with the timing on my GTO a lot because I ran a fairly radical cam and high compression and when I couldn't get 94+ octane I would have to retard the timing so the motor wouldn't ping.

You want some cheap performance, 78 cb750 carbs (espically F carbs). Accelerator pump carbs like on the GS and KZ and they are usually worth a good extra kick in the pants, plus smoother throttle response. you will need the rubbers off the same motor but it will make a difference. Also put your stock airbox back on and install a K&N inside.

Edit:
here are hondaman's archived posts on the sohc4 board. READ THESE. And when you are done read them 2 or 3 more times. I am currently looking for his post on cheap tricks on the 750 that is worth reading too.

http://www.sohc4.us/forums/index.php?topic=7401.0

he does describe the differences between the different K model's ignition timing but at one point he does leave out the different cams that honda used. according to honda there is only one cb750 cam but we know this not to be true now and there were several different cam timings (different than ignition timing) for similar grinds.

Also maybe it is time you think about suspension mods too. All that power is no good if you can't find a way to get it to the ground.


Edited by - geeto67 on Aug 21 2007 4:54:05 PM
 

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Geeto is correct you can change the timing but you sacrafice one end or the other.It has to do with valve timing ,compression ratios .Stock is compromises (NOT A BAD THING AT ALL) for OVERALL performance underline OVERALL.
Now if you have seen some one at the red light that cant keep their engine idling but has to keep reving it then it goes like stink once the cams kick in you know some one is driving a perpose built car and not a street car, or bike for that matter.


Stock is where its at for everyday driving hot cold empty road ,traffic bound road and stop light idle without the police looking at you sideways.

When you start making it faster its a compromise in either low .mid. or top end.This makes it not traffic or idle friendly ,also makes it slower in some power bands then stock and faster in the intended power band that it s parts were chosen for.

So all any one has to understand is stock isnt so bad its good very good.Lighten your bike add better shocks better tires better brakes so you can use all the stock engine has to offer is the performance edge you need to look at (not you personally but any one looking for FASTER)

Later fuel injection computer controled bikes a new chip will get you there.But old school bikes .Lighten(taking off weight and up grade stock suspension,chain ,wheels, tires, shocks,keeping stock specs optomium, add upgrade to electronic ignition would keep you from watching points and provide long life optimum ignition.
Change oil often,put good gas and additives to keep carbon build up down, just normal old school tricks, keep things well oiled and lubed should be pretty fast using every available existing horse power the factory gave you.

Now as lame and as unexciting as that sounds it has proven to be the winner everyday all the time.And thats exciting!!!

Im so far behind ,that I think Im in first.
 

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Aren't you the guy that last week made the startling discovery that you have to tune carburetors? Did you ever check the choke linkage, by the way?
 

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quote:
What the deal with advancing or retarding the breaker points timing. I've been told that doing one or the other can improve performance especially if your running a non stock bike. On my cb750 i'm running pod filters and 4-1 pipes with a megaphone muffler and i've just installed new points, condensers and plate. She's running pretty true now but i think i can push her a little bit more...

Banned From The Pubs..
'73 CB350(RIP)
'74 CB750K3 Cafe Thriller
Unless the modifications have changed the compression or you are running super (race) octane fuel, you should not have to worry about adjusting the timing. If you want to invest in the bike, I suggest u install a good electronic ignition. I have heard, that in older engines, if your compression is down, you should retard timing (a band-aid). Makes sense, but you might as well fix the low compression problem.

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Discussion Starter #6
quote:
I hate to bust your bubble sonny, but megs and pods are not really a heavily modified bike. For all intensive purposes the internals on your bike are stock and will react like a stock bike to changes.

running advanced or retarded timing on a stock bike isn't going to really do anything for you. your stock timing is a balance of low end performance and top end. If you change the timing the bike will run slightly better at one end of the spectrum and really bad at the other.

If you had a radical cam and big bore kit this would be something you would be looking at, but for just pods (which aren't a performance mod BTW) and an exhaust I woudn't bother with it. You won;t get anything out of playing with the timing also because the biggest restriction in a cb750 is the head. Port some of those passages and maybe you can start to see an increase.

In the old days (the 90's...ha) I used to play with the timing on my GTO a lot because I ran a fairly radical cam and high compression and when I couldn't get 94+ octane I would have to retard the timing so the motor wouldn't ping.

You want some cheap performance, 78 cb750 carbs (espically F carbs). Accelerator pump carbs like on the GS and KZ and they are usually worth a good extra kick in the pants, plus smoother throttle response. you will need the rubbers off the same motor but it will make a difference. Also put your stock airbox back on and install a K&N inside.

Edit:
here are hondaman's archived posts on the sohc4 board. READ THESE. And when you are done read them 2 or 3 more times. I am currently looking for his post on cheap tricks on the 750 that is worth reading too.

http://www.sohc4.us/forums/index.php?topic=7401.0

he does describe the differences between the different K model's ignition timing but at one point he does leave out the different cams that honda used. according to honda there is only one cb750 cam but we know this not to be true now and there were several different cam timings (different than ignition timing) for similar grinds.

Also maybe it is time you think about suspension mods too. All that power is no good if you can't find a way to get it to the ground.


Edited by - geeto67 on Aug 21 2007 4:54:05 PM
Yeh dont misunderstand I'm not trying to say my shit is suped up (I wish haha) but I'm looking at some little tricks that I may not know about...well great at least i dont have to fuck with the points again till a later date. Thx for the link I'll check it out. Other mods I'm thinking about like Koni shocks and maybe those new 34mm Mikuni carbs from Cycle X for example but will have to wait until after I sell my soul for a set of Tarozzi's <img src=icon_smile_tongue.gif border=0 align=middle>

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If you read hondaman's posts, he does talk about modifying the advance mechanisim for ignition timing to bight it back to K0-K1 specs. However to really reach the performance of k0-k1 you would need to also adjust the cam timing. Either operation is more than I would recommend for a newbie. Also it kills your fuel economy and makes the bike run fineky off of crap gas. Since NY gas is usually pretty rubbish to start there really isn't a benefit.

Koni shocks are kinda expensive. There are other cheaper alternatives. I got redwing shocks brand new oof of ebay for $160 delivered. Vipex perfromance sells a nice remote resovior type shock for the DOHC for $200. That sounds like it won't help until you realize that DOHC 900f stock resovior shocks were considered an upgrade to SOHC suspensions back in the day. be forewarned it will jack the rear of your bike up almost an inch. Hagon shocks are much better than stock too and I have seen them for under $100 a pair.

Those cycle ex 34mm mukunis are a nice setup but for balls to the wall performance I would recommend a set of CR carbs. Cycle-ex also sells them and they are far and away the best performance carb for a SOHC 750 there is. For $100 more than the mukuni kit they are a bargain.

I have DXF file for billet rearsets for a cb750 that a guy on the SOHC board gave to me. I am trying to see if somebody with a CNC machine can use them to mill these. If so - fuck tarrozi's and pony up for these badboys.
 

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ohh really? lemme see pls! [email protected]

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Edited by - wildcatmahone on Aug 22 2007 3:04:34 PM
 

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quote:
ohh really? lemme see pls! [email protected]

Banned From The Pubs..
'73 CB350(RIP)
'74 CB750K3 Cafe Thriller

Edited by - wildcatmahone on Aug 22 2007 3:04:34 PM
do you have the ability to read DXF files? Iam trying to find a pick of the bike they guy who gave the the files has. The rearsets looked real nice.


here is a link to vipex performance:
http://www.vipexperformance.com/
the shocks were $242 shipped to my door.


Edited by - geeto67 on Aug 22 2007 4:26:30 PM
 

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Geeto, I don't know if it helps but I can access dxf files and convert it to pretty much anything you want. I also have a full size plotter at the office.

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Geeto, I don't know if it helps but I can access dxf files and convert it to pretty much anything you want. I also have a full size plotter at the office.

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Lefty,

I just looked at the original files again and they are .dwg files and not .dxf as I originally thought. the DXFs came from my crudfe conversion program so I could see the files in rhino cad since my older copy did not have the ability to open .dwg files. I think I did not use the the DXF originall because the conversion program skewed the dimensions.

Let me talk to the guy with the CNC and see what file type he needs for the machine to read it and Then I will forward it on to you to convert.

define what you mean by plotter. Like the machine that can spit out a set of paper blueprints? or the one that can take a 3d real life object and convert it to autocad drawings?
 

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I have a full version of AutoCAD at work (it's what I do for a living) so I can work with whatever you've got. If you're really nice and I get really bored at work, I can probably draw them up in 3D just for shits and giggles.

I can print out blueprints (not actually blue) with the plotter.

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