Topic: Springs for cartridge emulators

[pmiller]

Hi. I am new to forums and new to working on bikes. I need to address the front suspension on my newly purchased 1978 cb750k. It needs new seals and was going to upgrade the suspension while at it. Have looked into the progressive springs and the cartridge emulators. I have real a lot of the posts on this forum regarding both but wanted to ask about them anyway. I'm on a tight budget for now. If money wasn't an issue I would get the valve emulators and new springs from race tek that seem to be the best out there. But instead was looking at buying the cartridge emulators from vintagecb750.com. My question is, can I use the stock springs that are currently in the forks with these emulators?
I'm definitely not taking this bike on the track but would like a more advanced suspension for improved handling for highway and mountain road riding. Will also being riding two-up a fair amount.
Suggestions?
Thanks!

[MRieck]

Go to Race Tech's site. You'll probably want .80kg or .85kg springs  depending on your weight

[SOHC4 Cafe Racer Fan]

Go to Race Tech's site. You'll probably want .80kg or .85kg springs  depending on your weight

+1
http://racetech.com/ProductSearch/2/Honda/CB750K/1973-78

[bwaller]

Do the RT springs for now, add the valves at a later date. Scour the internet for suspension tuning articles including preload, setting spring sag, etc. The RaceTech springs are best for tuning, as mentioned rated for you & your bikes weight, but are also shorter so you can build in the preload spacer you need to get the correct % of static sag. The best start is to disassemble, clean your forks well then set your oil at the proper height.

Cal mentioned shocks and those should be on your list too. It's a 78 but doesn't need to handle like an old tank. 

[pmiller]

Thank you everyone for your responses! I guess I will look into ordering the RT springs and wait on the emulators. Was hoping to be able to keep the stock springs and use the emulators for the improved handling.
Rear shocks are definitely on the list to replace. Currently working with a tighter budget than expected so I'll have to creep my way down the replacement list for now.

[Steve_K]

I would add that if you need to put new fork seals in, why not do the emulators then.  You got it apart do it then.  Easier to swap fork springs later if $ important.  I have done the RT stuff in several bikes and it worked great.  Just took time to set the preload to suit me.
Steve

[pmiller]

Thanks Steve_K.
That's kinda what I was thinking but I'm a total newbie to working on bikes. So you think I could do the RT emulator with the stock springs and then change out to RT springs down the road? Would I need to modify the stock springs to work?

[Steve_K]

You can use the old springs, but after 40 years you may need to increase or add spacers to correct sag.  I would also suggest that you use fork oil.  I used 20w in my 750.  Try some different weights and keep some notes.
Good luck and have some fun.
Steve

[grcamna2]

I believe your stock springs will be too long to fit the extra height of the emulators and will give you too much  preload,I doubt you would be able to even screw the fork cap back on.The emulators require a very good quality fork spring otherwise they will allow your forks to dive too far down under braking and cornering loads.They work well w/ the RT straight-rate quality springs.

[grcamna2]

Do the RT springs for now, add the valves at a later date. Scour the internet for suspension tuning articles including preload, setting spring sag, etc. The RaceTech springs are best for tuning, as mentioned rated for you & your bikes weight, but are also shorter so you can build in the preload spacer you need to get the correct % of static sag. The best start is to disassemble, clean your forks well then set your oil at the proper height.

Cal mentioned shocks and those should be on your list too. It's a 78 but doesn't need to handle like an old tank. 

+1

[pmiller]

Thanks again for everyone's responses! Budget is tight currently so I decided to just order in the new seals and replace those for now and play with the oil level.

[grcamna2]

That's a good choice pmiller.I would think the factory recommended fork oil(ATF)would work fine unless you needed stiffer rebound damping and then possibly 10wt.? But the ATF is less $ and had always been what i used for a complete fork job w/ a good result later.

[alacrity]

Contact Matthew Wiley at Racetech.  Tell him the bike model, tire type, your weight with gear, how and where you ride, and any other modifications to the bike.

He will tell you which springs and which fork oil weight and HOW MUCH of it.
ONCE you change the springs, the factory instructions for oil type and capacity is not applicable.  Their recommendation was for new springs in their new front end all to their design/engineering and manufacturing specs. You have 40 year old everything, which is already diff. You put new RT springs in, and you have a different front end.  AND it's totally worth doing this.  Night and Day.

[NobleHops]

He's not changing the springs dude.

[alacrity]

He's not changing the springs dude.

Oh, well in that case I guess I wasted all that good typing..