Author Topic: Just got a 77 CB750K and i need some good suspensio consulting from you monkeys!  (Read 1631 times)

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Offline Czotie

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Whats up every body! So I just bought a 1977 CB750K and she looks pretty good. The years have treated her very kindly. The motor is a 75, for some reason the previous owner ripped out the 77 and threw in a 75. Anyways, i have both motors which is nice cause i can work on the 77 while i ride the 77. Anyways,  I have a mutual friend who owns a shop in my home town and i dropped her off there after many many months of trying to move her. She starts and i rode her around, but the carbs need a big tune, gasket replacing, some ticking so im guessing the valves r bad and the tires are #$%*. The forks are practically frozen and this is where i come to you guys! I need some consulting on the suspension.

My mechanic friend does this as a hobby, so hes not trying to make money off of me but he wants to try his hand on my project which im all ears for. He wants to completely rip out the suspension and put in a modern one, which brand of new forks and seals and brakes and barings and shocks so on so on i have no idea. I know if i go that route it will cost me about 1500 or more. I have the cash, but personally i just kind of wanted to rip out the forks and completely refurb them, bleed em clean em and oil them up, rip out the barrings and clean them up and install new brakes. I will buy new shocks tho, that is a must. Anyways, i come to you guys about this. This is my first CB750 and i know some one on here will have good input on what to do about this.

Should i completely replace the front suspension and brakes? If so, what brands should i use? Or should i just refurb it all, i think the refurb would be fun (but i know the replacement would be safer) Im trying to get my bike on the road in a few months now and my buget is about 1200 a month to dump in. Any ways, what do you think!?!? I need help! haha :o






Offline xsmooth69x

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im not a monkey but ok....

if u cant fork the dough dont even bother doing a front end swap

if you do decided to do a front end swap u can just use the forks and triple tree from a cbr600

u will need a small spacer to align it up to the frame neck. there are plenty of threads about this.

honestly why do all that work? just rebuild the forks drain them out clean them up and replace the fork seals. done easy in one day.

in regards to the rear suspension u can go with a mono shock there are plenty of threads about that too. just weld on a bracket and pretty much done. but why would u do that. i dont really think its worth it. just get some good progressive springs. far cheaper too. why mod so much? i can understand cafeing it out and stuff by why go through so much work. get that beast out on the road and driving.
« Last Edit: May 29, 2012, 10:52:29 PM by xsmooth69x »
1975 CB550 (FINISHED?!?!?)
first motorcycle ever!!! ow and i dont know how to ride it either :D

raw rust rice venti quad shot cafe racing latte project aka my build..... http://forums.sohc4.net/index.php?topic=88853.0

black and white equation godzilla chalkboard 
1972 cb750 - next in line for some <3

Offline SOHC4 Cafe Racer Fan

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Rebuild the front forks with cartridge emulators (if you can swing the $), and pick up some progressive shocks for the rear, until you can afford IKON, or better yet Works, Ohlins, etc.
1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold

Offline wannabridin

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    • 1976 CB750K, under construction:
read Hondamans thoughts on how to make the bike feel lighter than it is.  from his post:

"I've often been asked, by those who've ridden mine, why my 750 "feels" like a much smaller bike. Yours can be made to "feel" like the hotrod CB450 with 750 power by doing these things.

#1. Replace the steering head bearings (little balls and tracks) with VERY HIGH QUALITY tapered roller bearings. DO NOT use the Japanese or other oriental ones: use Timken. There IS a significant performance difference. And, set them up slightly tight, as they will wear in after about 500 miles.
#2. Replace the rear swingarm bushings with tight-fitting, oil-impregnated bronze bushings. Change the oriental-style grease zerk fitting(s) with US-style zerks so the grease can actually be forced into the bushings. Lube those bushings generously when assembling them, and use new felt seals when you do.
#3. Get Timken or Reynolds wheel bearings for the front wheel (2 each) and the rear (3 bearings back there). They cost nearly 3 times as much as the oriental ones, and they are worth every cent.
#4. All of the CB750K-K5 models I have seen have the "optional" steering head damper mounts. Get one from Fox or a BMW shop and install it. Set the damping to medium for startup, then adjust to suit when you get used to it.
#5. Tires. Use ONLY ribbed tire pattern in the front of a CB750K2- or later model. You can get away with a blocked pattern on a K or K1 model, because they don't "shake their heads" during deceleration. A ribbed front tire pattern helps make the bike run more stably under most street conditions, and it does not "wash out" suddenly in corners. The rear must be a symmetric pattern, preferably a block pattern. The new "sideslash" patterns on today's crotch rockets will cause sideways drift under heavy acceleration on wet (or slick) surfaces with the 750 geometry. Sizes: K5 and earlier: front must be 3.25 or 3.50 by 19". Rear is usually 4.00x18, some later ones had 17" rears and should be 4.50x17. IF YOU USE TT tires, use the 4.10x19 front and 4.50x18 (or 5.10x17) rear, AND ON BOTH ENDS. DON'T use a TT on one end only, and DON'T use them for heavy touring loads, they'll be all over the lane. These tire size combinations preserve the already-short 3.25" trail on the front end of these bikes, as well as the load rating. Larger rear tires will cause wobble, every time, because they shorten the trail.
#6. For those of you who have short inseams: your first choice should be to install 12" length rear shocks. Get 110-lb straight-wound or 90/120-lb progressive springs. If you install "lowering blocks", you will get a VERY stiff rear suspension, because the increased cant of the rear shocks will not allow them to compress over bumps. Shy away from those blocks. After installing these shocks, lower the front triple clamps about 1/2" on the front forks.
#7. Use teflon-mixed oil in the front forks. Get teflon-coated seals that are slighty shorter in length (1/4" instead of the stock 5/16" to 3/8" stock units). These will "float" up and down slightly between the top of the fork retainer and the upper C-clip, which makes them seal better and respond to minor road irregularities MUCH better. Install the optional steel washer ABOVE the seal (good kits include these washers). Drill and tap the fork caps and install threaded Shraeder-type air valves (found at tires stores, used on mags), one in each fork. Run about 10 PSI pressure if riding single, 15-20 if carrying heavy loads.

If you do ALL of these things, you will not believe the difference the next time you hit a corner. It will feel like the bike lost 100 lbs somewhere..."

cartridge emulators will help out quite a bit, but can be a bit pricey for some (Racetech's are the best).  i have IKON shocks and they're the best bang-for-your-buck, personally.  Hondaman's thoughts and some consideration to the quality of components and care you put into installing them will go a LONG way.

1976 CB750K, currently under construction:
http://forums.sohc4.net/index.php?topic=64468.0

-And if you don't do it this year, you'll be one year older when you do...

Offline harisuluv

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2nd on the front end, the bike looks to be in good condition to begin with!  I bet those forks will clean up nicely.


Offline MCRider

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Rebuild the front forks with cartridge emulators (if you can swing the $), and pick up some progressive shocks for the rear, until you can afford IKON, or better yet Works, Ohlins, etc.
Great advice!  And a HondaMan swiingarm bushing rebuild and good to go.
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."