Author Topic: 1978 750k top speed (Read 4510 times)

SKTP · « **Reply #25 on:** February 04, 2008, 01:45:44 PM »

Thanks everyone...this forum rules!

Terry in Australia · « **Reply #26 on:** February 04, 2008, 02:26:09 PM »

No mate, the slick 50 fuel additive does not contain teflon, so your clutch is not contaminated with PTFE. Your clutch was slipping before you used it, and it still is. Either adjust it, or if it's beyond adjustment, replace the clutch discs. (easy job)

Some of the guys here know what they're talking about, and some are guessing. Nothing wrong with guessing, but it can be confusing when your just learning about these bikes.

Be careful what oil you use though, some (like Castrol GTX) have "friction modifiers" that will make your oil bathed clutch slip. Cheers, Terry.

Bob Wessner · « **Reply #27 on:** February 04, 2008, 02:58:14 PM »

I wasn't guessing, but went back and reviewed the "research" and somehow it drifted into discussion of 'oil' additives. My bad.

Terry in Australia · « **Reply #28 on:** February 04, 2008, 03:09:48 PM »

Don't beat yourself up Bob, I wasn't "naming names", and you were just trying to help.

BobbyR · « **Reply #29 on:** February 04, 2008, 03:52:57 PM »

Quote from: Terry in Australia on February 04, 2008, 03:09:48 PM

Don't beat yourself up Bob, I wasn't "naming names", and you were just trying to help.

I was this Bob that raised the Slick 50. I was searching my mind for what mistakes I have made or others have made when we first started.

I would first look at gearing, the PO may have wanted some more jump for commuting. Hence 8000 Rpm at 75 when the number should be like 5K.

Has someone decided that there should be zero play in the clutch lever and it is over tightened and causing slip.

Is the clutch plain worn out or are the springs fatigued.

Is he actually going 120Mph and the speedo is way off.

seaweb11 · « **Reply #30 on:** February 04, 2008, 03:56:01 PM »

If it were the gearing, wouldn't you think falling off the back end at every green light would be noticeable?

SKTP · « **Reply #31 on:** February 04, 2008, 03:56:55 PM »

Mom's on cell phones in mini-van were blowing past me while talking on their cell phones...

Terry in Australia · « **Reply #32 on:** February 04, 2008, 04:57:10 PM »

It's not gearing, it's clutch slip. If a CB750 typically does 60 Mph at 4000 RPM in 5th gear, to do 75 at 8000 you'd need a rear sprocket so big you couldn't fit a chain guard on your bike.

If your engine is screaming and smells funny, and Mom's in mini-van's are passing you, I'd bet Raul's left nut that your clutch is slipping. Cheers, Terry.

GammaFlat · « **Reply #33 on:** February 04, 2008, 05:51:34 PM »

Quote from: Terry in Australia on February 04, 2008, 04:57:10 PM

I'd bet Raul's left nut that your clutch is slipping. Cheers, Terry.

You, of course, mean Raul's left footpeg nut, right?

754 · « **Reply #34 on:** February 04, 2008, 06:22:59 PM »

Heyyy!! Isnt 90 MPH pretty darn respectable.. or...

ultra fast for a 77/78 K

..

754..>>>>>>>>>>>>>>>>>>running..>>>>>>>>>>>>>

BobbyR · « **Reply #35 on:** February 04, 2008, 06:56:46 PM »

Quote from: 754 on February 04, 2008, 06:22:59 PM

Heyyy!! Isnt 90 MPH pretty darn respectable.. or...

ultra fast for a 77/78 K ..

It is respectable, but they can go faster. Less drag then all those nozzles sticking out of the old models.

754..>>>>>>>>>>>>>>>>>>running..>>>>>>>>>>>>>

SKTP · « **Reply #36 on:** February 04, 2008, 07:32:18 PM »

https://www.partsnmore.com/cat_index.php?model=cb750_sohc&category=engine

1 of these:
CLUTCH COVER GASKET
Fits CB750K (69-78), CB750F (75-78) SuperSport SOHC Models.
High Quality Gasket.

6 of these
CLUTCH PLATE - FRICTION PLATE
Fits: Honda CB750 (69-78)
CB750K (69-75) uses 7 pieces.
CB750K (76-78), & CB750F (76-78) both use 6 pieces, plus 1 piece part # 39-1090 which you must order seperately.
Don't forget we sell Clutch Cover Gasket
part # 12-5037 seperately for this application

and 1 of these
CLUTCH PLATE - FRICTION PLATE
Fits: CB750K (76-78), & CB750F (76-78) both use 1 pieces, plus 6 piece part # 39-1052 which you must order seperately.
Don't forget we sell Clutch Cover Gasket
part # 12-5037 seperately for this application.

Maybe a new oil filter too while I'm at it...

Thanks guys

eurban · « **Reply #37 on:** February 05, 2008, 05:35:12 AM »

Quote from: 754 on February 04, 2008, 06:22:59 PM

Heyyy!! Isnt 90 MPH pretty darn respectable.. or...

ultra fast for a 77/78 K ..
754..>>>>>>>>>>>>>>>>>>running..>>>>>>>>>>>>>

Well only when you are giving that lard a$$ buddy a lift cause his sandcast just siezed up from working too hard to keep up . . . .

eldar · « **Reply #38 on:** February 05, 2008, 09:57:17 AM »

God for once I would have to agree with terry on this. How sad is that! If you can afford it, get the honda clutch plates. Others may work but I dont know how well.

SKTP · « **Reply #39 on:** February 05, 2008, 11:06:45 AM »

Any suggestions on where to get Honda Plates? I will search the forum as well...

blackhog02 · « **Reply #40 on:** February 05, 2008, 12:04:17 PM »

I'd try adjusting the clutch from both ends first maybe the PO just messed something up. Usually with these bikes it seems to be something simple. If you are not smoking the mom's in the mini vans down the highway there is something wrong. A bone stock 30 year old CB 750 should run 80-85 all day long with a top top speed well over 100.

Terry in Australia · « **Reply #41 on:** February 05, 2008, 12:21:33 PM »

Yeah mate, before you spend all that cash arm yourself with a flat tip screwdriver, a 12mm ring/open ender and a 14mm open ender (you might even still have the factory tool kit, which is fine) and attempt to adjust it.

New oil and a filter is always a good idea, so spend your money on some good quality motorcycle oil and a filter. If you do have to replace your clutch plates, you don't have to dump your oil, so no biggie if you do an oil change first and discover that you need to replace your clutch plates. By the way, I've just installed non-OEM clutch plates in my K0 and the clutch feels fine.

If you need some help with how to adjust your clutch, let us know, it's a piece of cake. Cheers, Terry.

SKTP · « **Reply #42 on:** February 06, 2008, 04:02:12 PM »

Going to tinker with my clutch this weekend...thanks for all the input

in other news...anybody know if these fit cb750s?

http://www.twistedthrottle.com/trade/productview/332/157/

I'm thinking yes.

* also, how in the heck do you take the clutch side grip off? I'm guessing brute strength?

Terry in Australia · « **Reply #43 on:** February 06, 2008, 05:09:44 PM »

Yeah, those extensions should work fine mate. To remove your grip (depending on how good it is) you can either just cut it off with a sharp knife, or just lever it up with a screwdriver and squirt some WD40 between the grip and the bar. It'll come off real easy then.

Just wash it out with some hot soapy water when it's time to replace it, and when it's dry, spray some of your wifes hair spray into it to work it back on, and stick it back to the bar. (not much worse than a grip coming off at speed) Cheers, Terry.

Sam Green Racing · « **Reply #44 on:** February 06, 2008, 06:15:23 PM »

SKTP, one thing that you have not checked or have not reported back with is your gearing.
If the gearing has been altered that could be your true top speed, just count the teeth on the two sprockets that your drive chain runs on.
It does sound more like you have a clutch slip problem, but it dosen't cost anything to check the gearing.

Sam.

SKTP · « **Reply #45 on:** February 07, 2008, 06:19:25 PM »

So I caved and just took it to my mechanic. He's a really cool guy. I told him what I suspected and he said "let me take it for a spin!" He hopped on and hit the highway. He returned after hitting wobbles at 95mph and said that the tach was pooched and that I had been babying the bike since day one. I then drove home and put my slightly dented (non matching to my current Green Speedo) original tach on the bike that I had never actually used...and wow! I'd say I was abot 35000 RPMs away from what I thought my redline was...Its my first bike ever, the only other bike I have ridden was a 250 at the "Ridercourse"...it feels like I have a totally differnet bike now...I feel like a bit of an idiot.

Thanks for all of your input here...Now I need to swap-out the working dented tach guts into the non-dented matching tach housing. The search function will not work for me here in the forums...can somebody please post the "how to open your clocks" post?

Thanks a million SOHC forums!

I ordered my risers (so the master cyclender brke line will clear my bar mounts) and will soon have drag bars with bar-end mirrors and a new found respect for where my redline is...I'll post some pics one I get it all together

Gregorymoto · « **Reply #46 on:** February 07, 2008, 06:26:53 PM »

Listen to Terry>

Good luck

super pasty white guy · « **Reply #47 on:** February 07, 2008, 08:06:43 PM »

Having just done this (phase 1 at least) to redo my faces, here's the summary for opening your clocks.

Method 1: Cut through the silver ring that joins the 2 halves with a dremel. Figure out how to rejoin later (glue, wire, buy clamps from carpy).

Method 2: Take a small screwdriver. Put clock face down on table. Push blade in between the clock and the ring and gently pry out. Do not twist the screwdriver. Work your way around the ring pushing out gently. Keep repeating the process till you've opened the ring enough that the halves seperate. Re-assembly is the reverse process, probably more difficult.

spwg

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Author Topic: 1978 750k top speed (Read 4510 times)

eldar