Question-------------------------
Followup To
Question -
Hi Bill, I'm Doc and a newbie to this very informative
forum. I have a '84 700sc Nighthawk that is really a terrific
bike except that it has been speed shifted in the past and
now is stuck in 1st gear.
yadda, yadda, etc.
My followup q is: do you have any tips on how to release the
timing/cam chain from the "old" motor so I can use it on the "new"
engine? I have both the shop manual and the CD from
Honda on this bike and neither has any details about pulling or
installing the cam chain intact. The engine I sourced from eBay
has a chain but it has been cut to release the head, I assume, for
separate sale by the eBayer.
Yeah, a cassette gear case would be sweet...I think they didn't
anticipate this bike remaining so popular after all this time. I have
62k on the clock (just a few thou are my miles) and the bike is still
a rocket and handles like a cheetah, and so easy on long hauls.
Can the "wheezy" clutch be attributed to a weak clutch plunger or
"pusher"...I've always wanted an air shifter, maybe this is the time
(ha!) I see these for sale once in a while and wonder how
impossible it would be to fit one to my ailing gearbox to sidestep
all my shifting woes. Still dreamin'.
Thanks again for your quick response(s). PPdd, Doc
Answer -
Doc, check this site out:
http://www.powersportspro.com/partsfish/login.asp
Sign up for free and log in, select add vehicle, choose Honda and
then CB700SC to view the
microfiche illustrations. The shift drum has an interesting ratchet
system built into the end
of the drum that you may want to check under the side cover,
before you tear the rest of it
down.
Hondas this old don't have cassette transmissions like MOTOGP
bikes, so you will have to
split the cases to remove the shift drum and forks. You may have
damaged gears that the
forks are riding in, so it may be a double motor teardown to get
the best parts from both
motors.
Note that a clutch that fails to release will intensify shifting issues,
so check the plates and
the release mechanism. Hydraulic clutch systems can get wheezy
and not pump sufficient
fluid down the lines to completely release the clutch assembly.
This causes gear drag and
rough shifting, especially downshifting.
If the engine is off and you can't rock the bike back and forth to
get the gears to change or
move from 1st, then you have some shifting issues to address,
either with the drum/forks or
the gears.
No easy outs here, unfortunately. Get a good shop manual, before
you dive in... OEM Honda
is probably best for this type of repair. Check for availability of
parts before you get in too
deep!
Bill Silver
AnswerDoc, The MORSE Hy-VO linkplate chains are endless, requiring full motor teardown to remove it from the camshafts and crankshaft. I have heard of the later version Nighthawks going 100k miles on original motors, but when you have everything torn down it is nice to freshen up the camchain and tensioner parts.
What a twit for cutting the chain! All you have to do is unbolt the cam sprockets and remove the camshafts to let the chain go back into the bottom end.... People do weird things sometimes.
The clutch slave cylinders can hang up or leak around the seal, just like a brake caliper. Master cylinders get cycled a lot, so the seals wear out over time and lose pressure like a master cylinder on a car.
Go into the shift linkage arm area and check the shift drum actuation parts before you dive deeply into this thing. At 62k there is bound to be wear, of course, but if the shifter parts are functioning normally, then there must be some serious problems with the transmission parts and/or shift forks.
Good luck with the project..
Bill Silver
