Author Topic: Old brick restoration  (Read 335 times)

Offline Lucky_Ted

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Old brick restoration
« on: November 27, 2017, 08:29:19 PM »
Hello everyone, first time posting here:


What I got is my old man's k75c and it has been sitting for about 8 years. It was retired due to "shifting problems". I've already ripped into the clutch and found that it needs an engine seal, a friction plate, and a rubber boot for the clutch arm. Also some debris fell from the garage and smashed the speedo. The bike has yet to be started, would starting it with a broken speedo cause any problems with any sensors or electronic brains in it? Clutch parts will get replaced as soon as I get parts in and an aftermarket speedo is next on the list, but in the meantime I was wondering if there were any other spots I should check with something that's been sitting so long. Are there certain seals that could dry rot that need checking or are there any considerations I should make before starting it up? Any help is greatly appreciated, this is my first time touching a bike and I'm not sure what I'm looking at.
  • Michigan
  • Broken down 87 k75c

Offline The Mighty Gryphon

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Re: Old brick restoration
« Reply #1 on: November 27, 2017, 08:52:50 PM »
There are lots of threads here about starting up old K bikes.  Biggest problems seem to be related to old fuel sitting in the tank and injectors.  It forms gum that clogs the injestors and the ethanol dissolves the rubber stuff in the tank.  Second majot trouble area is the plethora of electrical connections that get dirty over years of storage.  You may have to go through and do a wholesale cleaning of electrical connections with a can of DeOxit spray.

Last, when you say shifting problems, first thing that comes to my mind is a grub screw in the transmission that holds the shifter linkage to the shifter shaft.  How much slop is in the shifter?  If there is a lot of slop you will have a lot of missed shifts, both up and down.

More than a quarter inch indicates that the screw is loose and needs to be tightened.  This is a job that requires opening the transmission.  Took me a couple hours when I first got my K75RT to tighten the screw.  If you do it along with clutch work, you save the time to pull the transmission since it's already off. 
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
"Dohn f wit me, honkey, cuz I dindu nuffin'"

Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'92 K100RS "Moby Brick"

Past:
'82 Honda FT500, '80 Honda XR185, '78 Honda XL125, '76 Honda XL125, '74 Honda XL125, '71 Ossa Pioneer, '68 Kawasaki 175

Offline Chaos

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Re: Old brick restoration
« Reply #2 on: November 27, 2017, 11:07:56 PM »
+1 on not trying to start it before cleaning out the gas tank.  Also the rubber surround on the fuel pump tends to disintegrate in old gas, creating a multitude of problems.   A description as nebulous as "shifting problems" leaves the door wide open to speculation.  Clutch, grub screw, and with some 86-87's they used a shift drum that was not hardened properly, causing bent shift forks and jumping out of gear.  Usually it's cheaper to find a used transmission rather than tearing into a bad one and replacing parts.
1987 K75S    VIN 0231
Original litter & owner
185,000 miles and 5 paint jobs
2012 Ural Gear-Up
(BMW's bastard step child)

Offline TaosBrick

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Re: Old brick restoration
« Reply #3 on: November 28, 2017, 09:23:37 AM »
Chaos basically covers everything, save that it's ok to start it with the busted speedo (once you deal with fuel system) Speedo keys off a sensor on the final drive.
Flog It Every Day - I mean, the BIKE!
'92 K75, '73 R75/5 Café,'89 Yam XT350
Expect Nothing, Be Ready For Anything.
- Samurai Maxim

Offline Lucky_Ted

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Re: Old brick restoration
« Reply #4 on: November 28, 2017, 10:14:10 AM »
Thanks for the help guys. I admit "shifting problems" is highly nondescript. The best description I could get from the old man was that he had to nearly kick the clutch lever to get it back home on it's last ride. It got a new clutch cable before I got to it, and the "cup" boot on the clutch arm has been completely ripped up. I didn't think anything about the tranny itself, so getting a look at it before it goes back definitely helps. Again, thanks for the advice everyone!
  • Michigan
  • Broken down 87 k75c

Offline The Mighty Gryphon

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Re: Old brick restoration
« Reply #5 on: November 28, 2017, 11:14:55 AM »
"Kick the clutch lever"?  Sounds like a clutch problem.  Bad cable, or possibly the clutch arm on the back of the transmission is seized(a not uncommon problem).  Some of the inmates have installed grease fittings on that arm to allow it to be lubed from time to time.  Could also be a very badly adjusted clutch cable.

The boot is a fragile, expensive part that suffers when the clutch arm is allowed to drop with the cable disconnected.  To protect the new boot always support the arm when the cable is disconnected.  All it takes is a bit of string to tie it in the up position. 
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
"Dohn f wit me, honkey, cuz I dindu nuffin'"

Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'92 K100RS "Moby Brick"

Past:
'82 Honda FT500, '80 Honda XR185, '78 Honda XL125, '76 Honda XL125, '74 Honda XL125, '71 Ossa Pioneer, '68 Kawasaki 175

Offline Chaos

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Re: Old brick restoration
« Reply #6 on: November 28, 2017, 11:44:33 AM »
He must have had an interesting riding technique, I have a hard time getting my foot up that high.
1987 K75S    VIN 0231
Original litter & owner
185,000 miles and 5 paint jobs
2012 Ural Gear-Up
(BMW's bastard step child)

Offline Lucky_Ted

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Re: Old brick restoration
« Reply #7 on: December 04, 2017, 09:31:19 PM »
Update: getting all the parts I need for the clutch tomorrow. While I'm this far up the bikes business end is there anything on/in the engine that usually needs to be checked? The general consensus seems to be to leave the motor alone, but there's got to be SOMETHING to check before putting half of it back together, right? I've looked around the site but most I could find was the engine rebuild videos. Should I just wait until the startup for any funk to happen and troubleshoot from there? :dunno2:
  • Michigan
  • Broken down 87 k75c

Offline Martin

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Re: Old brick restoration
« Reply #8 on: December 04, 2017, 10:32:14 PM »
Fitting grease nipple to the clutch pivot arm will save you a lot of headaches. The occasional application of grease pushes out any crap. And it stops crap and water ingress. Easy job but the arm needs to be removed, normally drilled and tapped to accept a 6mm grease nipple.
Regards Martin.
 [ Invalid Attachment ]
  • North Lakes Queensland Australia
  • 1992 K75s, Lefaux, Vespa V twin

Offline The Mighty Gryphon

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Re: Old brick restoration
« Reply #9 on: December 04, 2017, 10:37:51 PM »
I'm not sure you posted how many miles your dad put on the bike, but you should bear in mind that these bikes take at least 20,000 miles to get broken in.  As long as the oil is changed, and the valve clearances checked the mechanical workings should be good for well over 150,000 miles.  Remember that you are essentially dealing with a car engine here.

Change the o-ring on the output shaft and do a clean and lube on the clutch splines. 

Check the air filter for mouse nests, throw in some new spark plugs, and balance the throttle bodies.  Run a couple tanks with Techron through the injectors.  Check all the rubber bits for holes and cracks.  Beyond that there isn't much the engine needs if it's got less than 100,000 miles on it. 

About the transmission.  If the grub screw is loose this is a really good time to address it.  Does the shifter flop around freely?  If so, how much?  My RT had shifting problems because that screw was loose.  You don't want to go into the transmission after the bike is put back together.

Have you done or made plans to do all the maintenance, brake bleeds, fork oil, cooling system, etc.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
"Dohn f wit me, honkey, cuz I dindu nuffin'"

Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'92 K100RS "Moby Brick"

Past:
'82 Honda FT500, '80 Honda XR185, '78 Honda XL125, '76 Honda XL125, '74 Honda XL125, '71 Ossa Pioneer, '68 Kawasaki 175

Offline Laitch

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Re: Old brick restoration
« Reply #10 on: December 05, 2017, 06:46:48 AM »
The general consensus seems to be to leave the motor alone, but there's got to be SOMETHING to check before putting half of it back together, right? I've looked around the site but most I could find was the engine rebuild videos.
Rebuilding a K-bike engine is uncommon need. You should look into the Repair Guidance section under the categories General Maintenance and Operation. As indicated previously in this thread, the fuel tank should be inspected and cleaned if necessary. Remove the filler cap assembly by removing the six screws in its flange then syphon out the fuel. That will allow a good look. Don't run any old fuel through it.
  • Along the Ridley in Vermont.
  • 1995 K75T 60,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline Lucky_Ted

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Re: Old brick restoration
« Reply #11 on: December 05, 2017, 08:47:18 PM »
I'm not sure you posted how many miles your dad put on the bike, but you should bear in mind that these bikes take at least 20,000 miles to get broken in.

About the transmission.  If the grub screw is loose this is a really good time to address it.  Does the shifter flop around freely?  If so, how much?

Have you done or made plans to do all the maintenance, brake bleeds, fork oil, cooling system, etc.


I think the bike is just under 50k, but it could be a little different, given that the speedo is pretty busted up (aftermarket speedo is on the shopping list).


In terms of the tranny, I think the grub screw may be fine? Is the shifter the foot lever that switches gears? If so, it doesn't move freely. When pushed down, the shifter makes an audible click, and pushing it up resets it (I'm assuming this is supposed to be shifting in/out of gear and totally normal?)


As for general maintenance post repair, I'm definitely replacing fluids, brakes, filters, etc along with all the suggestions you've made. I'm glad to hear that the fuel system will be my biggest worry. Also, good luck with Moby Brick, your winter project looks more in depth than mine.
  • Michigan
  • Broken down 87 k75c

Offline The Mighty Gryphon

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Re: Old brick restoration
« Reply #12 on: December 05, 2017, 11:18:45 PM »
Yes, the shifter is that thingy in front of the left footpeg.  You should feel spring resistance to any attempt to move it up or down from it's center position.  If it flops freely, the grub screw is loose.  On my bike the damn thing flopped at least an inch and a half before I could feel the spring.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
"Dohn f wit me, honkey, cuz I dindu nuffin'"

Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'92 K100RS "Moby Brick"

Past:
'82 Honda FT500, '80 Honda XR185, '78 Honda XL125, '76 Honda XL125, '74 Honda XL125, '71 Ossa Pioneer, '68 Kawasaki 175