Author Topic: intake manifold bolt mess  (Read 552 times)

Offline kaleb

  • Motobrick Curious
  • Posts: 42
intake manifold bolt mess
« on: May 26, 2019, 02:27:00 PM »
Hello again, motobrickers. My latest saga for your enjoyment:

Having identified air leaks around a couple of my throttle bodies (butane test) I decided to go all in and replace all three intake manifolds.

I bathed all six bolts in penetrating oil over night, but still three of them snapped off when I came to undo them.

I bought the best rated bolt extractor set I could find and a set of left handed drills. I filed the tops and centrepunched them, before drilling and attempting to extract. The pictures show where I am now.






Cylinder three has both threads intact, cylinder two has one intact and one bolt stuck and partially drilled out quite off centre, cylinder one has both threads with stuck broken bolts, one partially drilled out, again off centre, and the other in a total mess of multiple, failed drill-outs, a snapped off centre punch etc etc.

I had chosen a long (UK bank holiday) weekend to get this done, but didn't expect quite so much trouble! Of course I need the bike out of the workshop by Tuesday morning, and have nowhere else to leave it in pieces which rather precludes the total strip down I assume would be necessary to get the holes filled and rethreaded at a machine shop.

Does any body have any bright ideas? I don't mind if the fixing solution can never be undone again, I'd just like a nice, permanent seal on my expensive new intake manifolds....

Thanks in advance,

Kaleb





  • bristol, uk
  • k75 '93

Offline volador

  • ^ Proficient Motobricker
  • Posts: 111
  • NEEDS MORE CHROME
Re: intake manifold bolt mess
« Reply #1 on: May 26, 2019, 05:39:08 PM »
....
  • NYC
  • 1991 K100RS 1993 K75S ABS
FIVE BOROUGHS SISYPHEAN SOCIETY "WHEN LIFE THROWS YOU A CURVE... LEAN INTO IT"

Offline Martin

  • ^ Quintessential Motobricker
  • Posts: 3805
Re: intake manifold bolt mess
« Reply #2 on: May 26, 2019, 05:42:32 PM »
Might be cheaper to get a second hand head, engine or parts bike.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline volador

  • ^ Proficient Motobricker
  • Posts: 111
  • NEEDS MORE CHROME
Re: intake manifold bolt mess
« Reply #3 on: May 26, 2019, 05:48:24 PM »
At this point a machine shop or a drill press or a right angle drill with some sharp drill bits and thread inserts look like a solution.

Since you're pressed for time and space I would just get things back together with the old intake stubs. Regroup and get a lead on a shop or the proper equipment and parts to save that engine valve assembly section.

1.Apply a bead of sealant to all intake rubber stub mating surfaces.
2.Apply a light coat of silicon grease or Armor All or spit to inside surfaces of the intake stubs to make installations of the throttle assembly throats easier.

Between the 3 good bolts, the sealant and the plenum chamber on top that throttle assembly isn't going any where.
  • NYC
  • 1991 K100RS 1993 K75S ABS
FIVE BOROUGHS SISYPHEAN SOCIETY "WHEN LIFE THROWS YOU A CURVE... LEAN INTO IT"

Offline volador

  • ^ Proficient Motobricker
  • Posts: 111
  • NEEDS MORE CHROME
Re: intake manifold bolt mess
« Reply #4 on: May 26, 2019, 06:01:35 PM »
Apply a light coat of sealant or Plasti Dip to the outside of the old intake rubber stubs and wrap them with electrical tape if they leak badly
  • NYC
  • 1991 K100RS 1993 K75S ABS
FIVE BOROUGHS SISYPHEAN SOCIETY "WHEN LIFE THROWS YOU A CURVE... LEAN INTO IT"

Offline Martin

  • ^ Quintessential Motobricker
  • Posts: 3805
Re: intake manifold bolt mess
« Reply #5 on: May 26, 2019, 06:45:43 PM »
When removing broken studs or bolts it is best to start with a small drill bit and work your way up. Centre punching lightly at first to make sure it is dead centre, a light punch mark can be moved by putting the punch at an angle. Only when it is centred do you enlarge the mark. Start off with a small sharp drill and either use a drill guide or have a person eying the drill to make sure it is at 90 degrees to the surface. Go slow and frequently check to see that you haven't wandered off centre. Once you are down a couple of mm you can apply coolant, when you have drilled it deep enough upsize the drill. Keep checking frequently that everything is square. Upsizing the drill until you get to the size required.

If you are using Ezi-Outs follow their instructions, if you break an Ezi-Out they are a lot harder to remove than a broken bolt so care is needed. They can be removed but it is better not to break them. GO SLOWLY there is no need to rush, when you rush you are more prone to errors. Apparently some extractors require you to drill to a specific depth so that the extractor bottoms out. Applying heat (Hot air gun) and a good penetrating fluid (not WD40) and allowing it to soak in between heating and penetrant helps. Really stubborn bolts can require days if not weeks to loosen. I have used a pneumatic burr grinder on a couple of mates off centre extraction attempts. But you need to go exceedingly slow and have a steady hand and a good eye both of which seemed to have left me.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline natalena

  • ^ Proficient Motobricker
  • Posts: 402
Re: intake manifold bolt mess
« Reply #6 on: May 27, 2019, 07:43:43 AM »
This won't help getting out of the shop by Tuesday, but it's a good technique.
Build up a small levee of modeling clay around the broken bolt, so it looks like a volcano. Drip in penetrating oil, and forget about it for a couple days. Martin is right-on with the small to spec drill bit enlargement, use cutting oil (coolant) and go sloooooowly. As it stands, I'd be looking for a breaker yard part, and working on the studs when you have time to kill in the future.
  • East of Joshua Tree
  • 1987 K75s #0919
On Holy Quest seeking Techron equivalent for splines.

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6732
Re: intake manifold bolt mess
« Reply #7 on: May 27, 2019, 08:17:33 AM »
Following on from Martin and natalena, once the holes are cleared, use Devcon Aluminum putty to refill them. If you scrupulously follow the product's instructions, you should be able to drill new holes in the hardened putty then insert helicoils to provide threads for the new screws. Devcon works well to build up aluminum castings and it will firmly hold the screws.

When you drill out these holes, mark the depth of the hole on the bit with tape or a drill stop so you won't exceed it. Drilling out a snapped screw requires sharp drill bits, carefully center punching, an intermittent spray of penetrant on the bit to cool it while it is rotating, as Martin has suggested. I have always used reverse-direction bits. An improvised centering jig would help.

As you have learned, all this will take patience for a successful outcome.
  • Along the Ridley in Vermont.
  • 1995 K75T 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Soggz

  • ^ SuperNatural Motobricker
  • Posts: 639
  • 2 wheels are better than 4,but 4 wheels,2 bikes...
Re: intake manifold bolt mess
« Reply #8 on: May 28, 2019, 01:57:37 AM »
Apply a light coat of sealant or Plasti Dip to the outside of the old intake rubber stubs and wrap them with electrical tape if they leak badly
60mm heat shrink is better.
  • Down in Selwood Forest
  • 1986 K75C, 1982 Honda CX500EC Eurostreetbrat
One More Of These,One Less Of Those...

Offline Big_B

  • ^ Motobrick Curious
  • Posts: 76
Re: intake manifold bolt mess
« Reply #9 on: May 28, 2019, 03:10:37 PM »
OMG this is horrible to see. Am I wrong for thinking it could've been avoided with heat from a torch?

Hope things work out for you.
  • North Easton, MA
  • 93 K1100RS
'93 K1100RS 75K miles all stock w/Fox aftermarket shock Corbin seat.

Offline kaleb

  • Motobrick Curious
  • Posts: 42
Re: intake manifold bolt mess
« Reply #10 on: July 09, 2019, 06:20:20 PM »
Thank you all for the helpful tips. Yes indeed I suspect there were lots of ways I could have avoided this!

I managed to get the bike sort of out the way for the last 6 weeks under a tarp in a quiet corner, until I could make a little workshop space and time again.

The replacement cylinder head seems likely to be the most accessible solution, as they go for about the same as an hour of an auto-machinist's time here in the UK, and all of those I spoke to would need me to remove the damaged one, anyway.

For instance:

https://www.ebay.co.uk/itm/1986-BMW-K75-Engine-Cylinder-Head-Assembly-11121461169-FREE-UK-SHIPPING/282996181564?epid=1609542157&hash=item41e3e30a3c:g:lJoAAOSw9NhbFqg1

My bike is a '93 K75. Does anybody know if any k75 cylinder head will be compatible, or I should I just be looking at the later years?

Thanks all,
Kaleb
  • bristol, uk
  • k75 '93

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6732
Re: intake manifold bolt mess
« Reply #11 on: July 09, 2019, 10:05:37 PM »
My bike is a '93 K75. Does anybody know if any k75 cylinder head will be compatible, or I should I just be looking at the later years?
How I determine if a part is a suitable substitute is to go to the MaxBMW parts fiche for my moto's model, look up the part's number then go to all the other K75models and determine if that part's number is the same in each of them. If it is, then the same part from any of them will serve as a substitute in mine. In your moto's case, cylinder heads for the K75, K75C, K75RT and K75S all have the same part number and the fiche indicates there have been no changes over the years. That means if the head you buy came from any K75, it should work with yours. Another site used for that type of investigation is realoem. Ignore the ads inserted in the site like that PDF ad.


It would be helpful to know if the surface of the used head has been checked for flatness and warping but that is sometimes asking too much of sellers.
  • Along the Ridley in Vermont.
  • 1995 K75T 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Scott_

  • Forum Moderator
  • ^ Quintessential Motobricker
  • Posts: 1984
Re: intake manifold bolt mess
« Reply #12 on: July 10, 2019, 06:24:38 AM »
What I do when cross checking part #'s...... look up the specific part #, copy it, go back to the general part # search box, paste the # I'm looking for, then press the search box.  The results will be most every BMW model bike that the part was used on, USA or EURO market. 
Saves time instead of opening each model of ones I suspect might interchange.

If you use REALOEM, I think it will also cross check the BMW auto inventory as well for compatibility. It came in handy when I was looking for a replacement windscreen motor for my LT. BMW used the exact same setup for the automotive sun roof mechanism is some of there cars. Found a motor from a car breaker for like $20 and it was an exact fit, plug and play.
  • My Garage
Ride safe.


1997 K1100LT 0302488
1995 K1100LT 0302044
Garmin StreetPilot 2820
Garmin Zumo 550
"One who does not ask questions is ashamed to learn" Danish proverb

Offline kaleb

  • Motobrick Curious
  • Posts: 42
Re: intake manifold bolt mess
« Reply #13 on: August 05, 2019, 06:32:03 AM »
Thanks Laitch (as ever!) and Scott for your helpful input. I've got my new (used) cylinder head, in complementary silver as the black ones seem scarce to find, and have ordered a new head gasket...

It'l be a few more weeks before I can attack this, but I'll be sure to check in and keep you posted!

Best,
k
  • bristol, uk
  • k75 '93

Tags: