Author Topic: Phoenix Rising - '93 K75RT Fire Recovery  (Read 3668 times)

Offline brichbk

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #75 on: November 11, 2018, 04:29:34 PM »
I removed the cam chain, both cams from the valve side only to find that my torx plus 50IP bit doesn't fit the mounting bolts holding the valve side of the engine block.  So, thinking that it's a T45 I borrow a friends torx set to check the size only to find that the standard torx 50 fits the bolt. My understanding is that these bots were supposed to be Torx Plus but they look to be just Torx.  Any have any thoughts?

Torx or Torx Plus?


Torx T50 inserted in bolt head


Torx T50 vs Torx Plus 50IP (I'm holding the T50)

  • Central Valley California
  • 1993 BMW K75RT // 1982 Honda Nighthawk 650sc

Offline brichbk

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #76 on: November 11, 2018, 07:37:25 PM »
I got my heads off and found my #3 exhaust valve was bad.

edit:  anyone have a good spare exhaust valve?







  • Central Valley California
  • 1993 BMW K75RT // 1982 Honda Nighthawk 650sc

Offline brichbk

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #77 on: November 12, 2018, 03:07:09 PM »
I'm looking into options for getting my valve issue fixed.  Right now I'm looking at 2 options.

Option 1:  Cost $200-$400  I took the head to a machine shop today and was quoted around $200 (probably 2 hours of labor) to have all 6 valves reseated and the head cleaned.  They said I should replace my exhaust valve guides as well.  So I'm looking at the cost of guides, seals, and an exhaust valve plus the machining costs.  He also said that the exhaust valve isn't anything special, but that it's pretty standard and I may be able to find one for a lot less ($10-20) that doesn't come in a BMW box, the same thing for the valves and seals..  Does anyone have any experience with non-oem valves, guides, and seals for the K75? 

Option 2:  Cost $250-$350  Get a different head in working condition ($140-$200) and have the cylinder head and engine block milled flat so they can mate up snuggly.  The machining for that would be about $110.

Are there other I could look at or things I should be considering that I haven't considered yet?  Do you think one option is better than the other?

  • Central Valley California
  • 1993 BMW K75RT // 1982 Honda Nighthawk 650sc

Offline CNRED

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #78 on: November 12, 2018, 04:11:17 PM »
check your messages
  • Scottsdale, AZ
  • 1990 K75rt, 1992GSPD

Offline riots100

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #79 on: November 12, 2018, 04:16:21 PM »
I would go with option 1.  The original head with the original block.  New valves seats, guides, etc. seems like a good option given the condition of that one valve.  While you got things torn apart as you have, I would pull the crankcase cover and check the condition of the connecting rods and crankshaft.

Any idea what would cause a valve to deform like that?
  • Los Angeles, CA
  • 1992 K75, 2007 K1200GT, 1991 K100RS
----
BDJ

Offline brichbk

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #80 on: November 12, 2018, 05:57:00 PM »
I would go with option 1.  The original head with the original block.  New valves seats, guides, etc. seems like a good option given the condition of that one valve.  While you got things torn apart as you have, I would pull the crankcase cover and check the condition of the connecting rods and crankshaft.

Any idea what would cause a valve to deform like that?

The guy at the machine shop said that either tight valves or the valve guide was little loose and that would have prevented the valve from seating tightly and could have caused the damage.

The connecting rods look ok, although I haven't removed them just looked at them with the crankcase cover off.
  • Central Valley California
  • 1993 BMW K75RT // 1982 Honda Nighthawk 650sc

Offline The Mighty Gryphon

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #81 on: November 12, 2018, 06:17:28 PM »
From the photos, I would guess that it was way too tight, and never adjusted to the proper clearance.  (This thread should serve as a warning to anyone who doesn't think they need to adjust their valves, this is why you do it.)

Unless the engine has way over 100,000 miles, I would just get another (used) exhaust valve, lap it and put everything back together.  I seriously doubt that the guides and seals were damaged by a leaking exhaust valve, so unless I had a bunch of cash I needed to get rid of, I'd just replace the bad part.

Of course, I would be checking the other valves for damage, and replace any that were bad, but I'll bet this is the only one since I think you said the compression in the other two cylinders was still good.  The only other parts you will need are a head gasket and some shims for the valve adjustment.  (I'll bet all of the other five are tight as well.  Did you check them before you pulled the head?)
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'91 K100RS "Moby Brick Too

Offline brichbk

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #82 on: November 12, 2018, 07:47:22 PM »
Of course, I would be checking the other valves for damage, and replace any that were bad, but I'll bet this is the only one since I think you said the compression in the other two cylinders was still good.  The only other parts you will need are a head gasket and some shims for the valve adjustment.  (I'll bet all of the other five are tight as well.  Did you check them before you pulled the head?)

posted back post #45
Measured my Valve Clearances and here are the values I got.
Intake: 1) .13mm  2) .15mm  3)  .13mm
Exhaust:  1) .10mm   2) .10mm  3) .05mm
  • Central Valley California
  • 1993 BMW K75RT // 1982 Honda Nighthawk 650sc

Offline The Mighty Gryphon

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #83 on: November 12, 2018, 10:20:42 PM »
All of your exhaust valves were WAY TOO TIGHT!   

Check them carefully for signs of burning.  Sitll, I think that replacing the burnt one and lapping it should get you running again.  While you're at it you might as well lap all the others.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'91 K100RS "Moby Brick Too

Offline brichbk

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #84 on: November 18, 2018, 02:29:55 AM »
I found some m10x135 bolts I could use for the cylinder head bolts that are $1.99 per bolt rather than $11.98 per bolt.  The difference is the inexpensive ones are hex head rather than torx. Would it be bad to use hex head rather than torx?
  • Central Valley California
  • 1993 BMW K75RT // 1982 Honda Nighthawk 650sc

Offline Martin

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #85 on: November 18, 2018, 03:36:20 AM »
You need to make sure the proposed bolts are of the correct grade.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Laitch

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #86 on: November 18, 2018, 06:20:53 AM »
I found some m10x135 bolts I could use for the cylinder head bolts that are $1.99 per bolt rather than $11.98 per bolt.  The difference is the inexpensive ones are hex head rather than torx. Would it be bad to use hex head rather than torx?
To echo Martin here, the bolts have grade markings on their heads. Replace them with bolts of the same grade and type. Cutting corners on the grade of fasteners should not be considered. This isn't a bathroom vanity cabinet.

It was known that all valves clearances were too tight long before this point in the thread. A negative effect of those tight clearances wasn't evident in the compression numbers for cylinders #1 and #2. The condition of those components is unknown but the cylinders
seemed to be functioning appropriately according to the numbers. Being this far into the head presents the opportunity for the entire valve train to be evaluated in person by experienced technicians.

You could stop further evaluation and just treat the obviously defective parts and nothing else if you're feeling lucky.

Well, are you?
  • Along the Ridley in Vermont.
  • 1995 K75T 68,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline CNRED

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #87 on: November 18, 2018, 06:26:41 AM »
I believe I would echo Martin and Laitch sentiments. Used the proper head bolt. Cutting corners here will result in blown head gaskests, over heating and valve issues to name a few. After all the hard work you have put onto this bike to this point, it must makes good sence to put it back together with the proper parts.
Do it right or do it again..
  • Scottsdale, AZ
  • 1990 K75rt, 1992GSPD

Offline The Mighty Gryphon

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #88 on: November 18, 2018, 08:29:25 AM »
What is wrong with the old cylinder head bolts?   As far as I know, BMW doesn't require using new bolts when reinstalling the head.

As the others have said, if you do replace them, you need the same grade as the old ones.  These bolts are under a lot of stress and need to have a very controlled amount of stretch to prevent blowing the head gasket and/or warping the head.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'91 K100RS "Moby Brick Too

Offline brichbk

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #89 on: November 27, 2018, 11:46:13 PM »
Update:  I bought another head on ebay for $104 shipped.  I rented/borrowed a valve spring compression tool from a local auto parts store and removed all the valves and bits and put them in separately labeled baggies.  I'm all ready to take my original head to the machine shop to get the valves reseated and put back together with new seals.  While that's getting worked on I can remove the old gasket and clean the mating surfaces and work on getting all the other parts cleaned and ready to reinstall.  I've been reading that acetone is a good thing to use to clean the surfaces, any other suggestions?

Is this the next right step for the head after the machine shop to:
install the cams and adjust the valve clearances before I reinstall the head on the bike?
  • Central Valley California
  • 1993 BMW K75RT // 1982 Honda Nighthawk 650sc

Offline Martin

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #90 on: November 28, 2018, 01:17:38 AM »
Single edged razor blade in a holder, degreaser and green scouring pads. Keep the blade at a shallow angle to prevent gouging the surface.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline The Mighty Gryphon

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #91 on: November 28, 2018, 09:22:03 AM »
As far as assembly of the head, I guess it's six of one, half dozen of the other.  Personally, I would have the machine shop lap and assemble the valves and springs.  I would assemble the head to the block followed by the cams, chains and chain guides.  Once everything is assembled, I would check the clearances. 

Is the machine shop installing new valve seats?  I hope so, because that is the major wear point in the head.  If you are on a tight budget, at least do the exhaust seats.  Those are the most critical, and wear the fastest.  New seats will bring the head to almost brand new status.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'91 K100RS "Moby Brick Too

Offline brichbk

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #92 on: December 11, 2018, 03:49:08 PM »
Just got my cylinder head back from the machine shop.  It looks beautiful.  All valves reseated, new valve stem seals, 3 new valve guides, and the head cleaned and painted.  Now to put it all back together.









  • Central Valley California
  • 1993 BMW K75RT // 1982 Honda Nighthawk 650sc

Offline The Mighty Gryphon

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #93 on: December 11, 2018, 03:52:19 PM »
Holy Mackerel, that's pretty!!!
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'91 K100RS "Moby Brick Too

Offline natalena

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #94 on: December 11, 2018, 08:27:24 PM »
Gorgeous! It's always a shame to reassemble something that looks so nice exposed. They should make "skeleton backs" like on watches, so you can see everything moving.
  • East of Joshua Tree
  • 1987 K75s #0919

Offline brichbk

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #95 on: December 11, 2018, 08:37:23 PM »
Reinstall question:  When reinstalling the camshaft and journals the chlymers manual says to use "molydbenum disulfide grease" and apply it to the underside of the crankshaft bearing journals.  I have some Sta-Lube SL3331 engine assembly lube with moly graphite already on hand, can I use that instead?  I also have disk brake bearing grease but I'm thinking the assembly lube would be better. 

Here's a link to what I have, https://www.amazon.com/Sta-Lube-SL3331-Extreme-Pressure-Assembly/dp/B000M8RYUE/ref=asc_df_B000M8RYUE/?tag=hyprod-20&linkCode=df0&hvadid=312181776237&hvpos=1o1&hvnetw=g&hvrand=13435478275904665978&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9032277&hvtargid=pla-623685627567&psc=1
  • Central Valley California
  • 1993 BMW K75RT // 1982 Honda Nighthawk 650sc

Offline The Mighty Gryphon

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #96 on: December 11, 2018, 09:06:12 PM »
Be careful about how much assembly lube you use.  I can't say for sure, but on the second ride after I did some head work using moly assembly lube(a bit extravagantly I have to admit) the sprag failed to engage and I had to do an engine flush to get it to work again.

A very thin film should do the job.  It only needs to lubricate until the oil reaches the bearings.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'91 K100RS "Moby Brick Too

Offline natalena

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #97 on: December 12, 2018, 07:10:34 AM »
A very thin film should do the job.  It only needs to lubricate until the oil reaches the bearings.

I have not rebuilt a K motor; however, have blueprinted a 320i. A take-away from a dealership mechanic was to "use the lube delicately with a light touch, and do not let anything "float" on lube." Got pretty anal with this process of the build. Good Luck, and assembly Sta-Lube should be fine.
  • East of Joshua Tree
  • 1987 K75s #0919

Offline Laitch

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #98 on: December 12, 2018, 04:11:08 PM »
Got pretty anal with this process of the build.
Probably a good thing the engine was cold. :giggles
  • Along the Ridley in Vermont.
  • 1995 K75T 68,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline natalena

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Re: Phoenix Rising - '93 K75RT Fire Recovery
« Reply #99 on: December 12, 2018, 05:16:11 PM »
Probably a good thing the engine was cold. :giggles

Oh baby, but that camshaft was hot!  ;)
  • East of Joshua Tree
  • 1987 K75s #0919

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