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Thread: Only idiot in the world who rebuilt a K100 engine from crank out

  1. #1
    Registered User beemerguru's Avatar
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    Only idiot in the world who rebuilt a K100 engine from crank out

    For my '88KRSSE restoration...don't ask...I'm on drugs

    Anyway, took it all the way down..had the crank, rods, pistons balanced to .01 of a grm, the heads ported and breathed on, a set of euro cams, Ford injectors, K&N, Staintune, etc;

    When it comes on cam around 4K rpm, this engine is smooth as glass,,smother than any of my K75s...and stays smooth all the way to redline.

    Which where this question came from...was reving the engine in the garage last night..up to redline, off a little, back up,,,down, up etc. I noticed,...and a neighbor yelled...that I had flames coming out the tailpipe. About 1' of flame each time I rolled off the throttle.

    I thought I had everything adjusted for the break in procedure...evidently I missed something important..what could be causing the gas to dump and flame out?
    Greg Hutchinson
    R80G/S (4) 633CSi with 450K mile
    '68 R60/2 '88 K100RS Special Edition
    http://gregsgssite.shutterfly.com/

  2. #2
    Benchwrenching PGlaves's Avatar
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    The mixture is off, Greg.

    I'd find a dyno and a sniffer and get it dialed in. It could be a sensor. It could be the air door way off..
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
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  3. #3
    3 Red Bricks
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    Greg,

    You had been talking about messing with the fuel pressure regulator. What pressure are you running?



    LONG MAY YOUR BRICK FLY!

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  4. #4
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    Yup to what PG said but it can sure be fun. Got a turbo'ed rotary that make about 500 rwhp and is deliberately set way rich under full accel (its track only device) instead of adding alcohol or water injection to keep egt's in check.. Backing off quickly can shoot a 4 - 6 ft flame out the pipe with a backfire that sounds like a 12 gauge. Great fun to do this next to a competitors door and watch their reaction.....

    Depending on how oddly you were manipulating stuff in the garage it might never repeat on the road under load...Could be just an odd response time / recovery issue for an over rich condition..

    You sure you you've got a match for the injector size, duty cycle, etc with what the motor needs? Was it tuned on a dyno with AFR and EGT gear in place? Or are you just relying on stock stuff to work correctly? Easy to be off when building franken stuff if that's not thoroughly developed...

  5. #5
    NC Piedmont Rider ncstephen's Avatar
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    Hey Greg,
    What did you do about this?
    NCS
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  6. #6
    Registered User der verge's Avatar
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    Quote Originally Posted by racer7 View Post
    Yup to what PG said but it can sure be fun. Got a turbo'ed rotary that make about 500 rwhp and is deliberately set way rich under full accel (its track only device) instead of adding alcohol or water injection to keep egt's in check.. Backing off quickly can shoot a 4 - 6 ft flame out the pipe with a backfire that sounds like a 12 gauge. Great fun to do this next to a competitors door and watch their reaction.....

    Depending on how oddly you were manipulating stuff in the garage it might never repeat on the road under load...Could be just an odd response time / recovery issue for an over rich condition..

    You sure you you've got a match for the injector size, duty cycle, etc with what the motor needs? Was it tuned on a dyno with AFR and EGT gear in place? Or are you just relying on stock stuff to work correctly? Easy to be off when building franken stuff if that's not thoroughly developed...
    I had a 91 Talon TSi (back before that stupid movie came along that had one in it) that was turning just over 450 AWP. I had the computer dump very rich right at redline. It did the same thing: massive fireball. I miss it so much. There are not to many things in the racing world that are more intimidating than that
    02' K12LT ~ 83K '97 F650GS ~ 32K' 81 XS400 ~ 9K
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  7. #7
    Themason 42906's Avatar
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    Quote Originally Posted by beemerguru View Post
    For my '88KRSSE restoration...don't ask...I'm on drugs

    Anyway, took it all the way down..had the crank, rods, pistons balanced to .01 of a grm, the heads ported and breathed on, a set of euro cams, Ford injectors, K&N, Staintune, etc;

    When it comes on cam around 4K rpm, this engine is smooth as glass,,smother than any of my K75s...and stays smooth all the way to redline.

    Which where this question came from...was reving the engine in the garage last night..up to redline, off a little, back up,,,down, up etc. I noticed,...and a neighbor yelled...that I had flames coming out the tailpipe. About 1' of flame each time I rolled off the throttle.

    I thought I had everything adjusted for the break in procedure...evidently I missed something important..what could be causing the gas to dump and flame out?
    Tell me more about the injectors you are using. You say "Ford" injectors. I am not aware of any Ford injector that is compatible with our bikes but am always interested in new ideas. I have used a Borg Warner injector that crosses over to the Bosch part number, but do not have the BW part number handy.

    Also, did you advance the timing any? Advanced timing with high enough octane fuel could do this too.
    Experience is what you get when you don't get what you want.

  8. #8
    Registered User beemerguru's Avatar
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    The saga continues

    Something else that came with the flames...lots of smoke. And I mean lots! So thinking back, the light bulb came on and I remembered that I laid out the cylinder hone but in the heat of the moment, didn't use it. Been working on the engine for about 6 months and was a little to anxious to get in running again. Had pistons ready to go so just skipped that little step. New rings on a glazed surface..

    Which turned out to be VERY fortuitous.

    Because.....

    I then had to pull the head, pop the pistons out and got ready to do the honing thing. At the last minute, I decided to drop the crank so I had a clean shot at cleaning everything up after honing. That's when I discovered a spun bearing on #1.

    So the crank goes back to Armando.

    He mics it and discovers cracks so crank is a doorstop. I get curious and drop the pan and see a small pile of metal. Journal shot, metal in the oil passages, crank burnt..learning experience.

    Find another short clock with low mikes and it all goes to Armando to check the line bore, the crank, and that my balanced set of pistons will match the bore.

    Everything comes back checked and blueprinted to a .01th of a gram.

    Now time to re-re-reassemble the engine.

    It will run again...sometime....I'm sure...sorta.
    Greg Hutchinson
    R80G/S (4) 633CSi with 450K mile
    '68 R60/2 '88 K100RS Special Edition
    http://gregsgssite.shutterfly.com/

  9. #9
    Registered User beemerguru's Avatar
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    Block in, crank in, head on, starter in, alternator in, radiator in.

    When I got my first K back in '87, CC Products (San Jose BMW now) sold an injector upgrade complete with before and after dynos. Found out later the injector was from a BMW 318i car.

    Then at the Flagstaff MOA National I ended up camping next to a guy from TRW automotive who had a friend at Bosch. We talked about K engines and what could be tweaked. He said that his friend went through the Bosch injector catalog to find a substitute with the same physical dimensions but with a higher rated spray pattern. Very similar to what CC Products had done.

    The one these two settled on came from a multi-port Ford..just a different spray pattern..same physical dimensions.

    But more gas means you need more air (K&N) and a better exhaust (Staintune). Left the timing alone.

    This is years ago,,,but took the bike (same one) back to CC and got a dyno run. Another bump in toque and power over the 318i setup. Can't remember the exact numbers and the printout is long lost.

    So now this is something I just do to all the Ks. Upgrade the exhaust, air filter, and injectors..been a happy camper ever since.

    Now back to my regularly scheduled show of lunacy rebuilding this engine
    Greg Hutchinson
    R80G/S (4) 633CSi with 450K mile
    '68 R60/2 '88 K100RS Special Edition
    http://gregsgssite.shutterfly.com/

  10. #10
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    I've perused those tables myself.

    http://users.erols.com/srweiss/tableifc.htm

    Blessed are the idiots. They keep putting screwy ideas in my head.

  11. #11
    Registered User beemerguru's Avatar
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    That's what they did..all the options till they found one that worked.
    Greg Hutchinson
    R80G/S (4) 633CSi with 450K mile
    '68 R60/2 '88 K100RS Special Edition
    http://gregsgssite.shutterfly.com/

  12. #12
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    Ford injectors

    regarding Ford injectors. Back in 1999 my 85 K bike needed to go into the shop. This was just after I had gotten a computer and the advice on web sites! http://www.bmwmoa.org/forum/images/s...eadscratch.gif
    Electronic ignition box had to be replaced. The dealership also told me I needed fuel injectors... knowing that the IBMWR site had information on fuel injection i politely declined the offer of buying the originals.

    Made it home with a sniffling engine and took one of the injectors out, walked up to the local NAPA store and told him what i was looking for. Showed me the injectors for the BMW cages... then he pulled out injectors for the 4.9 big 6 that Ford had in their pickups.

    purchased 4 of them at the price of 30 bucks each. Popped them in and they are still firing good! Sold the bike to a friend back in 03.http://www.bmwmoa.org/forum/images/smilies/dance.gif

    tim

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