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1Back to top Go down   Engine block wear Empty Engine block wear Sun May 15, 2011 5:04 pm

shay

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Hi

My 1989 k100 doesn't run!
It has 160000 k's on the meter but it wasn't working when i bought the bike and i fixed it so i can't say if it is close to the real number of kilometers that the bike actually did.
All the tests i did brought me to a conclusion that the engine block is worn and low compression causes the engine to stop.cylinders 1,2,3 show 150 psi & cylinder 4 show 130 psi.
It does fire up after i pour some engine oil into the cylinders through the plug holes but after reving for a few minutes it burns the oil and dies again.
After asking for the advise of a local autorized workshop;i was told that this is a well known problem which happens in some of the k's and since the cylinders are covered with nicksil (mind my spelling),re-borring is not an option.
it appears that the only option i have is to either renew the piston rings (a short term solution)or to change the engin block which is not an option for me since it means that i will need to buy another bike and to make one from two but this bikes are rare and expensive where i live.
so i decided that i will open the engine and check the block for wear but before i order the rings and the gasket set i thought i should try to look for a good advise in the forum-
Did any one encountered this problem and solved it in a way which wasn't changing the block?
Thanks

Shay

    

2Back to top Go down   Engine block wear Empty Re: Engine block wear Sun May 15, 2011 6:54 pm

Guest

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I would be reasonably happy with 150 psi but discouraged by 130 psi, though that's not 'terrible' and no reason for an engine to not run, or to simply stop running. The problem would be that there is such a discrepancy between the cylinders and that could be a measure of re-shimming the valves because they might be too tight, thereby reducing the compression in those three cylinders. Have you tried to measure the valve clearances? It sounds to me like you're receiving advice in the extreme before a few basic questions have been answered. It is true, however, that you will not be able to re-bore the cylinders, but they take a nice shine to re-honing.

Anyone else care to offer up some more to this gent's dilemma?

    

3Back to top Go down   Engine block wear Empty Re: Engine block wear Sun May 15, 2011 9:00 pm

RicK G

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Does the compression come up to 150 after adding oil, if so then it is rings if not check the valve adjustment on the shims and correct all to be sure.
I would say that 130 would not prevent it running on all 4 but may give a slight decrease in performance.

The shop is right in that reboring is not an option but a gentle hone and new rings and if over 200,000k then new pistons as well and it is NOT a short term solution. I know of some Ks that have done over 1 million ks on the original bore with a change of pistons and rings at 300,000 to 500,000 mark.
Nikasil bores do not wear out, they will sometimes peel the coating of the cylinder which was more the case on some of the early 100s but by 89 it didn't happen very offten. The most common cause of the Nicasil breaking down is prolonged detonation which pits the surface usually above the top ring.
The best way to diagnose better is a leakdown test. It will let you hear leaking air and where it is leaking from.
Beware some authorized workshops are only authorized to take your money and some are honest.
Is it losing coolant, that could be the compression leak or leaking to the outside or an oil gallery any of these will mean removing the cylinder head.

    

4Back to top Go down   Engine block wear Empty Re: Engine block wear Mon May 16, 2011 10:46 am

japuentes

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Hi there, in my case I had the same problem but once the engine was open the bores and pistons were well in specification but rings were wore out, ordered new rings, small and big bearings, and been riding last 4 years. Important to check and rebuild if neccesary the valve guides, didn´t do mine and now have to plan for it.
Best regards
JAP

    

5Back to top Go down   Engine block wear Empty Re: Engine block wear Mon May 16, 2011 11:40 am

charlie99

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hmm stops running ???? wtf .... i would be checking the valve clearances real quick

rings grow with heat ...so better compression would result ....and so do valves ...but that results in lower comprssion ...or no seal ....it sounds to me that they are definatly too tight in the shim clearances and i suspect the compression becomes woefull by the sound of it .

dont fall for the line of a non-repairable engine ..many things can be done ...but as our friends above have suggested ...make sure all the simple things are done first ...and there is hope yet .

maybe just a good valve job is required ...by the sound of it this problem has been hanging round for a while , and im guessing pitting or burnt valves or seat maybe the worst case issue ...outside a service replacement of the rings ...and maybe the valve springs to refresh the good bits .

please measure the cams for lift and cam heights in relation to each other as well .

some other issues that may effect the running on the k100 series motors are ...ageing rubber ...these things should definatly be checked first .......look for cracked hose from crankcase to plenum ..this may severly affect the running ....also throttle bodies to head rubbers ...and the rubber hats on the vacume takeoffs on each throttle body ...including the line that runs off number 4 to the fuel regulator behind the plenum .
you say she has been sitting for a while .....please check all fuel supply components ,,,we have seen so many failed pumps ...blocked fuel filters and cloged injectors ....and poor rubber which falls apart .


i pulled my little 1600 toyota apart at 320,000 ks, new rings (standards refitted end gap after ....14 thou ...new factory = 12 ) + bottom bearings ...rework the head ...replaced 2 valves , valve seals and 1 x new seat .....she now has 444,500 ks and still going stong ...amazingly strong for a 22 year old and i dont give her any slack ....

i also did my little daihatsu tripple cylinder with similar readings 140, 140, 110 last year ...a 4 hour pull down, regrind of valves and back together fixed this baby....... she now reads 160 160 160 .....it seeems it was just pitting on number three valve faces ....probably from a poor adjustment ....many years ago and some sucking of oil which was deposited on the valve seats .


good luck

    

6Back to top Go down   Engine block wear Empty Re: Engine block wear Mon May 16, 2011 1:49 pm

club_c

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Seems like a couple of issues. The 'no run' sounds fuel related. When it stops running do you have fuel pressure at the fuel rail (where the injectors are)? If not, could just be a bad fuel pump or clogged fuel filter.

I agree the compression readings should not cause the bike not to run, and also agree the first item of business to diagnose that correctly is a valve adjustment.

Even if that doesn't totally solve the compression issue, to me it's not bad enough to take me out of the riding season. I'd deal with a valve grind/ring replacement (if needed) in the off season.

    

7Back to top Go down   Engine block wear Empty Re: Engine block wear Mon May 16, 2011 8:06 pm

ReneZ

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Don't think compression is your issue. I agree with the above comments, look elsewhere. Have a look at Bert's fault finding page.


__________________________________________________
Greetings from Florida! Having a 'new' K  :cyclops:    Surprised-o: 

Rene


BMW K100 - 1985 (0030029) Engine block wear Rain
BMW K1200GT - 2003 (ZK01223)
    

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