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con rod bearing cap

Discussion in 'Yamaha 250cc In-Line 4's' started by PhTanJo1, Feb 22, 2010.

  1. PhTanJo1

    PhTanJo1 New Member

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    hi guys!!it's been a while,i have problem w/ my 2kr bike,i always used my bike in red line,but my last trip was disaster,after a long hours of ride i heard a knocking sound inside the engine and i've already suspected that one of the bearing cap was damaged,upon at home i dismantled the engine and the bearing cap of the piston besides the magneto was damaged severely,and the pistons downside was cracked because of the excessive clearance of the con rod it created that hit pistons side w/ con rod neck, also the con rod inner portion where the bearing seats seems to be damaged,i always checked my bike before i go out oil,water,etc..what cause/causes this damaged?does each bearing cap of each con rod have different sizes?because i tried to put the con rod w/ bearing cap that is not damage but it is not snugly fit to that damaged one,crankshaft is one solid **** of metal right?or is it possible that it was also damaged?(anyway i don't have the tools that used to measure the thickness of those sttuff).tnx advance for the response!!!!!gud day to allll
     
  2. FZRSHREDDER

    FZRSHREDDER New Member

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    ouch that sounds bad. I don't know about the conrods or that deep in your engine. I think you've figured out why its a bad i dea to constantly redline your 20+ year old bike though. <!-- s:shock: --><img src="{SMILIES_PATH}/icon_eek.gif" alt=":shock:" title="Shocked" /><!-- s:shock: -->
    If i were you i'd be looking through the manuals available on the site, but if its as bad as it sounds, you might be looking for a replacement motor.
    Good luck.
     
  3. dave

    dave Well-Known Member

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    All the bearings are identical sizes, so it does not look good for you.

    The crankshaft is one solid piece and the bearing surfaces are finely machined. If it is damaged it needs to be replaced. Best option is another engine.

    According to one of our members, the FZR250 crankshaft starves for oil at hi revs and is prone to fail with prolonged abuse.
     
  4. PhTanJo1

    PhTanJo1 New Member

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    sorry for the late reply,that seems to hurt me a lot,i love my bike a lot,i didn't know i push it so hard,that would be a big problem if that would be the solution,here in our country these bikes are a bit rare and if you found one it is bit high in price especially parts of it even though it is second hand,now i learn my lesson,but i'm gonna consult this one to you dave,i ask a local machine shops here,they said that i would buy a bearing cap in it(in which i can find one) then i would bring the crankshft and the con rod w/ the bearing to them and they would refurbish it to become snug fit to the crnkshft,(you are right dave the crankshaft seems to be damage)but these would be pricy,i'm gonna need your opinion w/ these if any one tried it ?thus this solution would last or not?and one vehicle mechanic said that if it is not snugly fit try to put a thin sheet of copper in it because they do it in cars but this is not a car right?any idea? tnx for the reply it was a big help!!!hope i can ride my bike again,i'm gonna miss it,
     
  5. dontz125

    dontz125 Active Member

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  6. dave

    dave Well-Known Member

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    I would not have much faith in a sheet of copper to pack the bearing caps.. Might be ok if you were stuck miles from civilisation and it was the only way home.
    These engines require precision tolerances to handle the revs....
     
  7. dontz125

    dontz125 Active Member

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    Thought I posted this last night; apparently the computer ate it...

    From the BDK website: http://www.bdkraceeng.co.uk/Bike1.html

     
  8. PhTanJo1

    PhTanJo1 New Member

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    tnx for the reply guys,i've learned a lot from you all,i have to learned more about these bikes a lot before doing anything more beyond their limitations,i have to take dave's advice i have to look for another engine for these beast for sure,tnx!!!
     
  9. PhTanJo1

    PhTanJo1 New Member

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    dont'z i wish i could be near to that links that you gave,long way from home dude,i've learned a lot,tnx!!
     
  10. Romantix1

    Romantix1 New Member

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    Anyone know what happened to the contact @ rampart racing?
     
  11. PhTanJo1

    PhTanJo1 New Member

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    hi guys:

    i have to push my topic up,it is almost a year now since my bike was damaged,my plan was to find a fresh engine with my bike,but i could not find one here in our place <!-- s:( --><img src="{SMILIES_PATH}/icon_sad.gif" alt=":(" title="Sad" /><!-- s:( --> .so my last option here is to go to a machine shop for the crankshaft to be re finish/refurbish with new bearing rod and con rod(in which i could buy here and it is available).my worries is that,did any one try this solution?would my engine would last long?need your advice for this one,i need to get this bike on the road,i miss my bike <!-- s:-| --><img src="{SMILIES_PATH}/icon_bike.gif" alt=":-|" title="Bike" /><!-- s:-| --> ...tnx!!!!! happy new year <!-- s:biker3: --><img src="{SMILIES_PATH}/th_Biker_3.gif" alt=":biker3:" title="Biker 3" /><!-- s:biker3: -->
     
  12. yyzmxs

    yyzmxs New Member

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    Since the topic resurfaced .... has anyone here had the proper modification done to oil journals done? I am just wondering.

    I spoke to a friend of mine who has been riding and racing FZR400 for close to 15 years and at the same time is mechanical engineer by a profession, about the issue. He said, of course he's aware of it, but all he's done to prevent expensive repair was to modify the oil pressure relief valve, which is under the oil pan cover. He did emphasize that it is not a replacement for the expensive modification, but on the other hand is something most people could do/afford themselves. We didn't go into details since I am not going to do it until it warms up in my garage, but the way I understand it is that the valve is simple spring loaded valve which under a bit more preload will close a bit later and thus keep providing more oil when oil pressure increases.

    Has anybody try to do something like that?
     
  13. simidau

    simidau Well-Known Member

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    We tried it, not sure it the engines are lasting longer or not.
    We modified the oil gallery's and washered up the spring in the oil pump valve to increase the pressure before release.
    One of the ones we did it to died after about the same amount of use.
    We are working on getting perfect minimal tolerances for a set of bearings - which means crank machined to fit the bearings, however it's not on the top of the project list yet.

    Cheers
    Sim
     
  14. yyzmxs

    yyzmxs New Member

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    Just to make sure that I understood you correctly.

    You modified the oil journals and you washered up the oil valve and it still failed, in your opinion by oil starvation? Or you assume that it was oil starvation while the root cause could have been something else ...
     
  15. dave

    dave Well-Known Member

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    OK SIM
    What oil do you use? Brand? Grade?
     
  16. yyzmxs

    yyzmxs New Member

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    That was my first thought ...
     
  17. simidau

    simidau Well-Known Member

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    Penrite SIN 10 is what we are using, we were using Penrite HPR10 or 15 prior to that.

    Cheers
    Sim
     
  18. yyzmxs

    yyzmxs New Member

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    I have never heard of this brand, which doesn't mean anything .... Are they big in Australia with a good reputation?

    You didn't write the full grade number you use ... you said SIN 10. but what's the second number 10W-xx ..... plus SIN and HPR acording to the manufacturer website are car oils without JASO MA certification.
     
  19. dave

    dave Well-Known Member

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    The HPR 10 is a 10W-50 grade semi synthetic and I noticed on their website that it says not recommended for motorcycles.
    The SIN 10 is a 10W-70 fully synthetic oil.
     
  20. yyzmxs

    yyzmxs New Member

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    Both of them seem like car oils to me. Anytime it doesn't have JASO MA, you are asking for trouble, in my opinion, and opinion of others with much longer experience than me. I mean, on low rev motor, it might be OK, but not on a 250cc I4 with 18K redline ....
     

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