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Post by tony811976 on Mar 18, 2007 19:38:10 GMT
after using my bike for a total of around 10 minutes on friday the bike started to tighten up and eventually stopped   . i had been running 50:1 with good oil. i know it wasnt lack of lube as the piston is still ok no scoring or overheating. i took it apart today and found the big end bearing on the bottom of the conrod totally worn away  i can just see the rollers and they are flat.can i get the crank split and gen bearings fitted? now its all apart i will change a lot to genuine. i cant believe its gone so quick sureley these manufacturers tested their bikes.  its bone dry too unlike the rest of the inside but im sure thats down to heat build up not lack of lube. i really cant afford a new gen crank but i refuse to put a standard one back it will just go the same. also which way do i loosen the screw on the front sproket on the transfer shaft?.the screw is really soft and i had to drill it out can anyone shed some light on this? theres a lot of photos on the engine in bits but we really need a step by step strip and rebuild like a haynes manual . anyone feel up to it? lol |
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Post by tony811976 on Mar 21, 2007 7:34:44 GMT
can anyone shed some light as to why the big end bearings in the rod/crank wore flat and overheated? are they rubbish too or did i do something wrong? i had correct mix had run 2 tanks at 25/1 then she died on 50/1 synthetic piston and everything else is ok i dont want to buy new crank if something is wrong
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faucon
Stabilisers
!esreveR
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Post by faucon on Mar 21, 2007 9:42:24 GMT
i will never run less then 32:1 of oil on my gp3r, and i use the ipone s2(will switch for samourai). this bike may run at 16000. more speed you have, less time it stay in the engin, less chance it have to lub the crank. so more crank speed you have, more oil you use and the best. i use 50:1 on my air cooled only. can anyone shed some light as to why the big end bearings in the rod/crank wore flat and overheated? are they rubbish too or did i do something wrong? i had correct mix had run 2 tanks at 25/1 then she died on 50/1 synthetic piston and everything else is ok i dont want to buy new crank if something is wrong |
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Post by tony811976 on Mar 21, 2007 19:55:57 GMT
maybe it is too weak for a gp3 even though its the reccomended mix. ive had so much trouble with the reverse engine im tempted to put another in and sell whats left of the lump .i only bought if for fun so a few h.p lost if any wont matter, id go for reliability anytime over technology. cags have had such a bad name but mines been great
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Post by ninjanut on Aug 2, 2007 20:23:31 GMT
Hi everyone
our big end let go on sunday,can,t really complane tho, the bike has been riden and raced at matchams nearly every weekend since october 06.The bike is stock apart from polini small end,coil,clutch and 14mm carb.Gonna rebuild now with all polini parts and hopefully get some power gains.
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Post by ninjanut on Aug 2, 2007 20:27:45 GMT
had a couple off guys look at the crank,and said it went because the crank was not in centre of crank cases so was rubbing on one side making it wear.
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bmk
'L' Plates
"How mate,...........is that a rep?"
Posts: 30
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Post by bmk on Aug 3, 2007 21:10:29 GMT
Hello ninjanut.
Do you mean the conrod was rubbing on the crank?
I too have evidence of this on my sons machine.
I have around 1.5mm lateral travel of the crank in the cases which i have put down as the cause of the conrod wear.
When i bought a polini gasket/seal set there were two circular metal gaskets in it that don't appear on the polini schematic.
I wonder if these could go into the crank case somehow to take up this sideways movement.
Anyone know?
If needed i can post up some pictures to show what i mean.
Ken.
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Post by ninjanut on Aug 4, 2007 9:52:27 GMT
Hi Ken
I,ve been told by a guy that rebuilds genuine engines that the polini bearings are a slightly different size making the crank a tighter fit and not move left or right.He said you should need a crank case splitter to get the engine apart,but ours just fell apart with a light tap with a wooden drift against the end of the crank.We will be ordering parts for the rebuild next week and will keep you posted as to how much better the motor is as it goes together.I,ve been told to rebuild crank cases with as close to a .5 gap between crank and crank cases as possible so do not think your metal gaskets go on their.
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bmk
'L' Plates
"How mate,...........is that a rep?"
Posts: 30
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Post by bmk on Aug 4, 2007 10:47:41 GMT
Ninjanut. i've already done a rebuild and replaced the main bearings, seals etc. There was a small difference in the size of the bearings as you say. The rep bearings fell out of the casing on their own. Before you fit the polini bearings pop them in the deep freeze for about half an hour and they will fit straight on the crank and drop perfectly into the cases. ;D Here's that photo of the crank and the gasket/seal.  Ken. |
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Post by ninjanut on Aug 5, 2007 21:20:00 GMT
Thanks for the advice on fitting the bearings.
Our crank looks exactly the same as yours.Ours has rubbed on the clutch side,looks to be same on yours.Must be a problem here some where.We,ve not long picked up a 2nd bike for me to ride with my daughter and use as a spare bike on race days so i think i,ll be checking that one as well when i.ve rebuilt this one. I,ve got two genuine gasket sets and neither has metal gasket/seals like yours,so still cant help on this.
What crank have you rebuilt with?
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bmk
'L' Plates
"How mate,...........is that a rep?"
Posts: 30
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Post by bmk on Aug 6, 2007 12:50:58 GMT
I was going to replace it with a polini blue crank, but my son wanted a bizeta as we will be fitting a six port bizeta topend soon. I went on the bizeta website and found the brand new gold crank for the gp3 reverse, so i bought one of those. Silly money though, £160 Bit of an issue with the woodruff keys, as the keys they supplied with my crank were wrong. The clutch key fitted but the flywheel key was too small. However, the rep key fit perfectly so i used that one. I'll be stripping the motor down again this week to check the new crank and fit a new piston ring. If i find anything amiss i'll let you know. Ken. |
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Post by ninjanut on Aug 19, 2007 21:35:20 GMT
Got engine back from jvc racing this week,and he said that the crank cases have not been bored accurately,so making the crank not run parallel and also not centre in the barrel.End result is more pressure on one side of big end.Hopefully genuine parts being better quality,they can stand running out of true a little better.
Have ya stipped your engine yet Ken?Hope all was well
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bmk
'L' Plates
"How mate,...........is that a rep?"
Posts: 30
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Post by bmk on Aug 21, 2007 12:05:29 GMT
Hello ninjanut.
Yes, stripped down and everything looked as it was when new. ;D
This leads me to think the problem is with the rep crank in my case.
There's no sign of any wear at all on the bzm conrod.
As a footnote, that metal gasket come seal thing go's behind the clutch drum seal. (The big brown one.)
It does come in the gp3 seal kit, I've seen a picture on the crossan website. 143.065.003 Seal Kit Reverse.
Ken.
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. i had been running 50:1 with good oil. i know it wasnt lack of lube as the piston is still ok no scoring or overheating. i took it apart today and found the big end bearing on the bottom of the conrod totally worn away 
i can just see the rollers and they are flat.can i get the crank split and gen bearings fitted? now its all apart i will change a lot to genuine. i cant believe its gone so quick sureley these manufacturers tested their bikes. 
