Big End Bearings

just stripped and engine to replace cam chain guide support that had broken so decided to check all bearings and replace rings etc while I had it down, this motor was supposed to have had a new bottom end some time ago by PO what I found when undoing the big end caps was that the bearings are loose in the rods but tight on the crank journal it had no knock or movement in the big end but the bearing shells fall out of the rods, no bearing crush at all in the rod, bearings surface seem a little dark but not worn. has anyone else struck this as it seem strange to find bigend bearings that fall out of the rods. I suspect it may have been assembled without enough oil clearance but the bearings don’t seem to show any significant wear other than they seem to have pulled in on the journal and away from the rod.

Hi a few months ago I stripped a ff engine and found it had been stripped before upon further investigation found one main shell was tight on the crank and loose on the cases and seeing the shells are no longer available came to the conclusion they were either put back in the wrong place as they are all individually sized in pairs or a pair of shells from another engine maybe vf750 were put in to bodge it either way no quick answer to sort it out there are threads on here about zzr1400 shells cross matching but the locator lugs on the shells are in the wrong place I personally bought another engine stripped and checked it. also have you removed the sump and checked the oil strainer for silicone sealer blockage in the gorse which also seems to maybe lead to oil shortage and I have seen shells in cars that have no visible wear but are distorted through heat build up not seizure

I’ve heard of that before and have often thought it was down to the wrong size of bearing fitted, another thought i had was there is 3 sizes of crank pin bearings, coded, yellow, green and brown… and 4 size options, large and small crank pin and large and small con rod,
the yellow and brown bearing have just one size that fits,
the green one fits 2 sizes… large rod/large pin and small rod/small pin, so one of these sizes may not be as ideal as it should be, and maybe over 30 years of hot/cold maybe it distorts a little…

just a though… probably wrong ::slight_smile:

If there is a combo of small conrod/large journal then you could theoretically have a good fit on the journal and a loose fit on the large conrod, or small conrod/ small journal with large conrod, does that make sense?

Not sure what model your working on,but on FF/F2F and RF/G models the big end bearings for front rods are a different part number from the rear rods.
For example bearing A front is 13224-MB6-680 with the rear being 13234-MB6-680.
I’ve not a clue what the difference is but I’m going to find out.
Regards Bif

The only difference between the two is the oil hole location.
This may work in our favour as all you need to do is drill a hole in the correct location and you have another source of big end shells.
FE shells have two holes in each so fit front or rear rods
Regards Bif