tiger cub big ends are a weakness ,place a feeler gauge down the side of the big end eye that just takes up any side float.blast a load of petrol into the roller cage to remove any stiction from oil.then test for up & down play at various positions during rotation.if its suspect change it before it wrecks the rod.
<SNIP> blast a load of petrol into the roller cage to remove any stiction from oil. then test for up & down play at various positions during rotation.if its suspect change it before it wrecks the rod.
Run990 makes two good points that warrant repeating with the "reason why",in case they get missed. Big ends do not wear uniformly because of the reciprocating loads they carry, and also, the presence of oil in a bearing will mask wear.
So be sure to check the bearing dry, and inspect for slop at every orientation you can manage ... while it may 'feel OK' in one position, it may be beyond its allowable limit at a more heavily loaded position.
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Some late model Cubs came with a roller big-end , others may have been fitted with one over time. I have yet to see mine .
I have blasted it with wd40 ( to de-oil) and more than triple checked it from multiple positions , its not so easy to isolate the side to side from the up and down On a roller bearing you cant see ... so I placed a wood 1x1" against the conrod , front to back on the engine case , to minimize lateral movment ... and can "feel" consistant slight movement , up and down , from all positions where the little end is high enough to work with ... and hear the slightest ' tink -tink' as the rollers move in their races . No spots feels bad , different or worse than any other , but the amount of play is disheartening.
The p.o. installed a poorly-fit under-sized 10:1 piston in the cylinder with no discernable hone , which allowed front and back scoring of both the piston and bore ... and just tonite , on closer inspection , I now see how The original over sized intake valve , for this model , has " kissed" this new high-dome piston . I now see why the P.O. could not get it running "right" ... i am slowly getting used to the idea of having to split the cases on this low mileage bike ... and my growing 'things to buy list'
Fit the lower cr piston for a start. I fitted a Todd racing head to the D14 once. The head was designed for the low cr d7 but I placed it on a already 10:1 piston. It didn't run any better just became a bit noisier on the bearings.
I'd suggest if your in any doubt of the big end, get it done. That way you know it's right and will give you many years of good service. Otherwise you'll be preying for that bit between your legs in the hope it doesn't fail you ( the engine i mean )