TOPIC:

Same size piston pin.

Kawboy wrote: Same size piston pin.

Yep. And my *understanding* is the compression height is virtually the same. The combustion chamber between the 1300 and 650 are similar designs, so the piston is the right "shape". Wisco offers them in 66m (2mm OS for the 650).

Those are MUCH better pistons that what is in the Crusinimage BigBore kits. But the price reflects it.

Hi
Thanks for all the info think im going to buy the 1370 cc kit from ebay that supplier sells a complete fasket set too
I will post some pics along the way

Frank833 wrote: Those are MUCH better pistons that what is in the Crusinimage BigBore kits. But the price reflects it.

I know lots of guys that have run the CuriseImage pistons in 4 cylinder Hondas and been very happy with them. I have a set on the shelf ready to go in some day (not for a while hopefully)

Hi everybody
I eventually got black set bearings to plastic gauge. My question is , what would be the minimum oil clearance on a conrod journal be ?. They all measure close to .51. Should i fit brown bearings . That would bring the size down to around ,45

You could go to .045 mm (.0018") and be fine but I would prefer .051 mm (.002") for several reasons.

On Plain bearings, you need the oil to form a wedge to cushion the force on the 2 parts rotating against each other. The oil port on the crank created that oil wedge. Having more clearance up to a certain limit creates a thicker wedge to do the job.

A slightly higher clearance up to a limit allows more flow of oil to assist with cooling the bearing and journal and that's a good thing as well.

The worse thing you can do is fit a plain bearing too tight and not give enough room for oil to flow. The babbitt face on the bearing is a type of lead with a low melting point around 370 C. The operating temp of the engine oil is around 100-120 C. The wedging effect of the oil will whip up the molecules in that wedge heating up the oil in the wedge well above the overall operating temp of the engine oil and that's why we need constant flushing of that oil in the wedge to keep the babbitt well below that melting point.

The lubrication system will self adjust via the oil pressure regulator and accommodate clearances up to .1 mm (the service limit) so running the clearances at .5 mm will be just fine. If this was full out racing engine, I'd even go up to .063 mm to allow more flushing cooling on the rotating parts.

This is probably way more information than you need for making your decision but it's an opportunity to talk about "why" or "what" you should consider when fitting those bearings. Hope this helps,
KB