Bottom end (after a regrind)

[polo2k]

Hi all,
I got my crank reground and picked it up yesterday. Got everything cleaned up, spent ages getting everything immaculate.
Once I had all the shells in place I wound the caps down by hand (finger tight just to pull the caps together) and everything has gone tight.
The crank was out of another 1098 I had lying about as the flywheel mounting was in better condition.
The crank and all shells are 30thou. To the best of my knowlege the bottom end is completely stock.
What could be causing this? surely if the shells and crank are both to 30 thou spec then everything should be within tolerance otherwise the only other thing I can think of is that all the big ends and mains are undersize, but theres no machining marks on the block???

Please help, im muchos disgruntled!

[alex_holden]

I would start by checking that the new shells are stamped -30 and carefully measuring the reground journals with a 1-2" micrometer to check they are really -30 to within a few tenths of a thou.

I assume you assembled it with plenty of oil... A little tightness is to be expected but it shouldn't lock solid.

[MoggyTech]

Did the engineering firm who ground the crank supply the bearing shells? It's always a good idea to get the shells from the company that does the crank work.

[Alec]

Hello Ash,

you don't say if you assembled the main and big end bearings at the same time. If so remove the big ends.
First point is to ensure the caps are fitted the correct way round. Then tighten down one at a time checking for freedom of rotation, also making sure that the thrust are free. Basically, if there is a problem, doing one journal at a time will pinpoint the tight one.

Alec

[bmcecosse]

Yes - start with just the mains (and lots of oil) - and be sure it is free to rotate before torquing down the caps. If all ok - add one big-end at a time. It is of course essential that the big-end caps go back on the rods they came off - and the right way round. They should be marked either with numbers - or little punch marks. Again - just do one at a time - and make sure it swings freely as you nip up each one.

[polo2k]

hey all,
The shells came from the machine shop that did the work.
The shells were all marked 30 thou. I had placed everything on the crank but finger tight and then I was planning to torque them down indevidually, just an attempt to make sure that the rods didnt foul the crank as it turned.
i dont have any precision measuring equipment so ive had to take it up to them and I should get a call once theyve measured it.
*FINGERS CROSSED*

[bmcecosse]

Are you SURE you didn't mix up the caps ??

[wanderinstar]

I had a similar problem. Took it back to the chap who did the regrind, expecting the worst. He checked the caps came off the engine ( not got mixed up with others) he then took the caps off and lightly rubbed them with emery and the bearing surfaces in block. As apparently on the outer edges they get a thin sort of bead of old engine oil over the years. Rebuilt, and engine turned over as it should do.

[bmcecosse]

Very fine emery (or wet/dry) - with oil I hope !!

[wanderinstar]

Naturally.