Z1OwnersClub GB

Had my crank refurrbished recently, new everything plus balance and weld. Done by a reputable engineer. Built the bottom end back up, all good. Turned it over to pop on the pistons only to find No4 conrod small end is too tight. It's not the gudgeon pin as I swapped this with other rods and no issues. The pin goes in about 10mm but is too tight to push through by hand, it fits tight like a bearing fit and at 15mm in stops spinning. As it's the weekend I have not yet been able to speak to the engineer but anyone have any ideas? Could it be honed in situ or am I looking at another case split and start again? Needless to say I am not very happy!
Thanks
Dave

Yes! it can be honed in situ.
Is this new rods too or just bearings etc.

New Rods by the look of it. What honing tool do I use? So far smallest ball type hone I have located on the internet is 20mm - is that too big for my 17mm small ends.
Thanks for your help

Don't use a ball hone, you want a small 17mm brake cylinder hone.
https://www.ebay.co.uk/itm/1x-Brake-Cyl ... SwCH9eF6aH
For what it costs I would take it to an engineering shop/engine re-conditioners if you are not familiar with using a hone.
Before you do though , if a gudgeon pin will press through without too much force I would do a few passes with a spare pin to see if that eases it out.
It's possible the little end eye has had a knock and is slightly oval.
I've had a few like that over the years and pressing a pin through has sorted it out with no other issues.

Yes good advice thank you. its well out of my comfort zone, theres a few places round here I can try.
Thanks again
Dave

Spoke to crank company today, they recomended honing too but suggested i made my own tool out of 1/2in ally tube with a slot cut in it to allow some 120 grit wet and dry to be wound round to the diameter of the gudgeon pin then inserted into the small end and spun up good and fast on my drill while moving it back and forward a few times! Promised me I couldnt go wrong and if i did they would put a new rod on. Somewhat nervously I did as instructed, checking the pin fit after each few passes and I am pleased to say it now fits the same as the rest of them and the build can continue. Thank goodness!

pluto wrote:Spoke to crank company today, they recomended honing too but suggested i made my own tool out of 1/2in ally tube with a slot cut in it to allow some 120 grit wet and dry to be wound round to the diameter of the gudgeon pin then inserted into the small end and spun up good and fast on my drill while moving it back and forward a few times! Promised me I couldnt go wrong and if i did they would put a new rod on. Somewhat nervously I did as instructed, checking the pin fit after each few passes and I am pleased to say it now fits the same as the rest of them and the build can continue. Thank goodness!

Result - Pleased for you.

Pluto,

Would you mind letting me know who did the work on your crank please?

Many thanks.

Great news that you fixed it yourself

My ex-father-in-law has an early (1960’s) Lotus 7 which runs an 1100 side valve motor. Years ago he had to replace the big-ends so he dropped the sump and hand lapped the new white metal bearings with the engine in place! Ahhhh, the “Good Old Days”.