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Wrist pins too small

Posted: Fri Oct 01, 2021 6:54 pm
by Bmurphybcr
So I just got my cylinders and pistons back from the machine shop for my '73 suzuki gt250. Had to bore +.5mm because of scoring. I bought my pistons out of the UK from IMD on eBay. Guess I didn't notice that they specified that the wrist pins are 14mm. Now I have cylinders bored to the specs of these pistons and can't install them. So now I'm wondering if I can just use a different needle bearing. I wanted to make sure of the size first before I buy some. Near as I can tell I'll need a bearing that's id 14mm x od 21mm x 19.6mm. Is this the right size? Anyone have an idea where I could find any? This is the closest I could find, will it work? https://www.ebay.com/itm/Needle-Cage-Be ... 632-2357-0

Re: Wrist pins too small

Posted: Sun Oct 03, 2021 3:02 pm
by dollydog
hi mate, in not too many words, there is no easy way of doing this - apart from buying a pair of pistons with 16mm gudge pin holes. don't bother with oversized needle rollers. i've actually had phosphor bronze bushes made for some conrods to bring the size down to 14mm, but i was never happy with them. in fact the first time i stripped the top end one of the bushes had spun and then the top holes didn't line up. you have 2 choices: buy some 16mm gudge pin pistons or take the crank out and get 14mm gudge pin conrods fitted. as i said, unfortunately there is no easy way :(
cheers, dd.
p.s. forgot to add: the big ends on the 14mm and 16mm conrods are exactly the same, so an easy swap if you go that way. plus you'll be able to use later gt250 pistons, rg250 pistons and x7 pistons, all 14mm gudge pin sized.

Re: Wrist pins too small

Posted: Sat Oct 09, 2021 3:31 pm
by Bmurphybcr
Thanks. I went ahead and bought the right size pistons. Everyone I've spoken with about it said that's what they'd do. Not the cheapest option, but I want to make sure I do it right. Still waiting on them to get here. I just hope they aren't too small for the new bore.

Re: Wrist pins too small

Posted: Sun Oct 10, 2021 3:46 pm
by dollydog
put it this way mate, that's most definitely the cheapest way. if you think about the other way, it's a complete crank strip and rebuild to fit the smaller gudge pin conrods. as to the pistons being too small? i presume you took the pistons in with you when you had the barrels rebored? i'd be more bothered if the pistons were too big, as running the engine up to temperature, then stripping the top end down and looking for shiny high spots on the pistons, rubbing them down with fine wet n dry, fitting them again and repeating can be a right ball ache :D
cheers, dd.