OzVMX Forum
Clubroom => Tech Talk => Topic started by: suzuki447 on April 24, 2010, 08:28:54 pm
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can any one help i have 76 rm125 engine that has new bottom end in but someone has put larger rod in than standard the bottom end s good but small end is 19mm instead of 15-16mm so i get rebore and newpiston kit and she dont fit anyone know what model engine it could b out of thanks don
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Do you actually have a small end bearing?
The difference in size you mention would be about the thickness of the bearing?
If it is the wrong rod then I would also be concerned about it being the right length
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what numbers are cast into the rod?
a small end with ID of 19 sounds like its for a 14mm gudeon pin
RM125 77-80 has 14mm
RM125 76 has 16mm
also the 1980 wiseco book has another early RM125 with a 14mm pin. It has 56mm bore, doesnt say the year. looks like it may be a 75 or maybe some 76 models had 14mm pin and some had 16mm.
Im sure someone on here had the same problem as you and asked this same question so do a search in the suzuki section and see if its been asked before.
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Yep, GMC is refering to the needle roller bearing, you could be forgiven for thinking its just an old style type of little end with no bearing. I have been down the track with a RM125a using a cr rod kit and cr piston all seems to fit, but i am not totally convinced that the ports line up 100 percent-therefore port timing could be another issue. This little bike screams up top but takes a bit of comitment to get it there. Mine has been put to bed whilst i play with others.
Good luck
Brett
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http://ozvmx.com/community/index.php?topic=12399.msg121743#msg121743
77-80 RM 125 with 14mm pin uses 14 x 18 x 20 bearing
to me it sounds now like you have not got a old suzuki rod in there at all
A 19mm ID rod/OD bearing has a 15mm OD gudgeon pin.
Just down load the Wiseco piston book and you will find all the info im telling you now in there.
I can see modern KX 125's have 15mm pin with the 19mm OD bearing and there would be more.
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can any one help i have 76 rm125 engine that has new bottom end in but someone has put larger rod in than standard the bottom end s good but small end is 19mm instead of 15-16mm so i get rebore and newpiston kit and she dont fit anyone know what model engine it could b out of thanks don
There isn't a problem, the alternative rod rod just uses a 15mm wrist pin(a small end bearing 15 X 19mm) which are what all modern 125's use.The 76 RM will probably use a 14X18mm small end). Most 125's have a 22mm compression height. If you measure the bore an get a piston to suit the bore size(over sized Wiseco) from either KX/CR/RM/YZ/KTM/TM/HUSQ/GAS GAS all will be fine. Just check if the piston is domed or flat top. CR's(maybe KX's) are the only 125 that still use domed pistons.
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We've just converted 2 RM125A's to flat top Wossner pistons, more oversizes available, had to mod the head to get compression right, well worthwhile doing, bikes fly.
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Hey davey, would be good to get more info on the mod, did you use the std crank/rod, what model were the pistons listed for ,and did you shave /machine head ? does anyone know the physical difference (other than the larger bore) between the A barrel and the B/C? could you fit/adapt A to B/C ?cheers
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Ring me on 0412747729, it would take too long to type.
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Yeah no worries Davey, i'll give you a call tomorrow. cheers