| Author |
Message |
Adrian
| | Posted on Tuesday, April 05, 2005 - 8:49 pm: | |
My new Crank man, top racer Lea Gourlay, is trying to fit an RD350 crank into my spare T20 cases. The crank will be stronger, rebuilt to TZ spec, and will help me finish a few more races... But there is a problem - we can't find a rod to use!
RD crank pins are 22mm, and the rods are 110mm long. However, I want to continue to use Honda CR125 pistons (as they are superb, cheap, and availiable in 6 oversizes) and these come with either a 14mm or 15mm gudgeon pin size. There doesn't seem to be any rod that will connect the CR piston to an RD crank.
The nearest is a 175 Yam rod, but the big end is 2mm too narrow in width. (17mm needed I think)
Any ideas??? |
Peter Morey
| | Posted on Thursday, April 07, 2005 - 11:51 pm: | |
Adrian as you know I have already have a TZ crank fitted to my T20 and for the same reasons as you would like to use CR 125 pistons however the same problem concerning the lack of a suitable replacement rod kit. The only thing I have managed to come up with is from an Aprila V twin 250 racer however it's rods are only 108mm long so that means 2mm off the barrels and they cost around £240 each!!!
The problem is, as you know that Yamaha do not do oversize piston kits because their barrels are plated however I have been told pistons from a 1994 YZ 125 will fit a TZ crank and T20 barrels without the need for any modifications and Wisco do do oversize kits, this is what I think I will be using and it may well be something you need to consider. |
Adrian
| | Posted on Monday, April 11, 2005 - 4:00 pm: | |
Thank you Peter - I did know that a few racers have fitted TZ cranks, but I wondered how they solved the rod problem.
I've looked up YZ pistons and you can indeed get Wiseco oversize ones - 0.5mm, 1mm and 2mm only. I may go this way, although the pistons are a bit pricy. They seem to be the same price in US dollars as they are in UK pounds so maybe we should order online from the US.
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Peter Morey
| | Posted on Wednesday, April 13, 2005 - 10:52 am: | |
I don't know if this will be of any help but I have been told that an Italian Asso Karting piston fits (16mm pin size) don't know if is a staight fit or which one but might be cheaper.
My engine currently has YDS 7 pistons using a single ring and was very sucessfully raced in the 1980's (although engines are much quicker now), other pistons that fit are RD 250 and GT250 K,L,M none of which are nearly as good as the CR/Wiseco pistons. |
Dave Evans
| | Posted on Wednesday, April 13, 2005 - 10:54 pm: | |
Yes Peter, Asso kart pistons are a straight fit,although they are quite a long skirt, I don`t know if they are still available. I still have a pair that I used in that engine you have now. The YDS7 pistons were OK in themselves but the rings had a hard time. I also used Yam TD3 pistons but I expect they are hard to find nowadays. |
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Advice, help, chat, whatever!