Alternative rods and pistons

[eric123]

Who has any info about using CR500 rods and XT350(i think) pistons...Damn, think about that set up rephased...That would probably smoke my sportster, and my sporty eats HD Big Twins for breakfast

[Curly]

I don't know about the CR rods although I've heard them mentioned but the XT350 pistons would likely not work out. The XT engine is a 4 valve per cylinder DOHC design with valve reliefs molded into the piston crown to match. A better possiblity would be the YFM350/400 ATV piston. That's a SOHC two valve 83mm bore design.

[50gary]

There is a tech note in the XS650 motorcycles, and I can't remember the number but I wrote down the different combos with the CR500 rods (144mm length)
782cc = cr rods with 82mm Honda Hurricane pistons, Xt 350 pistons @ 86mm = 860cc. Halco says, for XT 500 Yamaha pistons you must use European long rods (130mm + 10mm 533 rods) These are 87mm = ??cc. For standard big bore Suzuki SP 370 pistons 85mm high crown. I believe they mean for the CR500 144mm rods. This whole parts bin thing is very interesting to me. The CR 500 rods are 144mm length and you must use pistons that have the same higher wrist pin either 14mm or 4 depending on your present length rods. the rod to stroke ratio for the 144mm is 1.945 Hope I got that mostly right. Cheers, 50gary

[eric123]

may i inquire as to what site you found this info on?

[50gary]

XS650Motorcycles.com It's the Bob Bertaut site. I forget which number the piston info is listed under but that's where I found the information. One of the members from the old Garage site posted the info there and email me but that was quite some time ago. Cheers, 50gary

[eric123]

??I've been through that site a million times, but don't remember seeing that info...guess that I will have to go throught it slower next time...Thanks 50gary

[50gary]

Eric they have those numbered postings and I usually write down what I'm interested in and save it. I just can't locate the scrap of paper. So day I'll actually have to learn how to use this computer. I do some checking. Cheers, 50gary

[Tackett]

Geek tip of the day:

You can have Google search just one site, rather than the entire Internet.

enter it like this:
site:<site name> <search terms>

site:www.650motorcycles.com Honda

This will return all links to "Honda" at www.650motorcycles.com

This is a search for Honda pistons at 650motorcycles.com
www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=site%3Awww.650motorcycles.com+pistons+Honda+

The only hit is this one www.650motorcycles.com/LongRod.html

Tackett

[1crazypj]

;D ;D ;D
I posted all that stuff originally
Honda CR500 MX rod kit fits fine. I have list of pistons that fit with it. All will need some modification, but even a small lathe can cope with machining aluminium alloy and making bushing for small end.
I found some more parts that fit,
I think a Polaris (watercraft) con rod will go in, its 140mm long, I've got a crank to take apart and get the numbers. Only 'problem' is small end is 25mm so will neeed bushing.
It would be same length as european rod so you can use Suzuki SP350 piston to get 840cc.

[Diesel]

So don't hold back 1crazypj... what are the pistons?!

[eric123]

Yes...Enquiring minds want to know...

[rod]

What is the benefit in using a Honda 500 rod?

[eric123]

more cc's

[50gary]

More cc if you go up in bore diameter. Longer connecting rods will help to elminate side thrust in the cylinder and the piston will spend more time at TDC which is a good thing. Indy cars will have a stroke to rod length ratio of up to 2.4 to 1. Take the stock 74 mm XS stroke and divide into the 130/140/144 mm rod lengths you'll get ratios of 1.756 to1, 1.89 to 1, 1.945 to 1 Cheers, 50gary

[rod]

Thanks Gary. So there are special pistons to match those longer rods, to get proper head and valve clearence? ;D