Long rod pistons

hotdog

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I have a motor I'm going to build & doing some research I think I would like to do the long rod conversion.
I know MMM now sells a kit for this conversion, however I would likewant to source parts myself. I have rebuilt many cranks & rephased before so have that side of it in hand.
MMM's kit has the rods with the bronze bushings on the l/end of the rod & I know HHB did one a while back & utilised the needle bearing for the CR500 rod.

What I want to know is what pistons people are using besides the MMM kit..?? I have read the some people have used Yamaha virago pistons for this mod - but have been unable to find any further detail. Kop was looking at Kawasaki pistons I think..??

Does anyone in the XS croud know what piston options there are for this mod & mods required to fit them up, or if there is an order code for one of the piston manufacturers to supply these pistons..?? - I dont expect to be able to back door MMM & source from Wossner pistons direct for this & dont want too, just if someone has done it before & had custom slugs made up..?? Or is it all too hard & should I just buy the MMM kit when I'm ready, as I'm sure there has been some R&D done with this..?
I would expect some one has had these made before in the racing or sidecar crowd.

Forgot to mention I have the Venolia pistons job number for this conversion & have asked them for a price. Anyone used these pistons before..??

Post here or PM me.
 
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I just sent in a file this morning to get quoted on having pistons made in a 750cc 10.5:1 compression for the long rod conversion. MMM's kit looks nice, but I have a hard time swallowing the price myself...

SP370 Pistons have been shown to work, and I have a friend right now trying to use some aftermarket KZ900 Pistons as well.
 
I haven't actually seen a completed long rod build online. Lots of talk, lots of pictures of various pistons, no actual engines. If you can get a friend to build one too custom Ross pistons are approx $100 each but you have to buy four.
 
Let me know what you find out please - obviously I'm guessing you intend to retail the pistons..?? or are you going to share your specs/order number...??? Who have you asked a quote from..

PM me if you prefer.
 
Just an update - I have contacted Ross pistons RE: having some custom pistons made up for this conversion. Someone has been kind enough to give me an order number for 80mm (750cc) 10:1 ~ 10.5:1 C/Ratio pistons & I have sourced the CR500 rods to be modified.
 
Over at the XS650 Gargarge They have a very long thread on alternate rods and pistons. Might find some good info there.
Leo
 
I haven't actually seen a completed long rod build online. Lots of talk, lots of pictures of various pistons, no actual engines. If you can get a friend to build one too custom Ross pistons are approx $100 each but you have to buy four.
PJ from the Garage built one years ago using modified Virago 750 pistons,you can use Virago 700 pistons, you can use use KZ 900/1000( There are the pistons I'm using) or KZ(GPZ)1100 pistons but modifications would be required or get'em custom made.
 
Just an update - I have contacted Ross pistons RE: having some custom pistons made up for this conversion. Someone has been kind enough to give me an order number for 80mm (750cc) 10:1 ~ 10.5:1 C/Ratio pistons & I have sourced the CR500 rods to be modified.
When you say modified in relation to the 500 rods,what do you mean? Did you contact 270Yam? That would be the correct Ross forging to use in keeping overall piston weight at the minimum to avoid being excessively heavy,you want a light piston as possible up top on that long and heavy rod.

You can also use the long rod pistons that 650central sells but you'll need to re-deck the block to compensate for the lower piston deck height or offset the pin bushing 1mm using the CR500 rods.

You'll also want to address the XS head port volumes to some what overcome piston pumping losses( even though the degree changes may seem minimal on paper, LR's do inherently effect the vacuum draw through the intake port) that are "Gonna" occur when used with the CR500 rod.
 
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Jack,
I was over at 270Yam's place last week & went through all my intended engine build ideas with him, while I was there I also checked out his 950cc motor & got some great shots of it apart before the assemly begins as well of some video of his 850cc side car racer running + some great ideas for my own build.

The Ross pistons have been specced up by Dave Raynor in Australia & he has been kind enough to supply me with the order number, I am now in contact with Ian Akiyama from Ross Re: my requirements & will see where to from there.

I wont be sourcing KZ or Virago pistons as I want to use the Ross pistons for this engine.
The cylinder head at this point will have its ports cleaned up & detailed & I will see how it goes from there. (unless someone has a cheapo OW or Lillie head they want to sell me for $200)

While at 270Yam's place I checked out his ported Lillie head & I will see how that works out for him, looks nice & has a decent price tag to go with it. I have tried to source alternate people to port a head for me - with no luck at this time.

Obviously MMM's kit runs the KX500 rod at 145mm c-c & as I have already got the order number for the Ross forgings I will be going the CR500 route with their 144mm c-c rods.

In relation to modifing the CR rods I was referring to bushing the LE down to a 20mm sizing, I dont like the idea of running a LE needle roller & the potentiall point loading issues that may occur from this & beleive the bushing will far outlast a needle roller in this application.

Also the Ross forgings have a little extra meat added to them to allow for CR adjustment as well.

hotdog.
 
I was in contact with Ian at Ross too awhile back but I came across a complete set of almost brand new 78mm KZ 900 pistons with liners that I wasn't about to pass up for 144.00,unfortunately I can't use the liners:shrug: I have welded up combustion chambers,so the KZ's are perfect for what I'm doing.

hope you'll post a shot of those new slugs when they arrive and a Vid of 270yam's racer.

Can't quite understand why you're having a difficult time finding someone to port your head being with all the enthusiast over there. To reap the full power benefits of Lillie head,I would assume one would have to use the appropriate piston to match the shape of the combustion chamber for the squish effect,the piston from Dave is more ideally suited for the stock combustion chamber.
 
What is the advantage of the long rod engine? more torque i'm guessing?

Well that'll really depend on who you talk to but from a racers perspective,a longer rod ratio will cushion the the power deliver to soften the explosive mid range and move it higher up the RPM scale to aid traction in the turns. If finally tuned to perfection, I would suspect a power gain could be had with the right engine components like ports,,valve sizes cams,headers and carbs.

Yamaha produced three different street bikes with various rod ratios and a race version and all produced a certain power delivery to suit a certain riding style.
 
dumb question here, but how is that motor in the video an 850cc? I thought the stock cylinders could not be bored out that much.
 
The stock block has it's thinnest area inbetween the cylinders where those air holes are. 270yam has a picture in his build thread of what happens if you go too far boring out the stock block. The Heiden big bore block doesn't have those holes so you can go a little farther. You're ultimately limited by the mounting stud tunnels, and that happens at around 880cc or 890cc. If you want to go bigger than that you need a longer stroke crank.
 
Any idea what the stock cylinders are safely capable of being bored out to? Roughly how many cc do you gain from a stroked crank.
 
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