700cc

[bloodhound]

700cc pistons

http://www.hoosracing.com/products.html

They fit in the stock sleeves and onto the head with no modifications. I started cleaning the stock pistons and noticed one one was uneven like some of the metal chipped off. I originally thought is was carbon build-up. I could put a 750 kit for $600( which would need a new heavy duty clutch), buy a new stock piston or buy this for $300. For the price it seems like a good deal. I would just need to have a machine shop bore them to the 700cc specs. Any thoughts, or items I have not thought about.

I am most worried about cylinder wall thickness anybody no anything about them or someone who has used them.

 

[Travis]

Don't know anything about them but some quick (and probably inaccurate) calculations, you'd need to increase the bore size by about 2.6mm. I don't know if the stock sleeves are up for that, but I really have no idea. Hopefully someone else can be more help.

 

[inxs]

- had a look at his site - i think these are the shell 700cc pistons @ 77.5mm which have been used quite successfully for many years...they used to be available in both high and low compressions...the ones in the photo look like high comp.

- getting used or new original pistons is always a bit hit and miss - you need to measure out the bores first to see how worn they are - you might find it easier to go up a size and get the cylinders rebored

 

[dwyatt]

I just bought a set of these pistons from Hoos, good people to work with. I researched this quite a bit before buying as this is going in a roadracer. The liners are plenty thick for this conversion and everyone I've chatted with that has gone this route highly recommends it. Easy enough to do, buy the pistons, bore the cyclinders, put it back together. You should feel a nice extra kick due to the increased displacement and higher compression ratio of the JE pistons. These pistons should give you 10-1/2:1 CR, so enough for a little extra hp, but should be fine on pump gas.

 

[inxs]

- interesting, and at 345 dollars plus head gasket and machining, quite a cheap way of sprucing up a motor, although a 750 kit including cylinder with larger fins is not that much more

 

[inxs]

- i think the liner has an OD of around 83mm, the spigot around 82mm which will give a liner thickness around 2.5mm or about 0.100in...you wont want to go much below 0.080in

 

[dwyatt]

Sounds about right, general concensus has been not to bore any larger than these pistons, go to different liner for 750cc and up. I was going to go with the big fin 750 cylinder from MikesXS and the 750cc JE pistons, but I wanted this bike to qualify for the CMRA F40 LW class, limited to 700c for aircooled, SOHC twins.

 

[bloodhound]

Yeah the guys on the garage said that same thing that, there should be no problems. thanks for your replies.

 

[Travis]

see, I told you I had no idea.... At least my math was pretty damn close!

 

[crash]

hey dwyatt any pics of the 83 xs

 

[inxs]

weight...326g
pin centre to crown height...dome...10.668mm... 0.420in...
width..77.5mm.. 3.051
skirt length n/a
boring tolerances .0030 (.08mm)
compression ratio...10.5:1

 

[dwyatt]

Can't wait to get them in the motor. I head home in less than 2 weeks and will tear into the motor then, it's already on teh workbench.

Crash, here'a pic of the bike before I started the conversion.

 

[crash]

nice base for a nice chop,keep us posted

 

[jay760]

I run a similar kit which is sold on ebay, although the kit might be cheaper to begin with, you do have to get the barrels taken out, which can take the price up to almost the same as the mikexs bolt on kit, when I bought mine was just before mikesxs brought out their kit, having just gone back to the uk and been able to compare my 760cc up to the 710 I ride here, what a differance 50cc makes, I thought they were comparable but after taking the 760 out 2 days after riding the 710 there is no comparison.