Hi all,

I've just measured the diameter of my 94/95 400 cylinder with a Vernier caliper and it clocks in at around 83.4 mm. What's the best piston for me to put in?

Also, if I want the crank rebuilt (new bottom end bearing and spacers) can I do it myself or do you need special presses etc?

Thanks.

 

Get a Wiseco piston and check around locally for the rebuild unless you want to pay big shipping costs.


www.hpd-inc.com

http://rittercycle.com/polaris.htm

www.hotseatperformance.com

 

Thanks for that, what's the best size of piston to go for?


I'm mainly after reliability, so don't really need too much power!

 

stock size of 83 mm or one over (0.020") , 83.5 mm. (correction) [img]i/expressions/face-icon-small-blush.gif[/img]
if your measurement of 83.4 mm is accurate, you would need to go to one over and have it bored.

 

vernier's are not the most accurate measuring device. I like to call them "verynear's".

 

I would personally stick with the Polaris piston. There is nothing wrong with wiseco pistons they are just a deferent composition with a high silicon content, causing them to expand at a slightly different rate then the stock pistons. If you machine the cylinder properly for these pistons you will not have problems, but you need someone experienced doing this to get the correct clearance.

I have had so many people replace the pistons with other then OEM and not bore the cylinder only to have the piston scuff or seize because of improper clearance.
A good shop will order you a piston, mic it and bore the cylinder accordingly.

As far as the bottom end goes all I can say is this area is were you can get yourself in a lot of trouble if you don’t have all the tools to do a good job!
Do some research and find a local shop that does this kind of work! The amount of information they will give you and the fact that you should have a engine you can rely on and only have to do the work on once will be money well spent!

Do what you do best and take the money and pay someone at what they do best and have all the tools for and you will probably be better off in the long run

 

SP..different not deferent [img]i/expressions/face-icon-small-smile.gif[/img]

 

Sadly I live in an area where good shops are hard to come by... I will order a nice new piston and get a local tuning shop to bore the cylinder to fit when I get it. Anyone have any experience of Namura teflon coated pistons? It seems a good idea, but are the pistons any good?

 

I personally would recommend a Wiseco myself.
Get the cylinder bored out 20 over and honed.

Have them measure it for you before you take it home, just to check.

I noticed you weren't in the US, if you were I would tell you to send it to RCR.... but I think shipping charges to and from the UK would be a little costly [img]i/expressions/face-icon-small-wink.gif[/img]

-Chris

 

OK... as pistons are soooo cheap in the States, I'm going to buy two (one for spare)... I'm probably going to go for Wiseco .020 oversize and get the cylinder bored and honed to fit.

Does this make sense, or should I buy one .020 oversize and .040 oversize for when that needs changing and get the cylinder bored again?


(I'm also going to buy a few head gasket kits and a load of other small spares - Polaris parts seem rarer than rocking horse poop in the UK!)