A new crankshaft is $660. Looks like the cost to fix mine will be close to $500, so I'm thinking to just buy a new one.

The motor really has low miles, but I'm ondering if I should replace the pistons, rings or both. With the rings I'm a bit worried if the new rings will be able to break into the nikasil cylinders?
_________________
james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm

If you are replacing the crank, why would you not replace the pistons and rings?!

A false economy if you ask me.
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

Like I said, I'm worried if the new rings will break in. The pistons don't real have any wear.
_________________
james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm

Why are you concerned about the rings? Every time you get a siezure and have the barrel replated you need new pistons and rings, and Honda fitted new ones when the bike was new, so what's worrying you?
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Beacuse I don't plan on doing anything to the cylinders. When Nikasil is new it doesn't have much of a hone on it, and when used it has even less. You need a hone to break in rings. Question is how much? Honing nikasil can't be done by the home mechanic. This has been a topic of many thousands of discussions with Porsche owners since they started using it on prodution cars in the early seventies. Some have had good luck, other not so good luck.
_________________
james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm

Some fail to break in cylinders and rings because they pussy foot around and end up glazing everything up.

With the strokers, I never set the motor rich, or increase the oil mix when running in. Just run it as is and it will break in.

When you start the motor for the first time immediately start blipping the throttle. Not too high (4 grand's enough) til the engine gets up to about 50 degrees, then blip up to about 7k until the engine's up to around 70 degrees. Then switch off and let cool to ambient temp. That's one heat cycle. Do this three times.

First riding should be up to about 9k for the first ten minutes with maybe half to 3/4 throttle. Not too much load but don't let it chug along at constant throttle. Increase to 10k for ten minutes, then start winding up to WOT and 11k.

Keep clicking gears up and down, and operate the throttle smoothly and you should have it run in in no time.

4 strokes seem to break in quick if you use a low quality oil for the first 100 miles or so. This is what we did on the boiler racers. Then switch to the good stuff. Using the good juice from the off just glazed the bores up no matter how we did it.

So you think I should be OK breaking in new rings on old cylinders?
_________________
james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm

Yes.

Especially since the options are all but zero!
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Actuallly the cylinders can be honed buy a company that does the plating, but I was hoping not to go to that expense.
_________________
james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm

I have always done a light ball hone to the cylinder(s) when replacing rings to de-glaze the cylinder(s). I've done it for 15 years and never had a problem. Accutally, I just had a melt down not long ago and had to rigid hone a cylinder which is a big no-no works great though. New cylinders have cross hatch marks in them when there are new so someone is honing these cylinders
_________________
1995 A kit TZ 250
1994 Rothmans NSR 300sp SOLD
1998 RM 250 freestyle/motorcross
1998 Meathanol burning CR 500 AF super retard/motorcross/sand dunes/play bike

Yes they are honed origionally with a special diamond hone.

Do you know what grit your ball hone is?
_________________
james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm

The price of a new crankshaft just went up to $730.
_________________
james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm

Ouch!
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Why should you need a hone to change rings ?

everybody is changing rings more often than pistons and even more often than cylinders ?

If you can't hone, you need to change cylinders everytime you change rings ?
_________________
Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

pbekkerh wrote:Why should you need a hone to change rings ?

That is normal proceedure when reuilding a motor. ut different cylinders/rings have different requirements. If it waas a chrome ring in a steal cylinder it would definatly need a fresh hone. Alusil is also tricky.
_________________
james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm