Hi all

I have been long time do not start my NSR250s, some of them just keep in my living room for standing beautiful.....

But now ! i'm starting to take them out to go trackdays.....I'm going to say helo to every NSR250 mates..

There's one question about the NSR250 cranshift rebuld....

I was told from one chinese guy that how to restore 3 bearings on both tow side and middle, the guy took crankshift to machine shop, Just directly took off and replace the three bearings.. And replace the two side cranshift to be in one. only take 20 mins and it has done...

In my mind, I'm doubt it, is that that easy! if so, i believe there's a lot of HONDAsssss coming next !

I believe there would be on head treatment first to take off....

Anybody who knows this rebulding process?? please make us more knowledge about
_________________
1996 HONDA RS250
1995 MC28 NSR250 SE red/white/green
1994 MC28 NSR250 sp W/ RS250 engine


Last edited by Hung on Wed Feb 22, 2012 11:00 pm; edited 2 times in total

I do not fully understand everything you say.

20 minutes is not a lot of time to spend working on a crankshaft.
If the workshop only spent 20 minutes working on your crankshaft, then I suspect that they only replaced the two outer main bearings.

I would expect it to take at least 90 minutes to replace all 3 main bearings. Even 120 minutes is quite quick.

TuckerBag wrote:I do not fully understand everything you say.

20 minutes is not a lot of time to spend working on a crankshaft.
If the workshop only spent 20 minutes working on your crankshaft, then I suspect that they only replaced the two outer main bearings.

I would expect it to take at least 90 minutes to replace all 3 main bearings. Even 120 minutes is quite quick.

Right ! 20 mins is rediculous, But how to rebuld it ? Someone knows the process of making NSR250 cranshift?
_________________
1996 HONDA RS250
1995 MC28 NSR250 SE red/white/green
1994 MC28 NSR250 sp W/ RS250 engine

Press it apart, inspect/replace bearings and rods if you can get them) and then assemble and balance. It takes couple hours to do a single cylinder Vespa crank, no way NSR can be done that quick, agree with Tucker, in 20 minutes best case scenario they replaced the outer bearings and seals .

Dmitry wrote:Press it apart, inspect/replace bearings and rods if you can get them) and then assemble and balance. It takes couple hours to do a single cylinder Vespa crank, no way NSR can be done that quick, agree with Tucker, in 20 minutes best case scenario they replaced the outer bearings and seals .

I was told from one mechanic guy that rebulding NSR250 cranshift(completely take connection rods out) need heat treatment first to crank, then pull single crank out, is that right?
_________________
1996 HONDA RS250
1995 MC28 NSR250 SE red/white/green
1994 MC28 NSR250 sp W/ RS250 engine

That's the difference between getting an NSR crank built by someone who knows what they're doing and someone who doesn't.

You'd be better off buying a new one! This is all going to end in tears!
_________________
Andy.
NSR-WORLD.COM

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You should NOT apply heat the the crankshaft to pull it apart.
To explain how to do this properly, to someone who has no experience, would require a small book and about 10 hours practical experience.
You need to find someone who is a specialist in rebuilding crankshafts.
Perhaps ask your local engine re-conditioner if they know of anyone?

Andy wrote:That's the difference between getting an NSR crank built by someone who knows what they're doing and someone who doesn't.

You'd be better off buying a new one! This is all going to end in tears!

That's right, I was saying that one guy rebuld it for 20 mins, I will not use that kinda crankshift,

Normally! brand new from HONDA on my NSR250 for 50000 Km rebuld(manual showed), but when we took off it, still good funtional on balance machine, that's HONDA! I'm not addicted to that HONDA, but its real and we had tried..

But...once rebuld it, we only go maximun 30000KM or less on street.

Take NSR250 to go track or race, then...less than 10000KM on crank. can tell why of that ?
_________________
1996 HONDA RS250
1995 MC28 NSR250 SE red/white/green
1994 MC28 NSR250 sp W/ RS250 engine

TuckerBag wrote:You should NOT apply heat the the crankshaft to pull it apart.
To explain how to do this properly, to someone who has no experience, would require a small book and about 10 hours practical experience.
You need to find someone who is a specialist in rebuilding crankshafts.
Perhaps ask your local engine re-conditioner if they know of anyone?

Do you have any recommended for that ? I'm in California and racing here, early and late will meet up the problem...
_________________
1996 HONDA RS250
1995 MC28 NSR250 SE red/white/green
1994 MC28 NSR250 sp W/ RS250 engine

It would be very difficult to tell someone on a forum how to rebuild a crank.

I've never managed to strip an NSR250 crank in 20 mins let alone rebuild one. And once it's rebuilt, the 'fine adjustments' can take literally hours if you're trying to get it within next to nothing.

The trick is to know when it's as good as it's gonna get.

.... 'yeah, nearly there'...just one more tap with the lead hammer and...ok f*ck.

Been there, done that

Matt, you are so right
_________________
I don't mind dying...I just don't want to be there when it happens!

Some cranks just cant be trued up perfectly.

If the crank pin bore centers are not exactly the same offset from the center line of the crank then you'll spend all day knocking it back and forth.

If you're left with any runout, make sure that it's inline with the crank center and the pin bore, and on opposite sides of the crank. That's about it.....put the kettle on.

Here's a quick rundown for a single cylinder crank:

If the runout is on the same side of the crank then the crank's either spread or pinched, so you need to spread or squeeze it. Always do the spreading or squeezing as far away from the crank pin as you can.

If the runout is at opposite sides of the crank at around 90 degrees to the center line of the crank and center of pin bore then it's twisted, and needs a wallop on the low side.

It sounds easy, but gets more frustrating as you get it closer to true.

An NSR crank is not much different as long as the center wheels are indexed accurately in the first place. But it does take longer. You can get them within Honda spec pretty quickly, but getting them on the money is a different story. But it's worth it as the engine makes more power after peak, revs harder and the crank lasts longer. Why wouldn't you do it?

Matt@TYGA wrote:Some cranks just cant be trued up perfectly.

If the crank pin bore centers are not exactly the same offset from the center line of the crank then you'll spend all day knocking it back and forth.

If you're left with any runout, make sure that it's inline with the crank center and the pin bore, and on opposite sides of the crank. That's about it.....put the kettle on.

Here's a quick rundown for a single cylinder crank:

If the runout is on the same side of the crank then the crank's either spread or pinched, so you need to spread or squeeze it. Always do the spreading or squeezing as far away from the crank pin as you can.

If the runout is at opposite sides of the crank at around 90 degrees to the center line of the crank and center of pin bore then it's twisted, and needs a wallop on the low side.

It sounds easy, but gets more frustrating as you get it closer to true.

An NSR crank is not much different as long as the center wheels are indexed accurately in the first place. But it does take longer. You can get them within Honda spec pretty quickly, but getting them on the money is a different story. But it's worth it as the engine makes more power after peak, revs harder and the crank lasts longer. Why wouldn't you do it?

I believe Matt said...and that's what i agree with..
_________________
1996 HONDA RS250
1995 MC28 NSR250 SE red/white/green
1994 MC28 NSR250 sp W/ RS250 engine

Matt@TYGA wrote:It would be very difficult to tell someone on a forum how to rebuild a crank.

I've never managed to strip an NSR250 crank in 20 mins let alone rebuild one. And once it's rebuilt, the 'fine adjustments' can take literally hours if you're trying to get it within next to nothing.

The trick is to know when it's as good as it's gonna get.

Matt

I believe the chinese guy is bullshit, or he is making garbage and the guy said only 30 dollars charge to work, good luck for his customers.

Matt, can you rebuld that, please PM me for price detail. I will send it to ya.
_________________
1996 HONDA RS250
1995 MC28 NSR250 SE red/white/green
1994 MC28 NSR250 sp W/ RS250 engine