cr 250 cranks

shaun everard · Joined: 28 Feb 2009 Posts: 111

Will a 2005 crank fit into a 2001 cr????

Ian Harrison · Posted: Wed Aug 11, 2010 12:04 pm Post subject:

Hi Shaun

This is the second time today that this question has arisen!!

The crankshaft will physically fit into the cases. The problem is that the big end eye comes very, very, very close to the cases so in the event of a main bearing or big-end failure you can more or less guarantee that you will split the cases.

You could of course "trench" the cases to provide a bit more clearance, but this will make the sealing flange thinner and more prone to damage from a gentler knock.

My advice is not to do it and just rebuild the crank with a new rod kit after 1 year and replace your standard 2001 crankshaft with new every couple of years.

Best Regards

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

shaun everard · Joined: 28 Feb 2009 Posts: 111

I'm guessing you were asked this by Andy Dean he asked if I new any one who would no I said yes you Ian the cr 250 God.... [/u]

james jackson · Joined: 02 Dec 2007 Posts: 305

Do the 05 cr cranks use a larger crank pin than the 92-01? how much bigger is it?

Ian Harrison · Posted: Thu Aug 12, 2010 7:00 pm Post subject:

Hi James

'92 - '01 = 24mm
'02 - '07 = 25mm

Best Regards

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

Jeff Pickel · Joined: 14 Mar 2009 Posts: 84

This crank will be going into a cylinder reed valve motor after the mods to crank for clearance issues and changing of bf.[/img]

[img]

[/img]

Ian Harrison · Posted: Sun Apr 29, 2012 4:14 pm Post subject:

Hi Jeff

Don't forget that if you skim the periphary, that the rod big-end eye will still protrude and describe the same outer profile as it rotates.

You may have to machine some off the outer of the rod big-end eye or the case, I have found the rod eye taps in one or 2 places, but not everytime. you may also want to do this to increase clearance anyway. The O/E rod is plenty strong enough. Don't know about some of the Taiwanese offering like Mitaka or Hot Rods.

Install the crank in the side cases one at a time and fit the cylinder and piston, so you can see what's going on.

Rotate and check for fouling or very close proximity.

Apologies if this advice is basic to you, but it may help others.

Best Regards

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

Christian Garcia · Joined: 22 Apr 2012 Posts: 19

What about putting the 05 crank in the 02-04 motors and getting rid of the tin covers? Is this a better option?

Christian Garcia · Joined: 22 Apr 2012 Posts: 19

What about putting the 05 crank in the 02-04 motors and getting rid of the tin covers? Is this a better option?

Ian Harrison · Posted: Mon Apr 30, 2012 11:26 pm Post subject:

Hi Christian

Yes it is, and we do it all the time in our race motors.

It's just a straight swap, no machining and no issues.

We have found the standard balance factor of the '05 crank fine for Superkkart racing where you are running between say 9,000 and 11,500 rpm.

Best Regards

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

Jeff Pickel · Joined: 14 Mar 2009 Posts: 84

here is what it looks like under the stuffers.

here is the crank installed in the cylinder reed case.

here is the crank after the machine work and different balance factor

Ian Harrison · Posted: Mon May 14, 2012 12:18 pm Post subject:

Looking good, Jeff

Be interested to know what balance factor you went for and how it works/feels in practice, once you have it running.

Best Regards

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

Jeff Pickel · Joined: 14 Mar 2009 Posts: 84

22 races later at 11,000 rpm no vib or issues.

Jeff Pickel · Joined: 14 Mar 2009 Posts: 84

good crank

Ian Harrison · Posted: Sat Feb 09, 2013 6:19 pm Post subject:

Hi Jeff

Great job.

Obviously just by skimming the periphery you decrease the balance factor as you remove more weight from the "bob-weight" side, where the crank flywheels are thicker. However, if you machine the outer of the big end eye you lighten it, which goes to counteract some of the effect of the skimming.

Beyond that I don't see any drilling or insertion of tungsten (Mallory metal) bar.

Just wondered if you actually know the percentage balance factor you are running, where in the rpm range you feel the worst vibration periods through the seat-of-your-pants Shocked

and the type of chassis that you use?

Here's 2 examples of variously weighted/balanced cranks for the same engine.

My own inclination (prior to start of testing) is an increase in crankshaft mass and a balance factor of around 75%. I'll post my results when the testing is complete.

Best Regards

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012