All Things CR250

Sam Moss · Joined: 28 Aug 2012 Posts: 16

On a cr250 we don't run water cooled cases but new twins do, other than DEA which uses a gallery at the front of each cylinder. I think gallery is the word I'm after?

My question is due to not having water cooled cases do we see a loss in power from cases getting hot around the crank and loss of possible pressure?

Ian Harrison · Posted: Mon Oct 08, 2012 6:04 pm Post subject:

H Sam

You could have just given me a call Wink

Yes, with "heat soak" the cases become hotter throughout a race. This causes the incoming cool mixture to be heated up and therefore the density reduced.

Less mixture into the cylinders = less power.

The DEA has heavily finned cases, so it looses heat to the air (like aircooled cylinder fins), whereas others circulate the cool water returning from the rads through the cases and then up into the cylinders to keep the crank chamber walls cool hence power remains more consistent.

Next time your at Anderson's ask Russell to show you the DEA cases, if he has one in the shop. The castings (they are sand cast) are a thing of beauty!!

Best Regards

Ian Very Happy

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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

Sam Moss · Joined: 28 Aug 2012 Posts: 16

Thanks Ian, I didn't think you'd appreciate a call from a noisy factory in the middle of the night Smile

Ian Harrison · Posted: Sat Oct 13, 2012 5:00 am Post subject:

Hi Sam

Your probably right!!

Glad to hear your keeping the wheels of industry turning Cool

See you at Donington Very Happy

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

Dan Davis · Posted: Tue Oct 23, 2012 2:59 pm Post subject:

Howdy All!
Does anybody (Ian Wink

) know the difference between the wrist/piston pin bearing called out for 1989-2004 CR250 with P/N 91015-KZ3-003 and the 2005-2007 with P/N 91015-KSK-731? Besides double the price for the earlier bearing?

On top of that, ProX calls out the same bearing for 86 and 07 P/N 21.1316

Different supplier maybe ??

Chris Reinhardt · Posted: Tue Oct 23, 2012 6:15 pm Post subject:

The older bearing is twice the price, generally in the Honda you are correct they found another supplier. That also means that the old part's life is on borrowed time. In general terms, the later stuff is of better quality, I know all the 125/250 stuff 05-07 was the latest and greatest before they put the kibosh on 2 strokes...

I see the wrist pin on the older models updates to a KSK model, so it's a matter of time for that bearing.

Maybe Ian has hands on experience with that bearing....

CR
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Roger Miller · Posted: Tue Oct 23, 2012 7:45 pm Post subject:

We have 2002/03 engines and use the KSK bearing and pin from the 2005/07 parts lists.

Dan Davis · Posted: Tue Oct 23, 2012 7:59 pm Post subject:

Excellent!
I'll buy a burger with that savings. Wink

Ian Harrison · Posted: Wed Oct 24, 2012 1:46 am Post subject:

Hi Guys

We always change the little end (wrist pin) bearing when we change the piston. That little bearing has a hard life!! KSK and KZ3 Honda bearings are interchageable.

I have to say that I have seen a few recent "early life" failures with the KSK bearing. I have spoken to other UK tuners/engine builders and they have seen the same thing. That's strange as the KSK actually looks stronger??? By "early life" I mean in less than the life of one piston. Not huge numbers, but perhaps enough to make you think it's a little more than a string of coincidence/bad luck.

The earlier bearing had a very dark finish on the cage (sort of very deep brown/gunmetal) as does the Prox. The KSK part number has a cage that is (currently at least) a mid-grey colour.

We actually source a high quality bearing direct from Japan (just waiting for new batch), or have found in the past the bearing that Pro-X supply to be very good also, although it does have slightly shorter rollers, so perhaps a tiny bit less stability, but the bigger side shoulder perhaps adds more strength to the cage. All the bearings have 15 rollers.

Apologies for image quality:

Right - Honda KSK little-end bearing
Centre - Honda KZ3 little-end bearing
Left - Prox little-end bearing

Dan - put that burger on hold

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

Dan Davis · Posted: Wed Oct 24, 2012 8:57 pm Post subject:

Oh well, i guess I'd rather pay $6 more now versus hundreds later. Thanks for all of the input everyone!

Sam Moss · Joined: 28 Aug 2012 Posts: 16

Any chance we could get away with something like this Question

Surely the rings are very prone to catching and making a big mess Question

http://www.bikechatforums.com/viewtopic.php?t=232424

Also could you explain eyebrow ports a bit more. Not much is said in Mr Bells book.

Gerry MacNutt · Posted: Sun Nov 04, 2012 1:58 am Post subject:

Hi, while were on the topic of the small end, will the 2001 wrist pin work on the 2002 motor?

John Benson · Posted: Tue Nov 27, 2012 7:12 pm Post subject:

Does anyone know the actual power loss from high water temp? Say the difference between 150f and 180? Thanks John.

Riley Will · Posted: Tue Nov 27, 2012 8:09 pm Post subject:

Over 140F is 10% on our engines. 180F would be 15%!
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Ian Harrison · Posted: Tue Nov 27, 2012 8:10 pm Post subject: