CR500AF update

[sticky throttle]

I ended up finding a Ti spring from a different manufacturer (RCS), that had the same OD as a
steel spring.  Even with that, I had to radius the case.  To do that, use a grinding disc the same
OD as the spring and run it off the center line of the case, I took off 2mm.  Remember, that
part of the case is not part of the transmission seal, just surrounds the swingarm pivot bolt
passage.  After grinding, hit it with 320 then 400 grit wet sandpaper and finish with WD40
and a Grey or Green Scothbrite pad to return the surface back to normal.

Here's a picture:



dogger

Ok I see what you've done. I'm in the same boat. I 'm thinking of possibly making a longer link, about 2mm, but then I need to mess with dropping the forks and or offset clamps.
I like the idea of coping the case because I dint have to mess with anything and still have a lot more adjustably for chassis set up. How much meat is in the case at that area where you coped it? I'll look at the parts to try and figure it out.

[GlennC]

Hey Dogger, I have a couple of questions for you.
Is this the build that is posted on the cr500riders site?
if so are you still doing a CR250 conversion in the near future?
I am considering puting a 2001 CR250 engine into a 2004 CRF250R frame, I was looking for some advise with the project.

GlennC

[dogger315]

Looks like you have an amazing piece of work there. Thats gotta be pulling 55+ at the rear minimum

Thanks a bunch!  Don't know what it's producing at the rear wheel, but it's enough to put a big
grin on your face.

I 'm thinking of possibly making a longer link, about 2mm, but then I need to mess with dropping the forks and or offset clamps.

Unfortunately, changing the length of the pull rods will not move the shock further from the case.  Because the dogbone position is fixed, longer
pullrods will only rotate the dogbone counter clockwise.  All this will get you is a change in the vertical axis for the shock (lower your seat height).

How much meat is in the case at that area where you coped it?

There is about 5mm.  Here's a picture:



My Ti shock spring is rated at 5.3kg/m.  It's the same diameter as a 5.8 kg/m steel spring.
Radiusing the case should work as well for your bike.

Is this the build that is posted on the cr500riders site?
if so are you still doing a CR250 conversion in the near future?

Yes, it's the same bike.  I'm working on that CR250 project right now.

I am using a 2009 CRF 250R frame and adding a copy of a 2007 CR250 cradle.
I'm taking this conversion up a few notches.  I used a handheld laser scanner
to scan the 07 and 09 frames and the 00 CR250 engine.  The plan is to do all
the design work using CAD (SolidWorks), then produce the new cradle rails
and engine mounts with CAM.  After a lot of digging, I finally sourced the radiused
corner square metric tubing that Honda uses for the cradle.  The engine mounts
will be reproductions of the OE Honda mounts using 6061 Aluminum stock.  I'm
using the hoop from an 07 CR250 donor frame, but the CRF hoop will work just
as good.

This conversion is proving to be much more difficult than the 500, partly because
of my insistence on no billet frame members, and partly because the CR250 engine
shape is more difficult to adapt.

Here's a couple of pictures of the 00 CR250 engine I built for the bike:





If you have any questions, PM me.  I'll be happy to fill you in.

dogger

 

[sticky throttle]

Wow Dogger Thanks!! I cant even explain how much you just helped me. It looks as though there is very little structural bearing on the swing arm pivot bolt at the center point of the case. It appears the pivot bolt has contact on the outward portions of the case and also looks like an actual steel collar pressed in to the case so there is no wear.
I'm still going to make a few calls tomorrow and see if I can find a smaller diameter spring at the same spring rate
and provide more clearance, even with it coped.
Thanks again!

[SachsGS]

Aren't the Honda frames a 7000 series self hardening alloy whereas the 6061 you would normally treat to T6?

I recall reading in DB magazine about a 2000/1 CR250 AF conversion, who did that one?

[Lolerbabop]

Will you try out the SmartCarb?

[dogger315]

Aren't the Honda frames a 7000 series self hardening alloy whereas the 6061 you would normally treat to T6?

Yes, Honda uses 7075-0 Alloy for the frame rails and extrusions and 6061-T6 for the various brackets and engine mounts.
The "0" state for the 7075 results in a tensile strength of 40,000 psi.   The "T6" state for the 6061 yields a tensile strength
of 42,000 psi.  That's the exact same combination I'm using.  The goal is to maintain the same strength and flex to preserve
the OE chassis dynamics.  That's not the case when you replace a tube cradle with a solid billet piece. 

I recall reading in DB magazine about a 2000/1 CR250 AF conversion, who did that one?

Not familiar with that test since the 2000/01 CR250s were already "AFs".

Will you try out the SmartCarb?

I may try one down the road.  Right now, I'm using a PWK S with TPS and a power jet.  The carb electrics will be run
with a Vortex digital, programmable IC.

This engine is a carbon copy of the engines TMR built for me back in 2000-01.  Those engine produced mid 50s
hp on VP MR2.  MR2 is no longer being produced so I switched to Renegade SX2.  The SX2 is a close copy of MR2,
so I'm expecting similar results.  54-56 hp in a bike that should have a dry weight under 200 lbs - If the smartcarb
claims are true, mounting one would be complete overkill on a bike like this.

dogger

[citabjockey]

Dogger - that bike ALREADY is complete overkill!   LoL

But I love it! Just have to find someone that can ride it to its full potential and then go to Monster Cup and take home $1M

54-56 hp in a bike that should have a dry weight under 200 lbs - If the smartcarb
claims are true, mounting one would be complete overkill on a bike like this.

dogger

[gpnewhouse7]

Dogger I'm a big fan of your work but in just wondering where you get the 54-56hp claim from? Have you dynoed these engines in the past or is it just a guess? Also is this at the crank or at the wheel?

I'm just curious because the new KTMs only make 51hp and KTM have always been known for having the most powerful motors.

Apart from that I'd just like to say great work on the 250 and 500.

[dogger315]

First, thanks to you both for the good word.

just wondering where you get the 54-56hp claim from?

Those claims come from dyno runs performed by Tom Morgan back in the
day.  This engine is a copy of the engines he built for Heath Voss and Co.,
when they were riding for Blackfoot Honda.  The dyno numbers were in the
53-55 hp range on race gas.  I have added oxygenated race gas (not legal
in AMA pro racing), which is good for 1 to 2 additional hp, so I'm upping the
number to 54-56 hp.

the new KTMs only make 51hp

Only ,  That's a big number from a stock production engine  The stock 00-01
CR250 engine only produced 47 hp in comparison and it was the king of the hill
at the time.  FWIW, it cost me almost as much as a new 250SX to build this
engine, but like my 500, it isn't a budget build.  Adding horsepower and
reliability doesn't come cheap.  Besides, what's the point of going through all
the trouble of building a two stroke conversion that's down 5 hp to the
competition?  The goal is to produce the fastest, lightest and the best handling
and suspended 250 two stroke on the track - whatever it takes or cost.

dogger

 

[gpnewhouse7]

Ahh okay.

And I put ?only? 51hp for the KTM because its had 12 more years of development not because 51hp isn't a lot.

[SachsGS]

Is that the Blackfoot Honda out of Calgary, Alberta?

[dogger315]

Is that the Blackfoot Honda out of Calgary, Alberta?

Yes it is.  They had a good, well funded satellite team with some
talented riders and a back door deal with Factory Honda for some
"works" parts.  TMR built the engines for them and those engines
were reportedly very close to the Team Honda engines according
to riders that had the opportunity to ride both.

because its had 12 more years of development

Interesting thought.  I remember talking to some of the folks at
Honda about this same subject years ago.  They said at the time,
the current design piston port engine had been developed about
as far as it could be.  Some of the engine builders I worked with
said the same thing. 

I am always bagging on Honda for ruining the CRs with the case
reed engine, but it may have been a case where funds and R&D
were being diverted to the fledgling four stroke program and the
case reed design never got a chance. 

If all of the R&D Honda normally put into an engine had been
devoted, the "RC" may have developed into another big power
arm stretcher like so many of it's predecessors instead of the
last place bike stinking up all the shootouts.

dogger