Vintage Dirt Bike Q & A

I'm replacing the fork seals on my '78 CR250R and need to know the amount of OZ's or CC's to put in each leg. I tried the "Search" and had no luck. Also, I'll be using 20wt. fluid. Thanks for any info.

275cc per leg. 20 wt is quite a jump from the 5 wt specified.

dogger

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1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R

Dogger315, thanks for the info. I'm kind of new to the vintage scene and a couple of guys recommended 20 wt. Maybe because I'm heavier (235 lbs.) than the average rider, but I did use stiffer springs from Vintage Iron. What would I notice between 5 wt. and 20 wt. ? Thanks again.

Suspension tuning is something you kinda have to sneak up on.
I like to establish a baseline with stock settings. I record this
information so I always have something to return to if my
testing gets me going in the wrong direction. I keep a log
and record every change and what it does or doesn't do.
If you race more than one track, this info can be a big help.

For years, Honda spec'd the suspensions on the 250s for the
"mythical" 165 lb intermediate rider. For many, this meant the
suspension was too soft and easily bottomed out.

Using heavier fork springs is a good idea. Upping the oil viscosity
three grades over stock may make the forks too stiff and also
too slow to rebound.

Since it is easy to change fork oil, I recommend you start with
10 wt along with the heavier springs. Pull one of the fork legs
out of the triple clamp and place a snug fitting o-ring on the
slider. Button everything up and put in a couple of hot laps
noting how the bike handles and feels. Then take a look at the
o-ring to see how much travel you used. This is the sneak up
part I was talking about. You can fool around with the oil viscosity
and the oil amount to "tune" the forks to your weight and speed.
Another device that might help is a set of air caps. This will give
you one more way to fine tune. There is also a good article in the
reference section by "Red Rocket 190" detailing how to add a little
plushness to the fork action.

Remember, whatever you do to the front, you will have to do to the
back to maintain balanced handling.

This is the "testing" portion of racing motocross. This is what the fast
guys with the big salaries do all week long and why they usually finish
the season with a much better bike than they started with.

dogger

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1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R

Check out the Al Baker mod specified in the CR Reference section...

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

How do you access the CR Reference section?

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

http://www.honda-elsinore.com/
Click on Reference....

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Thanks for all the help and information.

Any idea if the above listed capacities are the same for the fork of a 1976 MR250? Same weight oil as well?

-Thanks,
Craig

Since the forks on a 76 MR are a good deal smaller than the 78 CR, I would say no.
I'm pretty sure the oil viscosity is the same but I'm guessing the quantity is going to
be less.

Hey Ray, another MR question.

dogger

_________________
1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R