MX to Enduro Conversion Wisdom -or- "How to make a pain in the a$$ of yourself" <long>
sTeVe?
The following is an e-mail exchange between myself and Jim Smith,
formerly of CRE Imports. Jim has the patience of Job and answered all
of my questions. I reprint it here because it contains losts of cool
info for anyone converting an MX’er to and Enduro mount.
sTeVe?
Aged CRE 275 or whatever the heck it is pilot
Note: like a "Red Letter" edition of the Bible, Jims words are all
hightlighted (for those of you with decent software.)
We start after my first groveling e-mail begging for his infinite
wisdom and expertise.
>Steve,
>No problem, ask away.
>Did I build you a complete bike, or did you get a 270 kit?
I built it bit at a time. Actually I presently have two. One I built
with the 270 motor in it and a 16 oz A-loop flywheel and one stock 250
with a W00051A Ignition set. My current plan is to run my 270 motor
with the weight. I don't know if you read my post re: Speedsville but
I did more or less get the bottom end back by going to a 12/48
sprocket combo (CRE sent me a 116 link chain and I couldn't use the
13/52 sprockets I bought.) I had plenty of low end in the dry
conditions at Michaux. In fact, without the sprocket incident I had
the points for third, (I know, no "what if" games, I was just happy to
find out I can be competitive in the B class.) I am still concerned
that the motor may be too pipey in the greasy stuff. The 270 gives me
awesome low rpm throttle control and still has huge boost with a slip
of the clutch.
>Are you running race gas or premium pump fuel?
>What oil, and oil mixture are you using?
I run 3 gal 93 octane with 2 gal 110 octane Cam 2 at 40:1 Golden
Spectro.
>Suspension, we need to start with your riding style, e.g. do you
>ride sitting down for the most part, or stand on the pegs?
Since speaking with you when you sold me on the 270 I have been
standing more. I still sit when the turns are tight or they are
bunched together close (or when I'm really beat). I currently have
springs put in by a 220 lb rider and front Factory Connection and rear
WER valving. The WER seems to have too little rebound as it seems a
bit bouncy when hitting large objects. I like the heavier springs. I
was running stockers on the other bike (I'm 180 lbs plus I have a 10
lb tool pack and every conceivable piece of protective gear) but I
would get a filling knocked out and hear really loud metallic noises
if I hit a large ditch at speed. If I cranked up the compression the
suspension action suffered in the rocks. I really like the current
setup, I am thinking of getting Factory Connection to valve the rear.
>This also brings me back to my earlier question as to who
>built the bike? If I built it. I understand the starting point, and
>we can go from there.
You did the cylinder/head, but that's really it. Everything else is
a-la-carte.
OK, my plan is to use the best from both bikes for my bike and put
together a sale-able beater bike. My decisions to be made are listed
in parenthesis.
If I go with this, the race bike will have: 270 motor with (either
lighting coil or A-loop weight), new PWK 39 mm (with what jetting to
start, air box bottom is sealed and one way valved for Moonshine river
fording and only breathes through the top ), FMF Gold series pipe, FMF
Turbine Core Spark Arrestor, (or stock pipe with Acerbis 035, or
Answer RS2), I think I will stick with the heavy springs and current
valving unless you think it will be worthwhile to have the rear
revalved by (Factory Connection), I may sell the Answer
Pro-Tapers/bark busters/triple clamp (should I?), I couldn't feel any
difference. Other niceties on the newer '94: Excel Rims w/SS spokes,
Scotts Damper, Pirie Composites this and that, IMS pegs, IMS levers,
'96 plastics, CRE seat cover/graphics, tall seat foam, (I may be only
5'9" but I like the extra room it gives my legs when I'm sitting.)
Whew! I thank you in advance for wading through this.
Much obliged,
Steve
aged CRE275 pilot
nj...@webspan.net
To which Jim is kind enough to reply:
>Steve,
>Ok, so you run good gas, your have changed your carb. to allow
>for an idle circuit(if you need an idle that was a good plan).
>Jetting:
>Big bores require leaner jetting then a standard bore engine.
>Why? Well, since each stroke of the piston will move more air
>through any given carb bore diameter, creating a greater pressure
>across the jets which sucks more fuel. So, with out a vast amount of
>experience with the PWK carb., I will say that a main on the order
>of 168/165 will work well(170 for a 250), stock needle, 48/50 pilot,
>you may want to get a leaner slide, but this may not be required.
>Drive Chain:
>I assume that you talked with Raffi. A stock CR(E)(13/50) uses a 116
>link chain did you tell him you wanted to change the gearing.
>13/52 seems a little low. That is what I use on my 150's. It will
>make you ride at least one gear higher in the range.
>We used 13/49 or 13/50 on Kevins 94' Race bikes.
>Boingers:
>I would strongly suggest that you
>have the shock done by Rick at Factory Connection.
>Misc. parts:
>The lighting coil you have, is it one of my new billet units or one
>of the older cast units?
>Regardless, I feel that the lighting coil will provide a better
>response. The magnetic reluctance of the coil will provide considerable
>smoothing under acceleration while also providing better throttle
>response. This is due to the active deceleration provided by the
>magnetic field. Just adding mass to a flywheel slows the response
>on both ends of the spectrum. When you grab a hand full of throttle,
>it takes longer to accelerate the mass so it is smoother (slower rate
>of change), but this also holds true on deceleration. It takes longer
>to bleed off the additional energy so you tend to have a motor that
>pulls you deeper into a corner, or is more difficult to handle in a
>slimy rock garden, where throttle control is needed to maintain
>traction.
>Sealing air boxes - I have always tended toward not sealing the air
>boxes as per say. When I have been faced with a race like Black
>water, Moonshine, etc. I have made a one-way valve with duct tape
>to cover the bottom vent. When you jump into a river, it is a plus
>to have the water exit faster then it enters. Properly oiled air filter
>with a flapper valve over the bottom has always worked out for the best
>Sealing the air box, just holds water in once it gets in, and will tend
>to cause more problems then not sealing it at all.
>Pipes and silencers - It depends on what you want. Regardless of
>what pipe you use the Acerbis 035S/A silencer will provide more
>bottom end. The combination of an FMF MX pipe and the 035 is a
>good one on the 94'.
>Pro-Tapers - They are the strongest bars out there, period. If you
>have them keep them. They do provide some help with your
>arms/shoulders but this is diminished by the addition of barkbusters.
>They will provide a softer ride then Alumalites or Renthals and
>they will not bend.
>I hope that I have answered most of your questions. If not ask away...
>Have fun,
>Jim
Steve annoys Jim some more with more stupid questions:
>Ok, so you run good gas, your have changed your carb. to allow
>for an idle circuit(if you need an idle that was a good plan).
Actually I didn't buy it it came on the second CRE I bought. I do
like having an idle though.
>Jetting:
Read and understood.
>Drive Chain:
>I assume that you talked with Raffi. A stock CR(E)(13/50) uses a 116
>link chain
The bike came with 13/49. That in conjunction with the lack of
flywheel made the bike almost unridable for me at Speedsville.
(Luckily most of the course was FAST) I'm not horribly fast and I'm
pretty much a low to midrange rider. If I bobbled in the middle of a
hill and needed to let off, I had to slide the clutch to get it on the
pipe which generated wild wheel spin. Coming out of really tight low
speed corners required huge amounts of clutch abuse, I felt like I
was riding a clapped out 125. All I changed for the last race was the
gearing (to 12/48)and I was much happier. I could actually get the
power I needed to the ground without, in many cases, even going to the
clutch. I'd rather ride it a gear high everywhere else and have a
stump pulling power 1st gear to get my spodely butt out of trouble.
>13/52 seems a little low. That is what I use on my 150's. It will
>make you ride at least one gear higher in the range.
>We used 13/49 or 13/50 on Kevins 94' Race bikes.
Point made. Kevin probably can't even think that slow.
>Boingers:
>have the shock done by Rick at Factory Connection.
Done.
>Misc. parts:
>The lighting coil you have, is it one of my new billet units or one
>of the older cast units?
Cast.
>Regardless, I feel that the lighting coil will provide a better response.
>The magnetic reluctance of the coil will provide considerable
>smoothing under acceleration while also providing better throttle
>response.
Do the lights need to be on to get this reluctance? Maybe this is my
problem. Again, with the gearing I have now, I am more likely to stick
with the coil and let myself grow into the bike. There was less low
end with the coil than the weight but I can at least live with it.
>Sealing air boxes - I have always tended toward not sealing the air
>boxes <snip> When you jump into a river, it is a plus
>to have the water exit faster then it enters.
My concern is with the water entering from the bottom. One year at
Moonshine the river was 2.5 feet deep! I'll give the flapper valve a
try and seal the side joints again with silicone.
>Pipes and silencers - It depends on what you want. Regardless of
>what pipe you use the Acerbis 035S/A silencer will provide more
>bottom end. The combination of an FMF MX pipe and the 035 is a
>good one on the 94'.
Should I go leaner still on the jetting if I install the 035.
(yucchh! I hate repacking the 035.)
>Pro-Tapers - They are the strongest bars out there, period. If you
>have them keep them. They do provide some help with your
>arms/shoulders but this is diminished by the addition of barkbusters.
Can I make a shoulder bolt on the lathe and let the bark busters pivot
at the inner connection?
Jim, thanks so much for giving me your valuable time. I have learned
a tremendous amount. It is very much appreciated. If you don't
object, I'd like to edit and post some of this in RMD. Much of it is
useful to anyone converting an MX'er.
Thanks again
Steve
Jim Smith patiently replies:
>The total lack of an Idle circuit in the PJ carb. is a problem for anyone
> who is used to or needs a bike to idle. Just turning up the "Idle screw"
>which is in fact the choke circuit, causes the bike to run lean and become
>harder to start. When you run the carb. with the screw turned all the way in
>bike stops when you let go of the throttle, the carb. will meter fuel much
>better, and the motor will come alive in the low end.
>You will get more effect by running a light. The new billet units
>are much higher output and provide more smoothing. You may want to
>look into upgrading, by selling your original with the bike you sell, or to
>someone else and get the new unit.
>Your jetting will not significantly change with the 035, and they do suck >
>when it comes time to change, that snap ring is a bitch...
>The shoulder bolt will help, the draw back is that unless you have good
>quality metal bar end clamps (WER or End Eng.) they will work loose on
>you. I assume/hope that you have the End Eng. Pro-Taper bar clamps,
>they are the best ones out there.
>A further extension of the airbox flap is to use a piece of 1/8" wet
>suit material pop riveted to the bottom of the airbox as a flap seal.
>It kind of flaps around, but when you hit water it comes up and
>seals quit well. Back in my KTM/Husky days I used to do this.
> You will have to grind down a bit of the lip around the drain vent, however.
>Have fun,
>Jim
Thanks again to St. Smith.
Steve
aged CRE275 pilot