281 replies to this topic

[pablo83 TT Silver Member]

cleonard said:

It's in the forest service Spark Arrester Guide.  This is the publication that has every approved spark arrestor in it.  You are right that no ranger will know this so print out those few pages you need and carry them.  It's here http://www.fs.fed.us...OHV_SAG2007.pdf  The page requires a username and password.  Both are t-d

From this document on the 17th page from the begioning

thanks, I appriciate that.

[HeadTrauma Get Help Now]

I take the NFS's wording to mean that all the exhaust has to flow through the turbine all the time and that wastegated systems(which allow exhaust to bypass the turbine by nature) must still have a spark arrestor.

[Captain Midnight TT Gold Member]

pablo83 said:

That's pretty cheap.  I may be into it farther down the line.  What type of trigger is required?  Will the stock one work?

The stock pickup can be used, but the single tooth wheel is replaced with a 36 tooth wheel.

[pablo83 TT Silver Member]

HeadTrauma said:

I take the NFS's wording to mean that all the exhaust has to flow through the turbine all the time and that wastegated systems(which allow exhaust to bypass the turbine by nature) must still have a spark arrestor.

Yes, it sounds like you either need an arrester on the wastgate, or no wategate.

[cleonard I ride therefore I am.]

pablo83 said:

Yes, it sounds like you either need an arrester on the wastgate, or no wategate.

That's sure what it sounds like.  Oh well so much for that one.  I have used that document to get of of bogus spark arrester tickets on my stock exhaust.  I remembered the turbo exemption, but never really read it.

[HeadTrauma Get Help Now]

I think it probably is aimed more at utility equipment like diesel tractors, trucks, generators, trains, etc, that often use non-wastegated turbo systems.

The turbo may not knock the exhaust noise down enough to get away without a muffler/SA anyway.

[pablo83 TT Silver Member]

I got the materials for the manifold.  It will be made out of Sch 40.  All other piping will be thin wall.  I drilled the flange and cut it with an oxy-acetylene torch and cleanded it on the grinding wheel.  When I started to fit it up I noticed there will probably be interferance between the turbo and the fork brace as the forks compress.  So I need to put the bike back on the lift and removed the springs to re-check the travel.  Problem is I have another bike project on the lift so the turbo will be put on temporary hold again.  This is going to take forever.

[Ryanthegreat1 TT Gold Member]

Sweet!

Nice progress pictures, keep them coming.

[XR650L_Dave TT Addict]

Keep an eye on where the front tire e4nds up with the forks compressed, too.

That's the reason for the loopy left-hand exhaust pipe, I think.



Can't wait for the next installment- get to work!


Dave

[pablo83 TT Silver Member]

The turbo will have to be moved lower.  This is the original placement:


This is shown with the front wheel fully compressed, but I did not run it up and down to check for intereference.  It turns out the fork brace will hit.

But right now the bike is back together and running NA.  I was supposed to get an XR600R that I was going to install an oil pressure gauge on, but that deal fell thru. So I'm going to put a gauge on the NX to make sure it makes enough pressure to supply the turbo.  If anyone has suggestions on a good oil pressure gauge, let me know.

For now I'm going to document most of the mods I've already done to the bike.  Right now most of this information is in different places and I'd like it all together.

[pablo83 TT Silver Member]

Front end

I came up with a brilliant plan to move the rear rim (17x2.50) to the front and lace a 17x3.50 to the rear.  As it turns out, the holes in the rim are drilled at very specific angles so if the rim is made for a fat hub that contains drum brakes (like the NX rear hub) it will not lace up to a normal hub (like the front hub).  So I ended up buying a CARC front rim for the bike.  I like the rim, it trued up very evenly.

The 17” front rim drops the front end 2”.  I also owned an XR650L at the time.  The XRL’s front suspension happens to be 2” taller than the NX’s.  So I swapped the two front ends.  Then I put a rear lower link in the XRL to correct the geometry and I sold the bike.  At first I felt kind of crappy selling a bike with downgraded suspension, but as it turns out there are a lot of people who want a shorter XR650L.  The front suspension on the NX is now great for trails (although the sumo tires aren't that hot in mud or sand).

If you want to do this fork conversion on your NX you'll need the forks, triple trees, axle, speedo drive, speedo cable, wheel spacer, bearings, and brake caliper from the XRL.  You'll need to do a little grinding so the ignition switch won't rub, but otherwise it bolts right in. The steering lock will no longer line up, but that's not a big loss.  The biggest thing to consider is that these forks are 2" longer than the NX's.  To fix the geometry issue you can do a supermoto conversion or put a taller shock in the back to jack it up to match.  If you did nothing with the back it would not be a big deal. The longer front forks would give you more trail, and therefore more high-speed stability, but the bike would not corner as sharp at low speeds.

[pablo83 TT Silver Member]

Rear wheel / brakes

The rear wheel (17x3.50) and brakes are from an '87-'90 CBR600F "Hurricane". I've found a number of these bikes for less than $500 on Craigslist.  It was an easy conversion, but it required some welding. I cut the brake stay bracket off the CBR swingarm and welded it to the NX swingarm. I welded a mounting point for the master cylinder to the frame. I also modified the brake pedal (But I think you could use an XR650L pedal instead).

[pablo83 TT Silver Member]

Brakes

After doing the sumo conversion I took the bike for an aggressive spin around town and completely faded out the front brakes in less than a half mile.  I’ve since upgraded to an EBC 320mm front rotor which has stopped the fading.  I still feel the front brake is not strong enough and I hope to replace them with something more appropriate (as soon as I come into a crap-load of money)

The rear brake (CBR600F) is a two pot caliper so now the rear brakes work better than the front. This isn't a problem on asphalt, but on dirt it locks up too easily.

[pablo83 TT Silver Member]

Other bits

I have the RSW racing fork brace up front and I think it’s a great help in high speed turns.

For the rear fender I’ve spliced an Acerbis fender into the stock one.  It looks great, but I should have gone with the LED version.  The fiberglass patch between the two pieces is starting to come apart and will need some beefing-up this winter.

[pablo83 TT Silver Member]

rear shock

I've used an '95 XR200R shock for this conversion. Here's a pics of the two side by side:


The NX's shock is 13.5" bolt center to bolt center.  Any 1984-on XR200R, or XR250R should be the same (I think), but some are 13.25". The height can be adjusted by threading the lower mount on to a different height.  

The XR200 (non-"R") will not have a remote reservior.

Both springs came off without special tools, but I had to use a spring compressor to get the NX spring on the XR shock. The XR shock has a spacer below the lower spring seat. I've removed it to give the NX spring more room. It's the large castle nut looking thing sitting on the table:


Here it is installed in my dirty bike. It bolts in with no bracket modification.


The remote reservior line interferes with the airbox. Below is a picture of the gap left with the airbox resting against the remote line. I'm getting rid of the stock airbox, so this won't matter to me. The '82 CR450, or '83 CR480 shocks have a remote reservior line that comes off the side and shouldn't interfere with the airbox, but these shocks are 1-1/4" taller than the NX's, so they will raise the back if they will even fit.

[racetwins TT Newbie]

Pablo,

We talked last year, I have the NX in Woodland Park with a set of sumo wheels.

Considering no one ever modifies these old bikes you must have the trickest one anywhere. I am somewhat stunned at all the mods you have done to this bike.

I'm going to have to see this sometime.....Wow

Kevin

[pablo83 TT Silver Member]

racetwins said:

Pablo,

We talked last year, I have the NX in Woodland Park with a set of sumo wheels.

Considering no one ever modifies these old bikes you must have the trickest one anywhere. I am somewhat stunned at all the mods you have done to this bike.

I'm going to have to see this sometime.....Wow

Kevin

There's a guy named Carlos (I think he's in Portugal) who has an NX that's probably had more mods done to it than mine:

http://ateaofimdomun...120968504_yTvxc

But you're right, there sure aren't many highly modified NX's out there.  I took the bike out to Rainbow Falls yesterday.  The suspension is set way to soft.  I went off one of those jumps on 348 and bottomed the rear out and knocked the regulator off it's mount.  I didn't have any tools because I threw the trip together in a hurry so I rode home with the regulator hanging by the wires.

On my way in there was a guy hiking out.  He had come over a hill and it was all ice on the other side.  He slid to the bottom and couldn't get out because it was uphill ice in both directions.  He hiked out ten miles in his riding boots.  He said he would have to go back today with a quad and pull the bike out.  ouch.

We'll have to meet some time.  I'm planning a Moab trip in about 4 weeks if you're interested, but I'll mainly ride my WR.

[UncleBob TT Silver Member]

the "simple" answer on the turbo is to mount it lower and install a scavenge pump....that was what I ended up doing.  

Not what I prefer to do, but dirt bikes just aren't friendly to turbo placement.  Looks like you have more room than my DRZ.....

[HeadTrauma Get Help Now]

That or put it where the airbox is...

[UncleBob TT Silver Member]

HeadTrauma said:

That or put it where the airbox is...

wouldn't recommend it....it would compromise the size of the air box and cause tuning issues.