CRF100 Mini-Motard Build

[ACDNate]

I suppose it's more of a upgrade than build. Here's a little background

I bought the bike in this form

PO had stuck some Bridgestone BT45's on it and took it racing. Bike had sat for quite a while as he had moved on to a 85cc 2 stroke.

I went through the bike giving it a good scrub down. Put on some new bars and barkbusters, sorted out the jetting, got some heavy springs front and rear, and put my number on it.

After racing a few weekends I started working on getting things tuned in a bit better. I swapped the throttle to a TBolt 1/4 turn unit. That helped immensely in itself, the 2 handfuls the stock throttle required just didn't work for the track. I swapped out the stock 19" front wheel for a 16" XR80 wheel, and added a RSW Racing fork brace. I also ditched the airbox in favor of a pod filter and re-jetted accordingly. This really woke the bike up, particularly in the handling department.

I raced it the rest of the season in that form.

[ACDNate]

Fast forward to today. I looked at changing bikes to get myself a disc front brake and a bit more power. The cost just was adding up in favor of a newer bike. So I've turned my attention to upgrading the 100.

Earlier this week I found/bought a 1986 CR80 basket case.

I got it tore down and am currently working on getting the forks rebuilt to mount up to the 100 so I can have my front disc brake and a 17" front wheel. The brake system with the 80 was trashed so I'm still hunting eBay for a brake setup from a crf250. I'll then add the EBC rotor and caliper re-locator kit.

Next up will be the engine.

I've pretty much decided on the BBR120 kit. It seems to be as reliable as they come and will give me a bit more power. Some of the Kitaco kits look nice but I don't want to drop that much $$$ into a mini. I've got a guy who's well known for his head work lined up to rebuild my head/valve seats along with some porting.

From what I've read the BBR cam is essentially a stocker. I've read a handful of threads here discussing the various stats etc of available cams. I still can't make heads or tails of all the details. Can anyone share any experiences with cams for the 100? Any of these cams end up giving issues with valve/piston clearance?

What am I not thinking about?

What about the high volume oil pumps I've seen?

Thanks for any guidance...

[fgrote]

go with the bbr kit and sell off the cam on ebay , on the cam you can send your stock core to web and have the hard welded , there is a good chance it will kill your seals , the easiset thing to do is trim the bottom of the keepers, if you dont want to screw with sending a core , and triming the keepers go with a takegawa cam its a drop-in, just check the tower clearance

its a great cam also, the price is going to be about the same either way

also im a BIG fan of the HV pumps the more oil you can pump up into that head the better , the cam journals need all the help they can get.

You might as well get a atc200 carb off ebay while your at it, and your pretty well set

[ACDNate]

Ah good point on the carb, i hadn't mentioned it. Now the atc200 is that a 24 or a 26mm carb? Does it match up to the stock intake?

[fgrote]

its a 24 it matches perfectly, the xr200 is a 26 it bolts up but the oring on the carb is to big you have to run a gasket to seal it , its much bigger , in order for it to work to its potential you need to port the intake alot, ive been playing with the 26 but so far i haven't got it to work to my satisfaction

some people say its over kill ,cause the valves can only flow so much, i have a supermoto and what i ''think'' so far is it made the bottom stronger and loses some on the top , but i can't say for sure till i have time to dial it in more and do some more gps runs

[ACDNate]

I was thinking the 26 might be a bit big w/o going to larger valves. I do believe I'll go the 24mm route. I've seen some shagged out atc200 carbs goign for $75+ on eBay. Anyone try the knockoff 24mm carbs available from TB?

On a side note, I got more fork seals and steering head bearings ordered today from the board sponsor.

I looked at my 100 manual and found the service manual reccomended removal method for hte lower bearing is "using a chisel or similar" hahahahaha

Edited November 3, 2010 by ACDNate

[Kyron]

No frame brace?

I thought the XR80 had a 17" front wheel ?

[ACDNate]

No frame brace?

I thought the XR80 had a 17" front wheel ?

Doh! another thing I forgot to mention in my original post. I will indeed be ordering a frame brace from Banke Performance. Why Banke over BBR? Banke is cheaper

I'm not sure on the XR80 front wheel, but the rear 16" wheel is a direct fit for the front of a 100. The CR80 that I have the front end from came with a 17" front.

[gman255]

24mm carb from the CRF150F with also bolt on- have patience 200X carbs will turn up.

IMHO Stay away from the knock offs- you'll be much happier in the long run with a orginal Keihin.

Just to add to what "fgrote" has mentioned about After market Camshafts- .280/5" lift on the exhaust side is right on the limit. If you have seen the camshaft chart I've posted in this forum.. The largest aftermarket cams (for the stock cylinder head- with little to no mods) are the Web 68/69 and MegCycle 129x6 (256*duration)

Edited November 4, 2010 by gman255

[Footy]

No frame brace?

I thought the XR80 had a 17" front wheel ?

All XR80's have a 16" front wheel and a 14" rear wheel. I have a 17 inch front wheel on my XR80 because tire selection for the front 16" is very slim.

[ACDNate]

24mm carb from the CRF150F with also bolt on- have patience 200X carbs will turn up.

IMHO Stay away from the knock offs- you'll be much happier in the long run with a orginal Keihin.

Just to add to what "fgrote" has mentioned about After market Camshafts- .280/5" lift on the exhaust side is right on the limit. If you have seen the camshaft chart I've posted in this forum.. The largest aftermarket cams are the Web 68/69 and MegCycle 129x6 (256*duration)

Ok maybe a dumb question, but if the 150F is a 24mm carb as well, it would seem that they would be more available than the 200x carb. Why is the 200x carb the preferred?

As far as cams go, do the 2 you listed work w/o having to do any piston machining for clearance? I'm pretty inexperienced with valve train work and would prefer a relatively "drop in" experience if possible. I'll see if I can find your thread, I haven't seen it.

On the xr80 wheel note, I had a brain fart, Footy is correct.

[gman255]

Ok maybe a dumb question, but if the 150F is a 24mm carb as well, it would seem that they would be more available than the 200x carb. Why is the 200x carb the preferred?

As far as cams go, do the 2 you listed work w/o having to do any piston machining for clearance? I'll see if I can find your thread, I haven't seen it.

On the xr80 wheel note, I had a brain fart, Footy is correct.

Actually, I haven't seen a lot of used 150F carbs on ebay (haven't looked recently tho)- 200X's are (well- have been in the past) more plentiful- Plus The Old School XR 100 hot rodders have been using them for years (right Socal lol) Proven Reliable Performance that is a bolt on mod- BTW You'll also need a CR80/85 throttle cable.

The two cams listed are on the limits, they will need all clearance checked- especially the exhaust valve retainer to valve seal/guide as fgrote mentioned.

Including Cam towers (older styles) and piston to valve (IMHO).

Link to Cam post https://www.thumpertalk.com/forum/showpost.php?p=8915912&postcount=16

[XR100Flattracker]

Now thats more like it.I've been hoping to see some action on this site!You can build your own frame connector fairly easy and save a few bucks.I've made some gains with my bbr120 and 129x6 cam playing with cam timing.Hope to see more of your build,you will have to deal with the rear shock after you connect the frame,start scouting the web for works shock.

Bob

[ACDNate]

The rear shock has crossed my mind more than one time. When I complete what I have planned it's going to be a pretty big weak link. The buy in for it really chaps my arse.

$400+ for a shock for a mini is just insane. Not to mention I don't think I've ever stumbled across a used one anywhere.

I had hopes someone had stumbled across a compatible shock from another model, but the diminutive size of the 100 shock pretty well kills that.

I've contemplated trying to build my own frame brace, but for $120 from Banke I'll likely go that route.

[gman255]

Bob,

Thats Awesome your guys are still playing with the XR! (Sweet lil ride you got- man) So,, Whats your impression of the 129x6 cam in addition to the BBR kit? Were are did you end up with the cam timing?

I also have a few small projects in the works (I know is been awhile... lol) they will address some of the stock XR/CRF 80/100 chassis' short comings- ACDnate already has a lil inside Intel-(got you covered for next race season). But Gonna keep the cat in the bag- boys, Until I have a working proto-type. Should have a thread/s started before Turkey day... If all goes well.

G

[ACDNate]

I also have a few small projects in the works (I know is been awhile... lol) they will address some of the stock XR/CRF 80/100 chassis' short comings- ACDnate already has a lil inside Intel-(got you covered for next race season). But Gonna keep the cat in the bag- boys, Until I have a working proto-type. Should have a thread/s started before Turkey day... If all goes well.

G

yeah I got just enough intel to be confused Bring on the new thread!!!!

[ACDNate]

Sure enough I found a deal on a 200x carb right here on the TT classfieds.

Time is dragging ridiculously slow waiting on my fork parts to arrive.

[ACDNate]

My parts should be showing up by Friday this week to rebuild my forks. Parts list includes new seals, o-rings for caps, steering stem bearings,adjustable fork seal driver and a few other bits and pieces. This is my first fork rebuild and I'm left with a few questions.

1. When reassembling the forks, is fork oil a good enough lubricant for seals and bushings or do I need some other kind of grease?

2. I'm thinking of going with a 15wt oil since I'm way above the intended weight for the forks. What is the specified fork oil level? I can't see buying a cr80 service manual to get one number from it

3. The service manual for my 100, shows a special socket for torquing the steering head into place, and a specific torque spec. Can I get by doign this by hand?

[fgrote]

I Saw a xr100 frame brace on san francisco craigslist

[theraymondguy]

Courtesy of dumdotdog

Fork capacity-276cc, oil level-132mm[spring out, fork compressed] manual specifies ATF but I would use 15 or 20 weight fork oil to stiffen things up.

Swap out the head bearing balls & races for Z50R / CT70 cones & cups. You can (that is to say, I always have) torqued this by hand. Each bike is an individual, the top nut is there as a lock anyway. Be sure it doesn't 'rack' when the brakes are applied, and that the steering is free left to right.