Topics

1

Open Forum / Taddy B. on the KTM 350SX.

« on: August 16, 2011, 04:13:11 PM »

A short article on Taddy Blazusiak talking about the KTM 350SX-F (vs, a 250 2T) in Endurocross.

Anyone want to discuss religion or politics while we're at it?  

2

General Two Stroke Talk / Four stroke agenda affecting roadracing too.

« on: August 04, 2011, 08:17:54 AM »

Maybe it's well known already, but it seems as though the four-stroke agenda (tm?) is hitting the road racing world too.

Caught this blurb when looking over a race bike overview:

"With the four-stroke Moto3 class to replaced the current two-stroke 125cc Class in FIM Grand Prix racing, Honda will release the 2012 Honda Racing Corporation (HRC) NSF250R in America.

...

The NSF 250 R features a liquid-cooled, single-cylinder 249cc four-stroke engine that will be legal in USGPRU Moto3 and WERA racing in the USA, and others."

...

To twist the knife further... I quote HRCA:

"Just as off-road riders can purchase and race one of our full-on CRF450R or CRF250R motocross bikes, now road racers have the means to buy a race-ready track bike."

The price:  $28,600 USD.  28K is Ducati 'S' teritory.  What's a good Yamaha TZ or Honda RS or Aprilia RS worth?  A lot less! 


http://ultimatemotorcycling.com/2012-honda-nsf250r-to-america

3

Technical / Squish...

« on: August 02, 2011, 10:49:53 AM »

Is there a consensus on what to use for a clearance when setting the 'squish' on a motor?

In my V8 experience, IIRC, it'd be around .040" for a tight street motor - and anything over .055 or so is boo-hiss.

Do those specs carry over to a 250cc mx motor?

4

Photos & Videos / Trey Canard's crazy goon ride..

« on: May 24, 2011, 06:33:09 AM »

This is an old video many of you probably saw.. but for the last two days I've been laughing to myself every time I think of it.  Figured I'd put it up in case anyone hasn't seen it.

Trey Canard crazy goon ride

5

Technical / Pilot circuit jetting question.

« on: May 23, 2011, 07:17:21 AM »

This is probably going to sound pretty dumb.  Bear in mind I think I have jetting OCD, and I desire a lot of throttle control for slippery woods riding.

I've been fooling with my jetting, and am running a different needle with a slightly (correction) SMALLER root diameter.

I'm getting a slight stumble at 1/8 throttle that I can't clean up.  Off the pipe it manifests as a 'tat tat tat', until the motor snaps to life.  On the pipe, things work pretty well, with only a slight hesitation.

I've heard that 'tat tat tat' called "four stroking".   Is that caused by a rich condition, (a lean condition?), or is it just a byproduct of the engines porting design and being off the pipe?

I tried many air screw settings, and the further in I went, the fatter and worse the issue was.  I tuned the air screw out, and it worked best at 2 to 2 1/4 turns, so I put in one size smaller pilot.  It helped, but didn't make it go away.  Still running the air screw around 2 turns out.  (Keihin PWK, FWIW)

Bike runs clean up on the pipe, and will come down very cleanly when you chop the throttle from a high speed top gear blast.  I think I am close, but not quite there on the jetting.  What would you do??

6

Technical / Dragging clutch / notched basket?

« on: May 17, 2011, 04:28:11 AM »

Hey all,

The clutch in my 2000 RM250 is dragging pretty bad when disengaged. It's always dragged a 'little', but it just got worse on the last off-road ride I was on.  The clutch took some abuse on that ride.

I just took things apart, and the fibers and springs are in spec thickness wise.  I haven't found a good way to measure for any distortion in the driven plates.

My basket has what I'd consider light notching.  I've seen worse in examples online.  Does this look bad enough to cause heavy dragging?  It just feels like light dimpling.



The dragging is bad enough for the tranny to slam into gear and stall the motor when I select 1st or 2nd from neutral.  If I keep it running, the drag wants to get the bike rolling forward.  It's really a -heavy- drag.

Besides the basket, are there other things I should look for that would cause the dragging?

I don't believe it is clutch lever or cable related.  I removed all slack and pulled the (non reach adjustable) cable driven clutch lever to the bar.  Found the cable housing distorting a bit, so I swapped in my Magura hydraulic clutch.  Both do it.

With the clutch cover off, I can see plenty of throw being put into the clutch pack.  For whatever reason, I have a ton of drag.

Before the clutch went and started dragging heavily, at times it would snatch or chatter sharply at engagement. Not sure if that offers up any more clues.

I've hear that these clutches are prone to drag, and swapping in KX250 fibers and drivens are one fix.  Too bad I had just ordered a RM250 kit a day before this problem showed up.

Any thoughts or ideas? 

7

Open Forum / Vintage 2T road legal trailies?

« on: April 28, 2011, 01:53:37 PM »

I was combing through craigslist recently, and came across a sweet little Suzuki TC185.  I also saw the nice IT490 for sale on the site, and it had me thinking about a guy I was talking with out on the trails like, 15 years ago, who was riding a blue Yamaha dual sport two-stroke that I couldn't identify.

I've always been a fan of RD's and H1's and H2's.. and also Scramblers and vintage trailies.

It all got me thinking... I'd love a vintage two stroke trailie at some point.

Can anyone rattle off some names of some of the road legal two-stroke trail bikes imported here to the US?

Anyone have any experience or fun little stories about them?

8

Open Forum / The names "2T" and "4T"?

« on: April 15, 2011, 07:05:38 AM »

I have a really dumb question.  So dumb, I think it's going to degrade the collective IQ of this entire forum.

I know 2T stands for two-stroke, and 4T, four...  But where on earth does the "T" come from?!

I've been out of the sport for about 5 years.  Never saw that abbreviation prior - now it seems to be common terminology. I'm perplexed.

9

Non-Moto / Curious - anyone cut their handlebars?

« on: April 08, 2011, 06:47:42 AM »

Like the subject says, I'm curious to know - does anyone cut their handlebars down to be narrower?  More specifically, anyone do that for MX?

I've got my bike setup for woods riding, and am running some regular old CR bends that I cut down rather narrow for a little faster response from the front-end, and for ducking/tucking trees in the tight stuff. I want to say I'm down around 30".  I'm looking to make my bike a little more suited as an all-arounder.  Are there disadvantages to running narrow bars in MX?  Less leverage on the bars?  Little more prone to arm pump or feedback from the front end?

FWIW, I am running a steering damper.

10

Technical / Jetting a Keihin PWK w/adjustable fuel-enricher knob?

« on: April 04, 2011, 01:36:44 PM »

Hey all,

I'm having a little difficulty jetting the slow speed circuit and getting a clean stable idle on my RM250.

From the factory, the '00 RM 250's carb (Keihin PWK) has an adjustable fuel-enricher knob, with a small needle jet attached to the plunger. I suspect my problem may lie with the knobs adjustment.

The knob does not seem to serve a purpose like a Keihin PJ's choke does, in adjusting the idle speed. Not that I am aware of at least.

The '99 RM250 Keihin PWK doesn't have this feature. For the 99, the knob is non adjustable, and there is no needle jet below the plunger.  Both parts are however interchangeable in carb bodies.  Both carb bodies also have a slide idle-adjust screw.

Is anyone familiar with that adjustable choke knob on my '00?  Can you tell me what it's purpose is or perhaps what you have done to tune it?  I can't seem to get a reaction out of it.

Thanks,
-marc

11

Open Forum / New here - Intro...

« on: April 02, 2011, 05:59:16 AM »

Hello all,

This looks like a pretty fun forum, so I joined up yesterday. I will likely be posting here and there as I can, so I figured I'd drop a quick intro out here.

My name is marc, I live in Massachusetts. I've been riding dirt for about 20 years, off and on.  My first 'big bike' was a '88 CR125 in the early 90's. I loved that bike.  Kept it for a number of years until getting distracted my other motorhead related ventures in my early 20's.

I've dabbled in a fair amount of motorsports, but I'm good at none.  Sport bikes, road-race/track riding, drag racing, muscle cars, quads, snowmobiles, and hare scrambles come to mind.  I like to think I have a knack for wrenching, so I've always loved the tuning aspect of any sport.  Two stroke MX bikes have always been a favorite of mine.  I hate-hate-hate the sound of late model 4 stroke MX machines.  I've tried to like them. Really.  I had a new '01 Yamaha WR250 for a bit - traded it for my current bike.

I've currently got a '00 RM250 that I setup for woods and scramble racing about 6 or 7 years ago.  I've also got a '88 Honda 250R quad I had previously resurrected from great disrepair.  Both machines have been sitting for 5+ years.  I've got the RM lit again, and am late in the process of getting it back on the trails.  The quad will be a later project.

Both bikes are a hoot.  I'm looking forward to getting back on out the RM.  I'm mainly a woods rider, but would love to get out on a MX track this year.  We'll see how it goes..

Hoping I can add something moderately worthwhile to discussions here.

-marc