What bikes are eligible for what classes

[Simo63]

I know I'm gonna regret this. I usually keep out of these discussions for a few reasons such as I know diddly squat about the details and don't care either. But I gotta ask. What is this business re angled and horizontal fork lugs on YZ forks?

One other thing that some have forgotten is that the besides coming from a water cooled, linkaged bike, the horizontal lugged 43mm forks where also fitted with compression damping adjustment on the bottom of the fork leg that the "Evo Legal" H Model didn't have.  And many would consider that to be a performance gain similar to linkage suspension.

I think that is a line in the sand/rules that I can live with.  I just wish others could also.

[Sorelegs11]

IT's had these horizontal lugs, 43mm forks but no adjusments.

[Nathan S]

IT's had these horizontal lugs, 43mm forks but no adjusments.

Beat me to it.

Also somewhat relevant is that the YZ125L (NOT an Evo bike) had the TLS front brake and angled lug - and the external adjustment.

Does the external adjustment matter, particularly considering the cartridge emulators that most serious racers use anyhow?

[Simo63]

IT's had these horizontal lugs, 43mm forks but no adjusments.

Were they still monoshock in 1982 or had the IT range also gone to linkage?

EDIT: Just googled it, the IT250and 465 J's were still monoshock.  Next question then, did it have a horizontal or angled lug?  Best I can see the fork leg looks like a H model without the pressed on/over lugs.  Surely they would then be the angled lug?

Anyone got an original 250/465J they can confirm?

Double EDIT: .. Surely this would made the 1982 IT range evo legal judging by the pics.

[Nathan S]

IT250/465J are Evo bikes, but had 38mm forks and SLS brakes (with the angled lug).
IT250/490K/L are non-Evo, thanks to the linkage rear ends. They have non-adjustable 43mm forks, TLS front brake and horizontal lug.

The point was that the IT-K forks offer no performance advantage over the YZ-H stuff.

[Michael Moore]

FWIW, there are people who'll convert damper rod forks to modern cartridges.  They look the same from the outside and may retain fairly easy compression and rebound adjustment.

If done cleverly you've still got access to the compression adjuster though on the ones I've seen you'll have to drop the front axle out to access it instead of just leaning over and turning it with a screwdriver.

All the external adjuster does is allow you to save time tuning the forks without stripping them down to change the internal parts.  Most people aren't able to adjust them while riding around the track, though a time or two I've found myself in a position where I could easily reach over and touch the bottom of the fork leg. 

cheers,
Michael

[Simo63]

The point was that the IT-K forks offer no performance advantage over the YZ-H stuff.

Okay point taken

[firko]

Righto then .. my head is starting to hurt .. I'll just keep out of it from here-on in 

You lasted a lot longer than me.....good effort.

[bishboy]

I posted this earlier in the other thread Nathan started, but this seems to be where all the action is, some I'll put it up here.  I also forgot about about the whole lug position when I recently bought some forks for an evo project and am in process of buying the correct forks.


On a practicality basis I dont have any real issue on the use of drum brakes and associated forks (maybe exclude USD if any exist) if the rules were changed to allow, I think it wouldn't improve the performance much and allow more choice/availability and allow bikes to be kept as all one brand. 

The issue arises if we then say any air cooled engine is allowed, then we start down the path of bikes similar to those overseas, ie; RM500 engined RM400, KX500 engined KX250A5 etc.  But as this would result in a significant performance gain, it could easily be written into the rules that only engines from twin shock/non linkage bikes could be used. I wouldn't even have a great issue with a disc braked, air cooled, twin shock bike (are there any?) being made evo legal with a drum brake front end. 

I suppose the problem arises when you give a little bit of latitude in the rules, people will stretch that to breaking point.  This could be overcome with rewritten very specific rules, but then you don't want to turn the rules into something resembling legislation that you have to be a QC to comprehend 

[Nathan S]

A useful post, BBoy.

FWIW, the rare and expensive Simons aftermarket USD forks were around before 1985, to suit drum brakes. I can't say whether they're legal on an Evo bike or not.

The older RWU Simons forks are widely accepted on Evo bikes, so having aftermarket forks must pass the "OEM" test.

They weren't available until 1982, as best as I can tell.
I think this means they'd be illegal on a YZ250H Evo bike, but legal on a 1983 Husky XC250 Evo bike?!

I await the next round of abuse about how obvious this all is and I'm just a shit stirrer... 

[mboddy]

FWIW, there are people who'll convert damper rod forks to modern cartridges.  They look the same from the outside and may retain fairly easy compression and rebound adjustment.

That is why historic road racing classes now only require the forks to look like they are from the correct era.

[JohnnyO]

I think bishboys idea is pretty good as long as the rules are clear and reasonably brief.
With the Simons USD I don't think they belong in Evo as all brands bar Husky were single shock by then but Simons and Fox 44mm forks definitely belong in Evo

[Tim754]

If YOU are unsure it's legal for any class..... just do something you know is.   End of all worrying eligibility shit, more time to race or build or bullshit to ya mates or  take the missus for a walk then have a spa with the dog or..

[Davey Crocket]

Geez Nathan, you've got more reverse gears than an Italian tank......do the paperwork mate, let us mull over it and if it's good, we can submit it.....simple.

[Nathan S]

I want to Davey, but the current rules aren't clear enough to know what should (or should not) include.
Yes, the basics are easy. It's the detail where it all gets... impossible.