Cooling Fin Trimming,,,Legal or not

[Mick D]

Hi Members, this is not meant to be one of those long winded argumentative threads.

Its just that I am doing some Cylinder fin repairs and it would be easier for some of the ones I have, just to trim a few of them to match, that's all. I see WheelSmith in the day did it heaps to nearly everything in sight.

 

I saw on here once where Maico square barrel in a slider frame had them trimmed of at each side at the back in line with the angled head fins.
It looked great as well I thought.

Acceptable or not at a National scrutineering level.

Thx in advance.

[firko]

                                                                                 

[Tim754]

Yep has to be acceptable   Look at  some of the gorgeous BSA based CCM's fin work, and hey we may all have accidentally snapped a fin and has it ever stopped anyone competing?  Go for it mate

Try this site http://www.b50.org/index2.htm Look under racing or CCM or just drool over the whole site. Cheers

[firko]

The rule that covers it all is the seldom enforced 14.2.6.1-A Engines must remain externally unchanged. In reality it's a difficult to enforce rule when you consider that fitting an aftermarket head or a reed kit actually changes the external appearance of an engine so therefore it's illegal. That's silly of course and considering that folks have been chopping fins for half a century, I wouldn't disallow Wheelsmith style finning if I was eligibility scrutineer. My squarie 250 barrel shown above is an example of what folks have been doing for years.

[Tim754]

Speaking as a "former" level four scrutineer .I would certainly not "disallow" fin trim work for the above commonsense reasons either. Tim754

Commonsense    come on say it everybody     Commonsense...... now try using it!

[mustanggrahame]

Is commonsense allowed to overrule a fairly clear statement in the rulebook? I agree that it is "silly" but shouldn't the rule be changed? Isn't this an example of what Nathan is talking about?
Cheers, Grahame

[firko]

Is commonsense allowed to overrule a fairly clear statement in the rulebook? I agree that it is "silly" but shouldn't the rule be changed? Isn't this an example of what Nathan is talking about?
Cheers, Grahame

As the silly person who actually composed that particular rule, I totally agree that it's indeed an example of what Nathans talking about. It was included for a particular reason that made sense at the time but I can't remember what it was .  Nathan's right, there are a number of anomalies in MoMs that need addressing BUT what gets a reaction from me is his doom and gloom, Chicken Little predictions that the sky will fall if they aren't addressed now. That same common sense that Tim speaks of has been used by 99% of VMX racers for 20+ years when using MoMs with little major drama. I've been slowly but surely going through the VMX rules and hope to be able to present a new, plainspeak version for consideration by the commission within the next year or so. 

[FourstrokeForever]

Sheesh. Just as well removing fins is legal. I took a lot off my B50 head and barrel and just finished doing the same to the B44. I weighed what was removed for the B44 and it came in at just under 1kg (2lb) in saved weight. Now I just have to do something about my gut!

[pancho]

Reminds me,  back in the '60s at Boxers Creek "A" grader Fred Boyd couldn't get his methanol burning ES2 to warm up, so he nocked off all the fins that he could get at on the head with a hammer! Didnt look pretty but it flew!

 cheers pancho

[mustanggrahame]

Fair enough removing fins for methanol but why would anyone do it for a petrol burning engine? Maybe cutting slots in the fins could help with thermal expansion distortion, but not removing complete sections of fins. Aero engines have very closely spaced fins, so the argument to make space for more airflow can't be right.
Cheers, Grahame

[rowdy]

One of the CCM theories ,in the staggered fin was to assist in preventing mud build on the engine.
Usual practice on the CCM is to leave the head finning around the exhaust intact

Dave

[KTM47]

The rule that covers it all is the seldom enforced 14.2.6.1-A Engines must remain externally unchanged. In reality it's a difficult to enforce rule when you consider that fitting an aftermarket head or a reed kit actually changes the external appearance of an engine so therefore it's illegal. That's silly of course and considering that folks have been chopping fins for half a century, I wouldn't disallow Wheelsmith style finning if I was eligibility scrutineer. My squarie 250 barrel shown above is an example of what folks have been doing for years.

Mark In the 2013 MOMS Chapter 14 is one page and it is the year in pictures. Chapter 18 now covers Classic MX & Post Classic MX & DT. For this weekend the rule you quoted is cover by 18.5.1.5, 18.5.2.4, 18.5.3.3, 18.5.4.3 & 18.5.5.3. Yes there are other rules that need to be addressed also.

Unfortunately some officials like to cause trouble. As an example there was an official in NSW who decided that because the use of starting blocks was only in the GCRs as a junior rule they weren't permitted for senior MX. As this would be discrimination against those who are vertically challenged and the fairer sex, there is now a rule in the MX section 17.8.1.8.

But as someone said to me KISS (kept it simple stupid). Rick Doughty said to me by email "Keeping things simple is also important because the more rules you have the more rule breakers/cheaters you will have."

[Simo63]

But as someone said to me KISS (kept it simple stupid). Rick Doughty said to me by email "Keeping things simple is also important because the more rules you have the more rule breakers/cheaters you will have."

Truer words wee never spoken.  The more regulation we have, the more trouble we cause.  Keeping it simple and unregulated is the way to go IMHO.

[KTM47]

These are the rules some of the US Vintage guys use

http://www.americanretrocross.org/uploads/2013_Classes.pdf

One thing I find interesting is they permit any 500 2/- regardless of year. I have already seen a 1990 CR 500 in a Pre 90 race and also a 1992 model. The 1990 model didn't stand out but the 1992 does.