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Author Topic: Direct primary drive  (Read 6229 times)
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andychaos
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« on: May 11, 2016, 02:02:53 AM »

I have a mate coming over to the BMST with 125cc pushrod Honda, 125cc PP class.
He has asked me to ask you gentlemen if there are any rules that prevent him from removing the clutch. We are not talking a lot of HP here so I believe the plan is to reduce oil drag within the motor. He will have a direct drive then just push it off in neutral and slip it into gear.
Any thoughts?

Andy
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Speed Limit 1000
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« Reply #1 on: May 11, 2016, 07:21:31 AM »

Go for it. I bet if you look someone has done it. cheers
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Chris V
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« Reply #2 on: May 11, 2016, 08:52:27 AM »

now that you put engine work out in the open, somebody might contest you
and you might be in the P/A production altered
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« Reply #3 on: May 11, 2016, 09:13:03 AM »

Did he look at the rule book? The whole purpose of the production category is to race an unaltered, production bike just like came off the line. Although he may have a point that the rule book does not specifically state that you have to have a clutch, an inspector might have an issue with it because it is not an "originally installed" production" engine.
Here is the actual rule from the book on page 48:

12. A. PRODUCTION (P)
Use the same engines (gasoline only) originally installed in the specific motorcycle frame at the time of production and ensure it meets the definition set in the P frame class (See Chapter 4). Original equipment (OEM) shall include cylinders, cases (crankcases), heads, and carburation or throttle body (stock venturi size), kick-starter or electric starter. Displacement determines the class. OEM displacement specifications must remain stock.

GASOLINE ONLY. Fuel not permitted in this class. See Chapter 2, paragraph 2.F.
P engine class shall not run in M, MPS, A, APS or S frame classes

12. B. PRODUCTION, PUSHROD (PP)
The camshaft shall be located below the cylinder to head deck, and have push rods that open valves with the use of individual lifters. Paragraph 12.A above is also applicable.

He may be able to get away with it since the clutches are not inspected, but I think he is breaking the rules.

Don
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andychaos
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« Reply #4 on: May 11, 2016, 09:43:06 AM »

Its a long way to come and get a knock back which is why he asked me to ask the question.
As we read the rules it should be OK but as this will not be a permanent mod it can be easily returned to standard, so i think the solution will be for him to bring the standard clutch with him.
Good idea though???
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bbarn
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« Reply #5 on: May 11, 2016, 02:46:52 PM »

Its a long way to come and get a knock back which is why he asked me to ask the question.
As we read the rules it should be OK but as this will not be a permanent mod it can be easily returned to standard, so i think the solution will be for him to bring the standard clutch with him.
Good idea though???

I think the spirit of the rule vs the letter or the rule will make for a good show! I'll bring the popcorn...

Run it by the rules committee or the chair and get a ruling now and you won't have to worry about it later. Here on the forum it will make for entertainment but until someone officially says what is what it is all speculation.
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« Reply #6 on: May 11, 2016, 03:19:57 PM »

Use an assumed name.
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andychaos
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« Reply #7 on: May 11, 2016, 03:41:35 PM »

Cheers for the advice
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nrhs sales
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« Reply #8 on: May 17, 2016, 04:04:40 PM »

IMO that bike would need to run in modified class not production.  That is a pretty serious mod so saying it is "production" is pushing it.

But to be sure you need to run it past these guys:

tech@bonnevillespeedtrials.com
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andychaos
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« Reply #9 on: May 18, 2016, 02:02:07 AM »

So fitting bigger valves, welding up the head and a re profiled cam would be frowned upon too shocked
Not to worry he has decided to bring his standard motor.
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Chris V
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« Reply #10 on: May 18, 2016, 08:25:12 AM »

Why not run in P/AG  or P/AF Class I don't see any records set yet on the BMST-AMA rules and records
My wife picked up 3 record runs that way.
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ronnieroadster
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« Reply #11 on: May 18, 2016, 02:20:57 PM »

Cheers for the advice









 About using an assumed name ? Try Cravin Morehead that should work   cheers
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« Reply #12 on: May 18, 2016, 02:51:45 PM »

Cheers for the advice











 About using an assumed name ? Try Cravin Morehead that should work   cheers

that's practically John Smith.
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« Reply #13 on: May 21, 2016, 12:21:25 AM »

With a geared primary, and your clutch basket rotating backwards, an oil shield is useful.  My engines were fitted with a sheetmetal shield, closed at the bottom, to reduce oil drag on the primary drive gear and clutch basket.  The basket will clear out the excess oil as RPM increases, pitching it out of the open top of the basket enclosure.

The shield needs to fit tight against the clutch cover and the crankcase trans input support area behind the basket. You can cut windows in a spare primary cover, in order to work out your patterns.  Your oil shield needs to fit pretty close to the basket, for best scavenging.  Its primary job is to keep excess sump supply oil away from the bottom half of the basket gear.
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