Bigger tires = Less power?

[Dwight Rudder]

Dwight,

I think (hope) Tom was talking about the compression in his motor.  You destroyed 2 trials tires in 65 miles? What the hell were they on, your 525?  Don’t tell me you did it on your Hodaka! I have not used a Dunlop trials tire, so I can't speak for it's durability.

Pete Petrick

[/quote]

Yes, they were on my 525EXC.  I short shift and use engine torque a lot. I didn't hammer them or spin them much.
Dwight

Dwight Rudder
7 time ISDT / E medalist
8 time National Enduro Class Champion.

[bentrims]

Yep- I was talking motor compression and making the point that if my 125 Six Days will pull a 19" modern tire that mics out at 4.70 there should be no problem with most any 4.50 - 18 incher. BECAUSE the taller circumference adds to a taller gear ratio.

The standard tire being 3.50x18 was likely a good match to stock compression, carburetion and gearing.
TB

[bentrims]

I like the 19" rim for the simple reason of tire selection and availability.

I like testing new things on my race bike whenever possible. It currently runs an 87 KX 125 wrist pin, 79 CR125 stinger, 75 Elsinore 125 fork springs. May soon test a made to fit 175 yamaha pipe.
Clearly-This is not my fathers Six Days. But as Uncle Ron insists I will keep a Penton tank on it.
TB

[bentrims]

PS- Tire selection is ultimately a personal thing because the great equalizer is how skillful the rider can fan or slip the clutch and when he slips it.

[Lew Mayer]

And you DO know when to fan it.

Lew Mayer

[Dwight Rudder]

quote:Originally posted by bentrims

PS- Tire selection is ultimately a personal thing because the great equalizer is how skillful the rider can fan or slip the clutch and when he slips it.

That is funny.  The Sachs clutch is so small that even a little bit of clutch slipping is hard on it.  Not to say that you can't do it a bit but you better not do it a lot.  Too big a rear tire will cause the clutch to fail sooner as you need a bit of wheel spin to properly exit corners.
IMO,
Dwight

Dwight Rudder
7 time ISDT / E medalist
8 time National Enduro Class Champion.

[Dwight Rudder]

quote:Originally posted by bentrims

I like the 19" rim for the simple reason of tire selection and availability.

I like testing new things on my race bike whenever possible. It currently runs an 87 KX 125 wrist pin, 79 CR125 stinger, 75 Elsinore 125 fork springs. May soon test a made to fit 175 yamaha pipe.
Clearly-This is not my fathers Six Days. But as Uncle Ron insists I will keep a Penton tank on it.
TB

Testing new things on a bike that was designed to be raced 35 years ago tends to be a bit wasteful doesn't it ?  
Also there are more 18" tires available for your bike than 19" .  What does a 1987 Kaw wrist pin do for it ?  Why a CR125 stinger ?  
I would think that listening to the likes of Dane Leimbach and Doug Wilford and Paul Danik would give enough tips on how they made them go when they were new.
Just an Opinion,
Dwight

Dwight Rudder
7 time ISDT / E medalist
8 time National Enduro Class Champion.

[bentrims]

Dwight,
It seems you are irritated by the entire discussion so I will choose to end it here. Go to an MX sometime and just see.
TB

[bentrims]

Dwight,
Shoot me an email and we can talk about my anti-Elsinore/pro-Penton project. Lets do our absolute best to not be like the other sites. By doing this the kid on the other side of the room will be willing to raise his hand and ask how far to gap a spark plug.
Tom Benolkin
[email protected]

[firstturn]

Tom,
  Thanks for sharing some of your secrets. I think many of us enjoy hearing what you do to out run ALL the other branks 125, 250 and Open Class bikes.

Dwight,
  I think you should understand that Doug built the this engine and I think when Tom won 6 Motos back in April at the Texas AHRMA race that was a mile stone for any brand of bike.  I was PROUD he did it on a Penton.

Ron Carbaugh
Kerrville, Texas

[Dwight Rudder]

My feeling is that a vintage bike should be good representation of how the bike was raced during it's day.  To modify a bike to what it was not is a shame. I am against butchering good OE exhaustpipes.  Modifying the frame and swingarm or changing things to achieve a more "MODERN" look or feel.  There were NO racers in the 70s using 19" rear wheels although some of the British bikes in the 50's and 60s did.  Just my personal opinion.  By the way I have won motos in the classic 125 Exp. class against super modified CZ and Husqvarnas on my "STOCK" Hodaka Combat Wombat ( it even had the lighting kit on it. ).   USD Shocks were not even used till about 1977 and I hate to see them used today.  As Dick Mann said at the ISDTR banquet.  Vintage bike racing is about showing everyone what riding the old "crappy" bikes was about.  Even today we can get the stock forks working better than they ever did back then and we can use much better shocks, although I feel they should look similar to those used during the day.   Like I said this is only my opinion and I admit I am a bit of a purist. When I asked about a couple of the mods ( ie. Wrist pin and stinger ) I was serious and wanted to know why you went this route.  I could care less about a wrist pin change. (or fork spring change )If it isn't seen, I feel it is allowed if it is a improvement. I just want to know why you feel it was a improvement. Also why are you running a Classic class bike against Elsinores ?
Cher'o,
Dwight

Dwight Rudder
7 time ISDT / E medalist
8 time National Enduro Class Champion.

[Dwight Rudder]

quote:Originally posted by bentrims

Dwight,
It seems you are irritated by the entire discussion so I will choose to end it here. Go to an MX sometime and just see.
TB

Not sure what you mean.  I have been to MX events. I have raced Vintage MX events.
Dwight

Dwight Rudder
7 time ISDT / E medalist
8 time National Enduro Class Champion.

[Dwight Rudder]

quote:Originally posted by bentrims

Dwight,
Shoot me an email and we can talk about my anti-Elsinore/pro-Penton project. Lets do our absolute best to not be like the other sites. By doing this the kid on the other side of the room will be willing to raise his hand and ask how far to gap a spark plug.
Tom Benolkin
[email protected]

What do you mean about the Kid on other side of room ?

What is Anti-Elsinore ?  The Penton is a Classic Class bike.

You do what you feel is right.  I am only expressing my feelings and opinion on the subject.
Cher'o,
Dwight


Dwight Rudder
7 time ISDT / E medalist
8 time National Enduro Class Champion.

[firstturn]

Dwight,
  As long as you are expressing your feelings so am I.  Your ideas and thoughts don't always match others as well as what I think doesn't always match what others think.  I hope all of the Hodakas you are racing now are stock.

Ron Carbaugh
Kerrville, Texas

[cubfan1968]

Thanks guys for all the great answers / responces to my question. I really thought I'd get about 2 or 3 posts with an answer back like "yeah, you gain 20% more traction with a larger tire but you sacrifice 18.5% quickness" something like that.

I have learned alot from your feedback. Thanks

By the way I have a 4.60 on the rear of my Six Day. (the previous owner chopped off the chain guard) I ride alot of sand and feel it gives me more traction. The main detriment to speed on my mount is the 240 lb joker at the controls.

Rod Whitman
Omaha, Nebraska
1972 Six Day (Rider)
1972 Six Day (Project)