Building an AHRMA Cross Country Penton Six Day

[johnbowman]

Hello everyone! I hope that you are all doing well today.

I got home with my Penton Six Day project bikes this weekend. I'm about to start tearing them down to rebuild one AHRMA cross country bike for next year. They are practically identical. One was built in November 1971 and the other in September 1972. Both CMF. Between the two, I should be able to get one bike running. I will have to do a total engine rebuild. In  the deal, I got four large boxes of parts: engines, heads, ignition covers, etc.

I have read through the forum and the newsletters. They are a wealth of information. I have a question for the AHRMA cross country experts (regular Penton experts feel free to voice your opinion). If you were going to build a Penton Six Day to compete in AHRMA cross country (mostly woods, hills, rocks, and short straights), how would you build it out?

1. Engine - 5A, 5B, 6A, or 6B. Any mods.
2. Gearing - sprocket sizes and brands
3. Carb - size and brand
4. Tires - size and brand
5. Brakes
6. Intake mods
7. Exhaust mods
8. Suspension
9. Other common mods

I'm going to try to get this done in time for the next season. I have a pretty good budget for the project. I would rather do it right the first time.

Any comments and opinions would be greatly appreciated. I'm trying to not reinvent the wheel here. Thanks in advance.

John

[johnbowman]

Maybe I need to start off with a more simple question. I'm going to build the engine first. Which Sachs engine would be best for a cross country bike?

The more that I read about the Sachs engine versions, the more confused I become. I have at least four bottom ends. From reading, it appears that most prefer the "B" engines. Before I go spend a fortune on getting an engine rebuilt, I'd like to know that I'm building the best engine.

[Rick Bennett]

If you have a 6B then use it. The smaller crankcase volume makes more power. Use a modern ignition. Use a stock 27mm carb. Gear for the tracks you will run on, 13/57, 13/54, 14/57 and 14/54 are good choices.

[skiracer]

Don't cheap out on your suspension. Spend the the money on doing the forks and buying quality shocks. Also, buy quality tires. Forget "period correct."  Buys tire that work in the conditions you are riding in; rocks, roots, and mud. Remember, you are building a race bike, not restoring a bike, big difference. Have fun building it!

1976 250 MC5 Original Owner
1976 Penton 175 XC

[johnbowman]

Just finished looking at my engine inventory. I have the following choices:

6A - I have a complete engine that is locked up. It is in very good condition cosmetically. I have two bottom ends that are moving freely. I should be able to have a 6A rebuilt with the parts that I have on hand and normal rebuild parts.

6B - I have one bottom end with all internals intact and moving freely. It is missing all ignition components and all clutch components. It has minor (repairable) damage on the case and ignition cover from a thrown chain. I have extra cylinders, heads, ignition covers, and clutch covers. I would have to find the missing parts, have the engine case repaired, and engine rebuilt.

Any suggestions?

[johnbowman]

quote:Originally posted by Rick Bennett

If you have a 6B then use it. The smaller crankcase volume makes more power. Use a modern ignition. Use a stock 27mm carb. Gear for the tracks you will run on, 13/57, 13/54, 14/57 and 14/54 are good choices.

I just posted on my engine options. Do you think that the 6B parts would be available?

Which modern ignition would you suggest?

[johnbowman]

quote:Originally posted by skiracer

Don't cheap out on your suspension. Spend the the money on doing the forks and buying quality shocks. Also, buy quality tires. Forget "period correct."  Buys tire that work in the conditions you are riding in; rocks, roots, and mud. Remember, you are building a race bike, not restoring a bike, big difference. Have fun building it!

1976 250 MC5 Original Owner
1976 Penton 175 XC

Any suggestions on sources for the suspension? I agree about suspension. An hour straight getting beaten to death by poor suspension is no fun.

[Larry Perkins]

Hip ignition and Gary Ellis can hook you up for a good price.

Larry P

[454MRW]

HPI

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Penton
1976 MC5 400
1978 KTM 78 GS6 250
L78-79 MX6 175-250 KTM's
1976-78 125-400 RM's
2007 CR125R Honda
1977 MC250 Maico
2017 KTM Freeride 250R

[Larry Perkins]

Thanks Mike.  Pain meds and fat fingers.

Larry P

[johnbowman]

Here's an update on my build so far.

I'm going to use a 1972 CMF frame. I just ordered parts from Al to replace almost everything that was worn or needed servicing. I'm going to get it powder coated. There is a local guy that does a great job and is very reasonable.

I'm using a 6A engine. It has the transmission with the larger selector rod. I have two engines that should make one good engine. Gary Ellis is hooking me up with new engine bearings and an HPI ignition system. I'm going to have the engine completely gone through and every gasket, seal, and bearing replaced. I have one piston and cylinder that look almost new. It has a two over (54.43) piston. The cross hatches still look new in the cylinder. If it measures out okay, I'll use that. If not, it will be another call to Al.

I'm going to get an original Bing 27mm carb from Larry Perkins.

I'm going to run 13/57 sprockets and a case protector.

Thanks so much for all of the great advice so far. As a newbie, I really appreciate the help. Both Al and Gary are very knowledgeable about Pentons. They have been very helpful.

Now, on to suspension! Does anyone know a good source for AHRMA legal suspension parts? I'll need both fork springs and a complete set of shocks.

[Carl Hill]

Race tech sells fork springs that are high quality. They even have a place on their website that will calculate spring rate based on your weight and intended use. Ceriani forks were actually pretty good for their era. Work fairly well in the woods. As far as shocks go it comes down to how much you want to spend. Race tech has those too and I have heard they are excellent but too rich for my blood. I have Koni and gas Girling on mine, modern equivalents are Ikon and Hagon.

[tooclose racing]

Just to follow up on the suspension discussion, I used the 35mm Cerianis from the 73 thru 75 Pentons on my 1972-based build (the 72's used a 32 mm Ceriani). But they can be hard to find (Larry P - I thought you were trying to sell a set of these for awhile). I've used WER suspension (Drew Smith, former ISDE racer) to source fork springs if/when needed on my other bikes, but my stock springs were in good condition.

If you can find a used set of "newer generation" works performance (13.5 inches) shocks, they are the way to go.  Rebuildable (again, I've used WER) and my understanding is that there are parts available, even though "Worx" (their new renamed company) is not making shocks anymore last I heard.  I don't have experience with Ikon or Hagon, but Hagon's high-end build shock is still pretty affordable vs. Ohlin, Noleen, or Race Tech.  Maybe someone here at POG has ordered a set of those.  

I'll confess my first set of shocks on my Six Day were the Red Wings, not sure if they are still available. They were rebuildable too.  Finally, some folks use Progressives, but my understanding is that they are not rebuildable.

HAH - just saw your "wanted" shocks post over in the For Sale board.  You're way ahead of me.  ; - )

[Richard Colahan]

Where are you located John? What AHRMA XC series (national, regional...)will you be racing?

quote:Originally posted by johnbowman

Hello everyone! I hope that you are all doing well today.

I got home with my Penton Six Day project bikes this weekend. I'm about to start tearing them down to rebuild one AHRMA cross country bike for next year. They are practically identical. One was built in November 1971 and the other in September 1972. Both CMF. Between the two, I should be able to get one bike running. I will have to do a total engine rebuild. In  the deal, I got four large boxes of parts: engines, heads, ignition covers, etc.

I have read through the forum and the newsletters. They are a wealth of information. I have a question for the AHRMA cross country experts (regular Penton experts feel free to voice your opinion). If you were going to build a Penton Six Day to compete in AHRMA cross country (mostly woods, hills, rocks, and short straights), how would you build it out?

1. Engine - 5A, 5B, 6A, or 6B. Any mods.
2. Gearing - sprocket sizes and brands
3. Carb - size and brand
4. Tires - size and brand
5. Brakes
6. Intake mods
7. Exhaust mods
8. Suspension
9. Other common mods

I'm going to try to get this done in time for the next season. I have a pretty good budget for the project. I would rather do it right the first time.

Any comments and opinions would be greatly appreciated. I'm trying to not reinvent the wheel here. Thanks in advance.

John

Richard Colahan
1969 V1225
Upper Black Eddy PA

[johnbowman]

quote:Originally posted by Richard Colahan

Where are you located John? What AHRMA XC series (national, regional...)will you be racing?

Richard Colahan
1969 V1225
Upper Black Eddy PA

Richard,

I'm in Germantown, Tennessee. Right outside of Memphis. Last year, I floundered my way through a few events in the John Penton/Preston Petty National Cross Country Series. I plan on riding in as many of the series events as possible this year. Hopefully, I'll graduate from Novice Beginning Rookie Third Class to Novice Beginning Rookie Second Class this year!

John