Messages

The Gem reed valve questions keep popping up, but I don't remember anyone reporting that it made a big difference.  Anyone out there that has one on a race motor?  I keep hearing that the early reeds like the Gem were too small and verified this by talking to a noted vintage engine builder.  If significant money is to be spent on developing a Gem knock-off, why not spend it on newer technology.  Shops such as Replica Mechinen (spelling???) are grafting big reed cages to Maicos, etc.  Perhaps the Gem is not the way to go for racers. I'd love to have a reed on our race motor because they do work, but I'm not convinced the Gem is the final word in performance.  Can someone be found that can design one for the racers in our group?  Just my two cents on this subject.

Jon Noyes

I just looked at the results from Arizona.  They don't show post vintage at all.

Jon Noyes

My son Eric Noyes raced a '77 MC5 250 in the Historic class and Open and won all 4 motos he was in.  He is an intermediate rider (soon to be expert).  This is his second year of racing.  He also raced in vintage on an Elsinore, winning the first moto in each of two classes.  Alas, a crash took him out of the final motos.  I'd like to get him a vintage Penton to race, but he loves the Elsinore (go figure).  There were a few Pentons racing on Saturday and Sunday. I don't know how they did.  I pulled a head gasket off our spare motor (the only gasket I had) and gave it to a gentleman from Indiana (I think) so that he could race on Sunday.  I don't know his name or how he finished, but it was great to be able to get him going.  I know there were more Pentons last year.  It would be great to put faces with the names I see here all the time.  Some of you guys should get together and come out next year.  Let me know if I can help with making it happen.

Jon Noyes

Thanks for all your responses to my question.  So as I understand it, the pipes are the same except for the stinger.

Some paints require recoating within a couple hours or waiting until the paint is completely cured.  This could take as long as a month.  Depends on the type of paint.

 

The specs I have for a '76 with Marzocchi's indicates 260 cc per leg.  This is the spec sheet from Al Buener.

Jon

 

My son and I have a '76 MC5 250 we are prepping to race and are also very interested in the Gem reed kit.  We realize that the price may be astronomical.  Perhaps if we are reassurred that someone will offer a remake of this kit for a reasonable price ($250???)we can keep the bidding down and let everyone win.  Is this likely?  We have also considered the reed kit that Cycle Stop offers for the '73-'74 Elsinore.  It might be possible to adapt this kit to the Penton.
The Elsinore kit is $229 and this seems reasonable to me. I know the bolt patterns are similar.  I think the angle is wrong for the Penton, but perhaps an angled adapter plate would work. Of course, there's the question of how to properly modify the Penton piston.  Anyone out there with the Gem istructions that would be willing to share this info?  Should we fail to win
the GEM auction we will be looking into
the Cycle Stop kit as an alternative.
Although being racers we always are looking for an edge, in the spirit of sportsmanship I will gladly share any information we may
find in this regard with fellow POG members.  

Jon Noyes

 

I am bidding on the frame as well.  You don't have to bow out.

Thanks

 

I am a new penton owner (1976 MC5 250)which my son and I intend to prepare for racing.  I am interested in a set of steering head bearings for this bike.  Please E-mail me info at [email protected]
Thanks

 

I know jetting had been kicked around quite a bit, but I'm still confused.

My '76 MC5 with a Bing 54/36/102 has:

170 main
Needle ()
3.22 needle jet
45 pilot

Another '76 carb I have has a 190 main.


The John Penton article on Yahoo recommends:

#1 needle (is this the stock needle?)
165 or 170 main
2.83 needle jet
35 or 45 pilot

this is with a paper air filter

with the Twin air foam:

265 main (resp 170)
35 or 40 pilot
2.85 needle jet

What does resp 170 mean on the main jet?

Can I expect an increase in performance by changing to the 2.85 needle jet?

If so, do I need to order a #1 needle or is this stock?

I have a Unifilter oiled foam filter.

I am only looking for a starting point and realize I will have to optimize from there.

Second question

I had Mike Lenz modify my shift drum, so now I have second through sixth gears for MX. Where do I start with gearing? Stock is 14/52.
I'm thinking maybe 13/54???
Anyone out there racing a five speed?


Thanks

Jon Noyes

Help!

I have a '77 MC5 400 and a '76 MC5 250.  Someone cut off the silencer/stinger from the 400 pipe before I got it and welded on a big spark arrestor.  I would like to weld a new stinger and silencer on the end to replace the spark arrestor. Today I pulled the 400 pipe off to clean it up and noticed how much it looked like the pipe on the 250.  I placed the pipes side-by-side and took some measurements and as far as I can tell the pipes are identical from manifold to stinger.  Is this true? Are the pipes the same, or do I have a 250 pipe on my 400?

Thanks

Jon Noyes