Ebay D cylinder

[Gavin Housh]

I see a few folks are bidding up the D cylinder now on ebay. Just remember that the porting on most NOS D cylinders in no different that the cylinder that came stock on the B engined Pentons. If you want something special you will have to have it ported and have a boost port put in. This in not a cheap thing to have done and I would advise those that want to do it to just use the standard seven fin spigot type cylinder if you already have one. The six fin cyclinder does have the manifold type carb mount but it is a pain to make work unless you have an uncracked Monark manifold (unobtainable). You can purchase a Mikuni bolt on manifold from Pro-Flo but it will have to be modified (as well as shaving some aluminum off the inlet area on the cylinder to apadt a modern manifold) to work and it also lets the bottom of the mikuni vibrate against the top of the engine case. Even after all that you have to adapt the air box to the carb and that is a whole different can of worms. I bought Alan's last D cylinder some years back and it came with a standard size NOS piston. This thing was NOS nice but after all the work to get it bolted up it siezed. After tearing it down it turned out that the cylinder had a taper in it. The top was half a thousandth smaller than the bottom and the bottom only had .0015 clearance. That meant the top only had .001 and thats not enough when the piston heats up the engine siezes. So I had to have that fixed too. If you Have a late GS model Monark and you need a NOS cylinder to make it look stock then keep the bidding going. If not, I would say it's not worth the money. By the way I only paid three hundred for mine and it came with a piston. In the end I spent around a grand to make it work. Yes the bike is fast but who wants to have an AHRMA tech guy hassel you every time you show up to race.:(Gavin

[Larry Perkins]

Gavin,

I mean no disrespect with this and you make some very good points about a D cylinder verses a D GS cylinder.  Most people continue to think anything D is fast.  

The part I think is not right is your statement that the cylinder is not worth it.  If it brings it it was proven it was worth that.  I think it is not right for you to try and effect someone elses auction if you are not even a bidder.  It is not my auction but it is someones and they should reap the harvest of saving something for 30 years and offering it up.  What is something like that really worth? If people are willing to pay let the seller reap a long awaited harvest.  One day any Sachs NOS cylinder will be worth $1000 or more if there are any around.

Alot of the members here want stuff for free and I don't think that is right but it is the perogitive of the seller to give away what is worth money even though that helps to devalue all the parts people try to sell.

Nothing wrong with informing members of cylinder differences but leave capitalism alone and let someone make a buck and let someone buy something rare.  It is the business of the buyer and the seller.

Larry P

[bentrims]

Rob,
Curious how many mm's you widened out your transfers to? 30mm GS specs?
Thank you,
Tom B.

[rob w]

Hi Tom, Yes the transfer ports are widened to 30mm. Today I measured and compared this cylinder with a stock B , this is what I gathered. Besides the two extra boost ports above the intake - the transfers were widened and lowered, the exhaust is widened and raised - the intake was unchanged in width and lowered.
 Also the shape of the exhaust port as it exits the clinder is changed from squarish to round, so it flows out to the pipe better. And where the bottom of the transferes meet the liner, that's blended to a knife edge on the liner.
 The reed is made by DH, and the carb that was on it was a 32mm Bing. Speaking of Bing, are you dreaming of a white Christmas, I am.
If you have any other questions about these mods, don't hesitate to ask.
Write you later,
Bob W

[bentrims]

Thanks Bob,

Have you run this cylinder or recently acquired it? Looks pretty wild.

[firstturn]

Bob & Tom,
  After Christmas I will try to remember to measure the Reed Valve cylinder I have that belonged to Leroy Winters.  It was built by Ted Penton and is really a work of art.  Merry CHRISTmas to you guys and I hope you have a White One if that is what you want.

Ron Carbaugh