Pipes (and porting)

[Charles Todd]

Well,, my 250 originally had an aftermarket pipe on it from what I can tell but it has miraculously been lost over the years. The reason I assume this is because the fins on the head have been cut at an angle (cut, not broke,,) and it doesn't look stock. What companies offered pipes for these beasties? And would anyone be wanting a modern pipe for one? I will be getting some dimensions so I can roll one out for mine is why I'm wondering.,,,,,

Oh,, my cylinder is also been ported. It's signed M. L. 4 - 80 on the bottom of the bottom fin. Wouldn't anyone happen to know who that might could be huh? I live in east Barton rouge if that helps any?

[454MRW]

Circle F makes cone pipes for the 78-80 250 KTM's and Ace makes some for earlier bikes. What year is yours? Post or email a pic or 2 of the modified head. [email protected] Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[Charles Todd]

Mine is a 76. Ill take and post some pictures when I get home. Thank you for the info!!

[brian kirby]

Neither of those pipes would require you to cut the fins, and the way the Penton pipe routes, I cant see how you could even make a pipe that would both fit, and require you to cut the fins. But, thats what is so cool about these old bikes, every one of them seems to have a story and a mystery about some part or piece.

Brian

[brian kirby]

Jemco also makes pipes for them, it looks a lot like the ACE pipe.

Brian

[Charles Todd]

Brian,
The fins are cut about where the divergent cone would be expanding at and then transitioning into the belly section. I figured it just had a fat pipe lol

Ill go snap some pictures right quick of ports, head, etc

[firstturn]

As far as the M L 80 it could be Mike Lenz?  I am not sure he ever signed his work, but he won a lot of races with Penton and KTM bikes.

Ron Carbaugh

[Charles Todd]

The head fins (ignore the other motors an stuff in the background. Other projects lol)





The ports







And here's the signature


Something we do with the modern reed engines is port the reed cage (y'all prolly know that) so I figured I should take some pictures of the intake too



I realize that when I was cleaning up the ports trying to get the oxidation out of them I actually polished the intake side (derp) so I will be sure to go back and rough it up with a stone again


My uncles say that when they were riding it, it was a beast. When ever it came on pipe you BETTER be holding on and have it pointing in the general direction you hoped to go and that no matter what gear you were in it would stand up when it rolled into the powerband. We have a CR80 with an 85cc cylinder that was ran on a shifter kart (ports hogged out like CRAZY) that runs about like that.

So what y'all think???

[Charles Todd]

Any thoughts y'all?

The port work is very very very nice. You can juusst barely see the traces of tooling in the corners but the rest is super clean and you can tell a lot of time and care was taken in doing it

[454MRW]

The ports look well smoothed, but I will have to look at a 77-80 head tomorrow in the shop, as it looks like the fins are unmodified from that version, which is factory cut for clearance on the larger torque pipe. The earlier heads had full fins in the front, but somewhere around 1976-77 they changed the head for clearance reasons with the soon to be used updated pipe design. The casting # on the underside of the head should tell more about the version. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[brian kirby]

I'd have to go look at one of my heads to compare, but the fins look stock to me. I think some were cast shorter, and some were cut depending on what part of the head they are on. Someone here will know for sure though.

Brian

[454MRW]

I found a couple of reference pics on my computer for comparison from the early head, in this case a 175 to the later 78 GS-6 250 stock head with the angle cut fins. It looks like your fins are unmodified. Mike



Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[Charles Todd]

Thanks for the input Mr. Mike!! I guess I'll just have to find either a stock pipe or go ahead with having one made off my port map. I wish I had a way to throw a degree wheel on it so I could get the port map of it. But I have no way of doing that until I get the crank rebuilt, get a piston, get it bored (going up two bores just to make sure. An it's on maybe the first over bore (EZ-71 cylinder), get it all together etc etc etc. I REALLY need to get the cases that are on eBay for it. Mine are trashed.


Would anyone else be interested in a modern pipe?