Penton MC-5's in post vintage classes

[G Ellis]

The lower frame center mount where not always use. These frames are for 125-175-and I have seen some 250's that don't have the middle mount.I know that you don't want to put a 400 motor into a frame without a middle frame mount. Hope this will help  Later Gary

[firstturn]

Doug,
  "flipping the fork legs around backwards. I wonder how well that works."?
It doesn't...and do not ask me how I know[B)].


Ron Carbaugh

[Britt Boyette]

quote:Originally posted by G Ellis

The lower frame center mount where not always use. These frames are for 125-175-and I have seen some 250's that don't have the middle mount.I know that you don't want to put a 400 motor into a frame without a middle frame mount. Hope this will help  Later Gary

So it's alright to install a 250 into a 125/175 frame?

Britt Boyette
1976 125 MC5

[454MRW]

Actually, I have a 76 MC5 chassis that was originally a 400 Penton that I have just installed a fresh 76 400 engine into this week. it never has had the lower engine mounts and I don't plan on racing the bike with the exception of maybe a future Reunion Ride or similar event, so I don't plan on adding the mounts. I have seen more 76 MC5 frames without the lower center mounts than those with them, and I have a few 76 MC5 chassis.
The 125/175 chassis will accept the 250 or 400 engine, but the central exhaust mount tab has to be removed on the frame to install a 250/400 pipe. The 250/400 frame has the rear exhaust mount at the back of the frame beside the seat, but the 125/175 frame does not have a rear exhuast mount, instead it is near the airbox on the inside of the frame by the right hand upper shock mount. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[rob w]

On the topic of why some MC5 frames have bottom engine mount brackets, but the major majority do not - I thought we sorted that out one day, but I can't remember what the group's conclusion was.
It has nothing to do about them being for 400's though - I know that for a fact.
Unless they were on the very earliest 400's - because they're not on the later ones.

[Britt Boyette]

So, if your going to install a 250 into a 125/175 frame, you either have to cut off an exhaust mount or have a custom pipe built. Other than that, it should be fine?

Britt Boyette
1976 125 MC5

[Britt Boyette]

quote:Originally posted by rob w

On the topic of why some MC5 frames have bottom engine mount brackets, but the major majority do not - I thought we sorted that out one day, but I can't remember what the group's conclusion was.
It has nothing to do about them being for 400's though - I know that for a fact.

I sure wouldn't want to take on rocky terrain without having something extra down there.

Britt Boyette
1976 125 MC5

[454MRW]

I checked my chassis and spare frames this morning and have a total of 8-76 and 77 MC5 frames, which only one of them is a 125/175 chassis, and none of them have the bottom engine mounts. I always felt that they were omitted not only to save weight, but to make engine changes easier in the highly competetive motocross racing that they were aiming for at the time.
You can install a 1981 exhaust pipe with the stinger type removeable silencer without removing the center pipe mount bracket, but you have to use a 78 mc5 gas tank with the forward mounted petcock to clear the bigger design torque style pipe, or cap off the LH petcock on the 76/77 MC5 gas tank. I would sell one or two of my extra frames for $75 plus parcel post of around the same if you need one. I also have 78, 79, & one 1980 frame. Mike

There is a 125/175 frame on eBay right now # 300367971135. you can see the center exhaust mount bracket in the 2nd pic if you enlarge the photo.

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[G Ellis]

Mike give me a call,I would like a MC5 frame.  Later Gary

[G Ellis]

Ron I would like to know about flipping the fork tubes.:D:D Later Gary

[tomale]

that is interesting about the lower center engine mount, On both of the 76/77 MC 5 frames that I have, both of them have the lower mount. Same is true of any of the HareSramblers I have ever worked on too...quess I do not understand why some frames would not have them....not that I need to, not that it would make any difference. True it would make swaping out engines alot easier. Seems to me I heard story about a certain Penton ride at a ISDT event, had to replace a piston and did it in 15 minutes or something like that, that is pretty fast, I have taken the top end off my KTM and I never did it in faster that a couple of hours....but then I could never swap out a tire in under 30 minutes and even at that I thought I was doing pretty good...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[Britt Boyette]

Sounds like a Carl Crank story, maybe? Some people are awesome when it comes to changing tires, I'm on the other end of that spectrum. I do it but I hate it and it always takes a really long time.
 The reason the lower bolt question popped up is because I'm considering such a swap with the 125. I'm thinking about installing a 250 and storing the 125 engine on a shelf. I really want a MC5 250.

Britt Boyette
1976 125 MC5

[454MRW]

You would be better off, financially wise, to get a 250 frame and switch all of the major components to the new frame. They are all interchangeable, except the pipe and smaller carb, boot, throttle cable, choke cable, and possibly clutch cable, and you wouldn't have to worry about either modyifying your stock frame, or finding an 81 pipe and 78 MC5 tank for the pipe to work with the tank. You could then store your engine and original frame and use everything else.

If you would rather find an affordable 76 MC5 250, I have one that I have rebuilt the top end with a NOS 1st over piston, but can't seem to come up with a perfect enough set of wheels, cables, correctly jetted carb, etc, and it has sat all last fall and this summer waiting for me to finish it for around $1500. I do have wheels, but I am just too darn picky for my own good, and hate to build any part of it shoddily. It does have the repainted and installed airbox and an NOS carb boot, rebuilt and repainted Marzocchi forks, rebuilt stock Marzoccki shocks, freshly painted frame, swingarm and engine and very nice pipe. I have the correct carb that came on the engine, but it didn't run right at full throttle on another engine and I haven't determined why yet. The Motoplat hasn't been installed yet. I just need a good reason to finish it. if it was completely finished, I would expect it to be a $2500 bike easily.
I guess I have put off finishing it because if I can manage to get to tax refund time, I probably wouldn't need to sell it to satisfy my prior committments. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[Britt Boyette]

I would have to sell this one if I were going to buy another MC5. It's all about the money kinda thing.

Britt Boyette
1976 125 MC5

[Mike Lenz]

I have read about why Moiseev (spell?) ran the 7-8 inch in line forks. He felt the geometry of the bike would change too much with more travel, causing the bike to not corner as well. I dont believe it was a forward axle verses non issue, it was more of a travel issue.  For the tracks back then, and as I have asserted, for more tame semi modern tracks as we race post vintage on here in the midwest, less travel and the shorter "historic class" bikes can actually be an asset. Its cornering verses jumping when you talk suspension travel. Maybe I should shorten my travel up to 7 or 8 inches...to win!! Now thats a different thought!!!

I have never seen an MC-5 frame with the lower motor mount.  No problem for 400's as long as you keep your mounts tight and are using 76 or newer cases with the newer style left engine strut mount.  The old cases can break there in an MC-5 frame. I believe I was told way back when it was a frame flex issue as to why they were left off. All I ever raced were 400's, in MX, concerning the MC-5's, no bottom mount is not a problem. Some of the 77 GS-6 frames have the lower mounts. Probably for log bashing as one of you mentioned. The 77 GS-6 frames are basically the same as the mc-5 except for the frame breather aspect and a rear fender loop. A better set up it would seem to me for CC racing. By the way I have an extra 77 GS-6 frame if any interest.

I purchased the bike with the backwards forks (and dual mount pegs).  However, if James or amy one else wants a 77 dual peg mount frame, the same guy has another one with a 400 engine in it. Actually, the deal I made with this guy was I could have either one if the other one was still not sold when I go to pick it up the first weekend of Dec. However, if any of you really want one bad feel free to purchase the other one now, someone else may at any time. Otherwise, I will look them both over at that time and report back on their condition. The one I purchased is # 260496466606. The 400 is # 260496466937.