MC5 400/250 pipes

[gooddirt]

Are the 1976 and 1977 mc5 400 and 250 pipes the same ? In 1978 they came with the snail type right ?

[454MRW]

I believe the 76 & 77 MC5 250 pipes are the same, and most likely the 400 pipes are the same for 76 & 77, but the 250 pipe has a shorter and smaller diameter silencer than the 400, although they will both fit on each engine and interchange. The beginning diameter of the silencer, and the overall length of the actual silencer are the telltale differences, as well as the exit diameter of the perforated pipe and end cap, from what I have experience with. I have both versions.
The 250 silencer is 1-1/4" diameter where it is welded onto the pipe and is 10 1/2" long with with a 7/8" perforated core and corresponding hole in the end cap, compared to the 400 silencer which is 1-3/8" diameter where it is welded onto the pipe and is 12" long with a 1" perforated core and corresponding hole in the end cap. I used to think they were the same until I bought a few NOS end caps from a gentleman overseas and noticed there were different sized end caps in the box, which made me look closer at pipes I had for different 76/77 250 & 400 MC5 bikes.
I am not sure if there are any differences in the silencer ends of the Torque style pipes that started in 1978. Mike

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

[Britt Boyette]

Can you use a 78-79 pipe on a 76-77 250?

Britt Boyette
1976 125 MC5

[brian kirby]

I've never compared them Mike. Are you saying that the expansion chamber sections of the 250 and 400 are identical, and only the silencer is different? Exhaust flange opening is the same too?

Brian

'72 Berkshire

[gooddirt]

Thanks, will get my tape out. LG

[454MRW]

Britt,
As I previously mentioned in the MC5 125/175 vs 250/400 frame diffferences thread, the 78-79 pipe will fit a 76/77 250/400 frame, but you either have to plug the LH petcock opening on the gas tank because it comes too close to the pipe to install a petcock, or use a 78 MC5 gas tank, which has a farther forward mounted petcock and provides enough clearance for the petcock. I actually have a 74 HS MX tank on one of my MC5's, which also has a more forward mounted petcock on the LH side.
Brian,
Comparing side by side my stock 76/77 MC5 400 pipe to an NOS 76/77 MC5 250 pipe I have, they appear to be exactly the same, except for the silencer dimensions outlined earlier. In fact the overall length of the pipes are identical, with the longer, slightly bigger initial size of the 400 silencer (1-3/8") is just fitted 1-1/2" farther up on the pipe, or to simplify the explanation, the pipe is just cut off shorter before the 400 silencer is welded to it, which increases the diameter where it is attached. Even all of the factory creases necessary for carb clearance and frame reliefs for installation are identical on both pipes. from the looks, I think they made one pipe and cut it 1-1/2" shorter where it matches the diameter of the silencer used for the 400. Mike

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

[brian kirby]

That is good news Mike. This gives 400 riders some more options in pipes. Circle-F for example makes a pipe for the 74.5-76 250, but none for the 400. If the stock pipes are the same other than the silencer, Kevin at Circle-F can make that pipe but end it at the outlet of the expansion chamber instead of finishing it with his built in silencer. I asked him about doing just that for a Can-Am pipe he makes and he said that would be no problem at all, he could even send some stinger pipe and brackets for me to finish building the pipe on my bike.

Brian

'72 Berkshire

[454MRW]

Brian,
Sorry to be the bearer of bad news, but the 400 pipe on a 74.5-76 Enduro has a completely different inlet with a down-over-and-back complex entry into the frame and exhaust flange, completely unlike the design used on the MC5 bikes. Maybe Mike Gallagher or someone that has a Mint 400 can post a pic. It is very different than an MC5 pipe, & I don't have any idea if the MC5 pipe would work on a Pre-MC5 400 bike, or if the Circle F pipe would work on an MC5. I know that the Circle F 1978-80 pipe will fit the MC5 with some bracketry change and use of the 78 MC5 tank for petcock clearance, since I actually took the bikes down for him to build those pipes from and have a couple of them. Mike

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

[john durrill]

Brian , Mike ,
 Dont know which year this 400 Pipe is for but it may be of some help.
 This is an old article from Tec Tips.





john d.

[454MRW]

Since that says 400 Mint, I assume that it would be 74.5-76, but I was referring to a picture of the completely different angles of the front of the Mint 400 pipe compared to a 250 pipe. A pic is worth 1000 words. Mike

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

[checkcrew]

quote:Originally posted by 454MRW

Brian,
Sorry to be the bearer of bad news, but the 400 pipe on a 74.5-76 Enduro has a completely different inlet with a down-over-and-back complex entry into the frame and exhaust flange, completely unlike the design used on the MC5 bikes. Maybe Mike Gallagher or someone that has a Mint 400 can post a pic. It is very different than an MC5 pipe, & I don't have any idea if the MC5 pipe would work on a Pre-MC5 400 bike, or if the Circle F pipe would work on an MC5. I know that the Circle F 1978-80 pipe will fit the MC5 with some bracketry change and use of the 78 MC5 tank for petcock clearance, since I actually took the bikes down for him to build those pipes from and have a couple of them. Mike

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

Mike, hi,
here is a pic of my 74.5 Mint 400
2nd pic is my 74.5 Mint 250
these pipes are very different from the exhaust flange to the 1st frame mount !!
hope this helps,




Mike Gallagher, Camden County, NJ.

[Mike Lenz]

Wow this is getting a bit confusing so I will try and help.

74.5 thru 76 GS frame breather bikes 250 and 400 pipes are completly different.

76-77 MC-5 pipes are the same except for the stinger/silencer and are the old style non early snake type pipes.  They will also work on the 74.5-76 frame breather frames with some bracket work and make the 400 run much better.

78-79 mc-5's had the early snake type pipes. 250 being different than the 400. These pipes make both the 250 and the 400 run better yet. They will bolt right up to the 76-77 frames with a flat steel extention bracket for the front mount and plugging of the left petcock hole, or use of the 78 tank. If you run one petcock try and get some from 78, they flow more, or last I knew you could still order a #440 07 005 000 petcock from KTM that flows more and will work.

I use the 76-77 MC-5 pipes on my 75 400 and the 78-79 pipes on my 76-77 MC-5's.

[Britt Boyette]

Good work Mike!

Britt Boyette
1976 125 MC5