Penton Hare Scrambler exhaust

[Daniel P. McEntee]

Vibration will eat through rubber pad in a heart beat. Looks to me you are going to have to do some metal work somewhere. The simplest and quickest to me (if you aren't a stickler for looks) would be to make a chalk line on each side of the frame tube while the pipe is installed. Then remove the pipe, and find another piece of round stock to lay between the chalk lines, and start tapping it with a hammer. Lots of light taps, until it looks like you have at least 1/4" depression. I don't think this will affect the performance of the pipe, but I reserve the right to be wrong on that.
   Another way to look at it is the two points that locate the pipe where it it is the top rear mount near the silencer, and the lower mount underneath the pipe above the right foot peg. You need to somehow shorten the lower mount, then lengthen the upper mount. The bottom bracket on the pipe could be shortened by careful hammering or cutting and welding. Then test fit the pipe. If it all clears, then you remake the top rear bracket to suit. One way or another, I think you will have to rework some metal for this pipe to fit your bike.
  In my limited experience with Pentons so far, this probably isn't unusual for a part to fit one bike like a glove and then not very well on another frame. Given the almost hand built nature of each bike and normal human errors, it's gonna happen. I would think that you just need an honest 1/4" to 5/16" clearance between the pipe and the frame tube, or anywhere else the pipe comes near. You just gotta get the bike up on a stand where you can see it from a lot of angles and sight things out to determine which way you need to go. Just remember that if you increase clearance on one side, you take away clearance on the opposite side.
   Good luck with it,
   Dan McEntee

[454MRW]

A lot simpler solution would be to change out the rubber isolation mount on the lower side of the pipe with one that's not as thick which would bring the pipe down away from the frame. Not exactly stock looking but a good solution nevertheless. your mount does not look bent, but a slight bend might change it slightly. 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

[Andreas Piepke]

Thanks for the input! I will for sure need to go one of the routs mentioned, it can't stay like this.

Andreas

[454MRW]

I just went back and reread that you mention this is a 73 250 HS not a 74, which the pipe for a 73 has a slightly different mounting at the top left hand side above the engine and all of the 73 250 pipes that I have seen had the big club tail and not the MX silencer, which may be why the fit is tight, although the slight modifications mentioned should allow it to work okay. What threw me off was the red airbox, as 73's are yellow with a yellow tank. If it is actually an early 74 starting with 54-311 or later on the frame number, that pipe would be correct. I know when you got the pipe it has a SuperTrapp silencer on it that you replaced with an MX tip, but the perforated bracket on the pipe just above the engine is 74 style not 73. 73 uses a smaller straight tab, which might move the pipe and change the angle of the pipe slightly, which would also relive the observed distortion at the rear bottom mount rubber as well. I also notice that on that lower rear bracket insulator, there is a pinkish/tan color 1/8" thick heat insulating washer in place that does not belong there, it is however used on the rear position mount against the bracket on the pipe, and also on the front insulator above the engine positioned against the pipe bracket. In the following pictures is a 74 Enduro pipe with the same front bracket as you have, followed by a 73 pipe with the different style and position front bracket. That insulator incorrectly positioned would raise the pipe 1/8" by itself, and from the looks of the 73 yellow tank HS pic, the 73 mounting tab would lower the pipe some in the front, also changing the pipe position. Lasty, the same borrowed pic of the most common 73 250 HS pipe that I saved on my computer. Notice the rear mounting tabs for the rear fender, which differ from your 74 stamped tin mounting tabs on the corners of the rear fender loop, most likely identifying your bike as an early 74 Red Tank 250 HS, like my own 54-311. 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

[Andreas Piepke]

Hi Mike,

Your message has a lot of information! The VIN on my bike is 54-311 so I guess this makes it an early 1974 model like yours. That said, the pipe on the bike didn't come with the bike. I got it separately the way it is, except for sandblasting and painting, of course. However, the one that was on (was in bad shape) had the same front attachment tab as my current pipe, it was broken. So the exhaust seems to be correct then. The air box and tank are both red, and not painted but still with the gel coat. The seat is thicker than that on your pictures of the yellow bike. The engine was black, though, which is only the case for the 73 model as far as I understand.
Coming to the heat shield washer: I don't really have the right parts list for this year, I guess, and couldn't figure out how to place this component. The chosen ordering made sense to me. The metal holding bracket of the pipe is hot, so I put the washer between the metal and the rubber. This is to insulate the rubber from the high temperature metal and prevent it from melting. Where would you put that part? I could put it inside the metal bracket to lower the exhaust but I don't know what it would be insulating there.

Thanks for your detailed observations, this is definitely helpful beyond the pipe!

Andreas

[454MRW]

There is no need for an insulating washer in that position, because of the design of the bracket, which forms an open square where the mount attaches and air passes through that pipe mounting bracket, but the others have a more direct attachment, and do need the insulating washer. The assembly pieces depicted in the spare parts manual-007 clearly show no insulating washer in that position and one used in each of the other 2. Very early red tank 74 Hare Scramblers did have black enignes depending on the serial number of the engine. 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

[Andreas Piepke]

One more thing on the model year of my Hare Scrambler: while the VIN (54 311 .....) indicates late 1973 production, the little clock cast into the right engine housing half indicates March 1973. This was either a left-over engine or someone combined these two components some time back.
I'll try swapping the rubber mounts. This is easy enough to do.

Cheers

Andreas

[454MRW]

The clock date is when the cases are cast, which is before they are machined and then later assembled as a complete engine, which may occur quite some time later. What is the engine serial number? It is located just above the right hand ignition cover just below the cylinder fins. 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

[Andreas Piepke]

The engine number is: 54 30 003010. Does it allow identification of the assembly or installation date?

Andreas

[454MRW]

That sounds like the case casting # found by the clock date. The engine ID is a stamped in # like 3-54xxxxx directly above the motoplat ignition cover by the front engine mount bolt hole. My 311 dated frame bike has # 3-5401964 stamped on it. 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

[Richard Toghill]

The pipe on my 74.5 250 was completely trashed and my only option was to buy a new one from Dorino Pillon in Italy. It was a bit of a job to fit but looks and sounds fantastic and is an exact replica of the original - and it only cost £416 ($675)[][][]

[Andreas Piepke]

Thanks for all the input. So I switched the rubber mounts and put the one with the heat shield on the front mount. In addition I used the "tap-tap" method to make some more room between exhaust and frame. That worked, now I have clearance between exhaust and frame. The exhaust is still somewhat strained, visible at slight deformation of the rubber mounts. That can't be helped, I guess.
Richard, I already exchange emails with Pillon Dorino earlier this year. His parts do look awfully nice. However, he told me that he can't ship an exhaust to the US as it is too long. Maximum shipping length into the US is 1.0 m, while his exhaust for my Penton is 1.4 m long. The price he quoted to me on 4/30/2014 was 370 Euro (or about $460), quite a bit cheaper than the number given above. Richard did you manage to get an exhaust shipped by Pillon Dorino?

Thanks again for all your useful input!

Andreas

[454MRW]

Just out of curiosity to add to the information gathered so far on early Red Tank Hare Scramblers, were you able to find the engine serial number located by the front RH engine mount, if you don't mind sharing. 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

[Andreas Piepke]

Yes, I found the number cast into the right side engine case, and no I don't mind at all sharing it. The number is 3-5400253. Does this allow to narrow down the production date?

Cheers

Andreas

[454MRW]

Wow! That us the 253rd 250 engine produced. It must have been a lot earlier in 1973 than the frame. Compared to my 1964th engine produced in 1973, that indicates quite a lag from engine build to installation if that is the original engine. There is no telling if engines were used in a particular order, or just stock piled, then grabbed randomly for installation in a chassis as they were needed. Thanks, 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