74 400 - Aftermarket Pipes

[KJDonovan]

Just finished freshening up a 74 400 and took it for a shakedown run this morning and have one issue I am looking for some advice / insight on.  I picked this bike up this spring and it was all there but the PO made some rather extensive modifications (Husky Reed Block / PWK Carb / Magnum Pipe) that I really didn't care for so I decided to get it as close back to stock as possible.

This will just be a rider but just the same I wanted it close to stock.  So I am back to the stock 38MM Bing and the original intake.  But did not have a 400 pipe available and the Magnum pipe that was on it did not fit well where the pipe attaches to exhaust manifold.  The pipe in this spot has about 15 degree down angle and the PO forced it on the exhaust manifold, breaking 2 bolts and then just gooped it up with high heat RTV.  So I used an extra 74 250 pipe which fits perfect, but is just not right and anything over 1/2 throttle it just can't get the exhaust out fast enough and bogs like it has an exhaust restriction.  

So I have couple questions, first anyone else ever run one of the Magnum pipes on a Mint 400?  And if you did, did you replace the stock exhaust manifold with one that has a slight down angle?  I am asking because I don't know if a manifold with a slight down angle exists, if they do then I could probably get the pipe to fit well as all the brackets line up well, but it just has a different angle where it slips on the exhaust manifold.  If only straight manifolds exist, I will just chop the end off the pipe and re-fit it properly and re-weld it but would rather not go down that road if I don't need to.

Any ideas or advice is appreciated.

Thanks,

Kevin

[Mike Lenz]

78 and on have a down angled manifold, but down angled at about 30 degrees (from memory).  Will bolt up to an earlier cylinder.

[KJDonovan]

Mike,

Thanks for the information, much appreciated.  I ended up spending a good part of the day yesterday attempting to rework the Magnum pipe.  I basically cut it apart and tacked it back together in place trying to eliminate all the interference points and the downward stress on the exhaust manifold.  Previously, it was touching the frame in 4 places.  I was able to eliminate those but it still fits badly and the OD of it where is passes under the frame and out the right side is just too big, so large that I can't even attach the right side cover.  My best guess is this pipe was not made for a Penton or not this one anyway, but will have to do until I can locate a 400 megaphone pipe.

Thanks,

Kevin

[Andreas Piepke]

Kevin,

Have you ever looked at the Italian web page of Pillon Dorino? They make all kinds of parts for vintage KTMs, pipes included.

http://www.pillondorino.com/index.php?_r=2511&cat=5

Maybe this gives some guidance on how a correct pipe should look like. I exchanged emails with Mr. Dorino and was told that he can't ship anything into the US longer than 1 m. So a pipe won't work.

Cheers

Andreas

[Doug Knight]

What's so hard about cutting in half at a convenient joint. Use to do this with British sports car exhausts years ago

[Daniel P. McEntee]

Cutting the pipe in two before shipping occurred to me also. Maybe even leave it unassembled at a convenient joint? a couple of alignment marks scratched ito the surface will help when welding back together, or assemble on the bike to tack weld it for that perfect fit. I really dinged up pipes, I've cut them at the joints to make it easier to pound out crushed sections, especially when they have creases in them. Nice looking pipes, but notice no pricing. I'm guessing, if you have to ask, you can't afford it?
   Type at you later,
   Dan McEntee

[KJDonovan]

I looked into pipes from this supplier before and if memory serves the price ($600+) was just too much money to shell out for a pipe in my opinion, actually more than I paid for the bike. As far as ordering one in 2 or 3 pieces and then dry fitting it to the bike and tacking it up in place I would have no issue with that.  Same as Dan I have chopped up plenty of pipes to remove dents and creases.  I would also add that I believe Roberto from Parma Bike imports pipes from this supplier from time to time, but again just too pricey.  I will keep my eyes open for a used one, I am guessing someone has one hanging from the rafters collecting dust.
Thanks,
Kevin

[Andreas Piepke]

Last year I asked Mr. Dorino for a price and got a quote of 370 Euro for a 1974-1976 KTM 250 MC pipe. Shipping will have to be added. He also talked about sales tax, however, for an export outside the EU there should be no sales tax. Given today's exchange rate the price is more like $415. I didn't ask for a pipe shipped in sections, maybe I should.

Cheers

Andreas

[KJDonovan]

Just wanted to circle back to this post, as I have resolved what I thought was a pipe that was too small.  After going through the trouble of reworking that Magnum pipe I was still dissatisfied with how the bike ran so I took a step back and thought about it for a while.  

The bike was acting like there was an exhaust obstruction after running beyond half throttle for even short periods of time, but always recovered when I backed off the throttle.  It did basically the same thing with the aftermarket pipe which I knew was clear because I just cut it up and put it back together.  

So I decided to check and see if it was getting adequate fuel...bingo!  The cork in the tank cap was rock hard so it was not getting enough fuel quick enough past ½ throttle.  Took care of that and then went back to the 250 pipe as I hated the look of the aftermarket one and I didn't care to have it frying my leg all summer.  I pulled out all the old packing and burned it out again with the acetylene torch and then repacked it with some attic insulation.  

Put it all back together and problem solved.  Bike is a screamer, the more throttle you give it, the more it wants.  No hesitation, bogging, farting, pinging or any issues, just 100% nut from an idle to WOT.  With the bonus being it's a super easy starter, thanks to the compression release and a fresh motoplat.  Looks like I have a decent rider for the summer.  

[image]http://i621.photobucket.com/albums/tt298/KJDonovan/400R.jpg[/image]


Kevin J. Donovan
Foster, Rhode Island
72 Jack Piner
72 Six Day
74ish Mint 400
74 Hare Scrambler
71 Suzuki TS125
72 Montesa Cota 123
72 Montesa Cota 123T

[JCHubbard]

Kevin, congrats on getting that exhaust and gas cap issue worked out.

Curious about your compression release. Where did you mount/install it?  Did you utilize 1 of the 2 spark plug holes on the cylinder head or did you mount in the rear of the cylinder?  

Don't have problem starting my 78 400 MC5 (Enduro set up), but would love to minimize the stress on the KS shaft.  

BTW: Your bike looks GREAT!

Thanks,

JC

[KJDonovan]

John,

The head on this bike had the 2 plug holes so I installed the compression release there.  I just barely crack it when I kick it over and immediately release it.  Fires up first kick and purrs like a kitten.  Wasn't going for a pretty bike here, just a runner but it does look better than decent.  Colors are wrong, but I had plenty of red paint and not much white, so it I guess that makes it a 400 Berkshire.

Thanks,

Kevin


Kevin J. Donovan
Foster, Rhode Island
72 Jack Piner
72 Six Day
74ish Mint 400
74 Hare Scrambler
71 Suzuki TS125
72 Montesa Cota 123
72 Montesa Cota 123T

[JCHubbard]

Kevin,

Thanks for your prompt response.  I'm going to install mine the same way too.  Berkshire 400 -- has sort of a nice ring to it!:) That's a good lookin' runner! Thanks again for your help Kevin.  

Cheers,

John