Tired of cracked pipes and leaking exhaust manifolds?

[joseph hollinger]

No reward for being subtle. Do what Larry suggests and your problems are largely cured. Do what Chris suggests, along with what Larry suggests and your problems are almost certainly over.
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A lie gets halfway around the world before the truth has a chance to get its pants on. -- Winston Churchill.

[Andre Eriksen]

[Ken Schilling]

Hello Andre,

My being a machinist for ~18 yrs before being in metalworking cutting tool sales for ~15 yrs now, I can very much appreciate the time, creativity and craftsmanship of the items you've created (both the o-ringed cylinder head and exhaust manifold projects). You have solved your problem but here are some things that I've done in my experience that I believe added altogether have also solved any potential problems for me. Oh no, now I've just jinxed myself...!

Here you are addressing a problem that was especially common last year but since seems to have greatly diminished and/or vanished.

I'm convinced that RLV had a bad batch of R4 pipes go through production causing a rash of cracks & breakages. Many pipes were thrown away while some were repaired by RLV. I'm also convinced that shifter drivers/mechanics have gotten better at mounting the whole system.

The photos below show my R4 pipe which is ~ 3yrs old and has never broken or cracked. During the pipe's life I've used the same mounting and setup ideas for my '99 CR125 SKUSA Spec Honda:

- Hegar pipe and silencer support brackets. I've taken great care to add rubber bushings under each cradle to not only reduce vibration but also to adjust the height of them for the best fit. I also have slightly bent both brackets left or right for perfect alignment.
- SwedeTech 3 o-ring exhaust manifold. I use Viton -030 o-rings as the Viton is the best material for this application as it helps resist the heat. I squirt just a little bit of WD-40 on the o-rings to help the pipe slide on as I've found that doing it dry damages the o-rings and can even pull them out of their grooves. While sliding the pipe on I very slightly wiggle it around the exhaust manifold to ease installation. I also take care to clean the inside of the pipe header flange with WD-40 and/or Carb clean with a Scotch-Brite pad to remove any carbon buildup or o-ring residue. I find that a set of o-rings lasts a full practice & race day before excessive blow-by sets in.
- Akrapovich rubber isolated springs for the exhaust manifold and pipe/silencer connections. Note: I recently switched to using 2 springs on the exhaust manifold connections with no issues (I used to use 4).
- I've never used hose clamps on the pipe cradle as I believe that springs allow a little bit of "float" giving the pipe some freedom of movement/vibration if/when needed.
- I use a thin layer of rubber matting for both the pipe and silencer cradles allowing "float" giving the pipe/silencer some freedom of movement/vibration if/when needed.
- I also use one of those rubber "boots" around the pipe/silencer connection as well as RTV high temp silicone (red) inside the connection to help dampen vibration as well as minimize exhaust leaks. I also use two zip ties around the "boot" to hold it in place. p.s. - I don't use RTV high temp silicone on the exhaust manifold as I find I don't really need it and it makes a big mess...
- I've taken great care to make sure that the pipe & silencer are aligned perfectly as well as making sure that there is no pre-stress on any of the parts mounted meaning that the pipe and silencer rest lightly on both cradles and that the pipe is aligned properly on the exhaust manifold. This includes removing and rotating the silencer end where it meets the pipe to minimize any of the springs from "wrapping" around the connection. I also use RTV high temp silicone at this connection to help prevent leakage as well as vibration dampening.

Your results may vary...





p.s. - Jason/SwedeTech mentioned it above and is correct in that SKUSA has been testing a new twp piece R4 spec pipe with great success. The new design will help eliminate the previous problems as well as provide more mounting adjustability between the '99 & '01's and I've heard that it will come with a 6 month warranty.
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Ken Schilling
#21x / S4 / ProKart Challenge (PKC)
SKUSA Data Administrator

Good luck is where preparation and opportunity meet!!!

The opinions I express are mine alone and do not reflect those of any organization of which I am a member.

[Andre Eriksen]

Hi Ken,

If you read my original post you will see that I did some of my mounting the same way - for example I did not use clamps on the pipe to make sure there is not tension, I do not use silikone, there are rubber between the mounts etc. and as I also wrote - I have one pipe that I never had any issues with. It has many races and countless test days on it.

And then I have another pipe that cracked right away. I now have $800 worth of pipes and as I have free access to CNC machines etc. this was a quick fix for me and it works. It also does not leak black oil residue all over my engine.

I believe you and Jason that they have foudn a fix. Good for them - not so good news for all the people who already bought their pipes... My fix would also cost money to implement, however in my case it did not.

I am going to make som CNC made manifolds and then you can heat the end of your pipe and flange it out with no other modifications. It is not SKUSA legal but I am fortunate enough that is does not matter to me

Today I have an office job, but as I am educated as a tool maker (before I became an engineer) this is my way to still get my hands dirty with CAD drawings, milling machines and lathes (I've built quite a few of custom Harley's as well)
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2012 Formula Car Challenge Vice Champion (Pro Formula Mazda)
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2010 NorCal Rotax Masters Champion
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