The Sound of Silence. OEM silence.

Something has been nagging me. I wasn't able to put my finger on it until I looked at the date of my last post. Unfortunately what was nagging me was that the last time I posted was two months ago. In my most recent couple of posts, I mentioned a parts buying spree so that I could make the good old XJR400R a bit closer to its original stock appearance and performance. The first thing was getting rid of some aftermarket turn signals on the front. A controversial un-modification to be sure. In the following post of the series, I did a bunch of cleaning and replaced my countershaft cover. The last bit of work in my trilogy of repairs is going to be covered in this post. This was a long time coming and the end result was very worth it. Read on for more!

Here is a picture of the exhaust as it came when I bought the bike. I wrote about adding some extra packing to it to tame some of its roar a few weeks after first getting the bike. It is a copy of a Yoshimura style superbike system from the early days of superbike racing. Fun fact: what we now know as World Superbike started from the early days of American road racing. Anyway, it is a a 4-into-1 open pipe system with some fiberglass baffling. It would be great for racing. You can see why this design has been copied copied often. The original design is super simple with just a couple of cut and welded straight sections. The main pipe is a continuous diameter from the collector to the tail. With the baffle removed there would be almost no restriction for high velocity gas escape at red end of the tachometer rev range. At home trying to warm up a cranky, air cooled, four cylinder while my neighbors are still sleeping is a good way to get the stink eye.

Since it is a copy, the material choice has lead to some pretty predictable results. I am sure that the material is just mild steel with a pretty thin wall. The heat and vicinity to the often wet road surfaces here in Japan have taken their toll and resulted in some heavy, but not debilitating corrosion. On the plus side, the design and material selection gives a very lightweight system. In the picture to the right you can see the OEM two piece system I picked up on Yahoo Auctions Japan. The copy-Yosh complete pipe weighs less than the header end of the OEM set. The entire stock exhaust is almost three times heavier than the old custom piece. In this case I am specifically trying to add the weight. The back half of the OEM system has a large megaphone presumably full of baffling and more importantly it has a weird, bulbous resonator that knocks out the harsh tones of the revy little motor. 

Before cramming the new piece in place, I took some time to give it a clean and inspection. I paid a little over $100 US in the equivalent Japanese coin for the unit. I had to wait a while before something worth bidding on popped up. Most of my searches turned up foul, dented and crusty pieces not fit for reuse. As usual when this one came up at least two other equally nice looking systems also popped up. This one had what I was really after and that was a picture of the date code for the bike model it was taken off of. The XJR400 had a couple of generations and mine is the earlier one. While the outside appearance between the generations is very slight, the parts numbers don't always match up. This system was in the color I wanted, the condition I wanted and had the date code clearly marked confirming that it would match without modification. Easy choice.

Installation was surprisingly straight forward. Thankfully the old exhaust stud nuts were not seized to the their studs and actually came off pretty easily. There were no gaskets between the pipes and exhaust ports. I picked some up locally after I got the system delivered. As a one piece system, the old exhaust came right off once I was able to free up the header side of the unit. The OEM system was installed starting at the headers. With the gaskets in place, I had a hard time getting all of the nuts started on the threads. There were lots of tight spaces that my hands couldn't quickly reach. After a bit of struggle, I managed to get two or three nuts started and then tightened them up evenly starting with the inner studs. After the whole system was mounted I came back and gave them another go with the wrench. The muffler end needed a little bit more persuasion to get fully mounted. I installed the megaphone to the slip joint on the header and loosely installed the rear mount bolt on the right rear passenger step. There was a mounting bolt under the bike that supports the resonator which took the most time to get lined up. Part of my issue was using a bolt just a couple of threads too short. All in all I was able to do it in a hour's worth of messing about. I am quite pleased that my pre-move tool selection included enough tools to get jobs like this done. I still miss my full garage, but at least I can do some wrench turning on my projects.  

And here is the end result. Kind of looks like it was meant to be there doesn't it? Just like my desire to replace the stock turn signals, many people won't understand why I would want a heavy, quiet OEM exhaust on the bike. I like the roar of a fast bike as much as anybody. As I get older I find myself appreciating the original quieter engine melody. I didn't get a chance to ride the bike with the new system yet. I have some other repairs to do that are keeping me off the bike. I was able to start it up a couple of times in the driveway. It is definitely much more quiet. The overall tone and frequency of the exhaust sound also changed. It still purrs, but instead of sounding a bit wild and angry it is more ready and non pulsed. Kind of hard to describe, but so far I am happy. It looks good even if the muffler is a bit big. Ground clearance wasn't affected and I couldn't feel any interference with my boot heel. Super!

As I mentioned I am elbow deep in some complimentary induction system repairs. I actually have a good portion of the top side of the bike pulled off and in bins. I got a cool new tool that will be put through its paces with the work I am doing and I am hoping to cure an issue that has caused a bit of grief and cost me some cash. The riding weather recently is really nice. The cooler weather makes the bike run very well. Who knows if I will be able to get the repairs done and get a ride in before it either gets too cold or we go into some form of pandemic related lock down in my part of the world. I have plenty of projects to keep me busy, but it would be a shame to lose this weather. If you have a chance to ride, please take it and ride safe. Catch you next time!

Mat