The XJ550 was coming along nicely, until I thought I was done and it wouldn’t run right. First of all, it would only run with the choke on. Second, after tuning it to run without the choke, I noticed it would hang in the higher RPM’s and not drop. This was a little scary as it would sometimes stick or even climb up to 5 and 6,000 RPM’s!
After some inquiry, it sounded like my problem was a vacuum leak at the intake manifold. To test this, I would get the bike to idle at a consistent RPM. Then I would spray WD-40 all over my intake boots. When my RPM’s climbed, I knew that the boots were cracked and the WD-40 was being sucked into the manifolds. This meant my boots were old and cracked, and wouldn’t work.
New boots were like $240 for a new set of OEM parts!! Aftermarket boots were better priced at $119, but still way too much. At first I was devastated because it was going to take me a long time to be able to fix this problem. Then I cam across a reconditioning tip that would seal up the boots, and I was so excited. At first it was just to put Black RTV Silicone all over the boots. This would seal them up from possible vacuum leaks. This seemed a little lame and potentially very messy… forever. I did more research and I learned that you can also put a cut up bicycle tube over the boot. Then I learned you can do both, glue the inner tube on using the RTV silicone. The tube was $6, and the silicone I had from a previous project… much better priced!
Here’s my process. You can see in this first picture all the surface cracks covering the boot. Most cracks you can’t see unless you flex the rubber from the inside.
After a thorough cleaning of the boots, I slathered each one up in the silicone. I had to flex the rubber to make sure the silicone would penetrate all the cracks. My first go around with the inner tube was that I was going to cut them long, then trim them up once they were seated on the boot. This was a mistake because the boot has a tapering cone shape and the tube just kept slipping off making a huge mess. I had to cut each tube to size before I put it on with the silicone. They were each about one inch long with a little notch cut out for the vacuum port.
Here’s all four boots repaired. I ended up putting one more coating of silicone at the edges of the inner tube, just to make sure it was sealed up nice. I am very happy with how these turned out.
After getting the carbs installed again, I fired up the bike! What an immediate difference this repair made! The bike revved up beautifully and fell back down to the idle RPM’s upon release of the throttle. I drove it around the block, and it’s running beautifully. Success!