element51

the pistons move freely, i will to do a very thorough disassembly of the carbs. thanks for the tips!

I used pliers and the screws came right off.. can't believe I didn't think of it sooner. The diaphragms look good(im not sure if thats good or bad at this point haha), still rubbery and no holes or cracks. what else should i check?

those screws are stripped. i guess i have to drill them out and get new ones. Is there any place to get the diaphagm cheaper than $60??

how do you check the diaphragm? i opened up the petcock, but didnt take it apart. I didnt want to tear rubber seal by prying it open. if that rubber seal is the diaphragm, then its still intact. Also, wouldn't switching to prime bypass the diaphragms?

Stock air filter and jetting

It revs freely in neutral, so it's just happening under load. I set the valve clearances already, but that didnt do anything. Dont know how to set timing, but i dont think thats the issue since it only happens under load. The vaccum pipe looks ok but i will check again. However, switching the petcock between prime, res, and on has no effect.

Like the title says, I am experiencing a complete loss of power above 6k RPMs if i twist 1/2 throttle or beyond - it wont even rev past 7k. If I apply less than half throttle, it will happily go to redline. I have adjusted my floats to spec, and have tried it with floats adjusted to 25mm. I put in new main jets (135s), and cleaned+synced the carbs again but it still doesnt want to rev. The bike is running well other than that. any suggestions are greatly appreciated

just took it out for a spin today and the engine is much quieter overall, but the noise was still there. turned out that the center stand was hitting the crossover pipe on the exhaust.

the valves were on the loose side, so i tightened them up, and the noise seems to be gone while the bike is stationary. It's been raining here so i didn't ride yet but the valve adjustment seemed to do the trick.

thanks guys. I havent thought about checking for loose nuts+bolts, but will do so. Adding oil to the top of the line(even a little above it) didnt help. I also noticed that the noise happens most between 3-4k. I'll check the valves this week or the next

I am checking by looking into the sight glass on the side of the crankcase, it's between the lines, using 20w40. I will check valve clearances in the coming weeks, what gaskets do I need to order?

I sprayed starting fluid on the butterfly seals and the carb holders, but there was no change in rpms. is the procedure to check valve gaps in the service manual, or is there a write-up? Can I check the cam tensioner/chain at the same time?\ As far as oil, i changed it recently and its between the marks when the put the bike is on the center stand.

hey guys my 1980 xs400 is making a high-pitched chattering noise around 3k rpm. It's very loud when riding, and happens throughout the whole rpm range. It's been doing this since i first got the bike. Since the clutch was on its way out, I changed the clutch, and also synched and cleaned out the carbs. In a possibly related issue, the engine doesn't pull past 6k rpms at WOT. However, it goes all the way to 9k if i leave it at 3/4 throttle. I uploaded a youtube video so you could hear the sound. Any ideas? http://www.youtube.com/watch?v=ZtvLYmsoPH0

thanks for the response!

My buddy is parting out one of his old bikes and offered me his rear air shocks for cheap. Are there any advantages/disadvantages of air shocks on an xs400 compared to regular springs+struts? Any reason why I shouldn't get them?