engine noise

[dukid]

Hello, i recently bought a 1982 Yamaha XJ400, when getting it home i noticed that it made a weird clunking/ticking noise from the engine, some guys told me to check the valve clearance, i did and 2/8 valves were too tight so it shoulden't be the valves that are making the noise.

The bike has a pretty rough idle and plug 1 & 2 are kinda white while plugs 3 & 4 are black after just starting the bike up a few times.

I appreciate all the help i can get!

[Socer4m]

HI Dukid,,,,,first thing is to adjust the valves before causing any damage then,,,,,adjust the cam chain. This bike is different size than the forum bikes here which are 1100cc, but I am assuming the tuneup is about the same even though its a twin cylinder. on youtube or use a manual if you have one and adjust the cam chain, usually on the front of the engine. Also check the engine oil level, the manual should tell you if you check it on the sidestand or if bike needs to be vertical...then do a carb synch and idle mixture adjustment,,,,all on the carbs. If you dont know how to do that go to youtube or read the manual, .get a can of carb cleaner and dump it in the tank.......do all that and fire it up again and get back to us on the updates.....Mike in San Diego

[Socer4m]

almost forgot,,,,clean the plugs with sandpaper and spray carb cleaner on them,,,,adjust the gap on them and put them back in with some antisieze grease on the threads as these can easily strip the aluminum heads threads,,,,

[Tonyxs11]

first of Socer4m its a 4 cylinder, and dumping a can of carb cleaner is not the way to go !!!!!!!
if the plugs are different colours then their is a carb issue, the way to go is pull the carbs off and give them a proper clean and then set them up (float heights) then do a bench test before fitting them back on the bike, setting up a dummy tank will check for the carbs leaking, if so it could be the float valve needs replacing, i sign of black and sooty plugs.

[DEEBS11]

All good advice. Also, even though the valve lash was tight you could do a quick compression check with a meter. Remove all spark plugs (to cut down on compression drag) and test each cylinder with the throttle wide open turning the engine over with the starter motor. If one cylinder is dramatically different than the other three you might have a bent valve which would cause the noises you are describing. Carb cleaner in a fuel tank is fools gold. A worthless attempt to cut corners on a true carb disassembly and cleaning. Bottled carb cleaner is the wrinkle cream of the motorcycle world. Snake oil.

[LAB3]

A compression test would yield a more accurate result after the valve lash is properly set up. If the clearances are too tight one or more of them could very well not be seated properly.

As to noise there's a very common issue known as "cam walk" that could be causing it. The side to side movement of the camshaft often doesn't begin to show up until the engine has warmed up a bit. This is merely speculation at this point, if a video was posted with decent sound quality an experienced ear might help point you in the right direction.

As already mentioned, start with the basics! Get the valve lash set right, make sure the cam chain is adjusted properly and go through your typical maintenance steps like spark plugs, oil change etc.

[cajun31]

Hello, i recently bought a 1982 Yamaha XJ400, when getting it home i noticed that it made a weird clunking/ticking noise from the engine, some guys told me to check the valve clearance, i did and 2/8 valves were too tight so it shoulden't be the valves that are making the noise.

The bike has a pretty rough idle and plug 1 & 2 are kinda white while plugs 3 & 4 are black after just starting the bike up a few times.

I appreciate all the help i can get!

Tried to look up the schematics for your bike and they are basically unobtanium. What you have is a rare bike that was built and sold in a limited market. The suggestions you will get from this forum will be generic, meaning that most of us have never laid hands on your particular bike. I would suggest you go over to XJBikes - Yamaha XJ Motorcycle Forum. Very good site with many members that have XJ bikes. The 400 version was a rare size in XJ bikes. My understanding is that your bike is very similar to most inline fours. I also believe that your bike is equipped with YICS. In order to adjust the carbs, if your bike is like the XJ1100 you will need a YICS tool. The suggestions already given are good starting points on any vintage bike. Good luck with your project.

[DEEBS11]

I had an XJ600 Turbo for a while that I restored. I made the YICS tool from threaded rod with info of the internet. Weird things Yamaha engineers do.

[DEEBS11]

Dukid, earlier I had mentioned the compression test before the valve adjustment to save you some grief. I you have a bent valve, you will be wasting parts and labor on a valve adjustment which will have to be re-done after the valve is repaired. A few thousandths of an inch discrepancy in a shim will not change the compression reading as much as a valve that is not sitting on it's seat. If you find that a cylinder is off by 25% or more you need to concentrated your labor on removing the head and replacing the valve and perhaps the softer guide if it is ovaled out. If there is not a suspected bent valve then It's cost effective to go ahead and concentrate parts and labor on the valve adjustment/cam timing check.