How do I confirm cam timing is correct?

[vallartenses]

I just bought an 83 xs400 maxim (DOHC). It's complete and rust free but has been sitting for a couple years. I've cleaned the carbs (they were truly gunky, it took 3 days in the hot sonic washer to get them clean), installed a new battery, put on two new tires, and replaced a defective right bar switch. It now cranks and I get spark and have fuel ... but all I can get it to do is fire back through the exhaust. It seems that either ignition and/or cam timing is off.

Questions:
Which cylinder is #1?
Which ignition sensor, upper or lower, fires cyl #1?
Are there marks on the cam gears to confirm correct cam timing?
Where is the timing mark and/or TDC mark, and how is timing set on the bike?

I'm a parts guy in a motorcycle salvage shop (Stocker's in San Diego), and I'm having our tech guy do the work, but we don't have a DOHC manual and the only one I can find online is $80 directly from Yamaha. That's more than I spent for the bike! Can anyone walk me (my tech actually) through the process of making sure I get "bang" at the right time after "squeeze."

Your help would be most appreciated. It's a nice old bike and I'd hate to give up on it and consign it to salvage...

 

[drewpy]

I think there is a manual on this forum if you do search.

welcome to the site BTW

 

[vallartenses]

The manual posted here is for a SOHC, and the Maxim is a DOHC. If anyone has access to the manual for the twincam, however, it would be greatly appreciated.

Thanks for the welcome. In all the years I've been riding, this is the first Yamaha I've owned. I'd like to cafe it, but first I have to get it running!

 

[hmusket]

For every bike I've had, #1 cylinder starts on the left. For grins and giggles try switching the plug wires, and see if that helps. Unless somebody messed with the top end timing shouldn't be an issue.

 

[vallartenses]

Thank you for the suggestion... but I already tried that. That's why I think whoever had the bike before me rather seriously messed things up and I'd like to start from scratch to confirm things are correct.

 

[hmusket]

You might want to check out xjbikes.com. Even though its for XJs, they might consider your bike a Maxim and include information about that model on the site, and there may be other owners.

 

[foul]

http://www.xs400.com/forum/showthread.php?t=4503

Post #3 is DOCH manuals.

 

[drewpy]

there is something here that may help (in German)

http://xs400.net/wb/pages/technik-faq/motor/motorueberholung-12e-nach-70.000km-von-schelle.php

 

[bentwrench]

I just rebuilt my 82 DOHC, and I can answer questions 3 and 4.

Yes, there are marks on the cam gears. You don't need to drop the engine to see the cams, just remove the tank, remove the top engine mounts (the engine won't fall, but I needed a jack to move it back into place for reinstallation later), and then remove the engine cover (don't go circular around the cover - go opposite sides to prevent warping.)

On the left side of your engine, there are two circular plugs that can be removed with a quarter. The larger lets you crank the engine by hand (turn counter-clockwise), and the smaller lets you see when you're at TDC and lets you see your timing mark. Obviously, check your cams before you check your timing.

You can completely remove the cams if required without dropping the engine. The timing chain tensioner is on the back of the engine just under the carbs.

All that said, though, I'd start by checking your cams, and then double checking your carbs. I hope you visually balanced them before putting them back on - it doesn't take much for your engine to run like poo if they aren't correct.

 

[amkxxx]

Hi my bike runs poorly after rebuild. I've had some doubts when installing and timing camshaft. The manual says:"Turn the crankshaft so that alternator rotor "LT" mark aligns with the timing mark. Then position the camshaft so that the locating pin faces upwards" I didn't find a locating pin. What's that? i assumed it was a little hole in camshaft. Please advise!

 

[xschris]

The pin should be in the hole on the cam shaft. If you have points it is what turn the governor and if you have e-ignition what turns the rotor for the pickup coil.

 

[amkxxx]

Thanks, thats very helpful!

 

[ecaves09]

I'm having a lot of trouble with my timing. The names EJ, just put rings and a new head gasket on my '78 xs400. Ran before but was blowing oil from the right cylinder...anyways I'm having trouble with the cam timing and driving me nuts!!! Where should this be set? I've been told #1 loves facing down with the two lines horizontally, but the told they should line up with the head? (Which is slanted) can someone please post a picture of tdc #1 please?

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[xschris]

When the cam pin or the cam sprocket alignment mark ( if you have not removed the sprocket ) is at 12 o'clock this should be Left TDC. line it with the rotor ( also at 12 o'clock) marked LT. Then follow your manual for the rest of the timing and points adjustments.