40 mph...downhill....with the wind

qferret

I had the (mis)fortune of inheriting 2 junked XS650's to play with.
The '75 has most of the original parts. I stole the gauges, handlebars, other miscellaneousstuff from the '79.

I got the thing running, but the left cylinder didn't seem to be producing power.
Compression wasn't horrible, but leakdown kinda sucked.

I pulled the head and lap ground the valves/seats. ....world of difference on comp/leak

Now I can't get the timing to work out decent.
Before I took the head off, the timing mark would drift back & forth 3/4 inch or so, which I thought was weird.

How can I tell which cylinder is on the compression stroke when trying to set the cam timing? (aside from cam lobe placement, as it's the cam that needs moving...) Smile

650rider · WebMaster Joined: Feb 09, 2005 Posts: 431

Welcome to the site I really can't help with your question but, just wanted to be friendly to a new member.

Some one will be along to help I'm sure. Mostly I do the web mastering stuff around here.

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

First of all " Welcome Aboard " The timing is based off the right cylinder,so remove both plugs to relieve compression,then place finger in the plug hole ' but don't get it STUCK :roll:,rotate untill compression is felt,then glance at the timing marks on the stator according to the manual and continue to ratate till these marks line up. Adjust the valves at this time on that cylinder and points if ya have them,then proceed to the other cylinder,same procedure. When ya fire it up,nows the time to adjust the cam chain tension,you;ll want the plunger to have a slight in and out movement to avoid over tighting the chain tension....Jack

qferret

thx 4 the welcome and the tips.

So, for "static" timing, it doesn't matter which "stroke" the cylinders are on?
(just set to tdc and align the cam mark?)

grizld1

Correct. Set the punch mark on the cam sprocket vertical, the groove horizontal, and the rotor on the TDC mark. It's a 360-degree engine; the pistons move together, and the cam itself determines which cylinder's doin' what.

qferret

gracias

I'll try the whole shebang after work today again Wink

qferret

Sorry....didn't get a chance to try it today.

grizld1....not to 2nd guess (OK, I'm second guessing) Very Happy

but the advice you gave in 650rider.com/Forums/vi...t=167.html conflicts withwhat you gave me.....

Just want to be clear before I pull the head cover again, hehe

grizld1

Oops! That's what I get for going from memory! Groove vertical, punch mark horizontal and to the rear.

qferret

Progress!!

Static timing is right on the money now.

otor won't start now though.

Using a timing light while cranking the starter shows right cylinder in the ballpark.
(will "tweak" after successfully getting it running)

The left cylinder however, is retarded. Moving the point for that cylinder doesn't do squat....
I would assume something is worn out??

Possible reason it won't start at all:

I dumped a bit of seafoam on top of the cylinders while I had the head off (to check the oil seal) It took a while to seep down, but, as luck would have it someone must have used an impact wrench on the oil plug at some point.

I'll be borrowing an impact wrench tomorrow to remedy that & drop the oil....

kingwj

Did you lock the advance when you timed the bike? If your idle is a up and down you can have the timing marks jump around.

I was taught by a wise German mechanic to adjust valves when there is overlap on the opposite cylinder. The engine on the exhaust stroke has a bit of overlap where the intake begins to open while the exhaust is still closing. You adjust the other cylinder since it will be at TDC for the start of it's power stroke at this point so both valves are fully closed. It's also a good indication your camshaft is correctly indexed to the crank. Overlap is typically only a few degrees rotation so the timing mark should be real close to TDC at overlap. Rotate the engine 360 degrees to adjust the other cylinder. Remember the cam is going at 1/2 engine speed so this works. On multicylinders you need to take the firing order into account. Basically if the cylinder is in overlap the cylinder 180 opposite on the distributor is ready to be adjusted.

Good luck. Hope the tailwind won't soon be needed.

qferret

How does one "lock the advance"?

I tightened the screws holding the point mechanism, if that's what you're getting at. Wink

Pretty sure I got the valve clearance taken care of already.

Thanks for all the advice so far.

Friendly little community here... Very Happy

kingwj

you put cardboard or wedges or whatever behind the weights which are located behind the chrome cover opposite the points, you'll see exactly where they go when you pull the cover. These wedges spin happily and prevent the ignition timing from being affected by centrifigal advance while you time your engine. While you are in there check the springs and make sure everything is free and happy. When you have your low RPM timing sorted remove the wedges(I strongly recommend shutting down the engine first) and look at timing at 3500 rpm to check the centrifigal advance, there is another mark on the stator.

qferret

OK....got the plug removed & dropped the oil....

Ungodly amounts of metal shavings on the plug. I'm hoping that the former owner used the rear plug & the front one just has 30 years worth of shavings on it.. Rolling Eyes

Replaced the oil & tried to start it. It backfires in rapid succession now :))

Tomorrow, I'll "lock" the timing & see what I can come up with.

An electronic ignition kit is probably in my future, but I want to at least get it running "decent" before I stick any serious money into it.

qferret

Locked the timing & zeroed the right side in on the "F" mark
The mark barely moves when changing the left cylinder's point....
The closest I can get the mark is 1/4 inch or so BEFORE tdc

Any ideas?

grizld1

Try narrowing the left point gap to minimum spec., compensate by moving the plate (left cylinder adjustment) toward the advance side, then see if the right side will dial in. Also, see if there are any burrs, etc. impeding movement of the right side points.

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