Firing on one cylinder

Hutzpah · Posted: September 27, 2009, 3:26 am Post subject: Firing on one cylinder

My xs650 1979 is only firing on the right hand cylinder any idea what to check?

I have had the engine out over winter and put first over sized rings on standard pistons it was doing this the very last day I rode it but as the engine was coming out didn't worry about it at that stage.

Starts up and idles nicely on right hand cylinder only have so far looked at the spark plug it has visible spark when on the side of the head and all so had the timing light on and timing seems good.
Checked valve gap.

I had the carbs off not that long before I stopped riding it maybe that's the next thing to look at.

The good weather is knocking at the door so am hoping to get it back on the road for anther summer of fun.

thanks

Hutzpah

despecial · Posted: September 27, 2009, 4:32 am Post subject: Re: Firing on one cylinder

does it have points-if so is the lhs closed or burnt?
compression? burnt/broken valve seat?
clean the pilot circuit and the screen under the float valve
rubber inlet manifold kaputt?

??first over sized rings on standard pistons??

Hutzpah · Posted: October 15, 2009, 7:55 am Post subject: Re: Firing on one cylinder

Firstly thanks despecial for the comments.

Well I was wrong when I said "timing seems good"
I think I have a stretch cam chain as my timing is too advanced The bike is starting on the right cylinder but only runs on both cylinders when it is reeving up through the gears.The left set of points are set as far as they can go anti-clockwise.

Am I thinking on the right lines here that the cam chain is the problem?

Firstly I cleaned the carbs with carb cleaner then replaced high tension leads
that were old and one was leaking.

I was thinking of making the slots bigger to get through the summer or would
that be a sin and have effect on values etc?

Your thought appreciated.

Hutzpah

pamcopete · Posted: October 15, 2009, 9:09 am Post subject: Re: Firing on one cylinder

Hutzpah,

A stretched timing chain generally results in retarded timing.

xsleo · Posted: October 15, 2009, 11:14 pm Post subject: Re: Firing on one cylinder

When he had the engine apart to redo the rings, he may have put the cam chain on, one tooth off on the cam. This would put the cam timing off by 10 degrees. This is about how much room you have to move the points from centered to one end off the adjustment slot.
aking the slot longer will make the points move far enough, but the valves will still be timed wrong.
To check the cam timing. Line up the timing marks to TDC. The pin for the points cam should be straight up or down.
If the pin is off, the cam is off.

Hutzpah · Posted: October 16, 2009, 6:59 am Post subject: Re: Firing on one cylinder

"A stretched timing chain generally results in retarded timing."
Thanks pamcopete that killed that theory.

".. he may have put the cam chain on, one tooth off on the cam."
I know what your saying xsleo and it sounds good to me but I checked it like three times so I think its right at the time I was worried I might get it wrong and end up benting something which is not nice.

After work today I had another look at it and the left cylinder was nearly fireing on time and was getting warm at idle its like its got a mind of its own.
So I had a look at the ignition advance unit and the weights were stiff not springing back the springs are only a year old so I turned it over abit then they went loss.

I'm thinking that is the problem no time this weekend but next week I'll
pull it apart and have a look maybe its rubbing on that big nut behind the
advance weight.

What should I look out for?

Hutzpah

pamcopete · Posted: October 16, 2009, 7:43 am Post subject: Re: Firing on one cylinder

Hutzpah,

Count the pins. There are three locating pins. Some people think that there are only two. The third pin locates the advance mechanism (ATU)itself to the camshaft.

In the last month I have run into at least three cases where the pin was missing after an initial installation of the ATU or after a rebuild.

TeeCat · Posted: October 16, 2009, 7:54 am Post subject: Re: Firing on one cylinder

Hutzpah...

I happen to be planning to replace my ATU this very weekend. In doing so, I'm going to mark Pete's remarks on the weights as well, in the unlikely event that I'm missing a pin. But in my case, my weights were not springing back and it was causing a no-start and poor running situation, so I replaced the springs with one coil out.

If your weights are hanging at full or partial advance, your idle will be kloogy. Mine still acts up a bit that way, and hopefully we'll both find the ATU to be at least part of the problem.

TC

pamcopete · Posted: October 16, 2009, 2:02 pm Post subject: Re: Firing on one cylinder

hutzpah,

Well, if you haven't seen this video before, take a look. That's what the advance should do: (Note: video works better the second time)

Hutzpah · Posted: October 23, 2009, 2:04 am Post subject: Re: Firing on one cylinder

Thanks for the posts and pamcopete I haven't seen that video before and
I must say it says it all.
Unfortunately mine do not spring back the same I pulled it all apart
and couldn't see anything wrong but there must be so I'm going to have another look.
I'm a bit disappointed as I was riding every day this time of year.

Its the first real relationship problem I've had with her but I will keep loving her through it all.
I might buy her a single red rose and 4 litres of oil.

thanks again

Hutzpah

What Happened to 650rider.com?

Yamaha xs650