More questions

[teck_mountain]

Hello

Okay, I got my 79 xs1100 running but I can not get it to idle at low rpm or when I let go of the throatle. I've tried every thing I can think of pluse the ideas I've gotten from all of you. This included increasing the idle mixture screw, reset the carbs using the bread tie method, increased the large idle screw and so forth. Nothing has worked.

Was talking to a Mechanic in town who suggested the valve setting may be to much after cylinder head was cleaned and new valves put in. He stated that the valves may be sticking in a slightly open position. He suggested that I remeasure the clearance. Any one hear of this as being a problem.

Any other suggetion of what I should Do?

[MartyA]

If you suspect valve are staying open do a compression test. Don't have to disassemble anything. While the plugs are out, are they fouled? Wet? Or white and lean looking?

Does it crank like the battery is new? These bikes are notorious for acting up with a low battery. Well, they are notorious for lots of things, but start there.

[teck_mountain]

Compression level

Any idea what the compression should be with 1 over sized pistons

[skids]

Re: More questions

If you do take off the cam cover, make sure that the dots on the cams line up with the arrows on the cam bosses at TDC. I would definately do the compression test as was recommended, before I went through any trouble like this!

Originally posted by teck_mountain


Any other suggetion of what I should Do?

[MartyA]

Compression should be close to spec if everything is perfect - around 142 or so. 1 over technically increases the cubic area inside each cylinder, and if the stroke is the same the and the bore is increased theoretically compression should be slightly lower. OEM spec is 142 +/- 14 in Clymers.

Check the valves first - here is a quick and easy short cut way, without removing the cam cover. Remove the spark plugs, take the left side engine cover off (left as you sit on the bike) and rotate the engine with a wrench on the timing plate to "T". Watch inside #1 cylinder to see if #1 piston comes up to TDC when the timing plate is at "T". If you can't see inside use a soda straw or something like that resting on the top of the piston and sticking out the spark plug hole. While you are turning the engine watch the valve closest to the spark plug hole open and close. In sunlight or in a bright light you can see the one valve drop down and up. You can judge roughly if the valves are working in time correctly. At piston TDC the valve should be closed.

Now do your compression test. Hold the throttle open as you crank the engine to test each cylinder. If you are worried about valve timing it is the actual compression that is important. Usually it is the difference between the cylinders that is more important, but first things first.

[teck_mountain]

Questions

Thanks for the reply. I did the compression test and the results is #1 = 120 #2,3,4 = 85. Think I got a problem?

I pulled the cam cover and checked the clearance of the valvesn pads. I couldn't even get a .006 under the exhauses or intakes let alone .20 for the exhause or .16 for the intake.

I don't have the tool to remove the pads. I don't want to pull the cams as is took me a good deal of time to get the dots to line up with the arrow. (They still do, I check when I pulled the cam cover).

Suggestions, directions any help would be greatly apprieciated

A very frustrated

Teck

(I've been working on this thing since January)

[Ken Talbot]

Teck - don't forget that the .20 clearance is metric. If you could get a 0.005" feeler gauge in there, you would only be a couple of shim sizes too tight from .20mm In fact, .006" would be right on for a desired .15mm clearance on an intake valve. For the couple of bucks, pick up a set of metric feeler gauges and save youself a lot of figuring.....

[teck_mountain]

Valve Issues

Hi

The feeler gauge I used was metric. So what would you suggest

[Ken Talbot]

Hmm, .006mm would be way too tight and would certainly be problematic. If all the valves are that tight, that could well be part of the low compression problem as the valves are being prevented from closing.

I only leaped to my assumption on the gauge because I've never seen a metric feeler gauge any smaller than .038mm (0.0015")

Nevertheless, you are going to need a bunch of thinner shims. If you're not keen on removing the cams, I don't think there is another way to get the shims out other than using the tool. You might try borrowing one from one of the mechanics at a local shop if you can talk your way past the parts counter, or if you have access to a small independent. That might also be a good source of shims for swapping.

[teck_mountain]

But even more questions

Any idea what size shims I should begin with?

[MartyA]

The mystery deepens. You can't get a .006mm feeler under the cam lobe?
Ken might be correct, the valves might not be closing. Might as well check the rings as long as you are testing. Do the compression test again this time squirt some oil into each cylinder. Take the readings again. If no change it is likely the valves.

Did this bike run before? I am having a hard time with that clearance. Anything else he might check first Ken? Sure you got the correct valves when you did the valve job? Did you get the valve seats ground down? or just polished?

Remember teck you are looking for compression, not depression!

If you can't get the tool, you will have to remove the cams again to replace those shims. It does get easier the second and third time.

[teck_mountain]

More info

Hi again and thanks for all the great help.

Re did the compression test with adding oil and no change to the compression.

Remeasured the valves. I spent more time making the lob was facing directly up. I could get 0.08 under the exhause, may have been able to get 0.09 but no to .10 (my gauge doesn't have 0.09)

0.06 is the smallest I have and I couldn't get it under any of the intake valves

Does this Help?

[MartyA]

The only way I know how to figure shim thickness you need is to remove the old ones after you take the readings and calculate the new ones. You need the numbers on the bottom of the old ones for that calculation.

[Ken Talbot]

Okay, here's another bit of a trick - if the cam lobe is up i.e. truly vertical when you measure, you may not actually be measuring the largest clearance. I have found that by the time the lobe is vertical, is has gone by the lowest spot on the other end of the lobe and is starting to open the valve. Try bring the long part of the lobe back closer to parallel to the valve stem and see what you can slip in then.

[Ken Talbot]

Hmm, now I'm starting to think maybe whoever worked on the valves last goofed up on the metric/imperial part. If it was shimmed to .0025" instead of 0.25mm, that would only give 0.064mm clearance which is simply too tight. From the tables (for intake at least), you would have to step up two shim thicknesses to get to the correct clearance. As Marty says, you have to get the current shims out to see what they are before you can use the table to see which new shim needs to go back in. I.e., if you've got 0.064mm clearance with an existing 235 shim, you need to replace it with a 225.