I don't like how any of that sounds. Lol
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Valve shim size
- Thread starter brettp
- Start date
Compression specification range listed in the factory service manual is 156 to 184 psi. Higher in that range is better. Definitely do your valve adjustment before your compression test.
Make sure you have a compression tester that's trustworthy. The Amazon/Ebay cheapies are worth their weight in poop. Test the gauge against a known source of pressurized air like a compressor before you use it so you don't give yourself a heart attack when the crappy gauge reads exactly 37psi on every cylinder. You can rent a trustworthy compression tester from most auto parts stores.
If the compression is below spec, you can then test for bad piston rings by pouring about a tablespoon of engine oil into one cylinder at a time and repeating the compression test on that cylinder. If the compression reading shoots up after the oil treatment you have bad piston rings. If the oil produces no change then it's not the rings.
At that point there's a couple other things a home mechanic can do to diagnose leaky valves but we'll burn that bridge when we get to it.
Make sure you have a compression tester that's trustworthy. The Amazon/Ebay cheapies are worth their weight in poop. Test the gauge against a known source of pressurized air like a compressor before you use it so you don't give yourself a heart attack when the crappy gauge reads exactly 37psi on every cylinder. You can rent a trustworthy compression tester from most auto parts stores.
If the compression is below spec, you can then test for bad piston rings by pouring about a tablespoon of engine oil into one cylinder at a time and repeating the compression test on that cylinder. If the compression reading shoots up after the oil treatment you have bad piston rings. If the oil produces no change then it's not the rings.
At that point there's a couple other things a home mechanic can do to diagnose leaky valves but we'll burn that bridge when we get to it.
Ok, initial results:
Cylinder 4: 90psi
Cylinder 3: 90psi
Went to Cylinder 1: 60psi
I tested the gauge with an industrial air compressor set at 120psi and the gauge read 118.
Something is seriously wrong. I did the test by removing all plug wires, then pulling only the spark plug of the cylinder I was testing, screwed in the compression gauge, and let the starter turn over a few times.
I'm about to put a bit of oil in cylinder 4 (easiest to reach where it is parked in the garage) and redo the compression test.
Should my bike even be running with those numbers?!
Cylinder 4: 90psi
Cylinder 3: 90psi
Went to Cylinder 1: 60psi
I tested the gauge with an industrial air compressor set at 120psi and the gauge read 118.
Something is seriously wrong. I did the test by removing all plug wires, then pulling only the spark plug of the cylinder I was testing, screwed in the compression gauge, and let the starter turn over a few times.
I'm about to put a bit of oil in cylinder 4 (easiest to reach where it is parked in the garage) and redo the compression test.
Should my bike even be running with those numbers?!
You need to remove ALL spark plugs when doing compression test, also you must have WOT ( wide open throttle) when cranking.
Do this and crank engine until your gauge stop raising, repeat this with each cylinder.
Make sure to have good charge on the battery or hook up your good jump box to have good amount of current for engine cranking.
But if you didn’t adjust your valve lash to correct spec, I would do that first than proceed with compression test.
Do this and crank engine until your gauge stop raising, repeat this with each cylinder.
Make sure to have good charge on the battery or hook up your good jump box to have good amount of current for engine cranking.
But if you didn’t adjust your valve lash to correct spec, I would do that first than proceed with compression test.
Thanks for replying, Bo82CB.
If I remove all the spark plugs, why do I need to twist the throttle? Is that to open the carb butterflies?
How do you adjust valve lash on these bikes? I adjusted (most of) the valve shims, is there something else?
I am charging the battery right now, I noticed it giving up after this morning's test. I'll repeat the test after the battery is up with your suggestions. Thanks again!
Yep, it opens the carb butterflies to allow for maximum airflow. A compression test reads the *maximum* amount of pressure the cylinder is able to build.
Valve lash is the distance between the camshaft lobes at 0 lift and the surface they push on -- in this case the shim itself. Swapping the shims to the correct sizes to achieve 5 thou of clearance is "adjusting valve lash" or "performing a valve adjustment" on this bike.
Valve lash is the distance between the camshaft lobes at 0 lift and the surface they push on -- in this case the shim itself. Swapping the shims to the correct sizes to achieve 5 thou of clearance is "adjusting valve lash" or "performing a valve adjustment" on this bike.
It will run on those numbers but its not ideal. If you put too much oil in the cylinders it gives false high compression numbers as well....the oil take up combustion space causing high compression. You only need enough oil to get the rings a little wet...half a teaspoon at the most in my opinion. Once you get the valve clearances set to .005", get it running and take for a ride. Then recheck compression to see if it has gotten any better.
I didn't put too much oil in. I don't think anyway. I certainly didn't add more than half of a tablespoon.
I have more 260 and 265 valve shims on order. After I get those in I'll revisit the compression test. I do have. 005" on a couple, .004" on a couple, and a .006". And yet I still got those compression numbers.
I also ordered the rings for all cylinders to have them on hand. this will be my first time going into an engine beyond valves. Kind of excited to finally do this once.
Thanks for the help!
I have more 260 and 265 valve shims on order. After I get those in I'll revisit the compression test. I do have. 005" on a couple, .004" on a couple, and a .006". And yet I still got those compression numbers.
I also ordered the rings for all cylinders to have them on hand. this will be my first time going into an engine beyond valves. Kind of excited to finally do this once.
Thanks for the help!
I haven't mentioned this, yet, but the bike had trouble revving past 6k in any gear. If I let off the throttle it can pick up where it left off and climb slowly. In addition, after running the bike for any length of time, it will only idle for a few minutes then act like it is choking out and die. It WILL start back up. I have new air box boots and sprayed carb cleaner around everything between The air box cylinder boots and nothing lets air in. This is what brought me to the realization I have a valve problem (and now likely ring problem).
I wouldn’t go that far to say you need rings yet! Finish adjusting your valve lash and see how bike is running, and go from there. If your bike has been dormant for decade or less or more, you may have some surface rust on the cylinder walls, nothing terrible but enough to affect compression. Fire it up and run for little few miles then check compression again.
As far as I know the bike didn't sit dormant before I got it. I've been riding the bike for about a month now and it has always acted this way. I even put Berryman in it to burn carbon and rust of it. I'm not downplaying your comment, I was actually of the exact same mind! Shims are in next week and it will be raining the whole week. I'll have time to dig into it.
Thanks for the help!
This does not sound like a valve problem to me -- it sounds like a carburetor problem combined with possibly a failing ignition coil. Failing to rev through the whole range can be caused by clogged main jets in one or more carburetors, or a clogged air passage preventing the slides from rising properly. Could also be that the carbs are very badly out of sync.
Those airbox boots are tricky with their double-lips inside the airbox holes. Make sure you got them installed right and make sure all 8 clamps around the carbs are snug.
When the bike gets to that spot where it's warmed up and won't run, test for spark on all four cylinders. You might find you're only sparking on 2 of them. Failing ignition coils mounted above a hot engine often get worse as they get warmer.
Yes. There physically isn't enough room for the head to move up and clear its (long) mounting studs without hitting the frame.
Thanks, Sense. I, too, wondered if it could be a carb problem. Mostly a clogged pilot jet; that could definitely affect the idle. I sync'd the carbs a month ago but who knows, maybe it needs it again.
I checked the carb boots the other day but will recheck today.
I mixed 2oz of marvel mystery oil with a full 5 gallon tank of gas yesterday afternoon. Took it out for a ride last night and the bike went through the entire rpm range in all gears. Still a bit of hesitation to get passed 6k in first gear, but minor, then kept going. I added the MMO to help lubricate the top end and loosen the rings if one is stuck, etc.
I'll get the manual out today and reread the mixture and idle adjustment, then resync the carbs.
I checked the carb boots the other day but will recheck today.
I mixed 2oz of marvel mystery oil with a full 5 gallon tank of gas yesterday afternoon. Took it out for a ride last night and the bike went through the entire rpm range in all gears. Still a bit of hesitation to get passed 6k in first gear, but minor, then kept going. I added the MMO to help lubricate the top end and loosen the rings if one is stuck, etc.
I'll get the manual out today and reread the mixture and idle adjustment, then resync the carbs.
Resync'd carbs after finding all 3 lock nuts on the adjusting screw loose. Went out for a 5 minute ride (doesn't like to rev above 6k still), came back and idled fine for 3 minutes then sporadically would stutter. Sprayed carb cleaner around all boots; no change in idle.
IMHO, issue must be internal to chamber (rings or valves). Will try to complete valve shim clearance checks tomorrow and Tuesday. On that note, my exhaust cam has two notches. The manual says to line the notch up with the mating surface on the front valve head. Which notch do I use?
I also have a bunch of noise that I assume is the cam chain. Will it loose cam chain produce my symptoms? I assume a loose cam chain would have all kinds of different, and worse, symptoms.
IMHO, issue must be internal to chamber (rings or valves). Will try to complete valve shim clearance checks tomorrow and Tuesday. On that note, my exhaust cam has two notches. The manual says to line the notch up with the mating surface on the front valve head. Which notch do I use?
I also have a bunch of noise that I assume is the cam chain. Will it loose cam chain produce my symptoms? I assume a loose cam chain would have all kinds of different, and worse, symptoms.
Post a picture of those notches.
Your vacuum sync isn't going to mean much if your valves are still not within the correct clearance spec. Changing your valve shims will change vacuum and throw off your sync. Do it again when all your valves are adjusted correctly.
Did the carbs get rebuilt at any point? If not, the main jet or an air passage being clogged in just one or two cylinders can cause your problem.
I can't think of a reason why the valvetrain or the piston rings would cause the bike to not rev above 6k. If it were low compression due to worn rings or a scored-up cylinder, it'd simply be a lack of power overall. If you had valves that got burned up and they weren't sealing properly in one or two cylinders, the power flow would feel uneven and the engine would be running poorly no matter what RPM. If the valves were out of time, it would run terribly or not run at all. Why do you suspect rings or valves?
Yes, a loose cam chain will cause lots of clackity noises. You should adjust both cam chain tensioners by the manual's procedure. But in neutral at idle these bikes sometimes have chattery clutch baskets. Mine does. It's an issue that I'll solve if mine ever needs a new clutch pack but it's not worth tearing it apart to fix the noise alone as it doesn't harm anything.
Your vacuum sync isn't going to mean much if your valves are still not within the correct clearance spec. Changing your valve shims will change vacuum and throw off your sync. Do it again when all your valves are adjusted correctly.
Did the carbs get rebuilt at any point? If not, the main jet or an air passage being clogged in just one or two cylinders can cause your problem.
I can't think of a reason why the valvetrain or the piston rings would cause the bike to not rev above 6k. If it were low compression due to worn rings or a scored-up cylinder, it'd simply be a lack of power overall. If you had valves that got burned up and they weren't sealing properly in one or two cylinders, the power flow would feel uneven and the engine would be running poorly no matter what RPM. If the valves were out of time, it would run terribly or not run at all. Why do you suspect rings or valves?
Yes, a loose cam chain will cause lots of clackity noises. You should adjust both cam chain tensioners by the manual's procedure. But in neutral at idle these bikes sometimes have chattery clutch baskets. Mine does. It's an issue that I'll solve if mine ever needs a new clutch pack but it's not worth tearing it apart to fix the noise alone as it doesn't harm anything.
Hey, Sense. After doing the valve lash I continued to have the same problem; bike warmed up fine, ran ok up to 6k rpm then had trouble getting beyond that, and after a 10 minute ride would not idle longer than a couple minutes before sputtering intermittenly and then slowly die. I could always restart the engine but it will not idle for too long before sputtering intermittently and then eventually dying.
Weird observation: if I let the bike warm up and idle it doesn't seem to have that problem. It only shows up after I ride it.
The carbs have been off the bike and cleaned.
The reason I suspect valve or piston rings is because at 6k it acts like the vacuum is not lifting the carb slides.
I did a compression test and got a 125 on cylinder 1 (and I can smell a bit of gas out of the exhaust).
To your point about coils, I did a lot of research and found could act up more often when they are hot. I'm going to test both the primary and secondary coils (hopefully) today. But if the coils act up when hot, it would be ready to ride it first, correct?
I have never dug into the points or condensors but it doesn't look too complicated.
Weird observation: if I let the bike warm up and idle it doesn't seem to have that problem. It only shows up after I ride it.
The carbs have been off the bike and cleaned.
The reason I suspect valve or piston rings is because at 6k it acts like the vacuum is not lifting the carb slides.
I did a compression test and got a 125 on cylinder 1 (and I can smell a bit of gas out of the exhaust).
To your point about coils, I did a lot of research and found could act up more often when they are hot. I'm going to test both the primary and secondary coils (hopefully) today. But if the coils act up when hot, it would be ready to ride it first, correct?
I have never dug into the points or condensors but it doesn't look too complicated.
Your bike doesnt have points and condensers. Its honestly going to be hard to diagnose without seeing what its doing in person. But the main issues with these bikes are the valve clearances going tight, the never ending carb issues, coils and the little ignition boxes. Its also common to have the timing chain tensioners fail which can cause bad noise but can simply may need to be adjusted.
