Running on one cylinder at idle

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

The bike starts up fine, but only runs on the left cylinder at idle. The right side keeps poping. If I take the wire off the right plug, it won't make any difference except the poping stops. It does run on both if I give it a little gas though. I checked the spark and it has a strong white blue color. The bike hasn't been run in a while so is it possible that the timing is off? Can I set the timing while it is running to see if the right cylinder will get going at idle? I cleaned the carbs, but now I'm thinking of taking a second look at the idle curcuits. I just want to know if something else could be the reason. If the timing is off will it result in this? Is it possible that the right cylinder has poor compression? This is my first motorcycle so I'm not sure if this is normal, but sometimes when I'm kick starting the lever will have no resistance. But then I dont think one cylinder could wear out more then the other and if it had no compression it wouldn run at all.

grizld1

You can indeed inspect timing with the engine running. Use a strobe-type timing light. This may well be the issue if you have contact-breaker points; there's a pair for each cylinder. The intermittent resistance on your kickstart is probably due to clutch slip, and the slip is probably due to misadjustment. The kicker drives the input shaft of the tranny, so if the clutch isn't engaged, the engine won't turn. A badly abused kickstart gear assembly could also be to blame. There are a number of previous posts on this issue. You didn't mention what the right side plug looked like when you took it out. Also, how high do you have to bring the rpm's up before the right cylinder starts firing?

Before trying to dial in carbs, you should always be sure that cam chain tension, valve clearances, and ignition timing are correct. Did you remove, soak and clear the pilot jets when you cleaned the carbs? If not, a blocked pilot jet's a likely suspect.

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

Hmm, I tried to get the bike running on just the right cylinder but it keeps shutting off. When I pull the left wire off it dies even though I'm keeping the throttle open. I know it runs on the right side because if I connect the spark plug at about 2500 on the right side it gets a lot louder and the pipe starts putting out more air. I tried switching the wires from left to right to rule out a ignition problem, but it just wont start with the wires switched. This seems to mean that the ignition is at fault, but I checked the spark and it seemed fine. Confused

This is all new to me so I'm not sure how to check the timing and valves. I looked at the online service manual, but the directions arent too specific nd the pictures are blurry. Is there any more detailed explanation of setting timing,valves,points? Ohh and I don't have a timing light so I'm guessing I would have to take it to a mechaninc for that?

Can anyone tell if if this picture looks right? The springs seem like they dont have much tension. I'm not even sure what it is. Embarassed

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

I forgot to mention that the right plug is black and the left one tan.

mo650chopper

It may not help but you could reverse the spark plugs to see if the problem moves as well.

grizld1

The picture show the advance governor. When RPM's pick up, the weights are thrown out against the tabs on the rotor by centrifugal force, pulling the ignition cam rod to the advanced position. When RPM's drop, the springs on the weights pull the rod back to the retarded position for starting and idle.

Your situation with the online manual illustrates just why I do not recommend the factory manual to guys who are starting out. The graphics, even in hard-copy, look like 6th-generation photocopies-of- photocopies! Get a Clymer manual.

If you intend to do your own maintenance, you should buy a strobe-type timing light as well as a volt-ohmmeter and a bunch of other tools. Unless you have a lot of money to spend, you won't be able to afford to have maintenance and rehab on an old bike done for you. One idea is to swap favors (or cash) with somebody who's got a bit of experience, and get some help going through some of the basic operations.

Next question--did you put those plugs in fresh or did they come with bike? I'm guessing you're getting fuel to the right cylinder, judging from condition; possibly too much of it. Check the gap on the right cylinder points and check their timing statically with a continuity tester or ohmmeter. Inspect the air filters; the right side could be obstructed or dirty. Then put a fresh plug in the right side and see if you get any improvement from turning the fuel mixture screw on the right carb in (clockwise).

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

The plugs are brand new. I borrowed a compression tester from my neighbor (whose a mechanic) and I got a reading of 125 on the left cylinder and no compression on the right. He told me that this is caused by a stuck valve on the right cylinder, because there can't be such a huge difference between the two. He also said that if I replace it I have to replace both at the same time along with gaskets. Is there a possibility that the valve just needs adjusting or do I have to replace both like he said? The valve has to be stuck open because air is coming out of the carb. If the valve has to be replaced how much time and money am I looking at? Is it something that I could do myself? The biggest reason I bought the bike (for $150 with 9k on odometer) is to learn how all this stuff works. After putting money into replacing the seat, paint, battery, tools, and more it would be a shame to give it up.

grizld1

125 lbs. on the working cylinder is significantly short of spec., and it's impossible to tell you what your engine will need without a teardown inspection. It's unlikely that the intake valve would be so tightly adjusted as to yield zero compression; but I've seen it happen, and it's easy to inspect.

There are 4 alloy covers on your head. Remove them. There's a round plate on your left crankcase cover. Remove it, and remove the spark plugs. Under the round plate you'll see a big nut securing the alternator rotor to the crankshaft. On the casing over the rotor (the outside of the alternator stator assembly), you'll see some letters and a series of marks. Rotate the engine counterclockwise with a wrench on the nut until the mark on the rotor lines up with the rightmost mark on the stator. Under the covers you removed, you'll see the tops of the valve springs, and above them the tappets, with nuts locking them in place. Check the left cylinder exhaust tappet. If it has no play in it, turn the engine 360 degrees until the marks line up again and recheck. It's a working cylinder, and it'll have a tiny bit of play. Keep going 'till you find it. Using a feeler guage between the top of the valve and the tappet, check valve clearance. If it requires adjustment, use a small ignition wrench to hold the top of the tappet in place and break the locknut free. Turn the tappet in or out to adjust, and secure the locknut. Recheck the clearance to see if it's drifted.

Now check the right cylinder tappets, without moving the engine. If they're tight, with no clearance, that's as it should be. If one of them has clearance, it's either way out of adjustment or stuck. Rotate 360 again, aligning the marks. Again, check clearances. If one of the right side valves was loose and now shows a very wide gap when measured, set the clearances, close up, and try to fire. If a previously loose valve now measures close to specified clearance, you've found one that's sticking.

This may not make you feel better, but $150 isn't a bad price to pay for a rolling chassis (bike with no engine) with a title. If you remove the engine and remount it yourself, you can shave some significant bucks from a shop bill for a top-end rebuild. Review the procedures in a manual and see if you think you have the time, expertise, facilities, and commitment to invest in the equipment required to do the job. Don't assume that a stuck valve is even close to the worst-case scenario, either. Buying a rebuilt engine from a reputable source may be the way to go.

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

Do you suspect that the engine might be a throw out? I thought that 125 was a good reading. What would be the reading from a new or rebuilt engine? It's hard to believe that there could be much wear on it since it only has 9k miles. I'll print out your post and try getting at it tomorrow. Hopefully it will be just a valve problem, because it looks like valve parts are relatively cheap. It seems like you suspect something more serious. What, in your opinion would be the worst case scenario? I wouldn't be too upset with replacing the rings, since that would give me a chance to bore it out. Cool

The worst thing I can think of is a crack in the engine. By the way thanks for the help so far, hopefully I can get to the bottom of this pretty soon.

grizld1

Worst case? Holed piston, stretched rods, trashed cam and/or rockers, name it. You aren't dealing with a car engine here; you're looking at an air-cooled mill of about 40 cubic inches putting out around 50 hp. That's a lot higher state of tune than a passenger car mill, a lot more stress, and it's real easy to tear that engine up in 9000 miles or less. There's no water jacket here. A crack in the engine will produce a big oil leak, there's nothing to hide it. I don't know what year your engine is. From 1970-74 the engines ran a ratio of 8.7:1 at a pressure of 145 lbs. From 1975-early 1978 they ran 8.4:1 at 138 lbs. Late 78-79 engines ran a little higher at 8.5:1, 1980-82 units went back to 8.7:1. Sometimes engines that have sat awhile regain compression as the rings get worked again. A throw-out? I doubt it. But it's easy to put a lot of bucks into engine work fast. If the rods check out, the mains are tight, and so on, you might be able to do a core swap for a rebuilt head and head cover (they're line-bored and must be kept matched) and have your cylinders, if necessary, bored to new pistons and rings.

But the key thing is to find out if the right side valves are really stuck or warped, or whether the compression loss is caused by a holed piston, or whether--hey, I haven't seen this often, but I have seen it!--the right side valves are misadjusted to the point they don't close. Your engine could be fine. Good luck!

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

I followed your instructions and worked on the valves today. The right intake valve was much too loose. I set the clearances at .10mm for intake and .15 for exhaust like it said in the service manual. I remeasured a couple of times and the clearance didn't change. I also checked the cam tension. The problem is that the right side is still pushing air out the carb. It seems like I'm going to have to take the engine apart. Any tips or tricks to make it a little less painless? Is there anything I could try before I start tearing the motor apart?

grizld1

Bummer. If it had been set too tight that could have caused the compression problem. If you've set the valves and still have no compression on the problem cylinder, you're out of options as far as externally fixable conditions go. There are only two pieces of advice I can offer. First, get a good idea, from looking at the service literature, of what's going to be involved, and compare that to what you know of your own skills. Nobody can walk you through an engine overhaul with a few forum postings. Second, if you're going to have it done by a shop, let them do the whole job after you get the engine out of the frame. It's easier to check out a unit that hasn't been tampered with than it is to start with pieces. Good luck!

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

I called around today to see if any mechanic would do this for me and it seems no one wants to work on this bike. One guy told me he only does Japanesse bikes 20 years back. Another one I talked to said that the xs650 is a piece of sh*t and it won't ever be worth anything, he said he would do a valve job for 2000 but that I should just trash the bike and that he wouldn't give me 40 bucks for it. He told me to call him back when I got a real motorcycle. This really pisses me of since I allready put money into making this thing look good. I guess my options are either to fix it myself or try to sell it as is. Would this thing be worth anything in parts after I take the engine apart and for some reason am unable to fix it?

grizld1

Two grand for a top-end job on a 4-valve air cooled twin?! And that kinda trash talk on top of it? Gimme a break! What's your geographic area? I may know of a real motorcycle shop near you, or someone else may. "Real motorcycle," right. I have my '77 Yam and an '03 Zook SV650, both with tricked suspensions. Either one will eat a Ninja alive on a rough, twisty back road where the nose-heavy sportbikes start having compliance issues on washboarded corners; but it's so much more gratifying to blow their doors off with the old iron, giving away 25 or 30 hp, hammerin' off the apex while they fight the wiggles. And yes--if you have a good title and everything's there, you can recover some bucks from the right buyer.

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

I live in Chicago. There's suprisingly few motorcycle mechanics around here.

grizld1

OK--I'm assuming you have a car or truck and can drive a bit. Sounds like taking that engine downstate may be to your benefit. Ragan's Machine Shop(formerly Ragan's Yamaha) in Buckner, IL is a second-generation shop with deep experience with the XS650--the founder rode them professionally on the AMA national circuit back in the day. Their phone is (618)724-4894. My "home shop," Cycle Tech, in Carbondale, can do it; but things are a little disorganized there right now, due to a recent move. I'm going to get in touch with a couple of friends from the Yamaha 650 Society in the Peoria area and see who they'd recommend upstate.

Your engine will need to come out of the frame. The best way to do this without getting a hernia is to take off all the sheet metal, remove the battery, do all the engine removal prep (carbs and air box connections off, electrics unhooked, oil drained, crankcase covers off, etc.) and remove all the motor mounts and bolts except the bolt at the back of the engine. Take the nut off it but leave it in place. Now put some padding on the floor, lay the bike over on its left side, pop the bolt, and jink the frame off the engine. You can reinstall the engine single-handed the same way.

grizld1

I have two possibilities for you in Peoria. Gene Southard is semi-retired, and works Wed., Th., Fri., and Sat. only. He won't take an engine that's in pieces. He's trained some of the best around and knows the XS650 engine intimately. If you can get him to do yours you'll be in good hands. His phone is (309)682-3367. The other possibility is Shadetree Cycle, at (309)688-7279. One of the partners there, Trevor Imm, worked for Southard. These folks were also highly recommended. Good luck!

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

Thanks for the info. The guy at Shadetree Cycle was really cool and said he would work on it even if I brought it in pieces. I will see how far I can get on it by myself. I'm ready to take the engine out, but I still have to take the chain off. Do these chains use a master link? If not I guess you have to unscrew the nut and slip the chain off?

grizld1

Some have a master link, some have O-ring chain, some have what they came with and some have something else! The engine's a tight fit in the frame, and you don't want the chain in the way regardless. Refer to your manual for procedure; if you have an O-ring chain you'll need to find the marked link and either drill or grind the pins (you'll have to replace it anyway) or get a chain breaker. If you decide to remove the head cover, remember to work opposite-to-opposite and to loosen in very small increments. The head itself is massive but the head cover is thin and warps easily. The head and cover are line-bored, so if one's trashed they both are.

At the risk of sounding like an old fart who oughtta mind his own business, let me offer you a piece of advice. You have an engine and frame that match and are titled, I assume. This is a good thing. You also lack experience, but want to gain experience and learn. This is a very, very good thing; it means you view your riding iron as something more than a fashion statement. Unfortunately, one tends to tear stuff up in the course of gaining experience, and anybody who says otherwise is either a liar or too addled to remember. This is a bad thing.

Why not let the pro's do your engine work for you, and keep your eyes open for parts bikes? Untitled nonrunners are out there, and they go cheap. Find one, learn the internals on that, and you'll be able to learn the way med. students do--work on the cadaver before you do real surgery.

Good luck!

odw650 · Full Member Joined: Aug 05, 2005 Posts: 28

I took the head off, but this is definitely going to be a litlle too much for me. Thanks again for all the help and especially the phone numbers, I'll be taking it to one of the two.

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

odw650 wrote:

I guess my options are either to fix it myself or try to sell it as is.

Man don't sell your old bike it's worth more than money! Fix it up and ride with pride. I really love my old bike and am getting better at working on it all the time. I used to rebuild vw motors so I have a bit of background with rebuilds with cars and am trying to cary that over to my bike. I enjoy my bike so much that I'm building a barn / workshop to house my "hope to be" growing collection. Check the photo, my wife calls it the man shack!

What Happened to 650rider.com?

Yamaha xs650