| Author | Message | ||
     Sprintst |
Fired it up today, it died a few seconds later. Done that a few times lately, no big deal I thought Took off riding and discovered a big lag in throttle response, every gear. Not sure of rpm since the needle had slipped. But 6th gear, 70 mph rollon would cause it to misfire and chug. Similar rpms in the other gears It got a bit better on the highway, but went about 10 miles and it started really misfiring. Refueled, got back going, barely, since it was running on 1 cylinder I believe. Very little power, stalls easy, running rough, etc... Rode about 15 miles home. When I parked, within a couple minutes there was literally smoke pouring out the rear. I thought the engine running on 1 cylinder had locked the rear brake, but it was running so hot the exhaust (stock) had melted the rear spool and discolored the stainless steel exhaust tip. Now it was cooking the rear tire. Moved the bike, it cooled, all good. Pulled the rear caliper, blew out the pistons, cleaned best I could, reassembled. Pulled the rear spark plug, looked decent but the center was angled and the gap was beyond spec - too wide. Checked my old plugs, one was in spec on the tight side, the other out on the wide side. So, I'm guessing these bikes cook their rear plugs?? Not sure which of the old plugs was out of spec, but I'm guessing it's the rear. Hoping not to pull the front, I've only got a couple thousand until I need to do the valves anyway. Plan is to put the good old plug in the rear, see how she runs. Q - any additional thoughts? Do these just eat rear plugs, or should I be worried about how that cylinder is running? (Message edited by sprintst on July 06, 2015) | ||
| Shawns |
Never came across that. Make sure your injectors are working properly. Some times the coil plug isn't seated properly. | ||
| Reepicheep |
I don't understand how a bike running on one cylinder could cause the rear brake to lock up. Something is wrong with the bike. It could have been a fouled plug, I suppose, but it seems unlikely given your symptoms. | ||
| Shawns |
It is possible that the unburned fuel was ignited in the exhaust and did not completely burn causing soot to spray onto the rear wheel and affect(effect should have payed more attention in school)braking. Just a thought. | ||
| Reepicheep |
I don't think so. The problem with the bike was that it was running like crap (<- Technical term  ). Now why it was sputtering is hard to tell from the information at hand. You have to start the analysis from scratch and try and eliminate large branches of the tree so you can quickly get to the real problem. To run, a motor needs fuel, air, spark, and compression. Air is easy to check, pull off the airbox and look for a mouse nest. If there isn't one, or a sock stuck in there by a mechanically saavy ex girlfriend, you can probably cross that off your list of possible problems. See, you are already 25% of the way done! It gets harder to be precise after that. If you have a compression gauge and can get to the spark plug holes (which you probably can if you pulled plugs already), it is easy to do a compression check and make sure both cylinders have good compression. Mist them with WD 40 and crank them and compare the readings to each other and to the spec. I don't know what it is supposed to be off the top of my head, but if it is above 50 PSI and if both cylinders are within 10 pounds of each other, you are probably good with compression. Fuel is another interesting one. You can kind of eliminate it (maybe) by the symptoms. If spark is your problem, and it is intermittent, when it "comes back" it suddenly has a LOT of gas laying around, and you will get the mother or all backfires. Just ask somebody who had a cam position sensor fail. Bog, bog, bog, BANG. You can also monitor voltage levels, as if they are bad the computer gets crazy and really odd things happen. You can also crank the motor with the plug out but connected and with the body grounded, and look for that big bright blue spark when you crank it (and maybe some fireballs because the plug is near the plug hole which is spraying a nice 14:1 aerosol at your sparking plug... you didn't really need that arm hair anyway). Timing is a part of spark also, and it's easy to check timing, so just check and set it by the book and see if it gets better. Might as well do a TPS reset while you are at it (which could be argued over many beers as to if it is in the fuel or the spark category... if you are buying the beer, I'm happy to keep arguing). So that leaves fuel. I've never had a fuel problem on any of my XB's, so I can't be of as much help diagnosing that. There are plenty of posts about fuel pump problems, injector problems, fuel line problems, connectors, etc. They are a lot less common then other problems. | ||
| Torquehd |
The motor will not lock up the brake. They're two separate systems. Are you getting a "lean pop" (engine coughs back through intake when rolling off the throttle). If the bike is only hitting on one jug, it should be pretty obvious - it will sound like a (an OHC, water cooled) Blast. When you say rear spool, do you mean the rear sprocket? Not following you there. The exhaust should not be venting onto the tire, or anything else, for that matter. A plug being a little out of spec will not usually cause much of a problem. I've never heard of a plug setting causing such a dramatic running condition. | ||
| Sprintst |
I don't understand how a bike running on one cylinder could cause the rear brake to lock up. I assumed the heat caused the fluid to expand and tighten up the brake, and/or all the unburnt exhaust clogged up the caliper. This didn't happen, the smoke wasn't the brake, it was the tire cooking. Brake was NOT locked up, but I went ahead and serviced it and change the fluid anyway. Airbox was fine, no clogs. I do have a compression gauge, but I doubt that's an issue. Was out a couple days ago running a buck forty racing a corvette. KISS principal is telling me it's probably the rear cylinder wasn't getting spark anymore, since the gap was beyond spec Did watch voltage while riding, it was stable Rear spool - the spool to lift the bike. That's about 8" away from the exhaust outlet, and it was 1/2 melted. That's how hot the exhaust was. Exhaust wasn't venting on the tire, but it's only about 1" from the tire, and when the bike was parked that heat was cooking the tire} | ||
| Battyone |
Would the bike idle a little strange, then cutout very suddenly...as though it had been turned off??? Then restart fine, but just not quite feel right. | ||
| Sprintst |
Well bummer, rear spark plug replacement didn't work. Starts, runs, just has no power Really hate to drop the engine just to do the front plug, might as well do the valves when I'd done that much work | ||
| Shawns |
You don't have to drop the motor to get tho the front plug. A universal, plug socket and ratchet is all you need. | ||
| Nuts4mc |
Ign Switch? Grounds? look for the easy stuff first ....don't give up on the KISS principle | ||
| Brokengq |
Well spark can be ruled out obviously. I'm sure there's a maximum spec for the plugs before they're considered "too wide" and it probably isn't something listed in the manual. We only know the spec for when they should be installed. Air is ruled out too by the sound of it. Same with compression most likely. These bikes aren't known for compression loss. So fuel is where I land. Gummed injector maybe? Granted if it isn't spraying then you shouldn't have unburnt fuel in the pipe, but it definitely covers all the other bases (lack of power, etc.). Maybe try some injector cleaner and a short ride. See if it clears up. Or pull the injector and see if someone local can give it an ultrasonic bath. | ||
| Nikoff90 |
Injector could be dumping fuel and not misting it. Could also be leaking which could flood the cylinder. | ||
| Battyone |
Do a leak down test... not a compression test... From some of the early description especially the heat from the rear cylinder, I suspect a bent valve.Guess how I know??? | ||
| Sprintst |
Okay, I think she's fixed. I didn't see how it could be a compression issue, so I was still pursing ignition. Started pulling parts to get to the front sparkplug, but decided to test the rear coil first. Removed coil and plug, hooked it up, grounded it and hit the ignition. No spark. Repeat, no spark, but the bike starts. So that tells me the front coil and plug are working. Luckily I had a couple spare coils from the heads I bought to get a replacement cam and mounting bracket.... (long story ugh), hooked up a spare coil and houston, we have spark Button it all back up, seems to be running good, at least 1/2 block up the street and back. Long story short - bad rear cylinder ignition coil | ||
| Battyone |
If there was no spark at the rear cylinder...how did it get so hot??? No spark no heat. Did you need the cam parts for the rear cylinder? You didn't spit a shim by any chance? | ||
| Shawns |
You can still dump fuel and it won't ignite till it reaches a spot in the exhaust and then it will. | ||
| Sprintst |
Took it up on the Tail of the Dragon tonight. Ran like a champ, even got rid of the on/off throttle surging I was having I believe Shawns has it right, since I had no spark in the rear cylinder, all that fuel was dumping into the muffler and burning/partially burning The cam parts for for a previous repair over a year ago, just some bad luck and dumb actions on my part doing a valve adjustment resulted in a cascade of parts needing replacing |
