The engine also had the valves done by my machine shop buddy - they did not leak, for sure.
What the heck?
Okay, let me begin by reminding you guys that I'm new to tuning bikes. So many variables for a new guy. Anyway, I got the bike running pretty good, but it is still backfiring on the right side and idles all over the place and then just dies. It will be idling at 1100rpms and abruptly die.
Also there is a tapping noise in the engine. When I put my stethescope on the right side lower engine, near the oil filter, it is a distinct rapping noise.
So just for fun, I pulled the right side plug wire, which I noticed looked worn. The engine did miss a beat. It runs the same way with the plug wire on as it does with it off. Rpms don't change at all. What is going on? :?:
Also there is a tapping noise in the engine. When I put my stethescope on the right side lower engine, near the oil filter, it is a distinct rapping noise.
So just for fun, I pulled the right side plug wire, which I noticed looked worn. The engine did miss a beat. It runs the same way with the plug wire on as it does with it off. Rpms don't change at all. What is going on? :?:
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Yes, I remembered that...We are pretty much down to spark and spark timing......This could end up as simply as a disconnected wire to a coil......or misadjusted point.... or bad plug.....
OK Chris - this shouldn't be this hard...
Stop, step back, and re-zero here.
OK, left side runs, right side doesn't, it has spark at the right point -
1)After "running" for a minute, check the right spark plug - is there fuel on it at all??
2) Switch spark plugs - any change?? If the right side now runs, it's just a bad plug. NGK B8ES only, no substitutes please.
3) Switch plug wires - just run the one on the left side over to the right side and vice versa - any change??
If the right side now runs, it's either a bad coil, condensor, wire, or cap.
If you have a compression tester, check it (warm engine, open throttle, no choke).
Just to make sure that nothing crazy has happened - I recall you said at first it ran like a raped ape, so check if you can, let's make sure it's still ok.
Stop, step back, and re-zero here.
OK, left side runs, right side doesn't, it has spark at the right point -
1)After "running" for a minute, check the right spark plug - is there fuel on it at all??
2) Switch spark plugs - any change?? If the right side now runs, it's just a bad plug. NGK B8ES only, no substitutes please.
3) Switch plug wires - just run the one on the left side over to the right side and vice versa - any change??
If the right side now runs, it's either a bad coil, condensor, wire, or cap.
If you have a compression tester, check it (warm engine, open throttle, no choke).
Just to make sure that nothing crazy has happened - I recall you said at first it ran like a raped ape, so check if you can, let's make sure it's still ok.
You might want to try a compression test before you get into trying to solve a fuel supply problem. Leaking valves, worn rings, holed piston etc. will result in a non-firing cylinder no matter what else you do.
KERRY said:You might want to try a compression test before you get into trying to solve a fuel supply problem. Leaking valves, worn rings, holed piston etc. will result in a non-firing cylinder no matter what else you do.
Kerry -
The engine just got new rings and a professional valve job.
I'm looking at the engine this weekend sometime (Sunday I think).
I'll post what I find, I have the feeling it may be unusual...........
Second thoughts first: Have you done a compression check? Leaking valves, Low compression, the only way to get fire is to rev it up. And that's not a solution.
What actually happened when you pulled the plug wire off the "dead" cylinder - "The engine did miss a beat" - is that the motor fired once. That narrows down the problem a bit. Check the spark plug: clean, and gap to .025" Find a machine screw (#6 should be about right) that'll go into the plug cap and stick out a bit. A 1" should do. hold the head of the screw about 1/8" from the plug electrode and start the motor. You should have a spark from the plug electrode to the screwhead. That says the plug is firing (or shorted). It may also get your motor to fire, as that supplemental air gap - mechanics call it a "booster gap" - prevents any current from bleeding off the coil until the output voltage has peaked. The 450 ignition system, unfortunately, doesn't really have a killer spark at best, hence the popularity of conversion to electronic ignition.
I'm assuming you have timed the motor - that's the basic starting point for any problem analysis, since that affects everything else. If the motor runs on one cylinder and you ascertain that the other side plug is firing, that side has the wrong mixture - too lean or too rich. If the plug is dry when you shut the motor off, no fuel. If it's wet, too much fuel. The starting either test has been mentioned. Possible solution: Carb teardown, immersion tank (paintcan) carb cleaner, wash it off and put it back together. Solves a lot of problems.
What actually happened when you pulled the plug wire off the "dead" cylinder - "The engine did miss a beat" - is that the motor fired once. That narrows down the problem a bit. Check the spark plug: clean, and gap to .025" Find a machine screw (#6 should be about right) that'll go into the plug cap and stick out a bit. A 1" should do. hold the head of the screw about 1/8" from the plug electrode and start the motor. You should have a spark from the plug electrode to the screwhead. That says the plug is firing (or shorted). It may also get your motor to fire, as that supplemental air gap - mechanics call it a "booster gap" - prevents any current from bleeding off the coil until the output voltage has peaked. The 450 ignition system, unfortunately, doesn't really have a killer spark at best, hence the popularity of conversion to electronic ignition.
I'm assuming you have timed the motor - that's the basic starting point for any problem analysis, since that affects everything else. If the motor runs on one cylinder and you ascertain that the other side plug is firing, that side has the wrong mixture - too lean or too rich. If the plug is dry when you shut the motor off, no fuel. If it's wet, too much fuel. The starting either test has been mentioned. Possible solution: Carb teardown, immersion tank (paintcan) carb cleaner, wash it off and put it back together. Solves a lot of problems.
Careful with spraying the ether in while running. If it backfires then flames did... I mean could... shoot out the carb and spits ether on whatever is behind the carburetor and set it on fire and hard to put out quickly. My 750 wires are little blackened so I know.
My 450 had the same issue... A new set of points helped tremendously. It was getting spark on the one side but only erratically.
Also... If the points cover gasket is in bad shape the point spark can jump over to the cover and ground out causing erratic behavior.
My 450 had the same issue... A new set of points helped tremendously. It was getting spark on the one side but only erratically.
Also... If the points cover gasket is in bad shape the point spark can jump over to the cover and ground out causing erratic behavior.
Any updates on this issue? It's got me wondering as well..
GB :mrgreen:
GB :mrgreen:
Bill figured it out. The contact points cover was making contact with the points. :? Now, after making some adjustments, the problem is solved and the bike is running on both cylinders. Thanks again Bill.
I'm sorry for not posting a follow-up, but I felt a bit embarassed by my dumbness. I thought my motor was falling apart.
I'm sorry for not posting a follow-up, but I felt a bit embarassed by my dumbness. I thought my motor was falling apart.
When there's a problem, it's always a good idea to start with the basics, no matter how certain you are that you've done everything perfectly. Fuel, air, compression, spark. Know that you have those before you start troubleshooting. One other item that can happen: the rear silencer segment is a pierced tube surrounded fiber packing. If the tube rusts out, the packing stops up the rear of the exhaust. Incidentally, swapping secondary wires side-to-side only works with the single breaker 360º crank models. It won't work with the 180º crank models.
Hasn't happened to me but someone told me about this scenario once... thought I'd pass it alongChris Garrett said:The contact points cover was making contact with the points...
It's actually pretty common on a 450..........mitchellsk said:Hasn't happened to me but someone told me about this scenario once... thought I'd pass it alongChris Garrett said:The contact points cover was making contact with the points...
i find this subject interesting...i have had the same intermittant problem. thought condensor was acting up for the one side. I think i will put a thicker gasket on my points cover plate. also......why would they touch?....quirk in the mfg process that was overlooked? Doesnt really matter how but i will def take precautions.tbpmusic said:It's actually pretty common on a 450..........mitchellsk said:Hasn't happened to me but someone told me about this scenario once... thought I'd pass it alongChris Garrett said:The contact points cover was making contact with the points...
zx12ryder said:i find this subject interesting...i have had the same intermittant problem. thought condensor was acting up for the one side. I think i will put a thicker gasket on my points cover plate. also......why would they touch?....quirk in the mfg process that was overlooked? Doesnt really matter how but i will def take precautions.
It's easy to put the little spade connectors not quite right when you change points.
Easy enough to diagnose - your problems happen only when the point cover is on.......
first post here guys. really great forum...
this thread in particular is so helpful. i'm having the exact same issue. right side exhaust is cold on my 71 cb450- running on one cylinder i imagine. i can't wait to get home and swap plugs, then wires, then check points cover, etc. in case no one has said it in a while, you guys are great and it's just awesome to see some experts that are willing to listen and help. i look forward to making some great new friends here as i've got a real project on my hands. expect more posts to come.
-seth
this thread in particular is so helpful. i'm having the exact same issue. right side exhaust is cold on my 71 cb450- running on one cylinder i imagine. i can't wait to get home and swap plugs, then wires, then check points cover, etc. in case no one has said it in a while, you guys are great and it's just awesome to see some experts that are willing to listen and help. i look forward to making some great new friends here as i've got a real project on my hands. expect more posts to come.
-seth
I've had the insulation on wires from the points wear through where the wires pass through the front of the side cover. It gave me an intermittent miss the cause of which I couldn't find (don't you hate the ones that always work correctly when you're looking for them?) until one cylinder cut out and stayed dead. Not that I actually thought it was the problem, but I moved the wires (externally) around and the cylinder started firing again. Although the problem was initially hard to find, the fix was easy.
thats exactly my problem......sometimes when stand the bike upright off the kickstand while its idling it will happen so i got some in depth wire inspecting to do.KERRY said:I've had the insulation on wires from the points wear through where the wires pass through the front of the side cover. It gave me an intermittent miss the cause of which I couldn't find (don't you hate the ones that always work correctly when you're looking for them?) until one cylinder cut out and stayed dead. Not that I actually thought it was the problem, but I moved the wires (externally) around and the cylinder started firing again. Although the problem was initially hard to find, the fix was easy.
21 - 37 of 37 Posts
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