76 won't start
#1
08-30-2009, 03:42 AM
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76 won't start
I have a 76 Sporty, it had a burnt valve. Insted of rebuilding the head I found a set rebuilt on ebay, the old ones had some broken fins. I took of the old set of bolted the rockers on the new heads as my manual says I never dissasembled the rocker covers. Bolted them on to factory torque specs. after putting on the carb I set it the mixture screw to what the stock service manual says. It would back fire out of the exhaust and not start. I noticed the float bowl leaked, I put a carb kit in, a junk one most of the parts where just shawty craftmanship so basically I just used the gaskets. Set it to factory mixture and the same thing. Its has an adjustable main jet I can't find any adjustments for that in my factory service manual. I'm stumped on this one. I think it was too lean when I got it and thats what burned the valve up. Any help is appreciated.
#2
08-30-2009, 07:16 AM
What carb is in there? If it is a Keihin then this file may have the info you need to set up the adjustable main jet [click the word DownLoad top left] ...
http://cid-e2880b68d32bbca8.skydrive...ain%7C_Jet.pdf
Here are my carb cleaning notes, in case you overlooked something, followed by my pilot screw setting notes ...
1. Removing it from the bike should be straight forward. First thing when it is out is to check the pilot screw setting. Turn it all the way in until gently seated counting the number of 1/4 turns; then write this number down; then reset it.
2. I put mine in a vice to remove the screws, and for much of the following work. Wrap in a shop towel; close the vice gently taking extra care with the choke and throttle linkages. The vice is a needed extra pair of hands.
3. You must be very careful handling the float so as to not change the level. You must have the official specs for setting the level as in the FM, and check it, every time you dismantle the carb, as the last thing before putting it back together.
4. The jets are made of brass, a soft metal that is easily damaged. Use an exact correct size screwdriver. I ground a medium flat blade screwdriver down to exact size on my bench grinder to access the slow jet.
5. The general appearance of the inside of the carb is not necessarily a good indication of its condition. It can look spotless and have clogged jets, or look cruddy and have clear jets.
6. Ignore any advice that says to soak or boil the whole carb in carb cleaner. Rather, clean each individual part. Do not allow any solvents to contact any rubber parts [tip of needle, o-ring seal for bowl]
7. Make a list of all of the jets and passages for your carb using the carb manual or the FM for the bike. Then ensure that you can blow either compressed air or carb cleaner thru each one.
8. Remove the pilot screw and clean the parts and the passage. The passage contains in this sequence: pilot screw, spring, washer, o-ring. These are very small parts, especially the washer and o-ring. Usually the spring will easily fall out. One time i thought the spring was not in there because it would not fall out; i obtained a new spring and could not get it in! The technique for removing the washer and o-ring is to use a pipe cleaner: stick it in the hole, twist it around, remove it - you should see the washer and o-ring on the end of the pipe cleaner.
Remember that the purpose of the washer is to protect the o-ring from the spring and you will always get them back in in the correct sequence.
9. Dismantle the accelerator pump assembly noting carefully the sequence and orientation of the parts. Clean and inspect the parts. Replace the diaphragm if it is cracked.
10. Check the float level then carefully put it back together. I personally find it very confusing trying to decide which way to bend the tang if it is not correct. If the fuel level is low is the float high or low? Do i need to bend the tang up or down? On the bench the carb is usually upside down, adding to the confusion. Sort all this out before making an adjustment.
Best to replace the original Phillips screws for the bowl with stainless steel socket head screws.
Setting The Pilot Screw on Your IronHead
If the carb is old and dirty the pilot screw passage may be gummed up such that you will not be able to "gently seat" the pilot screw reliably. If this is the case remove the carb from the bike and clean it up. Some guys try to do carb work with the carb in the bike. IMO this is a very bad idea.
In the pilot screw passage there should be, in this sequence: screw, spring, washer, o-ring. [Often POs have installed these parts in the wrong sequence; remember that the purpose of the washer is to protect the o-ring from being damaged by the spring]. The screw usually comes out easily. The other parts may require some work. The best technique is to stick a pipe cleaner in the hole, twist it around, and, like magic, out come the other parts on the end of the pipe cleaner.
1. You need to have easy access to the pilot screw, easy enough to reliably judge "screw it in until gently seated". Loosen the front fuel tank mount bolt; remove the rear fuel tank mount bolt; prop the rear of the fuel tank up on a piece of 2X4; on some bikes this will not be necessary.
2. With the engine cold [so you do not burn your fingers] turn the pilot screw in clockwise until it is gently seated. Count the number of 1/4 turns as you do it; write the number down. Back it out to the original setting. You may need to return reliably to this setting after experimenting.
The "normal" starting point for this process is 1,1/4 [according to the 79 - 85 FM] or 1,1/2 [according to usual practice] turns out.
NOTE: An old HotXL magazine article recommends for Keihin butterfly carbs between 1/4 and 1,1/4 turns out. My experience is that this works best. If you are more than 1,1/4 turns out your pilot jet is too small.
3. The engine must be at full warm up. It will have very hot parts; to avoid burned fingers have a well lighted, comfy place to work.
4. Set the engine idling at about 1000 RPM. You want it to be idling at the slowest speed that is consistent with a smooth idle so that you can hear or feel slight changes.
5. Turn the pilot screw in clockwise until the engine idle becomes worse; tending to stall. Count the number of 1/4 turns as you do this. Then turn the pilot screw out counter clockwise until the engine idle gets good, then becomes worse, tending to stall. Count the number of 1/4 turns as you do this.
6. The best setting for your bike will be somewhere between these two settings. The FM says to use the leanest setting [most screwed in] consistent with a good idle quality. Some guys say to go between the two settings.
It should be between 3/4 and 2,3/4 [preferable between 1 and 2,1/2] turns out from gently seated. If it is not within this range you should change the slow jet.
EDIT: I follow the advice from the old HotXL mag article - set it between 1/2 and 1,1/4 turns out.
7. You may have to adjust the idle speed.
8. Make sure that the spark plugs are clean, then ride the bike around your neighborhood for 10 minutes. Keep it under about 10 MPH so that you are on the "idle port", not the "idle transfer ports", the "mid range port", or the "main jet" [see carb diagrams in FM]. Hopefully the plugs will come out a nice medium gray or tan color. If they are too dark you can screw it in another 1/4 turn; too light screw it out 1/4 turn, and try the ride again.
9. If they are really light or really dark the problem is not with the pilot screw setting. For example, too light might mean an exhaust leak, and too dark might mean the pilot jet is too large [among other possibilities].
10. My experience with this process is that after making a change i have to clean the plugs and go for a good ride [say, an hour or more] before i can trust that the new results are reliable.
http://cid-e2880b68d32bbca8.skydrive...ain%7C_Jet.pdf
Here are my carb cleaning notes, in case you overlooked something, followed by my pilot screw setting notes ...
1. Removing it from the bike should be straight forward. First thing when it is out is to check the pilot screw setting. Turn it all the way in until gently seated counting the number of 1/4 turns; then write this number down; then reset it.
2. I put mine in a vice to remove the screws, and for much of the following work. Wrap in a shop towel; close the vice gently taking extra care with the choke and throttle linkages. The vice is a needed extra pair of hands.
3. You must be very careful handling the float so as to not change the level. You must have the official specs for setting the level as in the FM, and check it, every time you dismantle the carb, as the last thing before putting it back together.
4. The jets are made of brass, a soft metal that is easily damaged. Use an exact correct size screwdriver. I ground a medium flat blade screwdriver down to exact size on my bench grinder to access the slow jet.
5. The general appearance of the inside of the carb is not necessarily a good indication of its condition. It can look spotless and have clogged jets, or look cruddy and have clear jets.
6. Ignore any advice that says to soak or boil the whole carb in carb cleaner. Rather, clean each individual part. Do not allow any solvents to contact any rubber parts [tip of needle, o-ring seal for bowl]
7. Make a list of all of the jets and passages for your carb using the carb manual or the FM for the bike. Then ensure that you can blow either compressed air or carb cleaner thru each one.
8. Remove the pilot screw and clean the parts and the passage. The passage contains in this sequence: pilot screw, spring, washer, o-ring. These are very small parts, especially the washer and o-ring. Usually the spring will easily fall out. One time i thought the spring was not in there because it would not fall out; i obtained a new spring and could not get it in! The technique for removing the washer and o-ring is to use a pipe cleaner: stick it in the hole, twist it around, remove it - you should see the washer and o-ring on the end of the pipe cleaner.
Remember that the purpose of the washer is to protect the o-ring from the spring and you will always get them back in in the correct sequence.
9. Dismantle the accelerator pump assembly noting carefully the sequence and orientation of the parts. Clean and inspect the parts. Replace the diaphragm if it is cracked.
10. Check the float level then carefully put it back together. I personally find it very confusing trying to decide which way to bend the tang if it is not correct. If the fuel level is low is the float high or low? Do i need to bend the tang up or down? On the bench the carb is usually upside down, adding to the confusion. Sort all this out before making an adjustment.
Best to replace the original Phillips screws for the bowl with stainless steel socket head screws.
Setting The Pilot Screw on Your IronHead
If the carb is old and dirty the pilot screw passage may be gummed up such that you will not be able to "gently seat" the pilot screw reliably. If this is the case remove the carb from the bike and clean it up. Some guys try to do carb work with the carb in the bike. IMO this is a very bad idea.
In the pilot screw passage there should be, in this sequence: screw, spring, washer, o-ring. [Often POs have installed these parts in the wrong sequence; remember that the purpose of the washer is to protect the o-ring from being damaged by the spring]. The screw usually comes out easily. The other parts may require some work. The best technique is to stick a pipe cleaner in the hole, twist it around, and, like magic, out come the other parts on the end of the pipe cleaner.
1. You need to have easy access to the pilot screw, easy enough to reliably judge "screw it in until gently seated". Loosen the front fuel tank mount bolt; remove the rear fuel tank mount bolt; prop the rear of the fuel tank up on a piece of 2X4; on some bikes this will not be necessary.
2. With the engine cold [so you do not burn your fingers] turn the pilot screw in clockwise until it is gently seated. Count the number of 1/4 turns as you do it; write the number down. Back it out to the original setting. You may need to return reliably to this setting after experimenting.
The "normal" starting point for this process is 1,1/4 [according to the 79 - 85 FM] or 1,1/2 [according to usual practice] turns out.
NOTE: An old HotXL magazine article recommends for Keihin butterfly carbs between 1/4 and 1,1/4 turns out. My experience is that this works best. If you are more than 1,1/4 turns out your pilot jet is too small.
3. The engine must be at full warm up. It will have very hot parts; to avoid burned fingers have a well lighted, comfy place to work.
4. Set the engine idling at about 1000 RPM. You want it to be idling at the slowest speed that is consistent with a smooth idle so that you can hear or feel slight changes.
5. Turn the pilot screw in clockwise until the engine idle becomes worse; tending to stall. Count the number of 1/4 turns as you do this. Then turn the pilot screw out counter clockwise until the engine idle gets good, then becomes worse, tending to stall. Count the number of 1/4 turns as you do this.
6. The best setting for your bike will be somewhere between these two settings. The FM says to use the leanest setting [most screwed in] consistent with a good idle quality. Some guys say to go between the two settings.
It should be between 3/4 and 2,3/4 [preferable between 1 and 2,1/2] turns out from gently seated. If it is not within this range you should change the slow jet.
EDIT: I follow the advice from the old HotXL mag article - set it between 1/2 and 1,1/4 turns out.
7. You may have to adjust the idle speed.
8. Make sure that the spark plugs are clean, then ride the bike around your neighborhood for 10 minutes. Keep it under about 10 MPH so that you are on the "idle port", not the "idle transfer ports", the "mid range port", or the "main jet" [see carb diagrams in FM]. Hopefully the plugs will come out a nice medium gray or tan color. If they are too dark you can screw it in another 1/4 turn; too light screw it out 1/4 turn, and try the ride again.
9. If they are really light or really dark the problem is not with the pilot screw setting. For example, too light might mean an exhaust leak, and too dark might mean the pilot jet is too large [among other possibilities].
10. My experience with this process is that after making a change i have to clean the plugs and go for a good ride [say, an hour or more] before i can trust that the new results are reliable.
#3
08-30-2009, 02:19 PM
Outstanding HDF Member
I have a 76 Sporty, it had a burnt valve. Insted of rebuilding the head I found a set rebuilt on ebay, the old ones had some broken fins. I took of the old set of bolted the rockers on the new heads as my manual says I never dissasembled the rocker covers. Bolted them on to factory torque specs. after putting on the carb I set it the mixture screw to what the stock service manual says. It would back fire out of the exhaust and not start. I noticed the float bowl leaked, I put a carb kit in, a junk one most of the parts where just shawty craftmanship so basically I just used the gaskets. Set it to factory mixture and the same thing. Its has an adjustable main jet I can't find any adjustments for that in my factory service manual. I'm stumped on this one. I think it was too lean when I got it and thats what burned the valve up. Any help is appreciated.
When you installed the heads, did you adjust the pushrods as per the factory service manual?
Are you certain you have the intake manifold O rings sealing completely? You do this by running your finger inside the manifold opening touching the O ring all the way around. Do that for all the O rings. They will feel even if they are installed and sealing correctly.
And last of all, as Mick said...... What carb do you have on the bike?
It will be a bit easier to give you some help if we know the answers to the above questions........... pg
#4
08-30-2009, 05:16 PM
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I never did adjust the pushrods, I will do that it ran before just too lean till it got to the point where only one cylinder had compression from the valve. The carb is a bendix. The book has two adjustments the mixture screw 1 1/2 turns out from seated and idle adjustment. It doesn't have anything on the adjustable main jet. I assume this wasn't factory on these carbs. There is no choke on this carb.
#5
08-30-2009, 05:48 PM
Outstanding HDF Member
I never did adjust the pushrods, I will do that it ran before just too lean till it got to the point where only one cylinder had compression from the valve. The carb is a bendix. The book has two adjustments the mixture screw 1 1/2 turns out from seated and idle adjustment. It doesn't have anything on the adjustable main jet. I assume this wasn't factory on these carbs. There is no choke on this carb.
Adjust the pushrods before you do anything else!
Are you saying the Bendix you have has an adjustable main jet, or does not have an adjustable main?
For a Bendix carb with an adjustable main jet, you set the carb as follows:
Adjust the low speed: Turn the low speed needle until it seats.
Open the needle out one full turn.
Close the main jet needle until it seats (or the spring is coil bound _lightly, not tight!).
Open the main needle 4 full turns.
Start the bike and warm it up to operating temperature.
Turn in the low speed needle in or out to obtain the smoothest idle possible.
Set the idle speed with the idle speed set screw.
With the idle speed and the mixture adjusted you are ready to adjust the main jet.
Get on the bike and run it up through first or second gear to 4500 rpm (or more)
Overly rich mixtures respond by breaking up or running rough at high rpm.
To lean out the main jet turn the mixture needle in a half turn at a time. As soon as the engine responds by pulling cleanly through high rpm ranges with first or second gear the adjustment is done.
You may have to go back to the low speed and idle settings to readjust those after the main has been set.
Now all this is going to allow you to set the carb, but you still have the problem of getting the bike started perhaps. See what the carb adjustment does. If you get that far then you have got the bike started and running at least.
Oh, and one last thing.....The carb should have a choke on it. I have the adjustable Bendix on my 1971 CH and without a choke I would never be able to get it started.......... pg
#6
08-30-2009, 09:00 PM
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I adjusted the pushrods it started but, its almost if the front cylinder isn't firing. The back exhaust pipe gets really hot but, the front just barley warms up. It has good compression and spark. Could it be the manifold isn't sealed against the head? when I put the manifold on I ran my finger around it and it felt good. Could it still be the pushrods they felt the same as the back.
#7
08-30-2009, 10:19 PM
Outstanding HDF Member
Start up the bike and remove the front spark plug wire while it is running.
Any difference in the engine now?
Stick a screwdriver in the wire cap and holding onto the insulated handle place the screwdriver shaft 1/8 inch away from the head or cylinder fins. Any spark jumping?
A leaking manifold will result in backfiring through the exhaust pipes and/or a rough idle,........... it will not kill a cylinder causing the spark plug to fail to fire or fuel mixture failing to reach the spark plug.
If your plug wires are both long enough, switch wires to the plugs and try running it. Both wires fire at the same time, so switching them will not cause a problem. If the front cylinder now fires and the rear does not, then it is a problem with the coil. I doubt this is going to be the case however.
Double check to make sure both wires are properly seated into the ignition coil and into the spark plug cups. I believe your problem is ignition, not a fuel problem.
As for the pushrod adjustment........A bad adjustment will not cause a cylinder to fail to fire, but it can sure burn a valve quickly. So if there is any doubt about what kind of job you did with that adjustment......do it over again.
Remember...... Rear exhaust lifter at it's highest point equals ready to adjust the front cylinder exhaust pushrod.
Ditto for all the pushrods. A lifter at it's highest point is the correct position to adjust the like pushrod on the opposite cylinder.
The correct adjustment will be so that you can just spin a pushrod 360° using one finger, no looser and no tighter than that................... pg
Any difference in the engine now?
Stick a screwdriver in the wire cap and holding onto the insulated handle place the screwdriver shaft 1/8 inch away from the head or cylinder fins. Any spark jumping?
A leaking manifold will result in backfiring through the exhaust pipes and/or a rough idle,........... it will not kill a cylinder causing the spark plug to fail to fire or fuel mixture failing to reach the spark plug.
If your plug wires are both long enough, switch wires to the plugs and try running it. Both wires fire at the same time, so switching them will not cause a problem. If the front cylinder now fires and the rear does not, then it is a problem with the coil. I doubt this is going to be the case however.
Double check to make sure both wires are properly seated into the ignition coil and into the spark plug cups. I believe your problem is ignition, not a fuel problem.
As for the pushrod adjustment........A bad adjustment will not cause a cylinder to fail to fire, but it can sure burn a valve quickly. So if there is any doubt about what kind of job you did with that adjustment......do it over again.
Remember...... Rear exhaust lifter at it's highest point equals ready to adjust the front cylinder exhaust pushrod.
Ditto for all the pushrods. A lifter at it's highest point is the correct position to adjust the like pushrod on the opposite cylinder.
The correct adjustment will be so that you can just spin a pushrod 360° using one finger, no looser and no tighter than that................... pg
I adjusted the pushrods it started but, its almost if the front cylinder isn't firing. The back exhaust pipe gets really hot but, the front just barley warms up. It has good compression and spark. Could it be the manifold isn't sealed against the head? NO. There is some other problem.
when I put the manifold on I ran my finger around it and it felt good. Could it still be the pushrods they felt the same as the back.
when I put the manifold on I ran my finger around it and it felt good. Could it still be the pushrods they felt the same as the back.
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#8
09-01-2009, 01:17 AM
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I switched the plug wires no differance with the back plug wire off. No fire, I did a compression test and both were the same. I adjusted the pushrods again. The felt the same so I don't think its that. Could it be a burned valve? I figured with the compression being the same I can't see them being a problem. The exhaust valve works I think cause you can feel compression come out of the exhaust.
#9
09-03-2009, 12:06 AM
#10
09-03-2009, 12:30 PM
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