Author Topic: Cb650, Carbs Blowing out Air, Exhaust sucking in air (Read 25683 times)

scottly · « **Reply #75 on:** April 13, 2013, 09:42:25 PM »

Time to start over. Do you have good compression on all four cylinders? What do your spark plugs look like? Pictures are worth a thousand words..

wdmcdonald · « **Reply #76 on:** April 13, 2013, 09:59:08 PM »

Tomorrow morning Ill take pics of everything. But, since my older post I tore the engine down and replaced all the gaskets an orings/seals etc. Now no leaks and great compression on all four cylinders. Set the cam correctly and adjusted the valves as per the manual but Im no expert so those could still be off. One thing I did notice though when I took it apart is that the spark plugs in cylinders 1 and 4 were black and 2 and 3 were toasted brown. or maybe it was 1 and 3 / 2 and 4 respectively. I'll take them out tomorrow and have a look.

scottly · « **Reply #77 on:** April 13, 2013, 10:03:32 PM »

Quote from: wdmcdonald on April 13, 2013, 09:59:08 PM

One thing I did notice though when I took it apart is that the spark plugs in cylinders 1 and 4 were black and 2 and 3 were toasted brown. or maybe it was 1 and 3 / 2 and 4 respectively. I'll take them out tomorrow and have a look.

Black plugs are a big clue; almost always caused by a carburetor issue...

Scott S · « **Reply #78 on:** April 13, 2013, 10:12:20 PM »

Throw those plugs out and start over. You'll never diagnose it with dirty plugs.

trueblue · « **Reply #79 on:** April 14, 2013, 01:42:51 AM »

Quote from: scottly on April 13, 2013, 10:03:32 PM

Quote from: wdmcdonald on April 13, 2013, 09:59:08 PM
One thing I did notice though when I took it apart is that the spark plugs in cylinders 1 and 4 were black and 2 and 3 were toasted brown. or maybe it was 1 and 3 / 2 and 4 respectively. I'll take them out tomorrow and have a look.
Black plugs are a big clue; almost always caused by a carburetor issue...

They can also be caused by a timing issue. The fact that it is hitting a wall at 5k says to me that your advancer isn't advancing. All that black plugs indicate is that your engine isn't burning the fuel properly. Check your timing using the procedure below, also don't forget to check your pulser gap, it does open up over time and causes poor running. Don't forget to ensure that your advancer is advancing, you can use a strobe type timing light. This is a nice easy thing to try before delving into the carbs and more often than not is the cause of any "carb" issues

The note on this page applies to all 650's and greatly improves how the bike runs

wdmcdonald · « **Reply #80 on:** April 14, 2013, 11:22:09 AM »

Ok so this morning, went back through and adjusted all valves. Also after the bike warmed up I checked the plugs and all 4 have spark. Cylinder three head pipe was cold though while the others were hot. Tested the spark and it was fine. When I put it back in and fired up the bike the number 3 cylinder header pipe started to warm up and get hot. So I dont know what happened there. Gapped the pulse generators an did the static timing but still nothing. See attached pic for where I have the ignition set.

scottly · « **Reply #81 on:** April 14, 2013, 11:50:19 AM »

You are firing 1 & 4 off the 2-3 pickup, and it's retarded as well. Rotate the pickup plate clockwise back to where it's supposed to be. Somehow you've swapped the coils, either the plug wires, or the small wires feeding the coils.

wdmcdonald · « **Reply #82 on:** April 14, 2013, 12:08:39 PM »

Well the plug wires are labeled should I just try moving them around? Also when I rotate the plate to the proper position the lobe on the advancer will not line up the pulser pickup.

scottly · « **Reply #83 on:** April 14, 2013, 12:14:19 PM »

If you can, just move the plug wires from 1-4 to 2-3 and 2-3 to 1-4.

wdmcdonald · « **Reply #84 on:** April 14, 2013, 12:21:48 PM »

Tried to but the wires a'rent long enough. Can I achieve the same result by swapping the yellow and blue wires that feed the coils?

scottly · « **Reply #85 on:** April 14, 2013, 01:00:12 PM »

Yes, just swap the yellow and blue at the coils.

Scott S · « **Reply #86 on:** April 14, 2013, 01:34:13 PM »

Holy c

Quote from: wdmcdonald on April 14, 2013, 11:22:09 AM

Ok so this morning, went back through and adjusted all valves. Also after the bike warmed up I checked the plugs and all 4 have spark. Cylinder three head pipe was cold though while the others were hot. Tested the spark and it was fine. When I put it back in and fired up the bike the number 3 cylinder header pipe started to warm up and get hot. So I dont know what happened there. Gapped the pulse generators an did the static timing but still nothing. See attached pic for where I have the ignition set.

Holy crap, that looks mega retarded to me. The cut out on the edge of the plate that's at ~10 o'clock in your picture should be under the top screw. The window should be at 12 o'clock. I'm surprised it runs at all!

Scott S · « **Reply #87 on:** April 14, 2013, 01:37:55 PM »

This is a Pamco ignition built on a stock CB650 plate. If you look under the screw at 12 o'clock, you can see a tiny pointer. That's what you use to set the timing marks.
Notice how the window is at the top of the plate?

By the way, since this is a custom ignition, it appears that mine is advanced. That's the way we had to do it to get the Pamco transistors to line up with the stock threaded holes on the plate.
For your bike, set it up like this but put the screw in the center of the cut out. That should get you close enough to start the bike, then set the timing.

wdmcdonald · « **Reply #88 on:** April 14, 2013, 03:13:03 PM »

Ok so I know where the plate is supposed to be... but it will not start when in the correct position. Not even close. Only in the weird position. I haven't tried switching coil wires yet but I will today.

trueblue · « **Reply #89 on:** April 15, 2013, 02:38:31 AM »

Ok, just forget everything you have tried, it's wrong. Set everything to stock, it will work. First of all rotate the pulser plate so that the window is over the pointer. Then turn your crank till the "F" mark lines up with the pointer. After that adjust your pulser plate so that the little bump on the pulser unit is lined up with the trigger wheel. If it won't start after doing that, swap your 12v wires on the coils from one to the other. The blue wire should feed your 1-4 coil, the yellow the 2-3

JimJamerino · « **Reply #90 on:** April 15, 2013, 06:41:53 AM »

I have a 1980 CB650C that runs great. I'll pull the pickup cover when I get home tonight and post a picture of it, if that'll help.

wdmcdonald · « **Reply #91 on:** April 15, 2013, 07:26:13 AM »

TrueBlue, Ok I will do this today. Only problem is, when I put the plate in the stock position, I cant rotate it enough to get the pointer on the cam lobe to face the bump on the pulser. Does that mean Im off somewhere else??

Scott S · « **Reply #92 on:** April 15, 2013, 08:20:38 AM »

Quote from: wdmcdonald on April 15, 2013, 07:26:13 AM

TrueBlue, Ok I will do this today. Only problem is, when I put the plate in the stock position, I cant rotate it enough to get the pointer on the cam lobe to face the bump on the pulser. Does that mean Im off somewhere else??
[/quote
Quote from: wdmcdonald on April 15, 2013, 07:26:13 AM
TrueBlue, Ok I will do this today. Only problem is, when I put the plate in the stock position, I cant rotate it enough to get the pointer on the cam lobe to face the bump on the pulser. Does that mean Im off somewhere else??

You don't want it to face the bump on the pulser. You use the pointer on the engine case to align the T and F II marks on the advancer plate.
Do you have a timing light?

Scott S · « **Reply #93 on:** April 15, 2013, 08:23:02 AM »

Look at the pic Trueblue posted.

104 shows it at idle, or at the T mark. 105 shows it when you rev the engine up (~2500 rpm) and the timing is advanced. It is now on the two II marks near the F. Am I making sense?

wdmcdonald · « **Reply #94 on:** April 15, 2013, 08:33:17 AM »

Maybe I'm confused. When I set the cam, I had the advancer plate set at 1.4T which is TDC. Then I put the plate in the stock position like shown in all your guys examples. With the window on the plate showing the timing marks. In the manual pic TrueBlue posted, it shows the pointer on the cam lobe pointing at the magnetic pickup on the pulser. But when I turn the crank to 1.4T, it doesnt line up and I cant retard/advance it enough to do so. But even so when I was trying the stock position the bike would not start at all.

I dont have a timing light. How else can I make sure Ive got things right? this is driving me crazy now.

scottly · « **Reply #95 on:** April 15, 2013, 08:42:38 AM »

1. Place the pick-up plate in the stock position, in roughly the middle of the adjustment range.
2. Swap the two coil wires.
3. Try to start the bike.

Scott S · « **Reply #96 on:** April 15, 2013, 01:38:49 PM »

Quote from: Scott S on April 15, 2013, 08:23:02 AM

Look at the pic Trueblue posted.

104 shows it at idle, or at the T mark. 105 shows it when you rev the engine up (~2500 rpm) and the timing is advanced. It is now on the two II marks near the F. Am I making sense?

Actually, I'm backwards here....pic 104 shows it at full advance. Notice how it's at the mark that's near the pin that the weights slip on to.
The pic 105 shows it at idle. It would be easy to mistake those two II marks for advance. You should be near the F1 mark at idle and all the way over at the II marks near the pin with the weight/C-clip on it.
Make sense?

scottly · « **Reply #97 on:** April 15, 2013, 04:11:50 PM »

Quote from: wdmcdonald on April 14, 2013, 11:22:09 AM

Ok so this morning, went back through and adjusted all valves. Also after the bike warmed up I checked the plugs and all 4 have spark. Cylinder three head pipe was cold though while the others were hot. Tested the spark and it was fine. When I put it back in and fired up the bike the number 3 cylinder header pipe started to warm up and get hot. So I dont know what happened there. Gapped the pulse generators an did the static timing but still nothing. See attached pic for where I have the ignition set.

I'm thinking after taking a good hard look at this picture that you don't have the advancer properly indexed to the crank. Did you remove the broken pin from the old advancer from the hole in the crankshaft? It looks like the advancer is rotated 45 degrees counterclockwise, so you had to rotate the pick-up plate to compensate..

trueblue · « **Reply #98 on:** April 16, 2013, 03:24:14 AM »

Rotate your pulser plate so that the window is over the pointer, then rotate your crank so that the 1-4 "F" mark is lined up with the pointer, take a picture and post it up so we know exactly what you are looking at

crazypj · « **Reply #99 on:** April 16, 2013, 10:57:26 AM »

Take the advancer mechanism off crank and re-check the drive/locating pin

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Author Topic: Cb650, Carbs Blowing out Air, Exhaust sucking in air (Read 25683 times)