Author Topic: Changed plugs now no power (Read 3845 times)

Bahumut · « **on:** July 04, 2011, 10:26:13 AM »

I've searched for a while today on the forums but couldn't find an answer (or simply missed it) for the issue I'm having today...

I had NGK D8 plugs in my 77 550 until it started running weird yesterday. I pulled the plugs and they looked a little dark in cylinders 1 and 4, so I bought D7s and did a carb tune (no adjustment needed) and now the bike pulls harder than it did in low RPMs, but has NO POWER at higher RPMs under load. I jumped on the highway and it wouldn't go above 70!

any ideas?

Deltarider · « **Reply #1 on:** July 04, 2011, 10:32:54 AM »

Odd. You didn't set the gap too wide, did you?

Fritz · « **Reply #2 on:** July 04, 2011, 10:47:40 AM »

Sometimes plugs are shot before they fire a single spark.
You should use D7ES (not DR7ES which is spark plug recommended by NGK).
But maybe it's something different that is not really related to your changing the spark plug type, like the spark plug sockets or brittle hight tension wires.

Cheers
Carsten

Psychonaut · « **Reply #3 on:** July 04, 2011, 11:01:48 AM »

Plug gap? Too much gap can cause a miss under load, usually peak torque and above at WOT.

Bahumut · « **Reply #4 on:** July 04, 2011, 11:13:04 AM »

ahh.. I honestly didn't even look at the gap. what should it be set at?

Bahumut · « **Reply #5 on:** July 04, 2011, 11:17:04 AM »

Quote from: Bahumut on July 04, 2011, 11:13:04 AM

ahh.. I honestly didn't even look at the gap. what should it be set at?

nvm, many results for proper gap in search.

thep1pe · « **Reply #6 on:** July 04, 2011, 11:23:09 AM »

24 to 28 thou

Bahumut · « **Reply #7 on:** July 04, 2011, 03:07:22 PM »

.. well, I checked the gap, it, except for one plug, was within spec. Still won't give me power at higher RPM. I can't figure it out. It's been a 1-step forward, 3-step back kinda day. I think I'm going to leave it alone for a while

Spanner 1 · « **Reply #8 on:** July 04, 2011, 03:29:45 PM »

Doest thou have an electronic ignition perhaps ??

Bahumut · « **Reply #9 on:** July 04, 2011, 03:41:46 PM »

Quote from: Spanner 1 on July 04, 2011, 03:29:45 PM

Doest thou have an electronic ignition perhaps ??

nah, I have the standard points and condensers.

Gearheadgreg · « **Reply #10 on:** July 04, 2011, 04:57:24 PM »

Dirty Air filter

Bahumut · « **Reply #11 on:** July 04, 2011, 05:16:26 PM »

Quote from: Gearheadgreg on July 04, 2011, 04:57:24 PM

Dirty Air filter

all four air pods are clean as chemicals and a rinse can get them.

sick_seven_fifty · « **Reply #12 on:** July 04, 2011, 05:38:11 PM »

Since you were having a problem with cylinders 1 & 4, could it possibly be that your advance for those cylinders is off? And going to a hotter plug worsened the condition? That would explain the power loss in the higher rpm range...

Veterans, throw in your two cents if I'm out of line...I don't want to lead you in the wrong direction...just giving some ideas.

Bahumut · « **Reply #13 on:** July 04, 2011, 05:52:33 PM »

Well, I definitely appreciate the idea. I've never jacked with the ignition timing and gap before, so I'll have to check that. I'm too faced on Jack D and anime on Hulu to mess with it for the rest of the night, but since it's my daily, I'll hit it hard in the morning

TwoTired · « **Reply #14 on:** July 04, 2011, 05:55:36 PM »

Did the power loss come along with the "pods" cleaning. What brand/style pods do you have?
Do you still lose power with the pods removed?
What to the plug deposits tell you?

Bahumut · « **Reply #15 on:** July 05, 2011, 05:18:42 AM »

Quote from: TwoTired on July 04, 2011, 05:55:36 PM

Did the power loss come along with the "pods" cleaning. What brand/style pods do you have?
Do you still lose power with the pods removed?
What to the plug deposits tell you?

Morning everybody. The new plugs are telling me the bike is running fine if not slightly lean. They're tan but cylinder 4 is a tinge whitish. The pods are the K&N style chromie types. I cleaned them after the power loss because I thought that might have been the problem. I'm too afraid to run the bike without some type of filter on the carbs; we have turkey vultures out here... If I suck one of those bad boys into the engine....

Bahumut · « **Reply #16 on:** July 05, 2011, 05:24:10 AM »

I have the same pods that this bike is using: http://www.bikeexif.com/honda-cb750-6

sick_seven_fifty · « **Reply #17 on:** July 05, 2011, 05:52:56 AM »

You put a timing light on it yet?

Bahumut · « **Reply #18 on:** July 05, 2011, 06:23:06 AM »

That's what a local guy said last night too. Building up this bike has been part patience, part buying tools. I don't have that tool yet. I guess I know where my lunch money for the week is going...

chickenman_26 · « **Reply #19 on:** July 05, 2011, 07:00:21 AM »

Quote from: Bahumut on July 04, 2011, 05:52:33 PM

I've never jacked with the ignition timing and gap before,...

Then you've not jacked with the most likely cause of both #1 and 4 acting up at the same time. When 1 set of points, 1 condenser, and 1 coil control the 2 cylinders that are acting up, wouldn't it make more sense to examine the ignition circuit before fiddling with the fueling? It's not likely that #1 and 4 carbs or pods suddenly both developed problems.

Stu

Bahumut · « **Reply #20 on:** July 05, 2011, 07:17:37 AM »

Quote from: chickenman_26 on July 05, 2011, 07:00:21 AM

Quote from: Bahumut on July 04, 2011, 05:52:33 PM
I've never jacked with the ignition timing and gap before,...
Then you've not jacked with the most likely cause of both #1 and 4 acting up at the same time. When 1 set of points, 1 condenser, and 1 coil control the 2 cylinders that are acting up, wouldn't it make more sense to examine the ignition circuit before fiddling with the fueling? It's not likely that #1 and 4 carbs or pods suddenly both developed problems.

Stu

I agree. The shop that did some of the work for me said they handled the points for me and I believed them because, up until this weekend, the bike ran great. I'll have to buy a timing light, learn how to check gap and tackle that this week.

sick_seven_fifty · « **Reply #21 on:** July 05, 2011, 08:02:31 AM »

I've never done it on these bikes, but timing is a piece of cake...You can get a light fairly cheap these days too.

Duke McDukiedook · « **Reply #22 on:** July 05, 2011, 08:52:02 AM »

You will want to pick up a dwell meter and timing light if you don't have them already.
If your condensers have not been chenged in a while you will probably want to change them.

How long have you been running with podz on this bike? Did you rejet to compensate for extra air intake?

Sounds like you could be possibly having some carb issues too- when was the last time your carbs were fully cleaned?

Bahumut · « **Reply #23 on:** July 05, 2011, 06:47:31 PM »

Quote from: Industrial-sized Dukiedook on July 05, 2011, 08:52:02 AM

You will want to pick up a dwell meter and timing light if you don't have them already.
If your condensers have not been chenged in a while you will probably want to change them.

How long have you been running with podz on this bike? Did you rejet to compensate for extra air intake?

Sounds like you could be possibly having some carb issues too- when was the last time your carbs were fully cleaned?

I was told the condensers were new. They look it but that doesn't mean much.
Pods since the rebuild began and ever since I've been running the bike (it didn't come with an airbox)
I rejetted.. It had 98 mains.. went to 130s. Fouled plugs. 125s: rich 120s: still rich but it ran nice. Pulling the carbs is easy.. putting those bastards back on is such a #$%*, but it can't hurt to take a look

Thanks for the tip on the meter and light. putting stuff down on my weekend shopping list:
-dwell meter
-timing light
-tin foil hat
-electronic ignition...

Duke McDukiedook · « **Reply #24 on:** July 05, 2011, 10:03:39 PM »

Points should work fine as long as the mechanism is lubed and the points are not worn down (and the condensers are not bad). Just make sure the dwell is set properly.

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Author Topic: Changed plugs now no power (Read 3845 times)