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plugs fouling

I did a compression check and good at 148-150 across all 4. Put in fresh plugs to warm up first and it ran great with those new plugs. great throttle response, but once I pulled plugs to do compression test, plugs were starting to carbon up, as usual!!??
 
What plugs you using? Float level set correct?


Hi dirtdigger, ya know a few years ago I posted the same problem and you were responding then. I posted a couple of times today with a whole list of things I had done between the last time you were answering my questions. Anyway if you search my username of untill62, there are todays other questions, but to summarize, this has been the same problem for a long time.
I had a detached retina, so for over a year I have not touched the bike. but this year I wanted try again.
I put in new electronic ign, new coils, new boots, new plugs ngk D8EA, new batt., cleaned tank, new non ethynol premium w/octain boost from amsoil, cleaned carbs again, checked float levels as per manual.And had same problem as before the new ign stuff.
Works great with fresh plugs. Great throttle response, idles fine. so before compression check(all were 146-150) I had fresh plugs and within 5 min., pulled plugs to do compression and they were starting to carbon. I am going to be replacing the boots between carbs and engine. They are original and I tried to soften while carbs were off, but they didn't soften as much as i'd like.
Wanna buy a 2nd owner bike. I have had it since 75. But would sure like to ride it!!
 
I had fresh plugs and within 5 min., pulled plugs to do compression and they were starting to carbon.

But, how does it run?

I went back and read through this thread. All this started after replacing the rings?

If a plug fouls from running too rich, what usually happens is unburnt fuel builds up on the plug until the spark flows through liquid instead of air. You remove the plug and can easily see that it is wet.

If a plug fouls from oil, a black residue will build up on the plug until it closes the gap and the spark flows through it.

I suggest you warm it up and ride it until you foul a plug. Then pull the plugs while carefully avoiding disturbing whatever it is that's fouling them and take some good clear up close photos of them and show them to us.


PS If the rubber boots were leaking, that would make it run lean not rich.

PS2 Go give this a read New Engine Break-in Procedure, maybe your oil rings never seated properly.

PS3 Chrome will block that link because the website doesn't use https yet. If you have that problem, get rid of chrome, it's garbage. Use Firefox or Edge.
 
Hi,I know I didn’t follow the break in procedure as described in the link you provided, but I know I haven’t put on maybe 50 miles since that happened. You asked how it runs, pretty well at higher rpm,and as I mentioned, great when fresh plugs are in. So I will take a picture when I know one is fouled out. They aren’t wet by the way. Thanks for the feedback on the boots.
Back to the breakin, how can I break it in correctly though, just burning thru plugs? Or is there any hope at this point? How would I know if I glazed over the cylinder walls and it can’t be fixed without pulling it apart again.
How would I lean out the fuel mixture to see if that would do anything?
By the way Dirtdigger, thanks for all the feedback before. I reread my last post and didn’t say anything but thanks
 
When doing a break in run it hard when you get engine to operating temperature dont baby it. Hard throttle to a fairly high rpm/high load then let off throttle and let it slow down with it in gear..do it a couple times. Loading the rings is what you are after. Did you hone till all the glaze was gone in the cylinders? Were the cylinders round and not tappered? If cylinders are not round then new rings will have issues sealing, round rings wont seal in egg shaped cylinders...

Use the choke to see if you are overly rich. While running, hold the throttle steady then slowly close the choke, if it boggs and gets worse its close or already too rich, if it bogs instanly then it is already rich if it takes a little bit of throttle to bog then the mixture is close, if it picks up and runs a bit better then it is lean. You can do this at different rpms, this will tell you if its main jet, slow jet, needle, etc. The float level is critical, close is not good enough. Not really sure how you are checking the level.
 
Dirtdigger, I ran it at 2000 and 3000 rpm and started closing choke and it ran the same until the choke was fully closed. So I would say, probably 90% closed at least before there was a change it how it ran. Obviously died when I cut off air. Curious what that tells you?
 
You also asked about float level. I tried to get them as close to 26mm above carb body, as the manual says. Stock floats.
I noticed 1 or 2 of the float valves is not completely shutting off fuel. I separated the overflow lines to find out which ones.
 
I would say its on the lean side, when the fuel mixture is close once you hit about half choke it will start to bog and feel rich. If it was rich it would already be falling on its face by the time it hit half choke. All this is done while riding it at the target rpm by the way, not free reving it with the bike sitting still.
 
I would say its on the lean side, when the fuel mixture is close once you hit about half choke it will start to bog and feel rich. If it was rich it would already be falling on its face by the time it hit half choke. All this is done while riding it at the target rpm by the way, not free reving it with the bike sitting still.

Ok, i’ll take It out and try it and see results after that.
 
Ok, i’ll take It out and try it and see results after that.

Ok, i took it out for a few miles and got same results. Ran at 3000&4000 rpm and as I closing the choke ran the same until maybe 90%-95% choke closed also attached, I hope you can see what 3 of the 4 plugs look like after maybe 3 Miles. They are dry.
IMG_0826.jpg
 
Dirtdigger, I cleaned plugs and took it out for a few miles. And at 3000&4000rpm started closing choke and same results, ran the same until 90-95% choke closed. No change until basically closed, then died of course. So after a few miles 3 plugs black but not wet. Starts to sputter a lot at lower rpm, but seems pretty strong with acceleration.
In your last post,you said target rpm,not sure what that means.IMG_0826.jpg
Any ideas?
 
target rpm=what ever engine speed you are trying to jet.

Still think either your float height is too high or needle in too low of slot. If the carbs havent been synced with vacuum gauge you can have them adjusted in a way that the slide is too high and you are sucking a little fuel from the main jet at idle. Its very hard to explain this online in writing. Its more of a years of experience thing. The actual honda manual does a pretty good job of explaining where your vacuum reading should be and the procedure. Everything is kind of connected when adjusting, you have to watch rpm while adjusting the carb synce while watching the vacuum readings....

You said sputtering at low rpm which now sounds like its getting extra fuel. If it has stock jets maybe try next size smaller but I still suspect float level, maybe drop a couple mm and see how it runs. saturated floats will cause the float level to be to high as well. At this point it may be worth forgetting everything you have done and start from scratch. Dont leave anything to chance, dont say to yourself well I know this or that is good...recheck it anyway. The problem is not getting fixed so you need to rethink your diagnostic process and start looking at it from a different angle
 
The pics are blurry in the exact area they need to be clear :(

You say 1 or more float valves are not shutting the fuel off? This is what they do, if they aren't doing it, the are malfunctioning and this needs to be corrected.

Do you have brass or plastic floats? The plastic floats can actually sink when they get old.

Pull out the needle and seat that isn't working and look at them under a magnifying glass. Find out why they aren't sealing shut. I've had to file off small burrs before. Either repair them or replace them. I test them by putting the seat in my lips and blowing through it while inserting the needle to make sure the needle completely closes the flow off. If they don't close, the bowl will overflow into the carb when it's running.
 
target rpm=what ever engine speed you are trying to jet.

Still think either your float height is too high or needle in too low of slot. If the carbs havent been synced with vacuum gauge you can have them adjusted in a way that the slide is too high and you are sucking a little fuel from the main jet at idle. Its very hard to explain this online in writing. Its more of a years of experience thing. The actual honda manual does a pretty good job of explaining where your vacuum reading should be and the procedure. Everything is kind of connected when adjusting, you have to watch rpm while adjusting the carb synce while watching the vacuum readings....

You said sputtering at low rpm which now sounds like its getting extra fuel. If it has stock jets maybe try next size smaller but I still suspect float level, maybe drop a couple mm and see how it runs. saturated floats will cause the float level to be to high as well. At this point it may be worth forgetting everything you have done and start from scratch. Dont leave anything to chance, dont say to yourself well I know this or that is good...recheck it anyway. The problem is not getting fixed so you need to rethink your diagnostic process and start looking at it from a different angle

OK,
I think i'll take off the carbs and lower the float height. The carbs haven't been synced in awhile. I have mercury gauges, not vacuum. it does seem like it's in the carbs. I have instruction when I got the gauges and they do spec how to do it for a 750. hope they are ok to use? I will go online and see if I can find a recent video to make sure i'm doing as per today's standards.
The floats are original. Wish I knew what they should weigh stock. maybe weigh them individually. should be the same.
I don't think they are saturated though. Seemed really light, when I had them off.
Thought I started from scratch with new everything and clean carbs, cleaned tank, new unethynol gas, and all new ignition. And everything still comes back to fuel mixture it seems.
when you say needle to low in slot, are you talking main jet needle?
 
Ya, I know the pics are dark, but at least gives you an idea. Black, but dry. The float valves do seem to be holding now. They are original floats. they don't seem to be plastic, more like a cork? I don't know.
 
The mercury will work they are just damped and slow to respond to fast changes, I prefer gauges because they move fast with the engine vacuum, you can see the vacuum pulses which helps with diagnosis and they move instantly with throttle and engine change. But you already have the mercury so they will get you pretty close.
 
Dirtdigger, I think you were right on the float height. I set the float height from factory 26mm to 30mm and after a few miles, which in the past, they would be fouled, they weren’t! Took plugs out; #1 was a little dark, 2&3 looked really good, 4 a little dark, but still had white. Still had good throttle response. I was very impressed! I think 1 may have been worse because it seems slow jet gets plugged very easily. When I first start it I always feel pipes to see if they are all firing. I can usually tell which cylinder is plugged. Seems impossible to keep them open, even with non ethanol and fuel additive.
So next step is to sync carbs. You said maybe needle is too low in slot also. Do you mean the jet needle? if so, spec says to start with at least 1 thread showing initially before syncing. Should I start with more threads showing?
Your suggestion on the float height has been the only one that has helped! So thanks
 
Dirtdigger , I did reply and hoping you got it. Looking for some more advice since your float height suggestion seems correct. Please see my question in last post. Let me know if you cant see it, then I will start it again. thanks so much
 
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