Author Topic: Exhaust #1 not hot (Read 2819 times)

ct_bobber · « **on:** February 17, 2014, 09:47:45 AM »

I think I have a problem with Cylinder #1 not firing correctly. It gets spark (I did law mower check, spark plug putting on the head block). Now, I think I have to check if it gets fuel. I took pilot jet and cleaned it. But I don't think I really know the right way to check whether or not the cylinder #1 gets the fuel during the idle.

Here is the picture of the #4 and #1 plug (I put both new at the same time and run for about a minute). #1 plug is clean and, to me, it looks like it didn't get fuel.

Am I correct? Sorry for rambling, I would like your advices on how to check the fuel to troubleshooting this issue.

thank you very much.

LesterPiglet · « **Reply #1 on:** February 17, 2014, 09:51:54 AM »

What bike?
First thing is unscrew the drain screw for that carb and see if it has fuel.

ct_bobber · « **Reply #2 on:** February 17, 2014, 09:58:15 AM »

Sorry, I should have mentioned that. It's 1975 CB750. I did drop the overflow bowl and yes, there is a gas in it. I measured the float bowl level at ~26mm (when the float valve is closed). I also looked to see that idle jet submerged in the fuel. I took the idle jet our and cleaned it. I could see through all holes. I have a new jet, but didn't try it yet.

LesterPiglet · « **Reply #3 on:** February 17, 2014, 10:03:12 AM »

This shows all removable jets, clean them all, and the carb body.

http://www.cmsnl.com/honda-cb750-four-k5-usa_model483/partslist/E++25.html#results

ct_bobber · « **Reply #4 on:** February 17, 2014, 10:09:42 AM »

I bought carb rebuild kit and will do it for sure. However, I would like to try to troubleshoot this and know for sure what caused the problem and then I can get the bike inspected and then I can take my time rebuilding the carbs.

but if is not possible, I'll just have to rebuild and clean them all.

LesterPiglet · « **Reply #5 on:** February 17, 2014, 10:12:25 AM »

When did your bike last run? If it's been sat for a while it's always best to give the carbs a thorough cleaning. When it's done properly you wont have to worry about them again. The carbs can be cleaned in a few hours. It isn't necessary to completely dismantle them, just remove all the jets and make sure all orifices are clean.

ct_bobber · « **Reply #6 on:** February 17, 2014, 10:16:26 AM »

I actually just bought this bike. I guess the PO didn't know much about it and ran the bike this way. I'll give the carb cleaning a shot. Do you think I should go ahead and replace all of the jets using the rebuild kit?

LesterPiglet · « **Reply #7 on:** February 17, 2014, 10:20:05 AM »

Jets don't need replaced unless they are damaged or the induction system is not standard.

tlbranth · « **Reply #8 on:** February 17, 2014, 10:53:19 AM »

I had a similar problem which was fixed by synchronizing the carbs. I'm not sure how the '75 works but if possible, stick a small screwdriver under the #1 slide and pry it up slightly while the engine is running. See if you get some heat then.

ct_bobber · « **Reply #9 on:** February 17, 2014, 10:57:06 AM »

Quote from: tlbranth on February 17, 2014, 10:53:19 AM

...stick a small screwdriver under the #1 slide and pry it up slightly while the engine is running. See if you get some heat then.

I'm not quite sure what "the #1 slide" is.

LesterPiglet · « **Reply #10 on:** February 17, 2014, 11:04:56 AM »

#21 in the above parts diagram.

ct_bobber · « **Reply #11 on:** February 17, 2014, 11:12:12 AM »

The part number goes until #20. Do you mean #11?

LesterPiglet · « **Reply #12 on:** February 17, 2014, 11:25:12 AM »

I apologise, part list got mixed up somehow. $:-\$ Part #21 now. The original link actually led to a K7.

ct_bobber · « **Reply #13 on:** February 17, 2014, 11:35:05 AM »

Quote from: LesterPiglet on February 17, 2014, 11:25:12 AM

I apologise, part list got mixed up somehow. $:-\$ Part #13

That's all right. Thanks for pointing it out. I was actually curious about that when I took off the the intake. I looked inside and it looks (visually) like the #1 smaller opening than the rest of the carbs. Do you think that might have been the source of my issue?

LesterPiglet · « **Reply #14 on:** February 17, 2014, 11:42:21 AM »

Could well be. Try the tip tlbranth suggested. Those carbs will need synchronised if you can see a difference.
Are you turning the throttle when trying to start? It wont hurt to give it a few little on and off turns as you are trying to start it.

ct_bobber · « **Reply #15 on:** February 17, 2014, 11:44:18 AM »

Will do and will report back. If this doesn't work, I'll get them out and clean

BobbyR · « **Reply #16 on:** February 18, 2014, 09:56:22 AM »

There was a case on here where the plug was damaged just enough it completed the circuit through the block to fire the opposite plug, but was weal on it's own cylinder. You can try swapping plugs and se what happens. Easier to do than most other things.

PeWe · « **Reply #17 on:** February 18, 2014, 10:04:32 AM »

Some start spray injected inside the actual carb /airfilter box will show lack of fuel. You will hear the difference.

ct_bobber · « **Reply #18 on:** February 21, 2014, 06:26:00 PM »

I'm happy to report that after rebuilding the carb, all 4 cylinders are now firing.

However, I have one other issue (I hope it's not) that I will need some advices from someone here. Cylinder #1 wasn't firing in the past, but now it is firing after rebuilding the carbs. I was attempting to tune the idle. While waiting for the engine to warm up, I noticed that there is white/gray smoke coming out around the exhaust #1 right where it connects to the head. I can't tell if it's coming through exhaust gasket or right on the exhaust pipe. It has burning smell. I shut it off b/c I'm not sure what's going on and am afraid if it would catch on fire. I'm not sure if it gets really hot or it's just burning something that were accumulated for awhile when the cylinder #1 was not firing. Does anyone have any idea what this symptom would be? Is it safe? I was planning to get a thermometer to measure each pipe and a fire extinguisher, just in case.

Any comment will be appreciated.

tlbranth · « **Reply #19 on:** February 21, 2014, 06:37:00 PM »

If you've been messing with the engine and getting oily hands on the exhaust pipes, they'll do that - smoke like mad for a bit. But it sort of sounds, from your description, that it's an exhaust leak. I doubt that it's a fire hazard in any event.

ct_bobber · « **Reply #20 on:** February 21, 2014, 06:42:07 PM »

Quote from: tlbranth on February 21, 2014, 06:37:00 PM

If you've been messing with the engine and getting oily hands on the exhaust pipes, they'll do that - smoke like mad for a bit. But it sort of sounds, from your description, that it's an exhaust leak. I doubt that it's a fire hazard in any event.

thanks for a quick reply. I think I will take the exhaust off tomorrow and check the gasket. Is it possible to visually see if the gasket is bad? Also, is it possible that this was caused by cylinder not running previously?

Thanks

LesterPiglet · « **Reply #21 on:** February 21, 2014, 06:52:53 PM »

I'm sure there would be a buildup of unburnt fuel in that pipe that would cause it to smoke for a while. Get new crush gaskets and replace them when you take the header off. They are cheap and will rule out a potential problem.
Very very little fire risk, don't worry.

Cb550F headerless

ct_bobber · « **Reply #22 on:** February 21, 2014, 07:10:02 PM »

the video is very cool

.

I was just attempting to visually check the head gasket when I found the one of the screws has stripped head $:-\$ What kind of tool would you recommend that I could use to get that screw out.

LesterPiglet · « **Reply #23 on:** February 21, 2014, 08:00:32 PM »

Vise grips and a blow torch.

ct_bobber · « **Reply #24 on:** February 21, 2014, 08:11:22 PM »

Quote from: LesterPiglet on February 21, 2014, 08:00:32 PM

Vise grips and a blow torch.

I actually was talking about the screw that hold the manifold.

this is not mine. My screw, the head (phillip) is already stripped.

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Author Topic: Exhaust #1 not hot (Read 2819 times)