Author Topic: Engine consultation (Read 3498 times)

yodagruv · « **on:** October 18, 2011, 04:10:18 PM »

Ok, my '75 CB550 ran fine before parking it for some upgrades a few months back. Today, only #2 cylinder is firing. As far as I can determine all cylinders are getting air and fuel, I believe they are all getting spark because I can loosen the plug wires and hear them arcing to the plugs, in fact sometimes I can get other cylinders to kick over by holding the plug cap loose from the tip of the plug. Where do I start looking to resolve the issue?

yodagruv · « **Reply #1 on:** October 18, 2011, 04:14:41 PM »

Let me add, I made no changes to carbs, ignition, fuel system, etc. Upgrades were LED signals and suspension mainly.

Bob3050 · « **Reply #2 on:** October 18, 2011, 04:23:41 PM »

The fact that you can get the dead cylinders to fire by holding the plug wire a short distance from the plug would indicate fouling plugs. If the fuel has been in the tank and carbs for a couple of months or more I would suggest draining and going with fresh. Good luck.
Bob

yodagruv · « **Reply #3 on:** October 18, 2011, 04:43:10 PM »

You really think the plugs could be fouled? They've only been in there for maybe 40 miles.

Greggo · « **Reply #4 on:** October 18, 2011, 04:49:12 PM »

Quote from: yodagruv on October 18, 2011, 04:43:10 PM

You really think the plugs could be fouled? They've only been in there for maybe 40 miles.

Have you drained the gas and refilled with fresh? Gas begins to break down after a month.

jtb · « **Reply #5 on:** October 18, 2011, 05:00:21 PM »

take them out & see.

yodagruv · « **Reply #6 on:** October 18, 2011, 05:21:39 PM »

Pulled a plug, definitely fouled. Black, dry coating. Carbon, right? That's from running too rich, huh?

yodagruv · « **Reply #7 on:** October 18, 2011, 05:31:28 PM »

Ngk d7ea are pre-gapped for these aren't they?

scottly · « **Reply #8 on:** October 18, 2011, 05:45:39 PM »

Quote from: yodagruv on October 18, 2011, 04:10:18 PM

Ok, my '75 CB550 ran fine before parking it for some upgrades a few months back.

Did you leave the petcock turned on during this time? If so, there may have been a slow build-up of fuel in the float bowls, which immediately fouled the plugs. Burn the soot off with a small propane torch, or try new plugs. If it happens again, suspect the carbs.

yodagruv · « **Reply #9 on:** October 18, 2011, 07:33:48 PM »

Negatory on the petcock. Change out plugs 1/4 real quick and she runs ok. I'll do 2/3 ASAP and shake it down. Thanks for the brainpower.

Danno · « **Reply #10 on:** October 18, 2011, 09:33:04 PM »

you need to clean your needles and seats again sometimes you can get away with pulling the drain plug and spraying carb clean in them to break things free or pull the fuel lines and run carb clean straight to the carbs that way but I would still pull the drain plug and spray them to clean out the bowls

yodagruv · « **Reply #11 on:** October 19, 2011, 03:59:04 PM »

Pretty sure the carbs are clean, had them off last spring and little riding since. I put new plugs in and fired it up for a minute at lunch today but TONS of white smoke came from the tailpipe. Do I just need to run it to burn stuff off from the cylinders not running?

Rigid · « **Reply #12 on:** October 19, 2011, 04:24:37 PM »

It won't hurt it to run until the smoke clears provided you have oil pressure and the oil is flowing freely. It is probably water and fuel built up from the nonrunning cylinders as you said.

Danno · « **Reply #13 on:** October 19, 2011, 09:49:31 PM »

Duanob · « **Reply #14 on:** October 20, 2011, 09:23:17 AM »

Quote from: yodagruv on October 19, 2011, 03:59:04 PM

Pretty sure the carbs are clean, had them off last spring and little riding since.

Last spring is a long time for our current crappy gas to sit in these carbs. I've had this experience before and my pilot jets were clogged from a white powdery substance left over from gas left in the carbs. Take your bowls off and you will see. Once I recleaned all pilot jets thoroughly, Idle air jets, and used canned air in all orifices I could reach, the bike started right up and ran great. You shouldn't let gas sit for more than a month.

dave500 · « **Reply #15 on:** October 21, 2011, 01:10:00 AM »

we dont seem to get that old fuel syndrome here so much,,i can leave mowers and weed wackers for ages and they fire up after a few tries,we run less ethanol and mostly have good non ethanol everywhere.

phil71 · « **Reply #16 on:** October 21, 2011, 01:20:40 AM »

"HI! HELP! My bike wont run. I've tried nothing, and I'm all out of ideas! I also reject any theory that takes work or money. What am I doing wrong?!"

oldbiker · « **Reply #17 on:** October 21, 2011, 01:27:19 AM »

Quote from: phil71 on October 21, 2011, 01:20:40 AM

"HI! HELP! My bike wont run. I've tried nothing, and I'm all out of ideas! I also reject any theory that takes work or money. What am I doing wrong?!"
[/qote]

Maybe it's because you got out of bed this morning!

trueblue · « **Reply #18 on:** October 21, 2011, 06:35:13 AM »

Quote from: dave500 on October 21, 2011, 01:10:00 AM

we dont seem to get that old fuel syndrome here so much,,i can leave mowers and weed wackers for ages and they fire up after a few tries,we run less ethanol and mostly have good non ethanol everywhere.

+1 I pulled a concrete saw out of the racks at work today, it hadn't been run for nearly 12 months, had fuel in the tank so I tried to start it and third pull away it went

lucky · « **Reply #19 on:** October 21, 2011, 07:25:08 AM »

Quote from: Bob3050 on October 18, 2011, 04:23:41 PM

The fact that you can get the dead cylinders to fire by holding the plug wire a short distance from the plug would indicate fouling plugs. If the fuel has been in the tank and carbs for a couple of months or more I would suggest draining and going with fresh. Good luck.
Bob

Four stroke engines almost NEVER foul a spark plug.
Two stroke engines do foul plugs regularly.

When ever a motorcycle sits the fuel turns to a varnish like gummy honey.
The float needles can and often get glued into the float needle housing.
Most of the time fresh fuel will dissolve it but you may have to take it apart and clean the needle jet and especially look at the idle jets because the hole is VERY small. Like .012 thousandths.

When the motorcycle sits for a couple of months you can expect some of these type of problems.

strynboen · « **Reply #20 on:** October 21, 2011, 07:44:21 AM »

this old honda"s can drown the plugs..are they first get wet of gasoline..they dont fire...even you drive longer distance and the engine gets hot..i alvays have ekstra plugs..on bike..glass blast them and tjek vith a megger..some can be re used..

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Author Topic: Engine consultation (Read 3498 times)