good day - 84 1100 2 weeks ago got my bike back on the road after 3 years. It needed coils so I got a used set online from a bike with 27,000 mi. Put them on and bike now runs perfect. I had forgotten how great these engines are.
After 250 mi, it wont hardly run around town. Rough running and will not idle at all. At freeway speed, I cannot tell there is a problem but i'm sure its still there.
Coil primary testing looks great at 3.1 ohms. Cannot get a number for the secondaries but I think i'm doing something something wrong as I am new to multimeter testing. Got a friend coming over to help.
Decided to do a compression check again as I had done that just prior to getting it running.
#1 - 140 lbs. #2 - 140 lbs. #3 - 115 #4 - 145 lbs
now compression is #1 - 25 lbs #2 - 80 lbs #3 - 80 lbs #4 - 85 lbs
I had filled up at a station and got out on the freeway, 70- 80-mph/112 - 128 kph. pulled over after a few miles to put on warmer gloves and have had the running problem ever since. Until I slowed I never noticed the problem.
How could the compression go bad so suddenly?
Obviously its a compression problem as I still have spark? have not put my fuel filter on yet.
Sitting for periods allows the idle jets to clog and give you the same symptoms you describe. Crappy gas... I have had some luck running Seafoam for a tank or two. But not after that long. You may need to pull and clean the carbs.
1) Do not use a fuel filter on a gravity flow FJ ('84-87) Fuel pump FJ's, yes...Gravity flow FJ's, no.
2) Check your valve clearances. You might have a tight valve. Adjust as necessary.
3) Check to make sure your vacuum petcock is staying open. Do a suck test on the vacuum line.
4) Clean out your tank and properly clean your carbs.
5) recheck your compression, this time on a warm engine and *the throttle held open*.
That's it Pat. Forgot to hold the throttle open. I'll do that and re-report numbers. Thanx
Have a Pingle old school petcock, after the stock one gave out. Tank is clean.
FJMonkey - bike was put away, carbs drained and dryed.
Could the gas cap vent do this?
I have another igniter to try also.
A blocked vent in the gas cap will starve the engine more at higher REVs when the fuel flow needs to be the highest. The rough idle is typically clogged idle jets. Just because you drained it, don't rule it out. If the idle is good when the choke is on and not so good when warm and the choke is off, the jets may be your problem.
I repeated the compression test. It does not look good. With a warm engine it reads
1 - 30 #2 - 110 #3 - 110 #4 - 110.
must be a head issue, at least, would you say? 52,000 mi bike Piston rings maybe too?
The sparks are weak visually and after you shut off the starter, about a second later, 1 or 2 spark plugs do a 1 spark discharge. My stock coil set looked that way visually [ weak blue spark ] and a different coil set gave me 250 mi of perfect running. Now this different coil set is doing the same as my stock set. oh well.....
Plan to pull off carbs and look at idle jets soon.
Well, both my coils are cracked. That solves the running roughly issue.
Someday I'll learn how to post pics here.
Dyna coils are our option here, then? Never have seen any NOS coils for sale.
Yep, I have Dyna green 3.0 ohm coils on my '84.
The coil relay mod will really wake them up.
Quote from: bigbore2 on October 27, 2019, 08:56:09 PM
Well, both my coils are cracked. That solves the running roughly issue.
Someday I'll learn how to post pics here.
Dyna coils are our option here, then? Never have seen any NOS coils for sale.
Yamaha coils
https://www.biketeile-service.de/Yamaha-FJ-1100-21399/en/electrics/ignition/ignitioncoilsbikespecific/coil12v1aa8231009.html (https://www.biketeile-service.de/Yamaha-FJ-1100-21399/en/electrics/ignition/ignitioncoilsbikespecific/coil12v1aa8231009.html)
Quote from: bigbore2 on October 22, 2019, 05:30:38 PM
I repeated the compression test. It does not look good. With a warm engine it reads
1 - 30 #2 - 110 #3 - 110 #4 - 110.
must be a head issue, at least, would you say? 52,000 mi bike Piston rings maybe too?
The sparks are weak visually and after you shut off the starter, about a second later, 1 or 2 spark plugs do a 1 spark discharge. My stock coil set looked that way visually [ weak blue spark ] and a different coil set gave me 250 mi of perfect running. Now this different coil set is doing the same as my stock set. oh well.....
Plan to pull off carbs and look at idle jets soon.
A leak down test would indicate rings, valves or both. 30lbs....are the valves fully closing?
a previous compression test this year before getting it running showed 140 lbs in #1.
Something must have broken?
Gonna pull the head and go from there.
thanx Balky. Did not see that till now. Just ordered Dyna coils earlier this afternoon.
Pat - Dyna coils are in.
Did you mount them with the spark wires coming off the front or towards the tank. Stock, as you know , come off the bottom of the coil. No clearance problems there.
And the coil relay mod? put in the search bar " coil relay mod "?
Looking at the Dyna coils, I see its a L and R orientation to to the spark plug outlet, so the lower bolt hole lines up.
That should pose no wire clearance issues then?
One of our original FJ forum members is a guy named Jon Cain.
Jon is a whiz at fabrication and he makes some custom brackets for installing the larger Dyna Coils on our FJ's, which is what I used, along with the Dyna RF wires and boots. I'll page Jon and see if he responds.
I can say that the Jon Cain coil brackets are the bomb, they make it easy.
I recall David Raforth (FJ_Hooligan) has some pictures of his Dyna coil installation, perhaps he will post them to this thread.
Here's a link to the coil relay mod: http://www.fjowners.com/index.php?topic=1755.0 (http://www.fjowners.com/index.php?topic=1755.0)
Yea, Im having a fitting problem with the coils. The lower coil mount/tube the bolt goes thru, the tube looks too long, is all. If I cutoff a little the coils should line right up.
Its also those rubber mounts on top are hard to get in the mount holes. They were a tight fit with the stock coils too.
What I remember doing is cutting off one side of the rubbers. Don't remember which side but probably the outside to push the coils apart.
Then I bought a longer bolt for the bracket. Done.
ok. I got the coils in. its a tight fit, for sure. I had to shave a portion of the casing of the coil to get them in as there is a raised thin long rectangular shaped part of the casing they print 3 Ohm and a number on. those two raised portions meet and make it necessary to remove them. I just trimmed it down to the casing level and it went together MUCH easier, no longer bolt needed. the casings do touch but it all goes together.
the trick is getting the upper coil post to slide into the rubber cap first. Its not a straight shot as the coil is too large. I filed the post edges and corners to round them as they were sharp and catching on the rubber cap. I used a little silicone grease to help with getting the post in. Once the upper post goes in, the lower post holes will line up.