Bad Mileage / Poor Performance

[Riding Again]

Thought I had it all worked out. Not performing like I think it should or as I remember my last 850 did 20 years ago.

1 - Mileage !@*tty at 25-30 mpg on interstate
2 - Seems to be rich (no plug chops yet)
3 - sounds more like a deeper growl at WOT, especially in 5th
4 - finding motor oil on air filter (blow-by?)

Things done

~6000 miles ago
replaced base and head gasket and valve seals

< 300 miles ago
New boots (air box and engine sides)
New o-rings (carbs)
Dipped and cleaned carbs
Checked and shimmed Valves
New Fuse Box
Cleaned (washed/dried) and LIGHTLY oiled air filter

<200 miles ago
New stator (not related, but ...)

Things checked
No gas in oil
Can't smell exhaust for gas at WOT on the road. (I guess that's what plug chops are for)

Any suggestions of where to go from here?

Really disappointed on performance and mileage. I did a 60 mile run on the slab the other day and I could almost see the fuel gauge moving from full to E as I rode. Cagers weren't nice either

I'm thinking--

WOT chops first
Re-clean filter next
WOT chops again
Filter removal(?) to improve air flow and WOT chop again?
Rejet and try again?

Mains are 115 on CV carbs

Am I thinking in the right direction?

[althomas101]

Re-clean filter next
WOT chops again
Filter removal(?) to improve air flow and WOT chop again?
Rejet and try again?

Sounds like what I'd do/have done. Since it sounds like you have done your maintenance items first, carbs should be the only thing left. Other options would be you could take it to a dyno shop, or install a wideband Air/fuel meter. PS. exhaust notes sound "dull" when the engine is running rich, if that helps any. PSS. don't forget that you have to "clean" the plugs by riding the bike for 10 minutes or so before you do the plug chop. Otherwise you risk having soot from starting the bike up.

[Guest]

Check the voltage at your coils from battery negative to coil positive and see if there is a drop from reading direct battery voltage.

[althomas101]

Good call, weak coils will kill gas mileage, and they tend to not show their issues until hot so you may not notice the misfires while riding.

[ClarkRU]

Try the plug chop idea - this will tell you a lot. You probably nailed it with the running rich guess.

[Riding Again]

PS. exhaust notes sound "dull" when the engine is running rich, if that helps any. PSS. don't forget that you have to "clean" the plugs by riding the bike for 10 minutes or so before you do the plug chop. Otherwise you risk having soot from starting the bike up.

I would call what I hear "dull" and good to know about "cleaning" the plugs.

I was wishing I had the wrench with me when I was on the "slab" as I had 20+ minutes of WOT, what a great read it would have been! Wait--I didn't want to be on the side reading plugs with cagers nearby

Check the voltage at your coils from battery negative to coil positive and see if there is a drop from reading direct battery voltage.

Good call, weak coils will kill gas mileage, and they tend to not show their issues until hot so you may not notice the misfires while riding.

I won't leave any stone unturned, I'll check the coils, but I did run new wires to them with the new fuse box to eliminate the coil relay mod. I won't say that I haven't considered needing to replace them with a Dyna set.

Would it be good to check the coil voltage after an extended (20 min+) ride versus just after the bike's warmed up?

Thanks for the tips! I'll try them out tomorrow.

[Guest]

Did you run the wires directly from the fuse to the coils? I hope it's switched if you did. The reason for the coil mod besides direct battery voltage to the coils is to retain the kill switch. It's really quite easy. Follow the coil positive wires from the coils to the cable bundle, and strip the wrapping off the bundle several inches toward the front of the bike until you find where the wires are twinned. go about two inches more, and cut the single wire leaving enough wire to attach another wire to each side of the cut. The wire going toward the front of the bike gets attached to the relay spade that closes the electromagnetic switch, 86. The other side of the pickup coil, 85, gets grounded. This will open and close the relay with the kill switch. Terminal spade, 87 goes directly to battery positive through a 10A fuse. Spade, 30, goes back to the coil wire where it splits for each coil. You might need that kill switch some day. 3M 33 electrical tape is good to wrap the cable bundle again. Anything less is throw away temporary electrical tape and will melt off with heat. A good pull up a long hill at WOT is plenty good enough to read your plugs. You might have to look around for a good place to coast into that's safe to check your plugs before you do this.

[Riding Again]

Did you run the wires directly from the fuse to the coils? I hope it's switched if you did. The reason for the coil mod besides direct battery voltage to the coils is to retain the kill switch.

I just replaced sections, leaving the kill switch inline. I think I'll reinstall the relay mod again to make sure the voltage is good.

3M 33 electrical tape is good to wrap the cable bundle again. Anything less is throw away temporary electrical tape and will melt off with heat.

3M 33+ electrical tape is the only stuff I use for electrical. When the need arises, it's supplemented with similar quality splicing tape (tape that melds to itself). .

A good pull up a long hill at WOT is plenty good enough to read your plugs. You might have to look around for a good place to coast into that's safe to check your plugs before you do this.

I happen to know where there's a few hills near by, useful for a good pull.

Thanks

[Riding Again]

Finally got out to do the plug chops.

Warmed the bike up with a 15 minute ride on the interstate.
Found a hill that went up 150 ft over 1 mile and scouted out where I would begin and end the chop run.
Changed the existing plugs to new plugs at the bottom of the hill.
Went through the gears quickly and settled into 5th for about 1/2 - 3/4 mile, trying to keep the throttle wide open with each gear change.
At the end point, I hit the kill switch and pulled in the clutch and moved to the side of the road and started pulling plugs.

Best I could do for time of day.

#1 plug


#2 plug


#3 plug


#4 plug


Back at the house, all together 3, 4, 1, 2 - left to right. (took the photo and then looked at how I set them up )


In reality, they all look good, though #1 could be a touch rich.

[Riding Again]

Here are the current running plugs (only 600 miles)

#1


#2


#3


#4



Plugs 1-3 look consistent whereas #4 WTH

[Buffalo Bill]

Looks like #4 has the problem, but #2 is OK, not the coil.
Check plug connections to #4, but probably not the issue.
Check the float level on #4 and compare to others. This could be the problem.
Check everything about #4.

[oldrookie]

Looks and sounds exactly like what I was dealing with last week on my GR. I agree with Bill, check the float level on four. I found that the float needle was sticking down. Replaced the float needle and all is good.

The symptom that clued me in was when I turned the carbs upside down. The floats should be "springy." The problem carb float would not bounce. It would just lay flat on the needle.

Plug looked exactly like yours and the airbox had fuel running out of it at one point.

[Riding Again]

Looks like back into the carbs

Fortunately haven't seen or smelled gas in the filter box.

I've also installed new plug caps.

[BigD_83]

Looks like back into the carbs

Fortunately haven't seen or smelled gas in the filter box.

I've also installed new plug caps.

I recently installed the Dyna Greens on my 650. I noticed the gas smell was back at idle, and I was getting sooty plugs (but not as bad as your #4).

Wait a minute, the Dyna was supposed to solve issues like that!

I dropped in on BCCap on Thursday, and I was nearly killing the bike, just (like 1/16th throttle) off idle. Did a run out to Point Roberts and back this morning, and the bike seemed OK at speed, but really twitchy down low, and my fill up said I was getting a little worse in the mileage department. There was a definite miss, that was getting worse.

I ran a test when I got home, and it seemed like I was getting no spark on #1 at idle. I pulled the lead wire off with no change in idle speed. Swapped the leads around with #4, and the problem followed.

I pulled the leads from the coil and checked their fit to the coil. Turns out that my crimping on the coil end of the plug lead left a little to be desired, was a little too narrow, and the contact was rattling around inside the coil housing. In fact, the rubber boot on the outside was not fully seated because of the coil mount tab on the frame, and I believe the lead was just falling out a little. It was that loose.

Long story short- you might want to check out the coil end of your leads if you are still having fuel mileage and performance issues, particularly if it is only on one cylinder.

[Riding Again]

Took the family on vacation this past week so no work was done on the bike until today.

Dived into #4 carb and found the float level was fine as was the bowl gasket and needle valve. Also, all the jets were clean. What I did find was that the diaphragm had slipped during the last session and not seated properly.

After an inspection showed no rips or tears, a careful reassembly and install happened and a test ride.

It felt like a normal bike again!

I'll be checking the mileage this week to see if that has helped it any and if not, I'll check out BigD's suggestion below.

Long story short- you might want to check out the coil end of your leads if you are still having fuel mileage and performance issues, particularly if it is only on one cylinder.