What else uses fuel on my 650?

[Steve]

I..., you'd see signs of gas in the overflow tubes, ...

His carbs don't have overflow tubes. Only the VM carbs have them.

.

[Steve]

... And there is no way a 650 should only get 21 mpg.

If you can't get it down to 21, you must not be riding it hard enough.

.

[MisterCinders]

His carbs don't have overflow tubes. Only the VM carbs have them.

.

Well, the overflow would end up somewhere.

These CV carbs are of the Devil, I tell you.

[BigD_83]

115 main jets are how much bigger than stock?
Why so many turns out on the mixture screw? Are you using the stock size pilot jet?
If it smells rich it is very rich, you can't smell just a little bit rich.
Have you checked your fuel levels?

I managed to get in the garage late this evening. Up to this point I do not think I had experienced anything as frustrating as trying to get the fuel level gauge screwed in. In fact, the Suzuki gauge CANNOT be screwed in to the #4 carb drain because the casting for an engine case bolt closes down the space too much.

The numbers are not too bad. If anything the fuel level is a little on the low side.

Using the service manual as a guide:

#1 6mm
#2 6mm
#3 7mm
#4 no reading

[salty_monk]

If you are using the stock air box I would go 112.5 at most. Did you raise the needles at all? The 2.75 turns sounds too fat for stock airbox. That's almost what most run with pods... What idle speed are you set at? Are you sure your calculations are correct (i.e. is your trip meter accurate? Have you tested it against GPS?)

Fat blue spark against the head could die off when running under load...

Just throwing out some ideas.

[BigD_83]

If you are using the stock air box I would go 112.5 at most. Did you raise the needles at all?

No to raising the needles, so far.

The 2.75 turns sounds too fat for stock airbox. That's almost what most run with pods... What idle speed are you set at?

I agree that 2.75 seems a lot. I am going to do another carb synch and highest idle, just as a triple check. My idle, based on the tachometer gauge is around 1100 rpm

Are you sure your calculations are correct (i.e. is your trip meter accurate? Have you tested it against GPS?)

I have not confirmed it, but I don't think I am off that much. I will definitely have another measure when I take the bike out for a ride this week. My place to work and back is a known quantity

Fat blue spark against the head could die off when running under load...Just throwing out some ideas.

Thanks, Dan. I appreciate the input. How do you envision the mechanism for loss of spark under load. In other words, how would I test for it?

[BigD_83]

An update...sorry no pics.

Jess and I went out for a ride last night and put a few miles on the tank. The bike reeked enough of gas that Jess was asking about it. After I dropped her off at the house I ran up to work to check the tripmeter, and it was close enough for government work.

I had a set of Dyna Green Coils waiting to go on, and I just needed an excuse to do it.

They turned out to be a minor PITA as the mounting holes don't quite line up the way their instructions say, and the mounting spacer ALMOST grounds out the bottom primary lead. Anyhow, I did get the coils on, checked them for arcing, didn't see any, and went for a spin. I added another 53km to the 47km Jess and I put on the bike since the last fill up.

The good news is the rather odorific exhaust was noticeably improved. The bonus is the bike feels like it is pulling harder with the new coils.

Reckoning this would give me a good starting point for checking fuel mileage, I stopped in to my local Chevron to fill up. To my delight, it only took 5.89L to get back up to my "full" mark. A rather small sampling, but that 5.89L/100km of stop and go riding in the city with minimal highway riding works out to about 40 mile/US gallon. That's more like it!

I'm not going to chalk the improvement up to just the new coils, but the reduction in gas smell indicates they are helping. Another problem was that I had been running low on tire pressure and I filled them up to the low end of spec halfway through the last tank of gas.

The real test is coming up when I get to watch the mileage over the next few tanks of gas, and hopefully with more highway miles to boot.

[tom203]

Hard to imagine coils/weak spark causing so much unburned gas, but I hope it's progress. The green dynas- primary resistance?? and are you using stock ignitor still?

[BigD_83]

Hard to imagine coils/weak spark causing so much unburned gas, but I hope it's progress. The green dynas- primary resistance?? and are you using stock ignitor still?

I know. I have a hard time believing it myself. As smelly as it was I kept expecting raw fuel to be pouring out of the motorcycle somewhere, but I can't find any leaks. We will see where it goes from here.

These are new from Z1 Green Dynas, and are spec'd at 3 (3.3?) Ohm. I did not measure them with a multimeter yet.

Yes to stock ignitor unit.

[The_Flash]

They turned out to be a minor PITA as the mounting holes don't quite line up the way their instructions say, and the mounting spacer ALMOST grounds out the bottom primary lead.

They were the same way on my 650 and eventually it did short out and started causing problems. Here's how I fixed it:

I wrapped the spacer in electrical tape and relocated the lock washer. So far I have spark on all cylinders, but I'm a little scared that the shorting out may have caused other issues. We'll see...

[BigD_83]

LOL!

that was my solution as well. I still have to go back and shrink-wrap the lug connectors to eliminate yet another potential corrosion/short point.

I just cannot believe how much of a difference the coils are making. I thought the bike was running well before, albeit very thirstily. Two fills ups later, 40mpg in city traffic, and last night a 105 mile ride with mainly open road cruising gained me almost 44 mpg.

EDIT- I think long term I'd like to fab a bracket that makes use of the far mounting hole. Probably wouldn't take much, even a piece of threaded flat bar might be rigid enough

[salty_monk]

You may also want to check you have full 12v to the coils. If not then you could run them from a relay ("Relay mod"). It's pretty easy to do.

My GS1000's gas mileage improved after I replaced the ignitor (faulty) with a Dyna S so it might also be worth testing your ignitor too... Clymer has a test procedure for it (or at least they did for my 80 GS1000).

It's very hard for a spark that is weak under load (when it looks healthy unloaded). I think this could be what you've found out...!

[puddle pirate]

I'm having the exact same issues on an 82 GS650E. The fuel is not going into the crank or leaking that I can find, and i'm only getting about 31 miles to the gallon. Did you have any weird measurements across your coils prior to replacement?

[BigD_83]

I'm having the exact same issues on an 82 GS650E. The fuel is not going into the crank or leaking that I can find, and i'm only getting about 31 miles to the gallon. Did you have any weird measurements across your coils prior to replacement?

No, my old coils spec'd out to OE measures both cold and hot.

One thing did happen a long time ago, and I had discounted it because the spec's hadn't changed. I was charging the battery on a trickle charger, and I had left it in the frame. I had mistakenly left the key in the "ON" position, and when I checked in the morning the left coil was very hot. Hot enough that some of the insulation (?) wax from the coil had dripped onto the frame. Even though the resistance numbers hadn't changed, I thought it was a big deal at the time, so I went ahead and ordered the Dyna Green coils. When I pulled the coils, both had some wax underneath, near their frame mounts.

Until now, I hadn't been getting in enough riding to notice any drop in fuel mileage, because the motorcycle had been an absolute gas hog from the day it was gifted to me, and I've been doing a lot of maintenance.

The voltage drop from battery to coils has always been good. I had a drop of no more than 0.5V from the battery. I can't remember what the latest absolute drop in voltage was, but I am still getting 11.88V - 12.03V at the coils while cranking. I am still considering doing the coil relay mod.

You might find a drop in mileage with your 4 into 1 and pod setup, too, but I wouldn't think 20 mpg.

Have you cleaned up your connections between the battery and coils? See SaltyMonk's note about the coil relay. A worthwhile mod if cleaning the connections doesn't bring your coil voltage back up.

[puddle pirate]

I'll check the coil voltage this weekend. I'm getting around 30 miles to the gallon. I"ll redo the carb sink and the Valves and verify they are spot on, then maybe pick up some Dyna coils if things don't improve. Thanks for the great write up on you problem and fix.