Engine miss
 

I've got a 1990 600 F1 that is having issues.

I've been through the carbs multiple times. They've been cleaned and had the needles and seats replaced. The plugs are new. The tank has been cleaned and it's filter replaced, and I just put a new fuel pump on it. I took it in and supposedly the floats were set, valves set, and carbs sync'd.

The issue I'm having is that it has a miss unless it's under load. It doesn't seem to matter what the throttle position is. It will miss unless I'm accelerating. Any ideas?

Thanks,

I am not trying to be a wise guy but try a different pump.

This ethanol they are putting in the fuel is causing all kinds of problems. My bike stumbles like a 2-stroke loading up and spits and sputters and then take off like a shot. When I go to a different pump it clears up. FI motors adjust to the crappy mixture but the carb motors suffer. Try some Seafoam in your tank. It helps to stabilize the fuel as the ethanol and gas separate and cause misfires.

Any change to the exhaust like opening up the pipe with an after market can, could cause a leaner mixture. Ethanol mixtures need to be enriched. Try a little choke and see if it clears up.

If it's not missing under load or with a little choke, I would say it's the fuel (ethanol).

what TimBucTwo said.

In addition to that. I would lean towards the pilot jets being too lean. that is the part of the carb that controls the idle. If the choke test makes it better, the pilot jets need to be richened, if it makes it worse, they need to be leaned.

Do you remember what you set them at?

Nothing has been changed on the engine or exhaust. I've played with the choke while riding, and it doesn't make a difference. I hadn't thought about trying a different source for gas. That may just be the ticket. I'll give that a shot the next warm day we get here. Thanks for the info.

When our Federal government 1st proposed phasing in ethanol blends (been available for years if wanted to buy it) I contacted Honda Australia about my F3. They wrote back with a warning not to use it & a list of things that ethanol petrol will effect. Seals, lines, rubber & plastic components & carbon build up. The myth will ethanol, its cheaper to produce & cheaper to buy. But in reality false economy because it does not detonate as efficiently as standard petrol & you use more of it. I know that a lot of older twins, (like Guzzi's) run like crap on it & I refuse to use it even in my car. So far its only been put in 92 RON, so I can still get non ethanol petrol anyway, but eventually it will get put in all our petrol.

I went and got the best quality gas I could find and it didn't help. I did narrow the problem down though. I got an infrared thermometer, and found that the temperature on cylinder 2 is quite a bit lower than the others. That pretty much has to be the one that is missing except when under load.

It sounds like you narrowed down the cylinder with the issue. Now its just determining if its a weak sparkplug, bad connection, or carb related. I would still lean towards the pilot jets not being set correctly. I would at the very least check them. You may find that one carb is adjusted differently than the others. Since its cooler than the others, I might lean towards that cylinder running too rich. If it is, it can easily cause the plug on that cylinder to intermittenly foul and create a miss. It can also cool the cylinder down by puttig in more gas than the other cylinders.

what i would check first is that the wire is good. maybe the wires are going bad. and check the coils. i bet its one of these two things.

Sorry to dredge up an old thread. It's been a long time since I messed with my bike. I was just missing it too much and have started back on it. I bought the factory float tool and have ensured that each one is set to 9mm. I also replaced the carb mounting boots while I was there. I wasn't able to get it running when briefly trying last weekend. Hopefully I'll have better luck this weekend.

What do you guys use for replacement spark plug wires?

Thanks,

-Ethan