Main jets or fuel filter?

[btgs1000]

79 GS1000. Valves adjusted and to spec. New Dynatek electronic ignition, cleaned, rejected and synced carbs (it has pods and similar to stock mufflers but shorter), moved the clip on the needles down one, new AntiGravity battery. I've got good spark and it runs strong when on the center stand through all ranges, but when I put it under a load while riding it, the mid to upper throttle just boggs down. Volt meter shows the charging system is working ok as the volts rise over 13 when you increase the throttle. I know the pilots are right and I now have 105 mains. It has the petcock with no lever that is set on prime with an inline shutoff (temporary fix) and a lawnmower fuel filter (until I can run a few tanks of high octane through it to clean it out). I noticed the fuel doesn't quite fill the fuel line after the fuel filter (it has a clear fuel line so I can see it) while the bike is running (you can see it trickling in but not keeping the line full). The vent hose is connected too. Do you think it's the fuel filter causing the problem or do I need to go up on the mains? It's so close to running great. I don't understand why it runs great on the stand but boggs on load. Mid range to upper throttle would indicate mains need to go up but I'm not sure it just isn't getting enough fuel to the carbs first.

[Agemax]

ditch the fuel filter and go up on the mains. 105's are far to small for pod filters and aftermarket pipes.

[tkent02]

What he said.

[Steve]

Ditch the "high octane" while you are at it.

.

[retcol]

Advice from Eric:
You should try it without the filter first.
Then, after that doesn't cure anything, you should drop the jet needle down to stock position.
If it still needs anything besides fuel/air screw adjustments, you might go up one or down one main jet size depending on your elevation.

[dorkburger]

Wouldn't there also be a filter in the tank , and if so could it be blocked?

[sedelen]

Wouldn't there also be a filter in the tank , and if so could it be blocked?

Not likely, your petcock probably looks like this, and that white thingy sticking up is your fuel filter. It would have to be clogged most of the way up to affect it, unless it is missing altogether.


What altitude are you at?

[Steve]

Advice from Eric:
...

Why doesn't "Eric" post this himself?

.

[btgs1000]

I found a bunch of sediment that made its way through the petcock and into my inline fuel filter, so I finally took the petcock off to see if the filter was missing and it is still in tact with no holes in it and its not gummed up either. Now I really don't see how the sediment even made its way into the fuel line. They are pretty large pieces too.

[tkent02]

Rust particles are one thing the petcock screen doesn't block very well.

HAve you thought about cleaning the tank?

[Big T]

You really need to clean the tank, maybe coat it - see the POR 15 thread

Then, ditch the fuel filter and go up on the mains

Where do you have the fuel and air screws set?

[btgs1000]

Yeah, I'm going to clean the tank over the next few days. Acetone to remove the varnish first, then I'm going to do the electrolysis with soda wash to get rid of the rust. Then new petcock rebuild kit, no inline filter and I've already went up to 107.5 mains, so hopefully that will do it.