Compression question

[CUBuffs]

I just went out and started it up after it sat for about 10 minutes or so. It's idling just fine. What the crap (can I say that?) is going on?

[skids]

If either the filter towers on the petcock are getting plugged, or you have inline filters that are restrictive, the cutting out would be worse at speed. I haven't followed the threads, but heat can change the pick-up coil wire resistances. Make sure that the vacuum hoses are attached to the petcocks.

Originally posted by CUBuffs
I just went out and started it up after it sat for about 10 minutes or so. It's idling just fine. What the crap (can I say that?) is going on?

[skids]

Ooops. you have specials. Instead, make sure the vacuum hose is attached from the octo to the manifold nipppple.

Originally posted by skids
Make sure that the vacuum hoses are attached to the petcocks.

[randy]

Tank cap vent? My best guess.

[CUBuffs]

What is the tank cap vent?

[John]

It's just a small passage in the gas cap to allow pressure to escape, or to allow the pressure in the tank to match the outside air pressure.

[CUBuffs]

Is that the little hole that's in the center underside?

[John]

Yup, it is.

[CUBuffs]

How do I check the vent?

When I opened up the cap it seemed to be under lots of pressure. Although I can't be sure if it sucked in or blew out.

[CUBuffs]

Crimped vacuum line

I've been checking my lines on the Octo and discovered that the left vacuum line is crimped at the petcock. Could that be the problem?

[TopCatGr58]

Very much so! No vacuum, and the Octopus doesn't allow fuel to flow. You can test this by turning your petcocks to PRIME, and drive it, and you'll probably be able to drive it for miles with no problem!

When you're idling, it's not drawing much fuel, so the flow/drip that is occuring from the low vacuum partially opening the Octopus is enough to keep it running, but once you got out on the road, your fuel consumption was faster than the Octo could flow with that restricted vacuum line not opening the Octo fully!
T.C.

[CUBuffs]

Tank Cap Vent

Can anyone tell me how to check the Tank Cap Vent to see if it's plugged? I took the 3 screws out from around the hole but can't get anything to pop off.

I took the beast on a longer ride after checking the fuel lines. Went about 5 miles to a friends house where it sat for about 20 min. On the return trip it sputtered and died 4 times.

[TADracer]

Guys, I always do a leakdown test with the piston in the test cylinder on TDC. It is a chore to keep the piston up on TDC under air pressure but it gives the best readings since the most ring wear will be at the top of the cylinder and you do not have to worry about if your cam is starting to open on the exhaust stroke. If air is heard coming out of the exhaust, the valve is bad. Likewise, if it is heard from the carb, the intake valve is bad, Some should be heard through the oil filler hole since the rings will always have some leakage but if it is less than about 10% of the air going in, the rings should be OK. If it is leaking 15-20% or more, new rings are usually in order. If you have a really good seal, your leakage should only be about 2-3 %. Try to use a 2-stage tester so you can directly read the percentage of leakdown. Also, if your cylinders are in good order, they all should be leaking roughly the same percentage of air. If one cylinder is leaking alot more than the others, your prob is in that cylinder. You may be able to rent this tester somewhere instead of springing $$$ for one.

Gook luck and happy hunting!

[TADracer]

Oops! Did I post on the wrong thread??

[prometheus578]

"Venting my frustrations"

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When I opened up the cap it seemed to be under lots of pressure. Although I can't be sure if it sucked in or blew out.

CUBuffs... mine has started acting the same way. Shall unlock the gas cap and ride to work like that tomorrow and see if that cures it.
Take the cap off. Should be able to put your dog-lips around the hole and blow through it.
Like John said, if that vent is plugged, as the fuel leaves the tank it'll form a vacuum inside, eventually, the vacuum will not allow anymore fuel to flow. Not a common problem, but I've seen it a few times. Usually after someone seals their fuel tank, and seals over the bottom of the cap, too.