brianmacza Posted August 6 Posted August 6 I have a funny feeling I have a stuck valve on cyl3 - finishing up the revamp on my '97 XX and couldn't get vacuum enough to enable the fuel flow from the tank - putting my tongue on the vacuum line I get a push-pull and not a suck. Moving the line to the other cylinders works fine - cyl3 is a problem any advice other than "open her up and see"? Quote
superhawk996 Posted August 6 Posted August 6 Compression test, then leakdown test if compression is low. An easy compression test is to listen to the engine while cranking. If the compression pulses are consistent it's probably ok, if there's a noticeable skip in the pulses then you have a cylinder with low compression. Have you started it, or just cranking? Is the 'revamp' because something happened to it, or just because it was sitting a long time? Quote
brianmacza Posted August 6 Author Posted August 6 (edited) Sitting for 4 years and needed love. New panels, wheel and steering stem bearings, fork seals, sprockets and chain, rebuilt carbs, new CCT, tires... Just cranking and doing checks prior to a first dtart Edited August 6 by brianmacza Quote
CALCXX Posted August 6 Posted August 6 It doesn't take much vacuum to open the fuel petcock diaphragm. Will the petcock open if you manually provide the vacuum? Suck it. haha You sure you have hoses properly placed on the fuel petcock? One is vacuum, one is overflow. Quote
brianmacza Posted August 7 Author Posted August 7 5 hours ago, CALCXX said: It doesn't take much vacuum to open the fuel petcock diaphragm. Will the petcock open if you manually provide the vacuum? Suck it. haha You sure you have hoses properly placed on the fuel petcock? One is vacuum, one is overflow. Petcock works fine... when I crank the engine with my tongue on the line to #3 it has pulsating pressure not suck Quote
rockmeupto125 Posted August 7 Posted August 7 I don't know if you can buy one commercially. I have a spark plug threaded air chuck (the male end). Putting that in the cylinder and putting pressure to it, you might be able to hear where the air is coming out. Even moreso if you just put a hose on it and blow through it. Here's what I've done in the past. Valves don't stick shut, they stick open. And often, they just need a little persuasion. You could: A)spray some starting ether in the cylinder and fan a flame over the spark plug hole. There might be enough gas pressure to jar it closed. B)Take some soft rope, like old clothesline, put the cylinder at bottom, and stuff all the rope you can in through the spark plug hole. Then turn the engine and compress the rope, pushing up on the valves. You might have to pull the rope out and feed it back in a couple times to get it spaced right to push on the valve, but it can work if the valve isn't stuck TOO tight. If it just stuck from sitting, it's entirely possible to free it up. Quote
superhawk996 Posted August 7 Posted August 7 Craziest stuck valve incident, I wouldn't believe it if I hadn't seen it and have no idea why it happened. Customer parks their forklift Friday, Monday it won't start. I discover 3 valves stuck open, I think they were all intakes. Prying upward was a no go. I removed the rockers and tapped on the ends of the valves with a small hammer while applying upward force to help the springs and they eventually closed. It fired right up and has been fine for years. Quote
superhawk996 Posted August 7 Posted August 7 11 hours ago, brianmacza said: Petcock works fine... when I crank the engine with my tongue on the line to #3 it has pulsating pressure not suck I expect there to be pulses, but only sucking and not blowing. 1 Quote
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