|
|
Post by ApeShit70 on Jun 30, 2019 0:28:52 GMT -5
Can having the lifters a little too tight. Not pushing the valves but with no gap at all make a 150cc scooter backfire? Or when throttle applied make it surge and almost stall repeatedly??
|
|
Rune 75
Scoot Enthusiast
Posts: 441
|
Post by Rune 75 on Jun 30, 2019 6:53:25 GMT -5
Can having the lifters a little too tight. Not pushing the valves but with no gap at all make a 150cc scooter backfire? Or when throttle applied make it surge and almost stall repeatedly?? Yes, and make it hard to start when warm. |
|
|
|
Post by GrumpyUnk on Jun 30, 2019 12:11:50 GMT -5
If the actual clearance is 0.00mm or 0.0", then the heat of the engine running will expand things such that the valve will not likely seat when at operating temperature. That could(no guarantee) allow intake gas to get pushed back into the intake, or pushed out past the exhaust valve, either of which could be held off the seat by said expansion. Once the unburned got out into either port, could it go BAM, sure.
As far as stall and surge. The same pushback of gas could blow back through the carburetor and upset(significantly) the flow of liquid/emulsified fuel in the various circuits. Then there would be zip/nada for the engine to inhale when things went the other way... so it would stumble & burp. I think, anyway.
I know that too-tight valves on a big fat 429 made the engine idle as if someone was doing Morse code on the exhaust or perhaps the points in the distributor. It shook pretty bad, and when the rocker arm lock nuts were backed off, started to idle like it was tamed again.
If you have adjusted your valve clearance too tight, and want to 'get by' with a rough approximation, take a regular business envelope, and fold it in half. Use that as a measure. It won't be correct(?) but it should allow you to get where you are going until you can have access to a measuring tool. Likely it would be a bit tappy, and if you find that too much, close up the adjuster 1/4 turn and see how that is. It really is not rocket science to adjust the valves, and the suggested clearance in the shop manuals depend on which manufacturer wrote the manual. I think it depends on how loud they want their machine to be, some going for quieter operation. With close clearance, you get max duration of the valve being open, opening sooner and closing later than a 'loose' clearance.
tom
|
|
