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Triton
Mar 28, 2011 19:45:57 GMT -5
Post by 90GTVert on Mar 28, 2011 19:45:57 GMT -5
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Triton
Mar 29, 2011 10:15:34 GMT -5
Post by reiko1078 on Mar 29, 2011 10:15:34 GMT -5
If I can't get it running I will try a leakdown tester In the mean time I retorqued my head nuts and got a good 1/2 turn out of most of them I raised the needle one slot and took her for a ride. BEst run yet for sure got up to an indicated 30 mph then she bogged heard a knocking sound and she died. Spark doesn't look tooo light but it's not the nice Brown that ive seen. I'm gonna put in an 85 then I have to go to work I'm close I can feel it
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Triton
Mar 29, 2011 10:44:02 GMT -5
Post by reiko1078 on Mar 29, 2011 10:44:02 GMT -5
Went to an 85. Same thing. The knock is more of a tick and when It starts the motor idles really low. Turn it off Then starts right back up no noise. What would this be? I'm guessing its damaging the cylinder and piston.
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Triton
Mar 29, 2011 10:47:38 GMT -5
Post by reiko1078 on Mar 29, 2011 10:47:38 GMT -5
Dr I may try what you suggested with the petcock. Would I need to get a new one? Or can I just take The vacuum assembly off? Are the stock fuel lines not 1/4 inch?
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Triton
Mar 29, 2011 11:26:05 GMT -5
Post by 90GTVert on Mar 29, 2011 11:26:05 GMT -5
Stock lines are 5mm or 3/16" or something like that. Here's dr's thread about replacing the petcock with a fitting for 1/4" line. You can use it that way, but it's best to install a manual shutoff. You can get 'em from small engine shops and sometimes hardware stores have them in the lawn and garden area. 49ccscoot.proboards.com/index.cgi?board=fuel&action=display&thread=1355I'm guessing the knock/tick is detonation. Have you checked your squish clearance?
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Triton
Mar 29, 2011 11:31:15 GMT -5
Post by reiko1078 on Mar 29, 2011 11:31:15 GMT -5
I've heard the term "squish clearance" before but I dont understand quite what it is
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Triton
Mar 29, 2011 11:42:16 GMT -5
Post by 90GTVert on Mar 29, 2011 11:42:16 GMT -5
The clearance between the piston and the head basically. You can use a piece of thick solder to check it. Bend the solder and put it in the cylinder so it reaches the edge. Keep your fingers and things out of th eplug hole of course. Crank the engine over. Remove the solder and measure.
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Triton
Mar 29, 2011 12:12:04 GMT -5
Post by reiko1078 on Mar 29, 2011 12:12:04 GMT -5
So the solder actually gets crushed between the head and the piston? What should the clearance be?
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Triton
Mar 29, 2011 12:25:42 GMT -5
Post by reiko1078 on Mar 29, 2011 12:25:42 GMT -5
Searched squish clearance and it brought up your triton #2 thread with the pic of the piece of solder that's been squished. Makes way more sense now. Do I measure the very tip that got Squished thin?
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Triton
Mar 29, 2011 13:29:02 GMT -5
Post by 90GTVert on Mar 29, 2011 13:29:02 GMT -5
That's a weird head, unlike what you should have... but yeah, measure the thinnest part. Hopefully you'll see around 1mm. Less is great for power, but the closer it gets the higher compression is and the more heat builds up. Too close and it's possible the piston could hit the head when things flex. .6mm is the minimum just for clearance's sake.
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Triton
Mar 29, 2011 15:33:03 GMT -5
Post by drawkward on Mar 29, 2011 15:33:03 GMT -5
Lower squish number = higher compression. Higher compression needs better quality fuel (higher octane) to ignite properly. Go to low on the squish (too high of a compression ratio) and you will have to buy race fuel (+$) to avoid top end damage (could result in bottom end damage if the top end fails) and poor performance.
"Top end" = cylinder, piston, rings, head, wrist pin bearing, wrist pin, and circlips. "Bottom end" = Crank, connecting rod, lower connecting rod wrist pin bearing, lower connecting rod wrist pin, crank bearings, and seals. Just the crankshaft assembly with new bearings and seals will run you the same price as a complete 70cc top end; not to mention the cost of tools to rebuild the bottom end, or paying a shop to do it - if you can find one.
That being said, are you willing to risk it? I'd go ahead and do that leak down test. Even with a brand new gasket, perfectly clean mating surfaces, and the correct torque; you can have a leak. They just happen - and even a very tiny leak will make tuning extremely difficult.
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Triton
Mar 29, 2011 15:52:27 GMT -5
Post by drawkward on Mar 29, 2011 15:52:27 GMT -5
Just read the part where you said you had trouble getting it to seat properly. Just take off the shroud, start it up quickly, and carefully spray a small amount of carb cleaner or if you want to be safe, some premixed gas around the cylinder base and head. Do it before the engine gets hot as to avoid a fire. Idle changes = leak. Lazy man's leak down tester. You could even just spray it into the cooling fan opening. Won't work as well though. If the leak is bad enough you could even be able to spot it (ie: fresh black crud coming from somewhere). I've been through this so many times on my scooters. Also thought a small leak wouldn't hurt until I destroyed a fairly new 47mm cylinder and racing piston (~$200 down the drain). I leak down test now. Saves me the head ache later, as well as eliminating that problem so troubleshooting is much easier down the line.
Tip: Intakes are notorious for leaks. Your stock pipe doesn't rev as high, so it doesn't have as much vacuum pressure coming through the intake, so the lean condition won't be as dramatic as with the high velocity air and greater vacuum pressure from your expansion chamber pipe. .
Also, make sure your exhaust isn't leaking. How well did you clean the gasket surfaces when you swapped them out? Reuse the used gasket? Dress the used gasket at least? A leak at the exhaust manifold will cause you to lean out fairly quickly. It'll also be pretty loud. If the combustion is louder near the head than the end of the pipe, I'd say it is leaking. Also, oil coming from exhaust manifold = leak. Good luck. Keep us posted!
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Triton
Mar 29, 2011 18:16:44 GMT -5
Post by reiko1078 on Mar 29, 2011 18:16:44 GMT -5
Thanks for the info guys pretty sure i have a leak that I need to find. If I do need to get my cylinder back off any suggestions how to do that since I had trouble getting it on?
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Triton
Mar 29, 2011 20:44:16 GMT -5
Post by 90GTVert on Mar 29, 2011 20:44:16 GMT -5
Very carefully. Honestly, that's about the best answer I have. Take it slow. Be as gentle as possible. Maybe you could get your fingers in the exhaust port to help you pull. Avoid prying, it's likely to damage a mating surface or cooling fin.
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Triton
Mar 31, 2011 10:49:29 GMT -5
Post by reiko1078 on Mar 31, 2011 10:49:29 GMT -5
Had to take a few days off from the scoot. Been working late this week hopefully some progress will be made This weekend
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