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Post by grumpyunk on Jan 23, 2020 10:06:03 GMT -5
You get popping out the exhaust for two reasons that come to mind. Fuel/air mix that was not burned in the cylinder finding some glowing particles in the exhaust, and BAM. You also get popping when you close the throttle while running at a good high rpm. The mix can get too rich because airflow is limited by the butterfly, but apparently there may be enough extra air in the exhaust/muffler to light off a burnable mix. Backfire from the carburetor is generally caused by a lean mixture. I have not had that one explained to me..., but have seen it occur on car & truck engines. tom
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Post by grumpyunk on Jan 23, 2020 9:59:09 GMT -5
Most fuel tank outlets have a sort of 'straw' sticking up from the outlet that keeps 'stuff' from getting into the fuel line. The straw is perforated plastic with small screening built in. If you remove the fitting from the tank outlet, the straw should come out with it and allow you to flush the tank clear of debris. You generally would use solids to clean a tank that had rust as a preparation for re-coating the inside surface. You can use chain, nuts and bolts, general hardware, BBs or even rocks. You do have to clean up after... Most times a good flush will do, but if you do have rust flakes, they can be loosened up using chunky stuff and shaking/rolling the tank. Kind of a mess. I have yet to see a filter 'before' the petcock, unless it is a remote mount version. If you are relatively careful to keep dirt away from the gas tank filler, there should not be a lot of 'stuff' getting inside to worry about. tom
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Post by grumpyunk on Jan 23, 2020 9:52:43 GMT -5
the cable end 'barrel' that attaches to the carb bracket should be seated fully so the cable housing is close to the bracket. Loosen the nut on the barrel and unscrew it to allow the cable to stick through the bracket further. Use the locking nut on the throttle side of the bracket to hold the cable housing securely. The same adjustment can be made at the handlebar twist grip. The two adjusters allow you to tighten or loosen the cable. The actual cable length does not change, of course. tom
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Post by grumpyunk on Dec 14, 2019 12:03:46 GMT -5
Pistonguy: "I was hoping you would Not take Grumpys advice and Not tear into the engine because your in real trouble now. The guy with three posts sends a young kid down the road to ruin in one post just plane Boils me.."
Well, realizing this is an old post, you sure are full of yourself. His problem, as related, was indeed discovered by taking the rocker/cam cover off. Just what did I send to ruin? The problem was there from the first post, all that happened was that Marty discovered exactly what it was.
It was stated he could not rotate the crankshaft. Given that, looking at the valve train was, in my mind anyway, a lot simpler than taking the whole thing apart. Four (some have more) fasteners to remove the cover is not really tearing into the engine, and taking things apart is how you learn. I have been fooling with engines for a long time. I try to pass on some of my knowledge and experience. I may have only a few posts on this site, but have thousands on a lot of other sites. Thank you for posting, but I disagree. I hope he figured things out. He likely has a bent/damaged sprocket on the crankshaft that the chain got into when it came off the cam sprocket and jammed. But, given it is from a year ago, and no more posts, we'll likely never know. tom
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Post by grumpyunk on Jul 23, 2018 15:39:47 GMT -5
Have you checked that there is oil in the crankcase? If it is too low, it won't lube nor cool, and things can go bad quickly when it gets too hot.
You should be able to rotate the variator 360 without binding except for the effort to compress the gas in the cylinder on the compression stroke.
A quick check to see if your cam & cam chain are functional and attached to an intact crankshaft & sprocket would be to remove the rocker/cam cover and watch what happens as you attempt to rotate the crankshaft. You can use a 17mm on the vairator or a 12mm on the hub of the cooling fan wheel. If the chain is slack or jammed up when you look, you will need to take things apart to find the deeper problem. One good thing is that unless you broke your connecting rod, the piston will still move, so it is not locked up. If the cam & rockers seem ok, go ahead and remove the cylinder head and inspect the piston motion as you turn the crankshaft. tom
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Post by grumpyunk on Dec 17, 2017 12:49:16 GMT -5
I think lost was referring to a Big Bore kit. The 39mm piston & cylinder can be replaced with a larger bore, reaching near 100cc of displacement. The external dimensions and appearance are exactly the same, big bore or not. Oversize bore kits are available on-line, and possibly at local shops. Check craigs list for them and possible installation service if needed. If you go to the largest size, you will be stressing the crankshaft & connecting rod more than a tiny bit. Longevity may be negatively affected. The smaller 47mm(vs 50/52mm) bore increases displacement to ~70cc, almost 1/3. Most are labeled 80cc kits, but they are not actually that large. Add a 70cc kit, and a larger bore carb, such as a 19mm or 20mm and you should notice a lot more power while hill climbing or running into the wind. Acceleration and top speed will vary based on variator weights, clutch shoe springs, and the spring on the clutch pulley. tom
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Post by grumpyunk on Dec 17, 2017 12:36:10 GMT -5
I would suspect fuel supply. The valve adjustment would not make it start & die almost immediately. If the fuel flow was a bit slow, it might starve the carb of fuel, causing stalling. If the vacuum operated valve doesn't open the flow, you will run on the fuel in the float bowl on first start, then vacuum from cranking or running will(should) open the fuel valve, and allow the float bowl to fill properly. Disconnect the fuel line before/after the filter, and place a catch bowl/can in place. Crank the engine over, and the flow should start within a few seconds(given the cranking generates enough vacuum) as the control valve opens. If not, check the valve(and maybe filter?) tom
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