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Post by oldgeek on Sept 1, 2015 21:12:47 GMT -5
While the timing was advanced a bit, setting it all the way back to stock did not completely cure the knock during deceleration. I had the scoot on the lift and I forgot to check if there is a base gasket installed.  I will check tomorrow. I am now thinking the carb may also be lean. Before I tore the motor down and found bad reeds I was changing so much I may have downjet the carb. I don't even know what MJ jet is in the carb now. Possibly a 92? The top speed was 54 this time, so maybe I can make this scoot a runner now that the reeds are straightened out. Lol! |
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Post by oldgeek on Sept 4, 2015 16:11:18 GMT -5
After many jet changes, needle changes, and even a carb change I still cannot get completely rid of the knock at deceleration. It is not always there, it kind of comes and goes. I guess I may need to lower compression a bit.
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Post by 190mech on Sept 4, 2015 16:48:36 GMT -5
What kind of head/combustion chamber are you running?
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Post by oldgeek on Sept 4, 2015 17:44:15 GMT -5
It is the 8 port 54mm autotech kit. I don't know what type of head it is, but I do not think it is a squish band style.
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Post by 190mech on Sept 4, 2015 18:46:45 GMT -5
I'd be looking at the head design,its gotta be trapping some burning mixture where it shouldnt be..
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Post by oldgeek on Sept 4, 2015 23:49:35 GMT -5
I'd be looking at the head design,its gotta be trapping some burning mixture where it shouldnt be.. Ohhh...I see, makes sense. Thanks! So I will chuck the head up in the drill press and reshape it with the flex tool, removing the ridge for starters. Time to look at some of Brent's documented work. |
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Post by Sitticuss on Sept 6, 2015 0:26:53 GMT -5
whats the squishy set at? you can have detonation problems with that setup if its too tight. I thought they all came with squish type heads.
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Post by oldgeek on Sept 6, 2015 7:42:43 GMT -5
whats the squishy set at? you can have detonation problems with that setup if its too tight. I thought they all came with squish type heads. I dont know what the squish is right now, I may have omitted a base gasket during rebuild. LoL! I have no idea what style head this one has, I just cannot remember. I based my comment to 190mech on the current picture of the autotech 8 port 54mm kit posted on feebay. I may pull the head today and find out for sure. |
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Post by 190mech on Sept 6, 2015 8:19:20 GMT -5
Do a squish check before pulling the head and post a pic of the combustion chamber..
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Post by oldgeek on Sept 8, 2015 14:45:30 GMT -5
Do a squish check before pulling the head and post a pic of the combustion chamber.. Squish measures .63 - .73 depending where you check it. I did omit the base gasket when I reassembled this build, I only used motoseal for some reason. I also used motoseal for the head, where I usually use copper spray all the time. In the picture of the head you can see a small ring of carbonized motoseal all the way around it. I guess that may have been causing my problems? Also the deck height is a little high, the base gasket should fix that. Copper spray on the head this time for sure. Not sure if I can pull the cylinder with the motor in this scoot, I am beginning to dread working on this thing.   |
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Post by 190mech on Sept 8, 2015 18:35:34 GMT -5
It could very well be the motoseal,if youve ever had a torch around silicone sealant,it tends to glow..Just the thing to light off the mixture before the plug fires.. I also noticed some dings in the head surface,something loose in there?? Looked thru Brents thread and found this brief head mod,it says a lot on this page; 49ccscoot.proboards.com/thread/436/triton-2-t2-89-110cc?page=107 |
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Post by oldgeek on Sept 8, 2015 21:57:38 GMT -5
It could very well be the motoseal,if youve ever had a torch around silicone sealant,it tends to glow..Just the thing to light off the mixture before the plug fires.. I also noticed some dings in the head surface,something loose in there?? I found some more problems, the piston was contacting the head ever so slightly mostly on one side of the piston. I am guessing it happened only when it got hot enough. Also the crosshatch looks like krap. After the thin stainless reed backer went through the motor a while back, I should have honed the cylinder, replaced the piston, or at least the rings but I didn't. All I did was use an old ring to scrape the ring grooves a bit where the rings were both sticking, and slapped the old rings back on along with a new reed block. So now I am going to order a piston kit and do it right. I am considering building a stockish motor for this scoot and dumping it. I don't like it much now that I have ridden it more. It just does not feel solid at speed, and besides it is a PITA to work on. I think the handling issues are because of the odd tire size, which forced me to put cheapo tires on it when I built it. Also the long shock I had to use on it pitches the seat forward in an awkward way. I may move this cylinder and crank on a long-case 99cc build for a Vento sized scooter. I think I would be much happier.  |
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Post by 90GTVert on Sept 9, 2015 9:43:55 GMT -5
I guess you helped to outline the practical limits of squish a bit more for us. I've only ran a ~100cc down to about 0.7mm and after reading what you said I don't think I'll be pushing any farther. I believe 2strokd said he has gone down to somewhere near 0.5mm in the past on a ~100cc, but for 1/8 mile racing use. I've never had much luck with a stock sized combustion chamber and anywhere near tight squish clearances, which is why you'll see me opening up heads so often with the big engines. If it's only showing 181psi though and your piston is kissing the head, then the easy way out should be to add gaskets. |
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Post by Sitticuss on Sept 9, 2015 10:55:58 GMT -5
I ended up with a squish of 1.4 anything lower and I just had detonation problems.
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Post by oldgeek on Sept 9, 2015 12:36:00 GMT -5
I guess you helped to outline the practical limits of squish a bit more for us. I've only ran a ~100cc down to about 0.7mm and after reading what you said I don't think I'll be pushing any farther. I believe 2strokd said he has gone down to somewhere near 0.5mm in the past on a ~100cc, but for 1/8 mile racing use. I've never had much luck with a stock sized combustion chamber and anywhere near tight squish clearances, which is why you'll see me opening up heads so often with the big engines. If it's only showing 181psi though and your piston is kissing the head, then the easy way out should be to add gaskets. I don't know what caused me to leave the base gasket out when I put this thing back together. Too many scooter projects going on at one time I guess? Anyway when I put it back together there will be gaskets at the base, and the head. |
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