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Post by 90GTVert on Aug 14, 2017 11:14:35 GMT -5
I'm not sure how universal they are (maybe differences in the frame/mount?) but here are some expensive ones : www.g-forcepowersports.com/EXHAUST-PIPESMINIQUAD-s/4346.htmMaybe find cheaper stuff (again if it fits) by searching for the popular Polaris models like the Sportsman, Predator, Outlaw, and Scrambler 50,70, and 90. I think up to 2006 was 2T.
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Post by ryan_ott on Aug 14, 2017 12:12:31 GMT -5
Plenty of scooter pipes I could maybe modify to fit. Are you saying this is for an ATV? Search Dinli, Kasea, Apex, Eton, mini quad exhaust. There are quite a few results on eBay for around $200. Some of the apex had a smaller expansion pipe on them stock, could be better then what you have, only if it's cheap enough. www.ebay.com/itm/362002177771
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Post by catchacuda on Aug 14, 2017 12:41:58 GMT -5
Thanks for the help vert. Ryan, its for my daughter's Dinli Dino 50. I was just eyeballing this, would need a silencer added of course The link you posted looks promising too, these lengths look pretty long, I -might- have to put the silencer 90° from the expansion chamber to avoid having it sticking out ridiculously far. Like so
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Post by catchacuda on Aug 19, 2017 0:36:02 GMT -5
As suggested by 90gtvert ive triple checked my durations, well, more than triple...
My *official* numbers are
156° exhaust 135° transfer
Squish clearance as checked by some folded over solder is .8
Im tempted to try raising the exhaust port a bit, while still retaining it's shape. Maybe try ~180° Any thoughts on that?
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Post by 190mech on Aug 19, 2017 3:37:44 GMT -5
180 would be a good starting point,you may want to go a bit more later...Check the port chord width(straight across,not curved around the bore)which should be 65% of the bore diameter..
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Post by catchacuda on Aug 25, 2017 19:56:10 GMT -5
Well, had been hearing some piston slap, I checked my ring end gap, they were "Yuuuge!" Compression was also pretty low. So, instead of sticking with the 49, I'm now at 72cc. It was a very cheap $42 kit from ebay. The transfers needed some "smoothing" they had a lot of casting flash in them. Oddly, the ring end gaps were nearly dead on. This thing will now do wheelies! Port durations are at 186 and 124, squish is .7 running the O-ring head gasket. Still eyeballing pipes, hoping to peak around 9-9.5k. Will also play with roller weights after the pipe. Surprisingly, no jet changes appear to be needed, at this time. Yet I have no idea what size jet is in my carb, there are no makings on it. All I know is the plug looks great, I hear no detonation.
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Post by ryan_ott on Aug 25, 2017 20:39:25 GMT -5
Most of the cylinder kits I've gotten have been really close with the ring end gaps also. Do check your mixture with a fresh plug or CHT. It's odd that no mixture adjustment was needed but your original piston also looks rich which may explain it. You could also check and clean your air filter. An overly dirty filter could cause a rich mixture.
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Post by catchacuda on Aug 25, 2017 21:20:04 GMT -5
Yes, I'll try upjetting just to see the effects. But some tweaking of the mixture screw and it's running pretty well. It sounds a lot healthier than the worn set-up. This site has been an immense help with this 40qmb, thanks guys
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Post by catchacuda on Aug 25, 2017 22:12:00 GMT -5
Stupid question, can I tune a two stroke with a wideband? I have an innovate motorsports LC1 buried somewhere. Will the oil cause any issues with the sensor? Also what kind of numbers are safe under part throttle cruise, and WOT?
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Post by 90GTVert on Aug 29, 2017 7:01:46 GMT -5
You can use a wideband on a 2T. The oil will foul the sensor quickly. Koso offers an adapter to help with this or you could install the wideband just for tuning and then use a plug in the bung. WOT should probably be something like 12:1 to 12.5:1. There are some numbers HERE, but it's targeted at liquid cooled machines. Air cooled engines will probably need to be a little richer to stay cool.
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