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Post by mrchilled85 on Feb 20, 2020 12:35:22 GMT -5
i know this has been posted up so much on the forum tho i cant seem to find one that has the same sound as mine
this is a full stock engine just been rebuilt with crankshaft , bearing , piston kit
bike runs nice but getting a bit of a knock when coming off the throttle and rpm is in the range of 2200-1800rpm
has a open air filer as i dont have a stock airbox around
running a 74 jet
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Post by chehystpewpur on Feb 20, 2020 15:04:25 GMT -5
that isnt spark knock. thats piston rattle it sounds like. spark knock or pinging usually occurs under a load at higher rpms while the motor is making a good bit of heat. low quality low octane fuel on high compression motors will also cause it but its not gonna happen at low rpms. you would need a coffee can for a piston to cause that by 2k rpms. what cylinder did you just rebuild your engine with? it may be that the kit you got has low quality control and the piston size vs bore is pretty far off. or your piston rings may have needed end gap adjusted and it wasnt so the rings could be causing increased friction and making the piston rock and rattle when changing directions. pull the head and look at the cylinder wear. youll see witness marks if the piston is flopping around all willy nilly. or you may see octogonal marks if friction is too high and its causing the piston to heat up and swell in the bore basically on the edge of a soft seize. did you use a new needle bearing for the piston and was it the right size? a seized bearing can also sound like that and so can a piston circlip stuck in the side of a piston after it came out. but the sound would usually be constant if the circlip popped out.
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Post by mrchilled85 on Feb 20, 2020 16:31:07 GMT -5
not sure as its a tnt standard replacement cylinder kit with pin and bearing set
taken the head off and no marks or soft seize marks
last one of the tnt kits i had was fine
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Post by chehystpewpur on Feb 20, 2020 18:18:41 GMT -5
no marks is a good thing. is the piston for sure in the right way? members have done that in the past and it will make it run and make funny noises. if you know the piston is the right way you need to check ring gap. you should also check squish if the head is back on already.
i havent heard of tnt kits but i did a quick search and all i brought up were the china kits. if thats the case it may be your problem. ive never had luck with china kits and i was about 50/50 on the taiwanese kits. i spent more money in the past trying to keep those kits running than just buying a good kit and enjoying it.
also what is your exhaust? and did you have that pipe before the noise started?
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Post by christopher on Feb 20, 2020 18:39:45 GMT -5
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Post by mrchilled85 on Feb 21, 2020 0:51:52 GMT -5
no marks is a good thing. is the piston for sure in the right way? members have done that in the past and it will make it run and make funny noises. if you know the piston is the right way you need to check ring gap. you should also check squish if the head is back on already. i havent heard of tnt kits but i did a quick search and all i brought up were the china kits. if thats the case it may be your problem. ive never had luck with china kits and i was about 50/50 on the taiwanese kits. i spent more money in the past trying to keep those kits running than just buying a good kit and enjoying it. also what is your exhaust? and did you have that pipe before the noise started? yep arrow on the piston is to the exhaust port not checked the ring gap yet or squish will check them after work today the exhaust is the stock that my bike come with from new and yes i used it with my old engine fine |
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Post by chehystpewpur on Feb 21, 2020 14:49:10 GMT -5
ok those are good things. ive seen seasoned engine builders almost put pistons in the wrong way and im like uhhh whatre you doin. its always good to know that didnt happen. i also seen that blue silencer and wondered if that was one of those ebay special exhausts. they used to be alright but now they arent the same pipe and could cause running issues. but if its old exhaust and worked fine before im pretty sure its the cylinder as those china kits can have all kinds of quality control issues. www.scootertuning.ca/en/hop on that site and page around for the cylinder kits your bike could use. maybe think about it. you cant go wrong with an athena top performances or stage6 kit. top performance is a taiwanese company and they know our motors very well. pretty much like a performance division but they dont make anything i need. a stage6 cast kit would be very fun on a stock bike and last a long time somewhere around 10k miles |
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Post by mrchilled85 on Feb 21, 2020 15:40:26 GMT -5
ok those are good things. ive seen seasoned engine builders almost put pistons in the wrong way and im like uhhh whatre you doin. its always good to know that didnt happen. i also seen that blue silencer and wondered if that was one of those ebay special exhausts. they used to be alright but now they arent the same pipe and could cause running issues. but if its old exhaust and worked fine before im pretty sure its the cylinder as those china kits can have all kinds of quality control issues. www.scootertuning.ca/en/hop on that site and page around for the cylinder kits your bike could use. maybe think about it. you cant go wrong with an athena top performances or stage6 kit. top performance is a taiwanese company and they know our motors very well. pretty much like a performance division but they dont make anything i need. a stage6 cast kit would be very fun on a stock bike and last a long time somewhere around 10k miles my other engine i built up is fine but this engine was just going to be a backup engine and i had 3 sets of engine case's so was something to do  i spotted something today when i was checking it over after work one of my stater place bolts have broken off so only has one bolt holding it on so not sure if that will do it or not but going to drill and tap it tomorrow and ordered a new topend gasket set as picked up Yamaha neos 50cc topend today off a running bike so going to give that a try to |
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Post by mrchilled85 on Feb 22, 2020 4:00:07 GMT -5
just taken topend off to find piston pin or piston pin bearings are shot
got a parcel coming today with a spare topend gasket set then going to fit the genuine yamaha neos 50cc topend to see if that sorts it
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Post by mrchilled85 on Feb 23, 2020 13:21:34 GMT -5
ok those are good things. ive seen seasoned engine builders almost put pistons in the wrong way and im like uhhh whatre you doin. its always good to know that didnt happen. i also seen that blue silencer and wondered if that was one of those ebay special exhausts. they used to be alright but now they arent the same pipe and could cause running issues. but if its old exhaust and worked fine before im pretty sure its the cylinder as those china kits can have all kinds of quality control issues. www.scootertuning.ca/en/hop on that site and page around for the cylinder kits your bike could use. maybe think about it. you cant go wrong with an athena top performances or stage6 kit. top performance is a taiwanese company and they know our motors very well. pretty much like a performance division but they dont make anything i need. a stage6 cast kit would be very fun on a stock bike and last a long time somewhere around 10k miles well sorted it now mate fitted a oem yamaha topend , pin and bearing i know the fan and covers are not on but only started it up to check if the knocking had stopped |
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Post by chehystpewpur on Feb 23, 2020 19:32:49 GMT -5
glad to hear you found the problem. i knew it had to be in the top end somewhere when i heard that sound.
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Post by mrchilled85 on Feb 24, 2020 0:56:43 GMT -5
glad to hear you found the problem. i knew it had to be in the top end somewhere when i heard that sound. after checking it over more turned out the piston pin was bent a small bit only by 0.8mm but think thats what had done it |
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Post by chehystpewpur on Feb 24, 2020 10:33:24 GMT -5
hopefully it didnt cause any harm to the big end of the rod. thats a good bit of force to bend a wrist pin.
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Post by mrchilled85 on Feb 24, 2020 13:27:33 GMT -5
hopefully it didnt cause any harm to the big end of the rod. thats a good bit of force to bend a wrist pin. had put my panels back on the bike today and went for a ride around for 45 minutes seems fine and done 19 miles tho i was stopping every 5 miles just checking it over to make sure every thing was fine and to let the engine cool off a bit i have put the stock airbox back on to and got it running at its best with a 82 jet as running premix |
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