Post by skuttadawg on Aug 8, 2013 1:57:05 GMT -5
I removed the airbox lid on a 2T and a 4T 50 and it bogged so bad I did not leave the driveway since I did not change the jetting . A Uni will have more air flow and noise and will require upjetting as would from going from a restricted exhaust to one that is not restricted . Now you can run without a muffler if you upjet enough but may get a ticket from it being loud as many Harley riders do . You can not run without a pipe as it helps remove heat from the head and without it it would burn up . A buddy who drinks too much broke his muffler and a few days broke the pipe off too . I warned him to get a new exhaust and even gave him a GY6 jet kit . Well he ignored my warning and it got so hot that the exhaust valve head broke off and ate up the head , piston and cylinder . On a 2T having a free flowing pipe with expansion chamber improve top end once the jetting is redone .
My Echarm has Ducatti EFI . One day I took off the airbox lid and filter and rode around . It did seem to help initial takeoff response but no top end gain . I let it cool and removed the muffler as mine is clamped onto the pipe where many it is welded together . Again bottom end gain , waaaaaaaaaaay loud but would only go 60 instead of 75 MPH . My header is larger in diameter than the GY6 150s as I bought a muffler for a 250cc and had to bore the the connector plate on the muffler with a Unibit . It did not have built in brackets so I had to use the strap inculded and an additional strap and bracket kit I bought . Sound was awesome as it was like a Honda XR250 sound but no gain on top end . My scooter dealer has a CFMoto Glory which has the same engine as mine but with a diff body . He has the same muffler and he had to MacGyver it to fit . He went the extra mile and installed an injector for a 250cc and had to buy an adapter plug for a BMW 325i as it had a diff type of plug . He also used a Dremel to grind the variator ramps . He had it dynoed at the rear wheel and it was 12.5 HP with a 13 to 1 fuel aspect ratio . Most are around 14.75 to 1 . He told me he hit 86 MPH with a car Garmin GPS unit . He drilled two holes in the airbox too .
The airbox does not choke the air flow like it looks like it does . Two holes drilled can improve airflow and will need rejetting . The airbox is great to protect water from getting into the carb , throttle body if equipped and the engine . A Uni or K&N style do allow more air intake , but without head porting and unrestricted exhaust may bottle neck the flow .
On my 2T 50 I replaced the airbox with a small Uni that is a vent cover and not an airfilter . I went from a 75 MJ to a
MJ and it improved takeoff and midrange with same top end . It did make more noise than the airbox with the extra flow of an open air filter . Well I later bought the proper red Uni airfilter , sprayed it with Uni filter oil . My dealer only had a 90MJ and no other scooter or motorcycle shop had any jet that was the size and type I needed . Well it idled ok and only had a slight bog but not like it was stalling . I only wanted to test ride around the block . Dang it soft seized , even melted the tip off of the spark plug and I had to push it home . It was 96 degrees outside grrrr . I let it cool and it would not restart . Compression was only 60 PSI which is half of what it should be on a 2T 50cc . I had to tear it apart and sure enough the rings were fried with the piston and cylinder scared up . I put on a BBK , reused the Uni and installed a racing pipe . Takeoff was less since unrestricted it did not have the back pressure like the stock pipe and once I had the jetting right was amazing how much more power I had at midrange and top end with it going way beyond the 50 MPH limit of the speedo display . I have made a few 150 riders mad as I outran them and told them it was a 50 with an exhaust leak hehee .
When I was 16 I bought a used racing Honda CR125 that had a .030 BBK . It ran good at first but soon had a power loss . I pulled off the head and saw the piston had so much clearance in the cylinder I could jiggle it . I got it bored to .060 over , and bought .060 over piston . Well it was a beast but ran hot as I did not upjet . I worried I would crack the cylinder from heat and a rock busted a big hole in the pipe that made it not run good at all . I went back to the machine shop and had a chromoly sleeve pressed in and bought a WiseCo piston instead of a Honda one . I could tell it was much better quality , forged , larger ports , shorter skirt and was lighter . I threw away the old pipe and bought a Pro Circuit pipe as thought it included a muffler but it did not and I threw away the old one like a dummy . I installed a way too large MJ which if you tried to trail ride it , it would bog then ZING like an angry bee . I also put in 250cc clutch springs since they were stiffer than 125 springs . The parts broke me so I rode it for two weeks without a muffler . It was so darn loud it made my ears ring and anyone I rode nearby as well . A buddy who lives 4 miles away could hear me in the woods near my house . I put on a muffler which helped unreal loud noise and it did perform better than without a muffler . I could smoke a stock 125 and trail close behind a stock YZ250 even though the 250 had way more power .
If you have a 4T 50 and want to get a BBK then I would get the big valve head from Scrappy which is ported like MillSC had on his hotrod . I think he used a 24 ( wow big ) mm carb without the intake spacer , Uni and after market exhaust
My Echarm has Ducatti EFI . One day I took off the airbox lid and filter and rode around . It did seem to help initial takeoff response but no top end gain . I let it cool and removed the muffler as mine is clamped onto the pipe where many it is welded together . Again bottom end gain , waaaaaaaaaaay loud but would only go 60 instead of 75 MPH . My header is larger in diameter than the GY6 150s as I bought a muffler for a 250cc and had to bore the the connector plate on the muffler with a Unibit . It did not have built in brackets so I had to use the strap inculded and an additional strap and bracket kit I bought . Sound was awesome as it was like a Honda XR250 sound but no gain on top end . My scooter dealer has a CFMoto Glory which has the same engine as mine but with a diff body . He has the same muffler and he had to MacGyver it to fit . He went the extra mile and installed an injector for a 250cc and had to buy an adapter plug for a BMW 325i as it had a diff type of plug . He also used a Dremel to grind the variator ramps . He had it dynoed at the rear wheel and it was 12.5 HP with a 13 to 1 fuel aspect ratio . Most are around 14.75 to 1 . He told me he hit 86 MPH with a car Garmin GPS unit . He drilled two holes in the airbox too .
The airbox does not choke the air flow like it looks like it does . Two holes drilled can improve airflow and will need rejetting . The airbox is great to protect water from getting into the carb , throttle body if equipped and the engine . A Uni or K&N style do allow more air intake , but without head porting and unrestricted exhaust may bottle neck the flow .
On my 2T 50 I replaced the airbox with a small Uni that is a vent cover and not an airfilter . I went from a 75 MJ to a
MJ and it improved takeoff and midrange with same top end . It did make more noise than the airbox with the extra flow of an open air filter . Well I later bought the proper red Uni airfilter , sprayed it with Uni filter oil . My dealer only had a 90MJ and no other scooter or motorcycle shop had any jet that was the size and type I needed . Well it idled ok and only had a slight bog but not like it was stalling . I only wanted to test ride around the block . Dang it soft seized , even melted the tip off of the spark plug and I had to push it home . It was 96 degrees outside grrrr . I let it cool and it would not restart . Compression was only 60 PSI which is half of what it should be on a 2T 50cc . I had to tear it apart and sure enough the rings were fried with the piston and cylinder scared up . I put on a BBK , reused the Uni and installed a racing pipe . Takeoff was less since unrestricted it did not have the back pressure like the stock pipe and once I had the jetting right was amazing how much more power I had at midrange and top end with it going way beyond the 50 MPH limit of the speedo display . I have made a few 150 riders mad as I outran them and told them it was a 50 with an exhaust leak hehee .When I was 16 I bought a used racing Honda CR125 that had a .030 BBK . It ran good at first but soon had a power loss . I pulled off the head and saw the piston had so much clearance in the cylinder I could jiggle it . I got it bored to .060 over , and bought .060 over piston . Well it was a beast but ran hot as I did not upjet . I worried I would crack the cylinder from heat and a rock busted a big hole in the pipe that made it not run good at all . I went back to the machine shop and had a chromoly sleeve pressed in and bought a WiseCo piston instead of a Honda one . I could tell it was much better quality , forged , larger ports , shorter skirt and was lighter . I threw away the old pipe and bought a Pro Circuit pipe as thought it included a muffler but it did not and I threw away the old one like a dummy . I installed a way too large MJ which if you tried to trail ride it , it would bog then ZING like an angry bee . I also put in 250cc clutch springs since they were stiffer than 125 springs . The parts broke me so I rode it for two weeks without a muffler . It was so darn loud it made my ears ring and anyone I rode nearby as well . A buddy who lives 4 miles away could hear me in the woods near my house . I put on a muffler which helped unreal loud noise and it did perform better than without a muffler . I could smoke a stock 125 and trail close behind a stock YZ250 even though the 250 had way more power .
If you have a 4T 50 and want to get a BBK then I would get the big valve head from Scrappy which is ported like MillSC had on his hotrod . I think he used a 24 ( wow big ) mm carb without the intake spacer , Uni and after market exhaust
MPH way beyond what it can do . Premium tires can also handle more weight , grip better , ride better and have a faster top speed rating . The trade off is softer tires do not last as long as hard tires . I feel more safer on my scoot with 13s than with 16s as the 13s are wider and have more contact with the pavement . On 10s and 16s uneven patches and cracks in the road surface it would get sketchy at times , but with 13s I ride over them with no sense of them affecting the handling . I love to have doughnuts ( fat tires ) as the 16s are not on the same scale as the 13s . Example they would be much wider if so .
MJ with a 50mm BBK so your running too rich down jet for a 50c will help .