ok first off i wish scooters had chains and sprockets i know them a lot better . So my scooter a sym jet 50cc derestricted ONCE UPON A TIME did 50mph on the clocks. my exhaust blew a huge sinkhole in itself so i had to replace that, so i went with a technigas trek.. i did have a leo vince tt fitted , and the technigas is slightly better on power than the tt . i also blew out the rear pulley and clutch, they were both stock units so i replaced them like for like , and the belt was a tad worn so i also replaced that but with a naraku belt. before the belt - pulley - clutch and new pipe it pulled upto 50mph on the flat via onboard clock. with a new rear pulley and clutch (oem ) a new uprated belt and a brand new pipe i lost 10mph top speed at best is 40-42 on flat . the two variables changed are the pipe and belt everything else is like it would have been , the pipe gives more power over a better powerband spread and the belt to what i know of is the same size as old one but a new fangle hard wearing job ......... SO what has caused the drop in top end speed .? Belt ? possible the belt is slightly smaller than the original and thus does not ride higher on the front face of the variator but is still able to get deep into the rear pully ? or the pipe is loosing the power due to its lower powerband spread than the highly short tts powerband ? on a bike i would just drop a few teeth on the rear sprocket and go a tooth size or two up on the front sprocket but scooters are very much different like you know how much slack is in a chain but looking at it and know if you need to loose or ad a link or two, but how does one find the most optimal belt length without purchasing a shed load of belts and trying each one ? I just want my top end speed back !!!
Have you had the belt cover off and run the engine to check visually if the belt is reaching top and bottom of respective pulleys? A belt that is too thin can reach the bottom of the clutch pulley but not the top of the vario, and vice versa reversed for a too thick belt. Or maybe a tad long in length than the original.
yeah i thought the same, i looked up the belt but the standard naraku belt does not give measurement , But i have found belts for the sym jet euro x and basi x ....... 737 -18 - 30 and also 734 - 18 -30 , also 736 - 18.5 - 28 its wierd that these belts are for the same scoot but have varied sizes ....... and the bike shop never gave me the old one back either so im kinda fluffed or going to have to find a sym OEM belt .
