I've got a 50cc scooter does 40 top end Good on acceleration I've put a new plug lead and 6.5 rollers in it and a new belt, but in between acceleration and top end its slow any ideas?

Your drive belt snapped. If it is a 50cc, 4 stroke engine, chinese scooter, with a 10 inch rear wheel, then you most likely need a 669-18-30 belt. That is the most popular scooter belt on the planet and is available for about $10-$35, depending on the quality you want. Any scooter shop can change it for you. It only takes about 15 minutes, but expect to pay a chargeable labor rate of .5-1hr since there are unexpected problems occasionally, and there is cleanup time, paperwork time, etc. It should cost about $30-$75 in labor plus parts. Any more than that and you are getting ripped off. You may have other worn parts in your transmission such as roller weights and variator guides. These tend to wear out on chinese bikes around 3000km+. If they are worn, change them while the technician is working on it. It shouldn't cost you any more labor, just the parts, about $12-$20 for the rollers, and $8-$12 for the guides. Cheap belts last about 2000-3000km, good belts last 5000-9000km. Pay the extra few dollars for the better belt, you won't regret it. If your belt broke prior to 2000km, then you may have a defective part in your transmission, such as the rear pulley. That usually comes as a "clutch pack" and generally sells for $40-$90. If you have more than 2000km, it probably snapped just from normal wear and tear. If you can't find a local scooter shop, you can reach us at www.solanocycle.com. We can ship you any parts you need. This repair is not recommended for novices. Although it is easy for those who know how to do it, you can damage your crankshaft and ruin your motor if you do it wrong. Hope this helps.

have you checked that the spark plug is tight and that the ht lead is on the spark plug?

I had the same problem. Broke 2 belts before I got online and noticed this site! What I found was, the roller ends were not turning freely. I had cleaned the hair (nasty) off the roller, but the ends were still not able to spin around without some force.

What I did was, removed the roller and on the 2 ends there are 2 black plastic caps which fit over the bearing, I removed the plastic caps and put a little WD-40 on the bearing, or any industrial lubricant, even new motor oil will work. After putting on the WD-40, I spun the roller end around a few times and the WD-40 lubricated the bearings and Voila! The roller end spun freely!! I put the black caps back onto the bearings on both sides, reinstalled a new belt, it's been working great since.

It saves the cost of a new roller.
Todd M, Fremont CA