Ok, I'd really like to hear your opinions on this folks. I've got a Suzuki Marauder GZ125, fuel injection, and I need to change the chain so while I'm doing it I'd like to change the rear sprocket for a smaller one. (1 less tooth I'm thinking) as I've got no top end speed, 55 and that's it. As soon as I get to a hill it's back down to 40!!! Will this help? Anyone ever done something like this? And yes I know I should just pass my test and get a better bike, but in the meantime is this worth trying?                                                                                                                                                                              

you will get slightly better top speed but will also loose acceleration in the process allthough it would depend on weight of rider in other words if you are as light as a feather then smaller sproket will prob improve things a little but in reverse if you not as light as a feather the bike being small capacity will strugle to pull away or up hill performance would suffer hope i havnt made it more confusing                                                                                                                                                                              

A  single tooth less on the rear sprocket is not worth doing, you will feel VERY little, if any, difference whatso ever.   In addition you will prob find the need to actually change down a gear next time you come to the hill in question. by raising the gearing as you have effectively done, it would be similar to being in a higher gear ratio ie in 6th instead of 5th.   I have zero experience of your bike, but would have expected it to have a higher top speed than 55, (Could be wrong here I dunno) an if its dropping to 40 on a hill, maybe its time to get your bike checked or as ya say,  get test done an go for a bigger one.                                                                                                                                                                                  

I'd forget about it LR.

Tony's probably right, you should be getting slightly better top speed than that, somewhere between 60 and 65.  But I wouldn't spend time and money trying to sort it personally, not if I was in a position where I was able to start thinking about my test.

Get some training done and take your test is my advice.  Then flog your 125 and get a nice little 500/600!  Do it!!!                                                                                                                                                                             

Thanks Wheely. Well I'm am a big girl so don't think it's gonna work lol

Tony, it's always been slow. Think it's just not a very good bike. Its been to garage for various things. Asked them about lack of speed. They couldn't find anything wrong. Just said get a better bike!!!!!

Geoff I think you're right mate.                                                                                                                                                                              

"Geoff I think you're right mate."

Bloody 'ell!!  You do?  Are you sure?  You're probably the first lol!

I may frame this lol!!                                                                                                                                                                             

Well make the most of it Geoff I don't often say it lol                                                                                                                                                                             

I would check your airfilter and choke control as said it should still do 60 and airfilter wont cost much                                                                                                                                                                             

Thanks jp I was thinking that actually. It was cleaned when I last had it serviced but it made no difference speed wise. Maybe time to change it. As you say they don't cost much                                                                                                                                                                             

get a 2-stroke 125, throw £600 at it, you will hit 60 in five secs, top out at about the ton mark.                                                                                                                                                                              

And you'll get plenty of practice with the spanners rebuilding it every 6-10k!                                                                                                                                                                              

not really, Malossi parts tend to be over-engineered for street use, pre-mix castrol power 1 helps ................................ and in any case, a crank rebuild is only three hours start to finish.                                                                                                                                                                              

The polini kit on mine was sh!te! Lol!                                                                                                                                                                             

depends what kit, they make everthing from cast iron sport kits all the way to 300bhp+/litre evo kits. Main enemy of tuning is lean jetting, many people set up with plug chops, but can't beat a large drum dyno set-up, which reproduces true loading. You jet slightly rich, then that covers you for winter, when the air is more dense.

but then it wouldnt be legal would it !                                                                                                                                                                              

easy to conceal a rev limiter, operates from brake lever code, dremel off any cylinder identification marks, VHT paint finish ............................. if you want 600cc beating performance with a learner bike, it's not going to be legal, but it can be incognito.                                                                                                                                                                             

I put a rear sprocket with 2 teeth less on an AR50 when I was a kid, just to try and get 70 down a hill with my feet on the indicators etc (usual nonsense - micron with no baffles, ported with a rusty file.)  

First gear was like an RC30 and my clutch would finally stop slipping when I hit 35ish but I dusted my mate's gs125 with ease.  Happy days!                                                                                                                                                                              

Will I get more speed from a smaller sprocket?     yes if you lose some weight, the bike that is, of course.                                                                                                                                                                             

My mrs had  a maurder 125. Now she is 7 stone dripping wet but it was SLOW.

She now has a yamaha ybr 125, and with me riding it, it will (sometimes) do 70mph with 60-65 being easy.....oh and i may weigh more than 13 stone :)

hope that helps you