i got a dna 125cc.. 4 stroke.. (stock), and it wont push more than 50mph on the straight, what can i do or put on it to make it faster...also is there any way of derestrictin it..thanks

jimmy, December 2009

buy a new bike

domwilde, January 2010

what plug u talkin bout scott? the coil?.. and are u askin if the inside or the outside of it is dyish black?? cheers mate......about the air filter,, would it be best to clean the one i have in petrol or just buy a new one?

jimmy, December 2009

yes jimmy the air filter element is inside the airbox above the transmission cover on the right hand side of the engine,its a sheet of sponge.

adam, December 2009

Sounds let you're flooding the engine. Take the plug out and see what colour it is, if it is a dry-ish black colour then you're running your bike too rich which could be because the airfilter is blocked or just the wrong settings in the carb.

Scott, December 2009

thanks for replyin guys.. im definatly gna start with ur points adam, cheers for those.. well i bought it about a month ago and there was a problem with the coil,, i changed it which made a change but still bad.. it only has 4500 miles on the clok so i guesin it hasnt been over used..so yh it has always done 50.,, the other thing is i sometimes get a strong wiff of petrol when the bike hasnt even been startd but thers no sign of leekages,, maybe it has something to do with that?.. the air filter your talkin about,, is that the one in the air box yh? and yh the oil is fine and it doesnt over heat.. cheers
jimmy

jimmy, December 2009

Thats definateley not right as bb says it should do about 65 mph so you have a problem there.Now it can be one of many things but i would start with the basics.
1,it could have a blocked air filter therefore rstricting the flow of air ,check it and clean it in clean petrol dry it and refit it.
2,the exhaust could be blocked if yiou have a freind with a dna borrow his pipe and try that or try removing the rear section temporarily and see if it revs out then it will be noisy and may also run weak but it should be enough to establish if the pipe is the problem.
3,it could be low on compression the vlave clearances could do with checking to make sure they are not overtight approx .012 on the exhaust and 0.8 on the inlet is the right clearance settings.
4,a common problem with the 4 valve leader engine is the rocker arms break on either the inlet or exhaust this allows the engine to run still if only one of either of the exhaust or inlet breaks or even both can break one of the rokers and it will still run but its unlikeley to break both at the same time.if it has broken one iof the rocker arms the intake volume or ability to discard the burnt gases in significantly reduced and this will caause a big drop in performance.if it has broken a rocker arm then fit a new one its easy to do.
as bb says did it do it suddenly or has it always been like it.the bike is restricted by stock parts only there are no restrictors to remove only upgrades likke a polini 170cc kit and larger carb and exhaust along with a secondary gear up kit will make a big power and speed gain.sort out your running problem before you do anything.good luck and let me know how it goes.cheers adam

adam bike doctor, December 2009

Hmmm. I had one that would do 65 restricted. I would suggest you have a few more problems than a simple deristriction.

Ok has it always done 50 or could you do more has it slowed with age? Have you had it long and do you know the service history. When was the oil changed last?
Have you checked the level of Oil and is it ok.
Does it over heat or is it normal. Post back with a few more details. There are some people on here who will be able to help.

BB, December 2009