will jetting damage your engine?

[sportrax stu]

hey guys i was just wondering if i put bigger jets on my 400ex will it damage my engine and will i have to re build it often? cos my m8 jetted his 50cc scooter and the engine blew up three times in three months!
any advice wud be good

[GPracer2500]

CORRECT jetting is good for the engine.
INCORRECT jetting is bad for the engine.

[underpowered]

why? bigger jets do not mean more power. you have to jet it correctly for what mods you have and where you live. Jetting is not simply putting in larger jets because you want to, it is a science that take time and skill to get just right.

[sportrax stu]

i know, i already have a k&n air filter and a powercore4 muffler, i had to take the muffler off and go with stock because it was overheating. i know i have to jet it but i was told it wud damage my engine. could you recommend me with any decent jet kits you know of?

not jetting in your situation will damage your engine...you are running lean since you have an aftermarket filter and have not rejetted it...

[underpowered]

Originally posted by sportrax stu
i know, i already have a k&n air filter and a powercore4 muffler, i had to take the muffler off and go with stock because it was overheating. i know i have to jet it but i was told it wud damage my engine. could you recommend me with any decent jet kits you know of?

correct jetting will do no harm. by running a pipe and K&N without re-jetting is much more likely to cause harm. The reason your engine was running hot was because it was lean due to the extra air going in and out of the engine.

a jet kit is not needed, you can buy the individual jets at your local shop instead of the whole kit

[sportrax stu]

i live in the u.k and quad parts arent as readily available here as they are in the u.s. do you know of any decent sites to buy the individual jets from? i was told jetsrus are quite gd?!!

[ohsobad_chevy]

Originally posted by underpowered
why? bigger jets do not mean more power. you have to jet it correctly for what mods you have and where you live.

Lean is mean.....A slightly richer A/F ratio will make the engine run a lil cooler. If you have to be one or the other.....definately be on the rich side. :o

[GPracer2500]

I've never bought anything from MotorcycleCarbs.com (http://www.motorcyclecarbs.com/index.cfm) , so I can't comment about their service or anything. But they do list an outstanding selection of jets--even hard to find leak and air jets and those pesky, easy to loose fuel screw o-rings.