i have been riding for about a year but don't know much about atv engines. so i have a few questions.

what does it mean when you talk about port work?

i saw someone talking about a 300 main jet, what is a common size jet?

when someone says they have a certain size piston, (ex. 84) is that in mm?

what is good engine size for a beginner looking to move up (right now I have a 300ex but it is a little tame for me)?

 

also what does it mean when somebody talks about thier engine being "bored .80 over"?

 

ummm lets see, you could look into a 400ex...

if i were you i'd check out a Z400, especially if u like to ride trails, the 400ex and the Z400 both top out around 70

and idk u could think about a scrambler like i have, 500 4 stroke auto w/4 wheel drive, personally i think the scrambler is the ultimate trail quad and she'll do around 65...

 

Every engine has ports for fuel intake and exhaust gases to escape. There is power to be gained by changing the size and even polishing those ports.

Jet size will vary by the carb and/or jet manufacturer. There is no 'common' size...however many bikes use something between a 140 and 175.

Yes, cylinder bore and stroke are in mm when talking about motorcycles. If someone says there cylinder is bored .040" over, that number is in inches, and refers to the cylinder being enlarged by that much and a larger piston is used.

If your 300EX is to tame for you, time to step up to a 450 or open class sport quad.

 

not sure about your other questions.. i know the bigger the number the more power........
i think it is mm or millameters.. i think port work is reffering to boring out the cylinder or making it bigger to accomidate a larger piston thus causing more displacement.. i think when they are reffering to being bored .80 over is that much bored over stock.... (i think)

I think i'm correct.... someone let me know if i'm wrong....



i would go with a bigger one (450 if hondas are your bike) if you have been riding the 300 for a while....

i upgraded to a raptor 660 after 8 months riding my wifes blaster.. and i'm glad i stared small to gain experiance..

 

lol u guys jumped right into the 450's!

uk that is considerabley alot more power then a 300ex....i mean he'd get used to it but if i were him i'd go for a Z or a KFX 400...anything else bigger then u'd want a raptor or pred...

just my opinion tho

 

He has a year of experience and the 300 is to slow. 4 or 5 years ago a 400 would have been the best choice. Now there are others.

 

yeah you have a good point

i guess it wont be long an the 450's will be a standerd sport quad too

 

Im also a NOOB, but I think I can answer some of your questions.

Every engine has what are called ports. These are the holes that the air/fule mixture and exhaust mixture flow through. Makin power in an engine is all about making it "breath better. Port work refers to either polishing or porting(making them bigger), or doing both to the intake and exhaust ports in an engine. This is usually done to improve top end power, or the power output at the upper end of the rpm rang.

piston size or bore size is in mm in atv an motorcycle engines and inches on car engines. On automotive engines when someone says they bored their engine "30 over" that means that the cylinder bore was increased .030 inches over stock to accomodate a larger piston. This would take a chevy 350 and turn it into a 355. Increasing bore size is another way to increse power, by allowing more fuel and air to enter the cumbustion chamber.

jets are in the carb which regulate fuel flow into the engine. The larger the jet size the more fuel the engine will recieve. it is hard to give a common jet size because there are so many different quads and carb setups. When doing upgrades such as exhaust and air box mods it is common to upgrade to larger jets, because you are allowing the engine to breath easier, which causes the engine to need more fuel to accomodate for the extra air that the engine is recieving.