Piston question

[hondaracing0144]

hey im thinking about buying the Wiseco Piston Kit .040 (75 mm) for a 001honda 300ex and i was wondering how much horsepower it would give me and one more thing what does adjusting the values do. cause everyone is adjusting and i was wondering what it helped or what it does.

first, if that piston is oversized it will not fit in your stock cylinder. so look on motosport.com and get a standard bore that is high compression. and adjusting the valves is only needed if they are out of adjustment, this is usually only needed on the 400/450 race bikes that are put to the test all the time. so i dont think you will have to worry about it for a 300.

[hondaracing0144]

o ok what would be the best bore cause my friend got his blaster bored to a 250 i think

[400exrider707]

Originally posted by 450r_mayhem
first, if that piston is oversized it will not fit in your stock cylinder. so look on motosport.com and get a standard bore that is high compression. and adjusting the valves is only needed if they are out of adjustment, this is usually only needed on the 400/450 race bikes that are put to the test all the time. so i dont think you will have to worry about it for a 300.

That couldn't be any farther from the truth. The 300ex uses a tappet style valve, and they go out of adjustment more often than the 450 with a shim and bucket style.

Valves use a clearance so once the motor warms up, the parts expand, and the gap closes, bringing it closer to touching. It's tough to explain if you dont know what a valve is or does. I suggest doing some research on www.howstuffworks.com or something similar.

As far as your bore, I would tear it down first, see how your stock cylinder looks. If its scored badly, then over bore. Otherwise I would just do a hone, and get a higher compression piston. Higher compression will yield far more power than a simple bore. I suggest a high compression piston and a mild cam for a great yield in power. What other mods do you have? When's the last time the motor was torn apart (if ever)? I would do some research or buy a manual and adjust the valves before anything. If they're out of adjustment you are already down on power, and risk damaging parts. It's a very easy job on the 300EX. Get the manual and do some reading...

that is why I said I think. my friend has had his 300ex for over 4 years now and has not needed any adjustments so i was just going by what i have seen. sorry to mislead you.

[hondaracing0144]

hey how much will the bore and the mild cam cost all together? And how is the lite piston differnt from the standard

[Slick Willys]

Hey man, like said in an earlier post, check out the bore. If its not scratched up at all at least measure it out and make sure that it isnt egg shaped or anything. Typically if there is a ridge on the top of the bore then it will need boreing. At a bare minimum hone the cylinder if your gonna get a new piston, otherwise the rings will not be able to seat. If it needs bored out only go the minimum amount needed, it goes in .020 incriments on a 300. going straight to a .080 over piston wouldnt give you enough more HP to notice rather than a .020. High compression is the way to go if your loking for more HP. Wiseco makes good pistons that I think go up to 12.5-1. If your gonna put a cam in it there are many differant options just do the reserch offered by the cam company and get the one that fits your riding conditions. Cams start around 100. Dont know about around you but I charge 35 for cylinder boring here in central michigan, probably ranges from state to state. Pistons start around 100 depends where you get it. You will need the piston before you can get the bore done. The machinist will need when boring the cylinder.

[wilkin250r]

Originally posted by hondaracing0144
hey im thinking about buying the Wiseco Piston Kit .040 (75 mm) for a 001honda 300ex and i was wondering how much horsepower it would give me and one more thing what does adjusting the values do. cause everyone is adjusting and i was wondering what it helped or what it does.


I've been around quads for quite a few years. What I say may sound a little insulting, but I don't mean it to be. Honestly, I'm just trying to help you.

You are a LONG ways away from any modifications. You have a lot of learning to do. You need to learn about compression ratios and how they improve power, you need to learn about high-octane fuels and when they are necessary or when they are useless, you need to learn about camshafts, jetting, valves, jetting, air filters, jetting, big-bore motors, jetting (and did I mention jetting?).

And you need to know all this stuff BEFORE you start buying parts and kits, so you know exactly what you need to buy, and what you can expect it to do.

Either you know it yourself, so you can do it yourself, or you pay somebody ELSE that already has that knowledge. And trust me, the second option is expensive ($60 per hour minimum for a shop to do all this work for you).


We're all willing to help you, but one step at a time. You've got some research to do.

[Slick Willys]

well said!!

[hondaracing0144]

thanks for the imformation but i wont going to buy it today or anything maybe later on dd i got a women that does all my work for me that unlocked my rearend and put new exerything back there for $300