True 300 (.080 over) questions

[hondardr4life]

Ok, so my buddy blew up his motor in his 94 300ex. So he wants to do an .080 over bore with a wiseco 11.1 piston, to make it a true 300, have me do a port and polish, and put in a stage 1 cam. How much power gains do you think he will get from this? Also, what kind of jetting (stock kehin sizes) do you think he should run? Last, do you think it will keep up with 400ex's? He has 22 inch tires, ehs racing airbox lid, and a yoshi full system. Right now he is very close to my quad in top end because of his 22 inch tires. But it doesn't have that much torque, so do you think it will be much more torquey if we leave the gearing on it the same 13/38?

[roostin_dale]

he will need a rev box too..and you might want a little more compression than 11:1..and possibly a 14 tooth front sprocket...and yes, it will keep up with a stock 400 if he can ride.

BUt with the bigger bore and this motor work your gunna need some air, you need some bigger intake valves too, and an air filter if he doesnt have one...on the Jets i cant help you, i dont even remember what i ran on my 300...

[44oEX]

it won't be a true 300....it's close but it's only 297cc

[honda250xrider]

I don't think the bigger valves will not be nessecary, You should worry more about the port work before you move onto the valves, the ports could use some freshing up and that would be a good start to increase the power, for ridingablity and trail riding i would go with a 11:1 compression. Try to get a somewhat aggresive cam in there to see some nice low end power gains. combined with the bore, porting work, high compression piston, this should be a pretty good setup.

[xx3003xrdrxx]

what do you guys think the top speed on that thing will be ? do you think hed be better running 20' tires and a 14 tooth front sprocket , or 22' in tires ? which would give you an even balance of tourque and top end ?

[44oEX]

unless you ride alot of mud go with 20's it will handle alot better then 22's. for the gearing with 20's and a bored motor you can run 14/36, with no problem, it will be a nice balance between pwer and speed, if you gear to low you will just cutout in 5 th.
as for speed, around 60-62

[hondardr4life]

Yea, that's his 300 were working on. It blew up because he did not know that it already had a .040 iver wiseco 11.1 piston in it, and he was running 87 octane, not 93 like 11.1 requires.

440ex- as for the whole gearing issue, do you think 14/34 would be a good power/speed balance on my 330??? It cuts out like crazy in 5th gear right now and 1st gear revs out so fast I never even use it, I just start in 2nd. And how much top speed would I gain by going down 4 teeht on the rear?? I will run dead even with a stock 400ex right now, but I have heard if you gear 330's right they will outrun a piped 400ex.

[44oEX]

yeah if it cut out in 5th right know you might as well go to a 34, thats what I have on the back of my 500ex and it works great, plus I love the look of the super small sprocket lol. you will lose a little power but if your gears a to short as is, you might actualy be able to take off faster ( more bottom end ) with higher gearing cause you won't have to shift as fast. I say go for it.

oh and you could also put a 15 in the front if the 34 is not enough
as for top speed if you can push your gearing, witch you should be able to do no problem, you should gane maybe 2-5mph

[xx3003xrdrxx]

so should i go ahead and put the 20' rears on and the 14 tooth front sprocket ? will this be better than running stock gearing with 22 inch tires ? i want an even balance of tourque and top speed , and witch will be more fun to drive in your oppinion .


thanks so much for hellping

[44oEX]

yeah def go with 20 it will ride alot better, and if you do then a 14 is a must, you might need a 36 tho I don't know if just a 14 will be enought to match for the diff in tire size

[xx3003xrdrxx]

ok good ! i have a wb stage 2 cam , harden rockers, hd valve sprrings , and a weisco .80 over piston , and a ehs airbox lid, uni filter , and a yoshi full system . and im planning on putting 20 rear tire on and a 14 tooth front , do you think ill be running with the 400ex ? stock ? and able to beat them maybe ? what if i got a carb would that make it run better ?

[44oEX]

well with the .080 over I would go with a 14/36 combo with 20.
with that you should be pretty close to a stock 400, if you want more power go with a 400ex carb on your 300ex, it will help alot.

[Trevor]

I'm running 13/36 gearing on my 300ex with just pipe,jet and filter works good

[44oEX]

what size tires you run?....22's...it won't work good with 20's

[xx3003xrdrxx]

so if i add a 14 tooth front sprocket will i still have tourque

[hondardr4life]

440, could you give me a link to where you got your 34 tooth sprocket from?? Because I can't find one anywhere, an dI think a 300 and a 400 can use the same rear sprocket.

[44oEX]

Originally posted by xx3003xrdrxx
so if i add a 14 tooth front sprocket will i still have tourque

yeah you will, you will lose a little but not much, you will have more speed tho


Originally posted by hondardr4life
440, could you give me a link to where you got your 34 tooth sprocket from?? Because I can't find one anywhere, an dI think a 300 and a 400 can use the same rear sprocket.

it's not that easy, the 34 is from a ATC 250R (honda), it's the same bolt patern as the 300 and 400. BUT you have to counter sink the holes for the tappered bolts, it's real easy.