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· Registered
110 Posts
Discussion Starter · #1 · (Edited)
I will try and start this. This might be common knowledge for some so sorry. I am gonna keep adding to this as I find info and I will credit where I find it at the bottom.

stock valve lash =.004
Stock jetting = 122 main , 120 main (high altitude), 38 pilot, stock needle position - 3rd groove
Wheel offsets - front = 4/144 rear =4/110
Stock gearing = 13 / 38
stock spark plug # - DR8ES-L

stock carb 32mm keihin with accelerator pump.

Ignition: CD with electronic advance
(300ex CDI will not work on 250x)

Ground Clearance : 4.6 in. (stock)

Will 400ex a-arms work?
yes, you will need a-arms, tie rods, and 400ex length shocks (16.25), and a shock relocater bracket, 400ex spindles are not necessary but are an improvement with this set-up,and yes stock brake lines will stretch far enough.

will a 400ex steering stem work?
yes, stops on bottom need cut off because there 180* off, and the little washer about 3/4 will need removed, it is roughly 1'' longer

will a 400ex carb work?
yes, i recommend it for engines that have at least the basic mods, such as pipe. filter, etc.. stock boots will stretch, all you need to do is re jet, and i recommend a 42 pilot jet

Hardweld rockers are only necessary for a hard weld cam -
EX. web cams. billet cams such as hot cams do not require hard weld rockers, they will actually cause damage to your cam

What is max. compression piston on 93 octane. - 11:1
any thing over is pushing and detonation could result.

engine idle speed = 1,400 +/- 100 rpm
stock pilot screw setting = 2 1/4 out from closed

engine compression with stock piston - 171 - 200 PSI

engine oil capacity -
oil change only - 1.6 quarts
oil and filter change - 1.7 quarts
totally engine disassembly - 2.11 quarts

*if you run a oil cooler about 2 quarts even on basic oil and filter change*

Front: Independent double-wishbone with dual hydraulic shocks, 5-position spring-preload adjust-ability; 7.1 in. travel
Rear: Swingarm with single shock, 5-position spring-preload adjust-ability; 7.9 in. travel

Fuel Capacity- 2.2 gallons, with a .5-gallon reserve

chain free play - 1 3/4 in. at most

quad clicks when start button is engaged -
its can usually be narrowed down to 2 things, assuming your battery has a proper charge, and it putting out correct voltage at (100% it should be reading about 13 volts)
now, its either your solenoid, or contact brushes in your starter

Common Rear end Swaps:
A 01 raptor rear shock will work but they are famous for blowing bladders on the 300ex. newer raptor shocks can be made to work. but because these shocks have a piggyback reservoir the left tube that goes to the airbox will need to be cut out and the hole in the airbox will need to be sealed up.

a 450R swingarm will also work, how ever this set-up requires tabs to be welded or bolted to the frame to accept the linkage. You WILL have to use a 250R rear shock, linkage is up to you, the 250r or the 450r linkage will work, carrier and axle, and rear brake line will also be needed. the swingarm is around 3 inches longer
the 350x rear end will also work
same as 250r
more info will be added by me constantly,, don't be shy feel free to add anything you think would be useful

alot of times it is your carb vent tube. the one that hangs down behind the motor. the problem is this tube gets submerged, you can either trim the tube shorter, or put a T splitter on it and add a different length hose. other possibilities are an exposed wire.

Thanks MUDD99

· Premium Member
23,587 Posts
4/144 and 4/110 is the bolt patterns for the wheels, not the offsets. I don't know what the offsets are though.

· Premium Member
18,211 Posts
I'm sure it's whatever stock rims are? lol

Bore = 74mm
Stroke = 65.5mm
Displacement = 282cc
Carb type = piston valve

· Registered
511 Posts
Suspension parts do NOT have to be from the same year as the suspension geometry has changed very little from start to now on Honda Sport atv's. Suspensions from any other Honda sport atv's are a great big upgrade. Pro-Fab atv used to make a 380 BB kit for the 300(I think they went out of business, I can't find them now) That produced crazy HP. The problem was the tranny wouldn't stand it. I pulled the output shaft out of the back of the cases on a couple of trannies before I gave up.

· Registered
9 Posts
I have a 93 300ex that runs but every once in a while I'm riding it would lose power or act like it ran out of gas, so I was wondering if I need a good carb clean or a new carb? So if y'all can reply that would be great thank you!
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