300EX build questions

[ish416]

I have a 98 300EX that I am planning on sinking some money into. It is a bit tired and many things will need to be replaced.

This will not be my primary quad but basically the backup-backup quad. As I have a KFX450 and a 416ex.

I have many components from a 250r, 400ex and Honda 450r that I plan on putting on this quad.

As for the chassis, I was thinking of going with stock 250R a-arms, 450r front shocks and a 450r or 250r swingarm and shock, 250r or 450r axle.

Engine:
I was also thinking about going with a 330 kit to get me moving around. I am 6'3 and 220lbs. I am not expecting arm ripping power but would like something with a little more snap than a piped and jetted 400ex. With the 330 kit running 11.5:1, 400ex carb, KN filter, full exhaust, good all-around cam, bigger valves and head word and maybe a cdi, what type of power should I be expecting?

I appreciate any help, thanks.

[smr]

looks like you are wanting to build something.

First off, It's a huge pain in the but to put 250r a-arms on the 300ex. It will require modifying the a-arms or the frame. Now the 400ex a-arms will bolt right up but the 250r a-arms will not.

I would also recomend a uni over the K&N. K&N is fine for just MX or dune riding but for the fine dust you will incounter in Indiana I would sugest a Uni if you want to keep your motor running.

[IRISH-RACER-14]

Originally posted by smr
looks like you are wanting to build something.

First off, It's a huge pain in the but to put 250r a-arms on the 300ex. It will require modifying the a-arms or the frame. Now the 400ex a-arms will bolt right up but the 250r a-arms will not.

I would also recomend a uni over the K&N. K&N is fine for just MX or dune riding but for the fine dust you will incounter in Indiana I would sugest a Uni if you want to keep your motor running.


i had no problems putting 250r arms on my 300ex

[smr]

you probabley had 400ex ar-arms with spacers. The mounts on the 250r are much wider than the 300ex or 400ex.

[IRISH-RACER-14]

no the were 250r aftermarkets

[smr]

OK..my bad...:rolleyes:

[TRXRacer1]

Originally posted by smr
OK..my bad...:rolleyes: You can roll your eyes but he's right. The 250r arms fit perfectly fine.

[IRISH-RACER-14]

Originally posted by TRXRacer1
You can roll your eyes but he's right. The 250r arms fit perfectly fine.

thank you sir:D

[smr]

Originally posted by TRXRacer1
You can roll your eyes but he's right. The 250r arms fit perfectly fine.

looks like both of yall know more than me. Please is there any more info you can give me?

Stock 250r a-arms have a wider mount. Yall are using after market with the spacers removed.

not gonna argue with you about this...I am just trying to give the man good information.

[ish416]

The 250r A-arms look like they should bolt up without any issues. If there are any then I will either widen my 400ex a bit and use the stockers on this or purchase stock 400ex A-arms.

My main concern is the with engine as, I would like to get this build right the first time and not have to screw with it later.

I have read and heard about the 330 kitted 300ex's running down stock 400ex's. Is this true? What is the most popular setup to go with?

As far as the KN Vs Uni air filter, I am not a big fan of the foam filters as they seem to fall apart fairly quickly. I have ran a few Uni filters on my 400 and was happy at first, then a few months later had noticed that it was basically falling apart. I have never had any issues with KN filters on my cars, trucks or quads after years of abuse.

[TRXRacer1]

Originally posted by smr
looks like both of yall know more than me. Please is there any more info you can give me?

Stock 250r a-arms have a wider mount. Yall are using after market with the spacers removed.

not gonna argue with you about this...I am just trying to give the man good information. I had OEM 86 arms on my 250x with zero mods. Don't know what to tell ya man.

[smr]

Originally posted by ish416
The 250r A-arms look like they should bolt up without any issues. If there are any then I will either widen my 400ex a bit and use the stockers on this or purchase stock 400ex A-arms.

My main concern is the with engine as, I would like to get this build right the first time and not have to screw with it later.

I have read and heard about the 330 kitted 300ex's running down stock 400ex's. Is this true? What is the most popular setup to go with?

As far as the KN Vs Uni air filter, I am not a big fan of the foam filters as they seem to fall apart fairly quickly. I have ran a few Uni filters on my 400 and was happy at first, then a few months later had noticed that it was basically falling apart. I have never had any issues with KN filters on my cars, trucks or quads after years of abuse.

You better believe that 330 kit done right will run down a stock 400ex. When we raced OMA they didn't run the schoolboy class so holden had to race against 450's. IF the start was short he could get the holeshot. He couldn't run with them after about 40 yards but the short shot that 300ex would pull. (btw, it was bored .080 over so it wasn't a 330.) I built a 330 for a guy and it would move.

330 kit with a 400ex carb will do wonders.

As far as the K&N and Uni....each his own. I like K&N on my trucks but I noticed dust in the intake when I ran them on my quads.

Like I said on the a-arms..the 400ex stock ones are awesome. You will just need to build a shock relocater. You can make any year 250r work but the 86's. The 86's actaully have a much bigger round pivet point that want fit into the slot. The 87+ you will have to do a little grinding to make them fit. Your's are aftermarket so you may be able to remove the shims.

good luck and PM me if you need any help.....I've built several of these and know a few more tricks.

[IRISH-RACER-14]

Originally posted by smr
.....I've built several of these and know a few more tricks.

carry on?:D

[smr]

what will you be using the quad for?

That can make a big difference.

for instance...if you mainly gonna use it for trail riding then I would not recomend the 330 kit....nothing wrong with it but you can get almost as much power cheaper. (Notice I said almost as much)

The bigy is how much youwant to spend.

For a buget I would recomend boring it .080 over and using the 400ex carb with a good pipe. You do all this for under $600 if you do the labor yourself.

Suspension, we have talked enough about a-arms that you most likely know what you want. Use the 400ex tie rods and that will make up the difference in lenth. DO NOT use the 400ex spindles....there is no advantage and it throws the angle off. I was never able to get the push out of holden's front end with the 400ex spindles. I say again...stay away from the 400ex spindles.

I also like to grind the stearing shaft to get a little tighter turning radias.

Rear end....I have seen so many different setups here it aint funny. Again if your on a budget I would recomend keeping your rear swingarm and buy a 2001 raptor rear shock. It will bolt right up. (it must be the rear shock with the remote not the piggy back...piggyback will work but you must modify the frame)

Some people beaf up the clutch but in three years of hard racing we never replaced a clutch in any of our 300ex's.

let me know what you are gonna be using it for and I'll make some more sugestions.

[IRISH-RACER-14]

Originally posted by smr
what will you be using the quad for?

That can make a big difference.

for instance...if you mainly gonna use it for trail riding then I would not recomend the 330 kit....nothing wrong with it but you can get almost as much power cheaper. (Notice I said almost as much)

The bigy is how much youwant to spend.

For a buget I would recomend boring it .080 over and using the 400ex carb with a good pipe. You do all this for under $600 if you do the labor yourself.

Suspension, we have talked enough about a-arms that you most likely know what you want. Use the 400ex tie rods and that will make up the difference in lenth. DO NOT use the 400ex spindles....there is no advantage and it throws the angle off. I was never able to get the push out of holden's front end with the 400ex spindles. I say again...stay away from the 400ex spindles.

I also like to grind the stearing shaft to get a little tighter turning radias.

Rear end....I have seen so many different setups here it aint funny. Again if your on a budget I would recomend keeping your rear swingarm and buy a 2001 raptor rear shock. It will bolt right up. (it must be the rear shock with the remote not the piggy back...piggyback will work but you must modify the frame)

Some people beaf up the clutch but in three years of hard racing we never replaced a clutch in any of our 300ex's.

let me know what you are gonna be using it for and I'll make some more sugestions.




400ex steering stem for a longer stem? is that right?

[smr]

We ran 250r bend renthals....These are a little taller so we never had a need for a longer steering shaft. I really don't even know if it will work.

[TRXRacer1]

Originally posted by smr
You can make any year 250r work but the 86's. The 86's actaully have a much bigger round pivet point that want fit into the slot. LOL, dude you're funny.

[ish416]

The main reason for wanting to build up the engine is because I would like to be able to hop on it and rip around the trails/yard/track and be satisfied with the power. I am looking for something around the 30hp range that is easy to ride. This does not have to be a full race engine as I have a built 416ex and fully built 450r to race on.

This is more of a nostalgia build as this was my first quad and I now have the finances to do whatever I want to it. I just think it would be funny to be able to line up against 400s and some people on 450s and run side by side down a drag strip or have them trying to chase me down through the woods and never be able to do so.

Also, as I have mentioned, I am big guy, at 6'3 and 220lbs. I have ridden a few piped and jetted 300ex's and all I can say is they are weak. They seemed a bit more impressive about 8 years ago when I was a bit smaller.

Since I already own this quad and have many spare parts from my 400, 450 and old 250r, I would like to just modify it and keep it.

I am just looking for suggestions as to what type of engine setup seems popular for all conditions.

[smr]

sounds good man. Like I said, I was able to get ours to run with the big bikes for the first 40 yards but after that it was over.

Now as far as woods racing goes, Holden won a couple OMA's and a midsouth on his 300ex racing against 450's. (he was about 5.5 and 150 lbs)

Since money is now problem then I would defanetly start with the 330 kit. You could also have the head ported, install bigger valves and a cam.

Like I said earlier, you will get the biggest gain from the 400ex carb and the header....(get a good header)

[honda250xrider]

Just doing the 330 kit will yield little without going inside the head.

The ports are already small for the displacement. Going with a 330 kit would also be wise to install larger valves. I would say +1 or 1.5 intake.

I would recommend as stated earlier and in this order:
carb
pipe
head work
cam
big bore

I feel your biggest gains will be from the cam and port work. After that you will then see a substantial increase of power with the bb.

[ish416]

Thanks for the info fellas. Just have a few more questions.

So, what kind of power would the following put down, and how smooth should the power curve be?

330 kit running 11.5:1, 400ex carb, KN filter, full exhaust, good all-around cam, bigger valves and head work and maybe a cdi.

Any suggestions as to what full exhaust system to run? I need something that is spark arrested and under 99db. Also, suggestions for a good all around cam.
One more thing, do the cdi boxes actually do anything or are they as useless as they are on 400ex?

[sameltoe]

Originally posted by IRISH-RACER-14
no the were 250r aftermarkets Thanks for letting me waste my money on aftermarket PRP brand a-arms, I read this article and figured if 2 people say they will work, then maybe they will?! Well i'm here to tell you they WILL NOT work with-out modification! If you want pics i will be glad to post that the 250r arms have a wider mounting point....

[TRXRacer1]

Originally posted by sameltoe
Thanks for letting me waste my money on aftermarket PRP brand a-arms, I read this article and figured if 2 people say they will work, then maybe they will?! Well i'm here to tell you they WILL NOT work with-out modification! If you want pics i will be glad to post that the 250r arms have a wider mounting point.... I did OEM, couldn't tell you about aftermarket. This was back in like '98. I just bought some LSR +2's and works for my 86R. I put the stock R arms on my 250x. Made shock relocation bracket and installed the shocks too. Worked great. It was 12 yrs ago so maybe I had to mod a spacer or something but there was no frame work that I know for sure.

[honda250xrider]

The engine setup sounds good.

I have used web cam's with good success, along with fst cam's.

Remember most cam's require you to harden your rocker arms along with a spring kit.

I wish i could recommend a pipe, but I never had to worry about db or a spark arrester.

Your setup sounds good and you will gain power throughout the entire rpm range, it should be able to pull a 400ex.

I have used tc racing cdi boxes, along with sparks cdi boxes. I do not know if they even gain any hp. I used them for the fact I was making power past the stock rev limiter.

[smr]

Originally posted by sameltoe
Thanks for letting me waste my money on aftermarket PRP brand a-arms, I read this article and figured if 2 people say they will work, then maybe they will?! Well i'm here to tell you they WILL NOT work with-out modification! If you want pics i will be glad to post that the 250r arms have a wider mounting point....

if you didn't spend a lot of money you can make them work by grinding them down. But that is only a part of the problem. Getting the shock angle correct is another issue. The 400ex and the 250r has a different shock angle. It can be done but it is a lot of trouble. I did it with a set of OEM 87's and it was a lot of work.

I don't think anyone led you wrong on purpose...you would be surprised at how many people think they are the same as 400ex a-arms. That's why I said I wasn't gonna argue the point any more.

[IRISH-RACER-14]

what cam would be best? theirs ones on ebay called hotcams or something. they use stock rocker arms and valves and springs?

[smr]

Originally posted by IRISH-RACER-14
what cam would be best? theirs ones on ebay called hotcams or something. they use stock rocker arms and valves and springs?

are you gonna port the head and install bigger valves?

[QuadCobbler]

If ru looking to get 30hp out of a 300ex motor (stock is 17hp) ur gonna need to do alot more work than a 330 kit a good port job, and so on. I would reserch more on the threds that have already been posted. Fully built TC race motors are puting out around 30hp and you can bet they have more than $600 in them. If you wanted to sink a bunch of money into it you would be further off getting a crf or yzf 250 motor, or better yet buy the hole bike use all the engine componets and part the rest out. you'd get 30hp out of a stock motor. IMO. Like I said reserch the previously posted threds. And just to add to ur a-arms debate. 450r uper arms will fit but the lowers will not the frame mounts on the 450r are wider.