A 1986 250R has been secured by of all people my Father, the original Darth Vader of 2-stroke racing, but his knowledge was with fully stoked go-carts and we're looking for the basics just in case modifications are in the future for us (he, he). It's bone stock so please pass along the add-on's, replacements or mods. that will help in the tweaking. I saved a valuable thread I've been referencing for my 300EX that basically went down the line with mods. to make in an order that made sense both financially and with respect to changes that were "radical". In other words the list told to add a pipe kit or make air filter and air box mods before it talked of swapping out a piston or cam. I know there's a lot of info out there on the 250R so now I just wanna tap into it. Any suggested sites to visit would also be appreciated.

Hillside Hawk

 

for engine mods check out this site

www.macdizzy.com

he has a kickin engine set up. am getting ready to send mine off to him.
do the usual first, fmf pipe, silencer, rad valve,K&N, re-jet carb, have done all that and my 86 kicks but now I want more HP
sorry I can't post a pic of my bike.
Oh ya if you still have the stock shocks on it before you get into the engine make sure you address this need, unless the engine needs it.

Later TheDoc250

 

These are the mods that need to be done to a stock 250r. The first thing is to put a pipe and exhaust on the quad. There are many good ones out their depending on what type riding you are going to do. 2nd go and get a good set of front shocks. Tires if you have not got them already. This is the first mods that should be made. Whit just those mods you can go racing and have some fun. Later you can get the engine worked on, axle, air filter, A-arms, swing arm, etc. Be carefull on what you get. Some of the mods that the mags do don't help the quad go any faster. I have built some top pro quads with only changing the shocks,pipe,and jetting. We finished in the top 5 at the end of the year with just those mods.

many 250r's
250x
400ex

 

Don't forget the cheapest mod: a CR250 head gasket to up the compression a bit and run Premium/Super gas

 

I got a cheaper mod, take off the airbox lid and throw it in the trash. Now cover up the air intake opening on the front of the airbox. Another cheap mod is a K&N filter, and if you are going to run without an airbox lid, I recommend an Outerwear for it.
If you like the thumbthrottle, but want something better, go to www.yakkeyracing.com and look for the silver BATT. It bolts on to your existing thumb throttle, and makes it much easier to use.

 

Thanks for the tip on the macdizzy.com website. It's loaded with plenty of 2-stroke information.

I got the suggestion of the CR250 gasket, will upping the compression by doing this require re-jetting?

You say just throw away the airbox lid? Can't I effectively modify the lid with screened holes like I did on my 300EX? That way I can avoid the need for an Outerwear. Why do you suggest covering up the front air intake opening?

Thanks for the replies, keep 'em coming!
Hillside Hawk

 

Just to chime in with my 2 cents, I'd recommend against using the CR250 head gasket for a bump in compression. The CR gasket is paper thin and very prone to blowing out. The ATC 250R head gasket is a bit thinner than the TRX gasket and will give a slight bump in compression. The other way to get a little compression increase is to have a shop mill .020" off the head and use the stock TRX gasket. As far as other mods go to give you a good low-mid boost, I'd say a set of Boyesen dual stage reeds for the stock reed cage and a Paul Turner midrange pipe. The reeds are relatively inexpensive and are far superior to stock and the PT mid pipe has strong low and midrange pull, but flattens out on top. An LRD pipe would also be a good choice. Unless you plan to ride in completely dry conditions, don't get rid of the airbox lid. Good luck.

 

the stock ram air intake thing is a waste of weight on a 250R, and it gets in the way of taking the head off while the motor is still in the quad...I'd yank it off and get a cover for the hole in the front of the airbox, I made one out of a lid from a spray paint can

 

As far as motor mods, I am running with the CR250 head gasket, and I have no problems with it. My motor has been ported and modified to take a YZ 250 piston, and I have it paired to a Bills pipe. I am also running a Boyesen Rad Valve. This combination was fairly inexpensive for the amount of bottom end power it produces. I race with people who are running CT cylinders, and Cool Heads, and all kinds of other super expensive aftermarket parts. My bike is easily as fast, and if not faster than all of them. Most of them have given up on these high cost setups and are working on going to what I have.

 

I am running a Bill's pipe, FMF silencer, stock carb, K&N filter(no airbox lid), FMF reeds and a CR250 head gasket on my Dad's 86. This thing hauls!! We are running the stock 13/39 gearing with 18 Turf Tamers in back. I was running this exact setup last year and I could pull a holeshot on anyone at the track!

As far as a sequential list of mods, here is a pretty good order:
Pipe/Silencer
Air Filter
RAM or RAD Valve
Tires
Front shocks, and stock rear revalve
Port/head work and a bigger carb
Bearing carrier
Wider a-arms
Swingarm(88 length)
Wider axle
Chassis, if you feel up to spending that much.
Although it is better to buy this stuff a little at a time, simply for reasons of price; I went ahead and bought everything at once. This winter I basically built an R from scratch including the motor! It was very expensive, but I think it is well worth it! Good Luck!!