I have recently boght an '89 250r that has extensive mods done to it. From what i can tell just from looking it has... leagers +2 +1 A-arms...Durablue X-33...FMF fatty gold w/DG silencer...full belly skids...works trips w/ res on front...tcs on rear....maybe ext swingarm???...reed spacers or ram valve (not sure which)..keihin carb...now here are the quesions..#1 is there anyway to tell the bore w/out taking off the cylinder? #2 what are the stock dimensions for an '89 250r? also an '87 250r?(length, width, height)...I am asking about all of this b/c as most 250r's are it was handed down from MX racer to MX racer and the guy i bought it from had no idea what has been done to it. Also this thing is SCARY fast! Since I have had it i have raced(100-200ft drags) banshees, 400ex's, lt250's, ds650's, raptor's, 250r's, 310r's,330r's, and even a couple of 125/250 dirt bikes...i have beaten all except the 250 dirt bikes..they kill me on top end. This thing rides almost like a banshee, meaning it will spin tires before t will pop the front end up. If this gives yall an idea ..it will leave 2 black marks on the pavement all the way to 5th gear. OK help me out with all the info you all can...i am gonna hate to have to open up the cylinder and tear the whole thing down just to see what i have.

 

You can tell what the bore is by just taking off the head and "mic"ing it. Taking off the head is simple. You can also measure the stroke with just the head off. As far as what porting has been done, unless the guy who had it done will tell you or there are some markings somewhere, or when you bought it there may be a shop receipt somewhere, you won't know.
If it was ridden in MX I doubt the swingarm was extended; if changed at all it was probably shortened. A stock swingarm for an 89 is aluminum and has 4 Allen bolts on the very back of the axle housing (this is for chain adjustment).
But, it sounds like you got a killer machine!

 

Yea i believe the guy i bought it from said it was ported and polished. The swingarm is stock then b/c it is just like you said....were all 250r swingarms the same? 4 allen bolts for adjustment and aluminum?

 

No, the swingarms changed in 88. The 86-87 was 1" longer, made of steel, gold in color and had 2 Allen bolts on the back. It is much heavier than the 88-89 model.
Also, the 86-87 A-arms have camber adjustment, the 88-89 don't. The 88-89 were forward 1" from the 86-87.
Therefore, all <u>stock</u> 250Rs have the same wheelbase.
BTW, Keihn is the stock carb for an R. You may have an aftermarket model, like an AirStriker. The model number is on the float body on the left side. Stockers are &quot;PJ&quot; model; 1987 is a PJ05A, etc.
As far as the porting goes, it can be ported for top-end, mid-range, bottom-end. With the porting goes a pipe for the proper application. Find out what kind of pipe it is and it will give you and idea as to how it was ported. Is it a FMF Fatty &quot;Gold Series&quot; or an STS? STS is the high-rev pipe, Fatty is the mid-range.

 

I guess it has a stock carb b/c it is the PJ model. As for the pipe it is a fatty Gold series. I would say it has been ported for midrange b/c it will almost ****** your arms off in 3rd and 4th gear. The A-arms have the camber adj. but that is from them being the leagers. I am going to add a cool head to it next week so i guess i will measure the bore then. by te way what are the best advantages to the cool heads? I have heard mixed comments on them.

 

The two biggest advantages to a cool head are 1. more cooling capacity, and 2. changable domes inside the head to adjust your compression. If you install one, do a compression test. If your compression is above 200 you will probably need to run race gas or a race gas/pump gas mix as 91 octance won't cut it anymore. If you have the money, definitely get one. Your next problem will be whether to get one that uses a gasket or one that uses an O ring. I, personally, would go for the O ring. Next, head stay or no head stay (that's where it's bolted to the frame on top). Hmmmmmm, lots of opinions on that one. I use a head stay bolt, but it's not a tight fit; I let the engine rock a little. If you can't line up the head stay hole with the frame hole, I guess you won't be using a head stay, but be sure to leave the frame piece in. Some people have taken them out which you really shouldn't do.
It does sound as if you are setup for midrange. It probably feels strong in 3-4th gears as you are probably just then getting decent traction!! How well will it pull 5 and 6? That's where you can really judge your power.
To further help you with your R, check out this site
http://pub20.ezboard.com/bhondatrx250r
More help and info than you will believe.

 

It pulls just as hard in 5t ad 6th as it does in 3-4. In 6th it wil keep on pulling until it sounds like it is gonna blow up...and then it still keeps pulling! Do they have rev limiters? i always just let off when i think i am getting too high up in revs. Thanks for the help and iwill check out that site