Xr250r

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May 3, 2001
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#1
what should be my next step, in getting my bike ready for my first hare scramble this fall, i have adjusted my shock and forks till i like it and removed the muffler baffle and airbox snoot. is there anything else i can do or should do? also how do you tell how loud a bike is? need to be under 100decibels is there a meter or some chart? thanks mike:confused:
 
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#2
The only maods I have done to mine you have already done except to add a set of bark-busters. If it is to be muddy out, I add additional coverage to the bars with a set of mud gards. I also try to spray the underside of everything with silicone spray to help the mud fall off. As far as noise goes, I am not sure how loud the stock 250 tip is with the baffle removed. i just know it is a lot quiter than what has been come on the new bikes except for KTM's.

I have had no troubles with the bike at all and has been 100% reliable. The bike has been used and abused and keeps on chugging.

Good luck
 
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#3
Bowhunter and Mgorman,

I'm curious what year XR250's you have and whether you needed to rejet after you removed the airbox snorkle and exhaust baffle?
I'm getting a CA 2002 model in a few weeks and want to do the same. According to the new issue of Dirt Bike magazine (they have a
shootout w. TTR250, DRZ250, XR250R, and YZ250F!) they said the XR was jetted perfectly with the snorkle and baffle removed.
Thanks. :)
 

nkd

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#4
need to rejet

Just took the baffle out of my 95 XR250 and
Baja Designs told me to rejet. I haven't done
it yet since I am in the middle of redoing the suspension,
rejetting and putting on DOT tires. Can't wait till
I get it on the road/trails again. Good Luck
Nancy
(AKA Harleygal);)
 
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#5
You would normally go up about two on your main and pilot jets after removing the snorkel and baffle.You may want to replace the airfilter with an aftermarket one ie...Twinair,Uni,or No Toil. The single biggest improvement you could do to the front forks would be to put on an Summers Racing Corp brace. The stock forks have way too much flex and the SRC brace really helps with roots,whoops and sand.The SRC cost $ 199 and is worth every penny ! Also if you have stock tires replace the front at least,the stocker washes out too easily. Dunlop 756's or Michlin S12 work nicely. I use a XR' Only pipe and I am satisfied. I would listen to a stock YZ 426 and as long as your bike is quieter than the yamaha(which are way too loud) it should pass for sound.:cool:
 
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Jonala

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#6
Bowhunter,

I have a 2001 XR250R.

dB levels are , Stock 82 @ idle, 92 @ 1/8 throttle
Small outlet pipe cutout, but with spark arrestor
92@ idle, 102 @ 1/8 throttle.

I would recommend, drilling 4, 1/4 holes around the small outlet pipe. It's cheap and allows the motor to breathe much better, while still being very quiet.

I have only changed the main jet = 140. The bike runs great!

You may want to look into a hot start kit. These little bikes can be a pain to restart when they are hot and you need to get going.:p
 
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#7
SB-RIDER

I HAVE AN 2001 AND LOVE IT. removed the air box snorkal did not notice much change other then noice. but after removing the baffle there was a large inprovement.


JONALA what small outlet pipe are you talking about ? befor or after the spark arrestor? and was that in lieu of removing the baffle if so then i'm too late.
 
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#8
Bowhunter,

I think I know what Jonala is refering to. Over in the Yahoo XR400 group, there was a guy named Gordon Banks who recommended a bunch of simple mods centered around drilling out some holes in the end of the exhaust baffle (the Honda fiches refer to this part as the "diffuser"). Everyone at Yahoo refers to these as "The Gordon Mods". I have included an excerpt from his original post below and it will give you a good indication of where and how to drill the holes. I like his idea of making the mods "tunable" by using set screws. The Honda fiches show the XR250 exhaust system to be very similar to the XR4. My riding buddy did these changes to his 01 XR4 and really likes it - even removed a flat spot in the throttle. My understanding is in the later model XR250/XR400's (98+?), the baffle is welded in so to remove it would require spot-welding a rod to it and banging on it. I'm going to do the drill mod myself. If this text is too long and doesn't post, let me know and I can e-mail the mods to you.

Lance

*** Gordon Bank's Post ***

3. Spark Arrestor (Muffler Insert or Baffle)
The Service Manual does not show or mention any differences
between the different years, but we know that the 96-97
models had a two-piece unit where the spark arrestor and the
end-cap were separate pieces. The 98-00 models have these two
pieces combined into one. To use an aftermarket insert, we
generally have to use the separate end-cap piece from a 96-97
model.

NOTE: After examining the stock muffler and spark arrestor,
and running some flow numbers for the different areas involved
with the numerous plates and baffles (both in the muffler and
in the baffle insert), I came to the conclusion that the
primary restriction to exhaust flow is the small final outlet,
which has an i.d. (inner diameter) of only 20mm. Without removing
the baffle insert from the muffler, examine the exhaust tip.
Notice the actual outlet, which measures 20mm i.d. (0.787").
Around this is a larger 'bright finish' ring which may be to help
prevent the rider from coming into contact with the actual outlet,
which probably runs hotter. Down in between the 20mm outlet and
the bright-finish outer ring, there is room to drill 1/4" holes
into the baffle to provide additional outlets, and thusly additional
exhaust flow area. Holes drilled in this area will be 'inside' the
spark arrestor screen, so the spark arrestor function is maintained.
On my spark arrestor, the area to be drilled is large enough to
accept a 1/4" bit (0.25"), but there's a benefit to using a #2 bit
(0.21") which I'll explain later.
Since the stock 20mm (0.787") outlet provides a flow area of only
0.4862 sq.in., and a 0.21" hole has a flow area of 0.0346 sq. in.,
each 0.21' hole adds 7.1% more flow area. Just three such holes will
increase the exhaust flow area by over 21%!
First I ran the engine with the undrilled baffle, to get a feel for
the stock sound level at idle, and while revving the engine. After
drilling one hole, I could barely hear any difference. After drilling
a second hole, I could hear the difference, but it was slight. The
third hole made a bigger difference, but still not objectionably loud.
The fourth hole took it over my limit, however, adding a definite bark
to the exhaust note. This, I decided, was a bit too loud, so I used a
1/4" (0.25") set-screw to plug the 4th hole. Had I drilled the hole
with a 1/4" drill but, I'd not have be able to plug it with a 1/4"
diameter set screw. This effectively reverted back to having just
three holes, and it also indicates that I can plug anyr or all of the
holes with 1/4" set screws to return to the stock sound level if
necessary. I guess you could say that this modification is "tunable"
by inserting or removing set-screws from numerous holes.

A brief test ride with stock jetting and the stock air box snorkel
in place showed that the added three holes made the bike run a bit
crisper, but it was also running too lean, which made the engine
overheat. This more-or-less proved that the added 21.3% flow area
was beneficial, and it had cost me nothing but a little time, and
it's totally reversible by plugging the holes with set-screws.

It is NOT necessary to remove the spark arrestor insert when
drilling the holes. The metal chips will fall either outside the
muffler, or into the screened area of the spark arrestor. Once you
have drilled the desired number of holes, you can then remove the
insert and shake out the tiny pieces if you so desire. If you don't,
they will eventually fly out the exhaust outlet anyway, since the
spark arrestor screen prevents them from falling down inside the
main muffler chamber.

Later, with the drilled spark arrestor in place, the air box snorkel
removed, and the header inlets ground out to 0.944" instead of the
0.75" left by the welding flash, I rejetted the carb, eventually
coming to the same setup recommmended by CYCLE NEWS, a 160 main jet
and a #60 pilot jet. I later switched to a home-made #59 pilot jet
(a smaller pilot jet drilled out to be larger than a #58, but not
as large as a #60). Still later, I lowered my float level to 13.5mm,
and limited the total float travel to 19mm, to imrprove throttle
response in rough terrain.

Now I'd like to offer a few thoughts about aftermarket pipes ...

Gordon Banks
Huntsville, AL
2000 XR400R
 

Jonala

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#9
Thanks sb-rider, for the complete explanation. Most of the mod's that I have done to my bike, were based on Gordon's article, MGorman's advise and the general wisdom of DRN.

I haven't seen the need to change the pilot, or needle clip position, due to the fact that my bike is a total rocket.;)
 
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#10
I might try to do this on my XR 250. yes I have noticed that that whole assembly will not come apart. It really restricts the air flow. Do you have any pictures on were to drill the holes because I am not sure how to do this. Would it be possible to take and cut out the inside of the baffle(the black metal inside the larger crome piece? or would that be to extreme. Thanks:cool:
 

Jonala

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#11
XR rider,

I've cutout the small outlet pipe, it was a real PAIN! The material is stainless steel. I used a lathe, made a special boring tool. Another option is to get a Thumper insert. There is a company in Oregon , that I don't remember the name of that also makes an insert that installs directly into the stock Honda muffler. Both of these inserts cost about $75.

The holes are located in the small ring space between the outlet pipe and outter polished cylinder.
 
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#12
Jonala,

Wish I owned a lathe! :) Do you remember what size your stock main jet was before going to 140?

Out of the options:

1. Drill holes in end of baffle ala Gordon Banks.
2. Cutout the pipe outlet.
3. Remove the stock baffle.
4. Remove the stock baffle and add an aftermarket tip.
5. Add an aftermarket insert (baffle).
6. New aftermarket exhaust.

I'm going to go with the first option because I know many others have had great results, its easy to do, its cheap, and I won't make my bike unneccesarily loud (others might not agree the last factor is a "plus") ;)

By the way, the June issue of Dirt Bike has a picture that shows how they removed the stock baffle from a 98+ model if you're so inclined. They spot-welded a piece of metal to the end of the baffle and banged on the metal until the baffle welding failed and it broke loose. Looks like a good way to decrease (increase?) stress.

Lance
 

Jonala

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#13
I don't own a lather either, I used the lathe at work.

I did not touch the spark arrestor section of the tailpiece.

Stock main jet was 122.

I have been lazy about jetting the engine perfectly. I'm very happy with the type power the bike makes now.
 
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#14
I agree with John on cutting the Stainless Steel. It was a big pain using convetional hand tools and a dremmel. As far as jetting went for my '99, here in Ohio it has been spot on with only an increase of one main jet size.

I tried a lot of different experiments with end caps and peices with the help of Jonola and found that it can be made quieter but stock has been the fastest at race pace. I keep the home made endcap around for play riding and right now it is on the back of my '89 Trans Alp

I also cut an aproximately 1/4" slot in the back of the plate that turns the throttle on the side of the carb to releive spring pressure. This allows the spring to unwind a little bit and take some of the preload off of it.

Now that I think about it, I also went up a few teeth on the rear sprocket because second was too low and 3rd too high for some of the hills in southern Ohio. If you are tall (6'+) you may want to run CR-HI bend bars. I also put a insert in my seat foam to make it a little taller. If you can find a "Stiffie" seat cover, it will accept a 1" lift and still have plenty of material left.

If you are over 200lbs you may also want to go heavier on the springs. I would not revalve unless you are planning to be doing a lot of jumping.

Scott Summers Dad told me to raise the oil level in the forks 30mm over stock but I have been happy with the max. level set by Honda.


mgorman
www.geocities.com/mxmike164
 
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#15
How did you guys get the baffle out? After taking out the 2 bolts and grinding the welds away with a dremel I'm still not able to get it out. Can't get much of a grip on it either.