Here goes.

Here are the current specs of my Bike.

90 XR250R Standerd Bore and no Porting.
White Bros E-Series Exhaust (4 rings at present).
White Bros Filter with mesh and snorkal removed.
Standard Carb - 138 main and 45 pilot

My Specs
Overweight 15 Stone, 5'10'', 39 going on 20 year old

I am now fitting a 34mm Pumper carb from an XLX350R
I am also fitting a 96 Header pipe which has a better exhaust opening and also has longer primaries which i think will add more torque.
Will be replacing the white bros filter for a K&N. I

The question i have is do i fit the replace the 128 main with a 138 main jet or go slightly bigger due to the increased air flow?
I can add more rings to the e-series but not sure how many. Dont wont the bike to load due to the current climate here in the UK.

There seems to be some large variations in jetting specs between bike years and Jap or US specs

I have searched many threads regarding jetting but everyones bikes are differant so am looking for advice on jetting my bike right unless some one has similar specs to me.

Cheers

Dringeruk

Bristol TRF Webmaster

I have the xlx350 carb on my bike and a friend has one on his... (we spoke before here)... They are both bored to 280cc.

I called him and he checked his notes...

pilot : 42
main : 130
Needle position : stock (didn't touch it).
fuel screw - 2 turns out but may have fine tuned it from there...

We live in the pacific northwest U.S. where conditions are similar to the U.K. -> moderate to cool temps with quite a bit of rain, altitude near sea level to 2-3k feet.

Oh, and my friend jetted the bikes, he is a honda factory trained tech with over 30 years experience - so this will be fairly close for you - you might go in a tad on the fuel screw and stick with a 128 main (given that you are a 250 and we are a 280cc...).

You will need to stretch out the boot on the air filter side to "get her to go" - but it will 'bolt on'.

jeff

Hi again Jeff

Thats great info much appretiated.

How come the main is only 128? My original set up was 138, does that mean it was to rich?

At least i can bolt it straight on though without getting another jet.

I'll let you know how it goes over the weekend.

Many thanks

Dringer

The jets will be different for a couple of reasons...

You might have been rich on your main - most here jet rich. Some more than others...

The accellerator pump supplies fuel during accelleration - allowing one to go leaner on the main and the bore is different (different velocity and venturi effect on main).

For a 350 - it was probably jetted lean - but it was okay, because they add alot of ethanol to the fuel in brazil - they have very little of their own oil and import almost all of it.

Just a reminder -> You will see when you pull the bowl off - but it uses the round keihin jets for the main - not hex like your stock carb.

jeff

Well heres the latest report.

The carb fitted with no problems at all, well pleased. Had to have a dent removed from one of the primary pipes and when it came back it wouldn't fit so used the following formula an old engineer once told me :-

Application of heat + large mallet = nicely fitting exhaust :applause:

Amazed at how the bike now starts and ticks over. Spot on wether the engine is hot of cold.

Took the bike out for a ride have but have a slight problem. There is a hessitation from 1/3 to 2/3 throttle its not a stutter but a lack of power. Had a quick check of the plug although not a full rev shut off check. The plug looks grey/tan all over the insulation and electrode and deposits of black down the sides of the main body of the plug.

I am running the 128 main but a 45 pilot as thats what came with the carb.

I assume it is running to rich. If so whats my next move. Do i change the needle position down one to lean it out or down jet.

I've tried the e-series with 6 disks as 1.66'' = 8 disks, .96 = 4 disks and mine is 1.5'' so about right for starters?

If your there oregan_rider as your the man. :worthy:

If she was rich, the plug would be almost black everywhere. Are you sure the accelerator pump is in fact working? Your first post at the top of the page, you say you are running 138 main, now this post you say 128 main? What are you running ? Is the squirt of the pump adjustable?

Here is a pic that will help you adjust carburation.

Hi

I was running a 138 in the original standard carb and asked if i should put a 138 in the new pumper carb or stick with the 128 that it came with....which is what i did.

Here are the now specs of my Bike.

90 XR250R Standerd Bore and no Porting.
White Bros E-Series Exhaust (6 rings at present).
White Bros Filter with mesh and snorkal removed.
96 XR Primary pipe which has longer primaries than my 90 standard pipe.
34mm Keihin pumper Carb - 128 main and 45 pilot

Still My Specs
Overweight 15 Stone, 5'10'', 39 going on 20 year old

The carb is brand new out of the box so assumed i wouldn't need to start adjusting when the pumper cam in, also i thought some people set up there carb without the pumper to get it working right as the pumper only adds an extra squit of full on throttle response and not if the throttle is held steady. I'm probably wrong. Sorry if this sounds stupid but i am new to these pumper carbs.....cant you tell.

I understand that if it was running very rich the plug would be black but surely there are degrees of richness and not just rich, OK or Lean?

There isn't any popping on deacceleration which have had in the past when it was setup to lean which helped me come to the conclusion it may be rich?

Feel free to put me straight. Here comes the abuse :)

what did you do for the choke? is it cable operated now?

Dringeruk said:

Hi matt88

As i've only just fitted the carb i just pulled the lever by hand.

SO far i havent fitted a choke cable but will probably use a longer cable from the decompression lever which i dont seem to need anyway.

i was thinking the same thing. do you think you could fit another one of those levers on the other side of the bars if you were to keep the factory decompression system? you dont think the factory cable will be long enough?

one more question- where did you get the carb from?

matt88 said:

I haven't got a factory lever, i uesd one from a mountain bike, does the same thing. Just have to lake a new cable up to length.

You could set up a small pull cable just at the carb as there is a cable bracket there.

To be honest just holding the lever while it starts isn't a problem as once its running it doesn't seem to need the choke anyway, and with the pumper it seem easier to keep the engine running until warm.

Got it from ebay although they also do online direct sales but its £117.

Heres the link

http://cgi.ebay.co.u...1QQcmdZViewItem

If you do order one ask them to use extra packing. Mine was delivered ok but it was lucky as it was only in a box in a large jiffy bag.

Dringeruk said:

Given my experience with it - I think you are fat (rich) on the bottom and a tad lean up top...

Drop to a 42 pilot - or try going about 3/4 - 1 turn out on the fuel screw with the 45 pilot (until you can get the 42 pilot). If you leave the 45 and don't lean out the mixture screw - you will have alot of trouble with hot starts.

Fatten the main to a 130.

FYI - The accelerator pump is actually quite aggressive - my friend delayed his by bending the tang that pushes on the plunger.

Are you describing "roll-on" conditions - or behavior at a constant speed.

Oh, and if you only had it out for a short ride - it takes a bit for the accelerator pump to get fully primed. Make sure you have blipped the throttle enough to take care of this before drawing any conclusions...

For the choke - you can buy a choke cable and mount from an XR250L. I listed a couple of other options in my previous thread.

jeff

"Given my experience with it - I think you are fat (rich) on the bottom and a tad lean up top... "

I hope your talking about the jetting :eek:

"Are you describing "roll-on" conditions - or behavior at a constant speed."

Yes roll on conditions as though i want to accelerate up to full speed.

"Oh, and if you only had it out for a short ride - it takes a bit for the accelerator pump to get fully primed. Make sure you have blipped the throttle enough to take care of this before drawing any conclusions..."

Aaagh OK. Something else i've learned.

I'll get some jets on order and let you know how it goes.

Many thanks for the info.

Top Man :thumbsup:

Some things are best jetted rich on top and lean on the bottom... And blonde... ;)

Your jetting may be slightly different from mine, but not too far off. Different bike, slightly different fuel and your exhaust is free-er flowing than mine. Don't worry about the needle position until you get the main up to 130, the pilot down to 42, and the accelerator pump fully primed. Given your description - Sounds like the accel pump wasn't in full operation yet.

jeff

Seems like a nice carb, wonder if it's worth shipping it from UK to Canada ?

Fitted the 42 pilot and 130 main and went out for a longer ride tonight.

Much better when rolling on the throttle but if you roll it on too quick at 1/3 to 2/3 then it bogs only slightly. Wheel comes up easier now in second though.

Definatly a great mod. Bike feels crisper and starting is now a doddle. Still not like my mates CRF250X (not suprising) but much better than before.

The e-series exhaust is to loud with six disks so i'm going to go back to four to see if it quietens down. Hopefully will also stop that slight bog which i assume is not being quite rich enough?

I have got a standerd exhaust off a mate but it has no quiet insert and is very load. Saw a mod on the forum for a home made insert so may give that a go. People on EBAY in the UK asking for £20 plus for a standerd XR quiet insert :eek:

These after market pipes are dear so not sure what to go for.

Cheers

Dringer

Dringeruk said:

The e-series is a great pipe - the megaphone section adds mid and top power and it is also 1.5 pounds lighter than the stock pipe. There is a quiet insert for the e-series - you insert a couple disks and then the insert goes in the stack and they you add a few more disks. It won't fit if you try to put it on first. You can also get a 180 degree diffuser and add it to the e-series. A friend of mine did this and it is much quieter with good power. I'll dig up the part numbers for you on these and post them.

The choke on this carb also actuates the throttle for a fast idle - the combo makes for very easy cold starts. And the fuel mileage is still quite good. I did a trail ride of 64 miles and it looked like I still had half a tank left.

By the way, your XR has more HP and torque than your mate's CRF250X below 8-9k rpm. Like 30% more torque.... This means less wheelspin and more "go-go" when the going gets tough. Get him on a tight trail and walk away from that boy...

Oh, and throw that K & N filter in the trash - it passes alot of dirt and clogs easily. Horrible thing. Cut the backfire screen out of the stock filter cage and run the foam filter of your choice. Stock filters best, the CRD looks good. I have a UNI and will be pulling it off - in fine dusty conditions I continually see fine dust on the intake air boot.

jeff

oregon_rider said:

Hi Jeff

I've heard of the quiet insert but have yet been able to source one here in the UK or one available to the UK ? How much do they reduce the noise by?

Ran mine tonight with 4 rings in the exhaust instead of 6. Bike didn't feel like it had as much power but definately quieter. Gone back to 6 for the weekend ride out.

Any one have a drawing, photo or dimensions of the quiet tip. Seen the picture on there website but doesn't tell you a lot.

Dringer

I'll try to round up the links to the e-series quiet insert this weekend for ya - I looked around and didn't see it in my initial search. I have one up at my friends shop and will ask him to take a pic of it if I can't find one.

What I called a diffuser before is actually an exhaust shield - you can get a 180 degree and a 360 degree exhaust shield - the 360 degree one aims the exhaust back. Hot setup is to run the quiet insert plus the 360 degree exhaust shield.

My best friend/ master honda tech suggested you move the clip on the needle down one notch to deal with the 1/3 to 2/3 throttle bog (now that you have jetting closer). This will richen this throttle range.

jeff

"I'll try to round up the links to the e-series quiet insert this weekend for ya - I looked around and didn't see it in my initial search. I have one up at my friends shop and will ask him to take a pic of it if I can't find one."

If you can get some dimensions as well would be great, then i can fabricate one.
"What I called a diffuser before is actually an exhaust shield - you can get a 180 degree and a 360 degree exhaust shield - the 360 degree one aims the exhaust back. Hot setup is to run the quiet insert plus the 360 degree exhaust shield."

Still searching for the parts for sale. If you see any let me know.

"My best friend/ master honda tech suggested you move the clip on the needle down one notch to deal with the 1/3 to 2/3 throttle bog (now that you have jetting closer). This will richen this throttle range."

I done a full thottle run to check the plug. It was a nice tan colour. Since i started this thread i have more understanding of how the jetting works. I was going to move the needle so now you have confirmed it for me.

Cheers

Dringer