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95 xr250r with xr250l pumper carb trouble

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I have a 1993 XR250R with an XR250L pumper carb that I picked up cheap enough on Ebay (because the bike had no carby when I bought it)

The carb is very clean and looks to have done very little K's

The trouble is the throttle sticks when revved, Usually seems to stick at around 2000 RPM approx (no tacho ofcourse) or even higher sometimes, It will usually drop back to idle if the throttle is blipped

I have eliminated the throttle & cables being the problem by removing the cables all together and the carby still sticks even though the throttle is certainly bottoming on the idle adjustment screw? The return spring on these carbys is pretty heavy duty too

(Please dont mention or ask anything about the cables & throttle, They are not the problem)

From what I have found googling and read on forums it may be wear in the slide/bore which with vacuum pushes the slide towards the motor which would create problems, There is no major scratches or gouges on the slide or slide bore but there is a little bit of play if I wiggle the slide front to back of course due to how the linkage works

Also the linkage has no play at all so that is also eliminated

I have also read that the air cut off valve/diaphram can cause idling issues also but according to the diagram below the pumper carb never had one installed

http://www.motosport.com/dirtbike/oem-parts/HONDA/1993/XR250L/CARBURETOR

Has anyone else had this problem? If so, How were you able to fix it, A new slide or do I need a new carb body? Or could it possibly be something else

I would like to be able to afford a new Mikuni or FCR but at this time of year that is out of the question, I may have to buy another good second hand carby and build one good one out of the 2 if need be

I imagine the carb body would wear being aluminum and the slide being steel

Any info or help would be greatly appreciated

http://imageshack.us/photo/my-images/232/p1010739r26.jpg/

http://imageshack.us/photo/my-images/94/p1010741r26.jpg/

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When it sticks, have a screwdriver handy and back off the two screws on the carb top cap/cover about 1/8 turn. I actually use a right-angle phillips, like the one below, but with a finer tip for the smaller screw head.

TwistyTools.jpg

Good luck. :lol:

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Thanks Ramz

Im open to any suggestions but could you please explain how the cap would be making the throttle stick & why you would want to undo the top cap?

Looking at the slide/bore I would say it is not the reason for the throttle sticking as it really has bugger all wear if any, Im sure they would have had some very slight movement when they were new

I found this thread that mentions an "XR250 that would hang/hunt on a high idle and it was due to a missing O-Ring on the idle mixture screw">

http://www.thumpertalk.com/forum/showthread.php?t=922948

The o-ring looked fine when I removed the mixture screw

I will order a gasket that comes with some larger jets also and see what happens when its all back together super clean with new o-rings & gaskets

I found this guide which shows the 250R & 250L carby differences>

http://www.4strokes.com/tech/honda/xr250lmods/

I have ordered a gasket kit which has the larger

40 Pilot jet (38 stock)

125 Main jet (122 stock?)

My needle jet does have 6 position adjustment and the main jet has (I think) 124 on it (24 is mainly visible but the 1 is possibly close to the burred up flat screwdriver section and hardly visible)? That would suggest someone has jetted it up slightly, Is the 124 main possible/available?

This is the kit to suit earlier models, Same gaskets & o-rings ofcourse but with the larger jets, A good way to upgrade the jets and rebuild at the same time

http://www.motorcyclespareswarehouse.com.au/products/kh-0831n-carb-repair-and-parts-kit-1

Also forgot to mention my bike has some kind of aluminium exhaust that must flow pretty well compared to stock considering how loud it is, Damn noisy!

It also has heaps of compression, Im pretty sure the motor may not have been rebuilt yet!, Considering the condition of the bike which still has the factory paint code sticker on the rear of the frame (NH-138), The clean filler cap sticker near rear brake reservoir and the chain tension sticker on the swingarm all intact and not even damaged or ripped at all, Pretty amazing for a 93 model bike, Unfortunately some ding bat had removed the speedo (so im unsure exactly what little amount of K's it had?), Carby, Sidecovers and front brake caliper before I bought the poor thing, Why I dont know?

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Im open to any suggestions but could you please explain how the cap would be making the throttle stick & why you would want to undo the top cap?
You do not remove the top cap, just back the screws off 1/8 turn and see if it fixes the problem.

The carb body flexes and will bind the slide/pivot shaft if the top cap screws are too tight - happened to me and a friend on different XRs within about a month of each other. We found the fix on his bike while riding on a snowy trail late in the season - glad to finally fix it cause riding the snow with a cantankerous carb was stressful, to say the least.

We didn't believe it, but back the screws off and it didn't stick - tighten them up and it stuck. Repeatable. :lol:

May well not be your problem. :)

I found this guide which shows the 250R & 250L carby differences>

http://www.4strokes.com/tech/honda/xr250lmods/

A newer version is here:

http://rickramsey.net/XR250L.htm

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Ramz

Thanks for explaining it with a bit more detail (Yes I meant just undo the cap not remove) I was thinking along the same lines of what you just explained but I cant see how it would happen, With the carby sitting on the bench moving the slide up and down and looking it is certainly dropping back to the idle position every time it is moved? But weird things do happen I spose

So were the symptoms you had similar to what I explained? It sticks at a random amount of revs but usually drops back to idle when the throttle is blipped?

Looks like im not alone atleast>

http://www.thumpertalk.com/forum/showthread.php?p=10846621#post10846621

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Was it installed on the screw in the correct order? When putting the assembly together, the spring goes on the screw first, then the washer, then the o-ring last, then the assembly gets inserted into the bore.

The o-ring looked fine when I removed the mixture screw

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I actually didnt take note of that when I disassembled it so that is a possibility

It may have been put together wrong when I received it, We will find out when I put the carby kit in and put it back on and fire it up?

If I am unable to get this carby sorted I may have to fit one of the Mikuni TM33's>

http://24.73.80.100/ProductDesc.aspx?code=TM33-8012&type=0

I have read that the stock XR250 cable will go straight on the tm33 but the cable mount setup seems pretty tall and looks like it may hit the bottom of the fuel tank?

Edited> Looks like it should fit OK on the older XR's too>

http://www.allensperformance.co.uk/images/gallery/xr250r01.jpg

Anyone know where a TM33 can be found cheaper?

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Received the Carby kit today that was express posted on monday, Fitted the carby kit, Stabbed myself in the finger with the phillips head screwdriver, Fitted the carby on the bike, It started second kick with no choke (because I was simply too lazy to fit the choke cable back on that comes with the XR250L carb) and I now have no sticking throttle at all, Very happy apart from my finger, It runs a lot stronger and starts much easier too, I had to use the choke every time to start it before

Im guessing it was something to do with the air mixture screw as mentioned earlier by Trailryder42, It may have been incorrectly fitted and also blocked a bit too but it is certainly cleaned out now and running sweet

I need to order some (127/128, 130, 135?) main jets and have a play around with them now

If you need a carby kit these guys are great to deal with>

www.motorcyclespareswarehouse.com.au

Just got my Trailtech dash setup yesterday ($55.00AU Delivered to OZ from the USA) and ordered a Trailtech Vapour (stealth) today, Cant wait to finally get it on the road sometime after chrissy

Edited by XR250INOZ
EDITING

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Yes good write up

I have installed the larger pilot jet (#40, The pilot & main jet also had the larger aerator holes too) but was unable to install the larger main jet because the earlier model carby kit I got ofcourse had the longer hex head main jet which is meant for the non pumper fuel bowl, I realised that would be a slight problem before ordering but easily fixed, I have ordered the 125, 130 & 135 main jets in the shorter slot version which will solve that problem, I massaged the stock jet for now but would prefer to use the new main jet tube as it has the larger aerator holes as listed in the 250L mods

(the kit came with a new air/mixture screw, spring, washer & o-ring too)

I shortened the pump spring also when I first got the carby

After I dial in the main jet, I think that is about all I can do with the carby for now until I upgrade, It is basically an XR250R spec carby with the added pumper

I cant see why the non pumper carb is recommended? It may be jetted much leaner but that can be fixed and isn't a pumper carb better?

No hesitation/bog with this carb

I have added a new UNI filter to my order with the new TRAILTECH VAPOR (stealth) speedo, Need to fit a road/trail front tyre next as I will be on the raod a fair bit commuting to work next year, Getting close to being a sweet bike

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I received my new jets before Christmas and never had a chance to checkout the threads etc, Turns out the new jets screwed straight into the non pumper XR250R needle holder??? &%$#@!, So the info I found that says the jets/jet holders have different threads is confusing or plain wrong?

So basically to sum it up, If you have an XR250L pumper style carb all you need to do is order a carb rebuild kit for the earlier 1986 - 1989 XR250R (Keyster Part number KH-0831N) and you carb will be jetted to the non pumper specs

The kit I used came with the slighly larger #40 pilot jet

125 main jet (Although hex head) So i ordered a 125, 130 & 135 main jet from ebay (max1830) Saved a couple of dolars, My local honda dealer quoted me around $10ea for jets, Nearly had to ask where the lay-buy counter is

http://www.ebay.com.au/dsc/max1830/m.html?_nkw=slot+jet+keihin&_sacat=0&_odkw=slot+jet+keihin&_osacat=0&_trksid=p3911.c0.m270.l1313&LH_TitleDesc=1

The short slot jets fitted straight into the Non pumper needle holder with the (6) larger aerator holes, The air/mixture screw is also included>

http://www.motorcyclespareswarehouse.com.au/products/kh-0831n-carb-repair-and-parts-kit-1

Other XR kits available>

http://www.motorcyclespareswarehouse.com.au/search?q=xr250+kit

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