A forum for owners of Yamaha TTR250 trail and enduro bikes!

I thought I would upload this for people wanting to understand the TTR250 carb. Hope you enjoy it.

 1994 standard Teikei Y30P                                                                                             2004 standard Teikei Y30P

Tools needed for the job

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Small flathead screwdriver.

Medium flathead screwdriver.

Medium Philip's head screwdriver.

Small Philip's head screwdriver.

8mm spanner.

6mm spanner.

12mm open-ended spanner.

toothpick or probe to remove old seals.

Nail or similar to remove the float pin.

1.5mm drill bit to make float pin holes a bit bigger.

Air compressor (& or carb cleaner).

Fine wire for cleaning the diaphragm jet (I used a strand of throttle cable wire).

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Parts needed for the job...

Top Gasket : 4GY-14198-01-00

Side Cover O-ring : 1HV-14147-00-00

Diaphram 0-rings x2 : 5Y1-14397-00-00

Diaphragm : 4GY-14940-00-00

Diaphragm Springs x2 : 6G8-14275-00-00

Float Chamber Gasket : 4GY-14384-00-00

Pilot Jet #50 : 43F-14342-25-00

Please Note: The jet's used below are from my bike, so you cannot use these unless you upgrade first. I did not need the float set on either of my carburetor's so this is not shown.

I will be starting with an already stripped carb but to remove these components is the opposite so you shouldn't have any trouble.

First thing is to make sure you have soaked the carb overnight in solvent (if clogged).

Then blow all holes & air holes out with an air compressor (or spray solvent) & clean all components.

Make sure all holes in your jets are spotless including sideways. You should see the holes below...

Now that all is clean,fit jets.

If fitting a larger main jet unscrew the main jet from the nozzle using the 6mm & 8mm spanner's (if standard)...

Then screw the new one in tight.

Fit your needle & float. To do this, slip the needle retaining clip over the float, than install so that you can see the TK on the float...

Then slip the splash stop cover over...

Moving to the float bowl,fit the diaphragm & o-rings into bowl,making sure they seat properly....

I like to use a smear of rubber grease for a long-lasting result. Any excess grease should be wiped off with a clean rag.

Rubber Grease

PBR rubber grease is a high performance Castor oil-based grease designed to preserve and lubricate plastics, rubber and components such as O-rings, valves, diaphragms, cups and seals. It is available in a range of pack sizes for both retail and the workshop.

Now the tricky part...Installing the spring...

To install the spring...place it on the top of the diaphragm with the bowl upside down.. Now install the cover making sure that the spring stays seated properly.

Tighten the two screws.

Now turn the bowl over & install the check valve... Note: This can get lost easy so be careful!

Now fit the bowl gasket & tighten the three screws.

Moving on....

Fit the side cover 0-ring making sure it's seated properly...

Now fit cover & tighten

To install the throttle lever, first use rubber grease (or copper) on the shaft.. Make sure the spring goes in correctly...

Install the large rubber seal to shaft & small rubber seal to the hole above (middle of spring).

Then make sure the plastic washer goes on...

Then pre-load the spring...To do this install the spring to throttle levers & turn until it goes into place making sure that it does not ''catch'' on the carb body when turning. When fitted it should look like so....

Once that is in,fit the clip from the top. This will go on next to where the plastic washer sits.

When taking this off use cir-clip pliers or two screwdrivers to start it off than turn it around & remove it when in the right position to do so.

Note: The plastic washer goes closest to throttle lever.

.

Now fit the diaphragm lever spring...

Then fit the diaphragm lever arm. To do this push it down with a flathead screwdriver while tightening screw...

The screw is pictured below.

If you have not already fitted the slider screw you should now do that...

If you want to get a bit more out of the top end, the stop screw can be adjusted. To do this loosen lock nut & adjust until it does not touch when the throttle is turned to full throttle then screw it back in until it just buts up on full throttle.

Now fit the top gasket & install the top cover. Four screws at the top...

Next make sure the O-ring is not perished... Install the air fuel mixture screw making sure the spring is fitted. To adjust this turn all the way in & one & a half out. (usually better at two & a half). To check this start the bike & turn in until you notice a change in revs. Then turn 1.5 to 2.5 turns out.

There is a copper washer that may need annealing but not likely...

Fit screw & tighten.

Moving on...

Check choke seal to make sure it is not perished...

Fit choke plunger with the 12mm open-ended spanner.

If your needle does not have a conical point that it will need replacing as well. In this case it was not needed.

Also it would be a good idea to drill the float pin holes out a bit so it's not hard to install & doesn't break in the process,you will need a 1.5mm drill bit for this.

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Installing the needle set

First thing to do is buy the part....

Then take the top cover off by removing the four screws at the top.

Now remove the diaphragm lever arm retaining screw, making sure that the spring does not get lost.

 

Then remove the slide-arm retaining screw, pictured below.

Now unscrew the two screws from inside the slide (pictured below).

Unclasp the plastic needle holder & spring.

Now undo the cir-clip & put the new one on.

Standard setting is the middle clip position...

If you have not replaced your jets, than may need to set it to two from the bottom.

Now install locking washer making sure it goes in its locking position...

Fit the plastic needle holder making sure that the new spring goes on first.

 

Put the needle in the slide & fit the slide arm with the two screws making sure that the cut out in the slide goes to the back of the carb, as pictured below.

I found that it is easier to put the screws in the slide arm holes, then lower it down without bumping, causing them to fall out of their holes.

 Now, fit the slide arm retaining screw pictured below.

Fit the diaphragm lever arm making sure that the spring stays in place.

To do this push it down with a flathead screwdriver while tightening screw...

 

Then put the top cover on.

 

Job done

 

 

Good luck.