Cobra XR-1010 Manuel d'utilisateur télécharger pdf (Page 2)

XR250L Project

September ‘94

Page 2

Carburetor and Jetting

The accelerator pump carb on the XR-L looks like it has potential. Pumper

carbs can be jetted to get rid of that nasty four-stroke hesitation on the bottom

and give good power on top too. However, the non-pumper carb from the XR is

ultimately a better performer because it is designed for more air/gas flow. The

needle and seat on the pumper carb are designed to make the bike EPA legal

(lean) and are the biggest impediment to performance.

But, if you want to stick to the stock pumper carb, there are a few things you

can do. The carb is jetted too lean. If you do any of the intake or exhaust

mods, then it will be way too lean. Install a 125 or 128 main and a 40 or 42

pilot as a start (sea level jetting). While you have the float bowl off, remove the

pilot adjusting screw. Be careful with the spring, metal washer, and o-ring.

Heat the end with the small ear on it, and the ear will fall off. Reinstall the

screw before remounting the float bowl. The pilot air screw can now be

adjusted throughout its range.

There are too many hoses on the California model carb. If you don’t need to be

EPA legal, remove the purge control valve and canister and two extraneous

hoses. Consult pages 1-22, 1-27, and 5-10 in the Service Manual to see which

hoses to remove. Seal the holes in the carb body with short lengths of hose

that have been plugged with shoe goo or something similar. You can seal the

carb body directly if you trust yourself.

Besides hoses, there are two other differences between the California and

49-state carbs: the part numbers are different for the throttle slide and carb

top. I don’t know the extent of the physical differences, but I would guess that

the slide cut-away is different, and the carb top has a throttle limiter.

The XR250R and XR-L carb bodies are nearly identical. The complete XR-L

carb was derived by drilling out the extra channels that were already cast into

the standard XR body. Extra hoses were added, and a different float bowl,

choke mechanism, and jets were used. The similarities and differences are

summarized below:

XR250R XR-L

Main jet

Pilot jet

Needle

Pilot air screw

Float bowl

Choke

Accelerator pump

Actuation

Float bowl vent

Float bowl overflow

Emissions hoses

long hex head, 125

raised thread, large aerator

holes, 40

adjustable

tall, allows main jet access

via removable bottom plug

lever on carb body

none

push/pull cables

none

short top hat, 122

same except small aerator

holes, 38 or 40

fixed

limited adjustment (ear)

short, no main jet access

remote via cable

yes

same

none on 49-state model,

2 on Cal model

1 2 3 4 5 6 7 ... 13 14

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Cobra XR-1010 Manuel d'utilisateur Page 2

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