Dirt Bike FAQ

If you want to spend a little more money you can have the flywheel lightened at BBR for a hundred bucks. This will let you motor rev like a 2-stroke and make it pick up RPM's fast. If you do alot of wide open riding, this is the thing to do. "This will take away some of your bottom end."

If you still want more than get a big bore kit. If you do go with the big bore kit thin you will need to go with 26mm carb. The stock carb was not made to handle a bigger bore than stock.
P.S.- It is better to buy a complete kit than have the stock cyl. bore. Watch e-bay for these items and do not buy a china knock-off.

Normally,,all those type motors are very easy to start if the engine is in Good Condition,,,or even fair condition.
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Some things that can make them hard to start.

*Low Compression.
That can be caused by several things.
You Really need to have the compression checked with a gauge to determine if it's within proper range.
Should be about 120 psi minimum.

If it's Less than that,nothing will really help much.

"Low Compression" is usually thought to mean "burned-up / wore out Engine",,,,and that's often true.
But not Necessarily.

Valve Clearance Adjustment,,and Timing Chain condition will affect it also and make the compression a bit lower.

>>>Adjust the Valves to .003"
That's Looser than recommended setting of .002".

>>>Make sure the cam chain is adjusted right.
Sometimes the adjuster "sticks" and doesnt really work right.
Also need to check the chain for wear.
Both things are easy to do.

CARBURETOR:
These things are so small even the Tiniest amount of gum/varnish/deposits will make them behave badly.
Easiest thing to do is try some Cleaner added to the Fuel tank.
Use FUEL INJECTION cleaner,,,not "carb cleaner"—it works much better.
Chevron Techron ,,or Seafoam are 2 good ones.
Don't Overdose it thinking that "more is Better".

You may ultimately have to remove the carb and take it apart to clean it.

The Intake Manifold "never" gets loose on original,genuine Hondas.
On all the Clones,,,,it's a crapshoot.
If they Do get loose the Gaskets will leak air,,and cause hard start,bad running.
Or,,if Carb has ever been removed ,,,it's tuff to get them to re-seal without using new gaskets.

Ignition System/Spark Plugs:
Most of the late model versions all have electronic ignitions.
They usually work OK,,,and are Usually NOT adjustable.
When they FAIL,,,almost always it fails like a Light Bulb.
They just Quit Working at all,,,,no mysterious misfires,,no intermittent problems that come & go.

So IF it sparks,,and eventually Runs,,,
there's 99% Odds the CDI Ignition is working OK.

Spark Plugs.
Try an NGK Iridium Plug.
DO NOT expect it to "FIX" anything,,or even Cover-Up any sort of problems elsewhere.
Make sure everything Else is in good order First.

They are NOT Magic Plugs,,,but they DO improve starting because they can fire under a much wider range of conditions,,including Weak Ignition system,,,or partially flooded,,,very cold temps,,,etc,etc

They're expensive ,$8~10.
It Wont FIX anything,,but they can definitely help

Get a Service Manual if you can.

If You cannot find one,,,early Honda 50 & 70 Manual is Close enough to give You general basics

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You will have to register,,but You can get Free Manuals here
http://www.repairmanualclub.com/

These will help.
Remeber,,these are NOT Identical to Yours,,not even the same engines,,70's and 90's are Different.
But they can give you an idea how the things are laid out,,,and valve adjustment,timing chain stuff is basically the same.
Carb Clean/Rebuild PROCEDURE is sorta generic,,,things like that.

Consider them only HINT,CLUE,or GUIDE,,,,and NOT actual,accurate service manuals for Your bike

Honda S90-CL90-C90-CD90-CT90 Shop Manual

Honda SL70, XL70K1 Factory Shop Manual, English

Good Luck with it

KTM has the best suspension, lightest weight, most options and the most power. It is the most expensive and parts can be hard to get. The suspension is great but fussy to adjust.

The Yamaha is great for both racing and trail riding. YZF is better for racing and the WR for trails.

The Suzuki and Kawasaki are about the same and are good for both and they have very tough motors.

The Honda has great suspension and is easy to ride fast but the motors wont last the longest.

BTW, Cycle News sucks and I wouldn't put much trust in what they say. They mostly do street bikes anyway.

weak compression, two strokes need to be rebuilt alot sooner then 4 strokes .. being its an 87 it might be time for an overhaul two stroke motors are pretty simple to rebuild
if compression is the case
you need to mic the cylinder to see if it needs overbored or if you can hone it
piston rings/head gasket base gasket and piston rings.. pretty cheap and somthing like 6 bolts and normal hand tools to get the head off you have no timing to mess with

and then it could be carburation .. if its running too rich it could be fouling the spark plug
if its too lean it might not be getting enough gas to start

being its a big cube two stroke it might be just how your starting it they can be tempermental

try not touching the throttle and slowly pushing the kick start down "not trying to start it" let it come back up and slowly push it down again thus priming it without flooding it

and then give it a good solid kick and barely just barely twist the throttle try that a few times …. it just might start … if it fails
try holding the throttle wide open n kicking the crap out of it … without the priming it stage before it
then you have a problem other then it just being tempermental

when it starts up .. does it run fine? if it wont idle after it gets running and cuts up at anything below 1/4th throttle it might be a cloged idle jet .. might just be a dirty carb

the list goes on and on, i would personaly start with the cheaper things, spark plug .. adjusting/cleaning the carb,

if you have a buddy with a compression gage i would test it ……….a simple way to test compression without a gage would be taking the spark plug off and holding your thumb over the plug hole pressing down .. and push the kickstart with ur hand if air blows past your thumb as u try to hold the hole closed….. you have enough compression for it to run right

The racing derived bikes, like the WR (based off the YZ), is basically a racing bike with different gearing and a few trail oriented changes. Usually they keep the same high-output high-compression racing motors, which can be finicky. Some of them even recommend a rebuild after every racing season (or more frequent!), though trail riding doesn't put as much strain on it. The XR has an air cooled engine, which I've noticed can get VERY HOT in the summer when your not able to move very fast for a while. The racing derived bikes tend to be liquid cooled, but are a tad more high-strung. I've had issues with both bikes with hot starting, especially after being dropped (the XR not as bad, but sometimes it can be stubborn). If you get a bike that uses a decompress to help start (WR does, XR has one but doesn't need it), it helps if you can get one with an auto-decompress exhaust cam (greatly eases starting), or electric start (though I personally won't ride a bike that ONLY has an electric start). The WR I believe has come with a decompress standard for quite some time now (and I think electric start now too), but I had to retrofit my older model with the cam. 2-strokes do tend to start easier, I will concede that to them ;).

Things you want in a trail bike:
tons of low-end torque
disc brakes, front and back
lower, wide ratio, trail gearing
comfortable (enough) seat
probably more I'm forgetting…

almost all bike manufacturer's make a good trail bike around that displacement class. Hit up the bike forums and reviews and see what people have to say about the bikes your looking at.

best of luck on your decision and have a blast!

edit: forgot to mention, if you like the Honda CRF250, check out the CRF250X model, it is the Honda equivalent to the WR, with the different gearing, etc. from the full out racing bike.