well-worn '84 200m - it was running fairly well, but fouling
plugs with black soot, so probably running rich.
other factors: muffler rusted out, so little or no back pressure.
air cleaner is gone - made a runner from the
carb throat to the airbox, and covered the airbox
with cheesecloth. probably lower-than-stock
restriction.
also, it starts easily when cold with no choke ( another sign of
running rich ? )

now, it's running well at small throttle openings, but cuts out
and stops firing at anything over 1/2 throttle, any gear, any
speed.

Ideas ? I'm not familiar with the carb - I see a large screw on
right side ( as you face the front of the bike ) , and a smaller
screw ( actually, a small knurled **** with a slot on the end )
on the underside of the carb, down by the bowl.

is one screw mixture, and the other idle ? Which is which ?
The large screw on the side, does it meter air or fuel ? In other
words, does backing it out admit more air or more fuel ?

I'm thinking I should try to lean it out a little and see if
it improves, but kind of hate to mess with it, since it runs
now.

(Bear in mind this is a $150 toy, so $200 solutions probably
won't happen )

thanks

 

Thrasher, when you are at about half throttle the air-screw has little or no relevance, you need to be looking at the needle jet and main jets if it is a carb mixture problem at all.

With the mods/condition of the exhaust and air filter you should be running a little lean.

1. First thing you should do is buy a can of carb clean and clean the carb good to get rid of anythig that could be obstucting an opening. This requires opening and taking the cabr apart, it's a lot easier than it sounds.

2. Then it to richen the needle jet you must first take off the top of the carb. Attached to the top of the carb you will find the slide with a spring between the cap and slide. You then detach the slide by compressing the spring and working the cable end up a cut in the slide. Now you should have a slide with a needle sticking out of the bottom.

In a secure place (the clip and retainer will jump out and dissappear forever into a blackhole) push the needle in and it will come out of the other side with the retainer. Put the retainer (the retaiier looks like a spring shaped like a V )aside and look at the needle, toward the end of the needle (top) you will see about 5 slots cut into the needle. In one of those slot will be a clip. To richen the 1/2 throttle mixture you must remove that clip and place it on the next lower slot.

Now reassemble the slide and place it back on the bike and go for a test run. If it got better but still has problems, repeat the proccess above and drop the clip another slot. If it go worst, take if apart and place the clip one slot higher that where you found it originally.

Once the 1/2 throttle problem has cleared up you want to do plug chops (run the bike wide open for and few second and shut the engine off while it is running wide open) look at the plug. It should be coco brown or even paperbag brown. If it is black you need to take the bottom of the carb off and change the main jet to a smaller one and repeat the test. If it is white you are runnig too lean and need to get a bigger main jet and repeat the test until it is at the desired color.

In general at idle the slow jet and airscrew control the mixture, at 1/4 throttle the slot jet and needle jet rule, at 1/2 the needle jet controls with the main just starting to kick in. At 3/4 throttle the main jet controls with the needle jet helping just a little and at full throttle it's all main jet.

 

trx250 - thanks very much for so much good info.

I'll pull the carb, and clean it, and go one slot richer
on the jet, and let you know how it turns out.



Thanks for takin the time to write out step-by-step. 'preciate it.
[img]i/expressions/face-icon-small-cool.gif[/img][img]i/expressions/face-icon-small-smile.gif[/img]

 

Hey guy,
I'm new to this forum so please be gentle.
I have a problem with my honda 200atc runing rich too. It's a 83' that has been bored out(I don't know how much)with the 46" rear end(outside to outside of tires), the air cleaner that is in it does not restrict very much,if any, air.I have the needle set to the last slot on the end and still have the same problem. I even have to carry extra plugs in case it fouls out in the woods, which it has.
I have a new needle in it but like I said, same problem.I am willing to bet that it has the original jet in it . What size would you suggest? Could it be the needle seat and if so how would I change that? I mainly use it for deer season and some playing around.It throws mudd like you wouldn't beleave.
Any other suggestons you might have would help. Thanks: