84 250r help

[joenovosel]

This bike was non running. New gas cleaned carb and it fired up. Tried to get it running better today but no luck. Po said he replaced head gasket and couldn't get it to start. Now when its idling it seems ok. I tried giving it some gas and it seemed to slowly bog down and due out. Then it would take a minute till it restarted. It seems to smoke quite a bit when giving it gas but not at idle. Carb is clean and has a 120 main jet in it. Spark plug was a 8 and getting very light spark. Swapped in a 7 and now its nice bright spark. But the plug kept coming out wet and slightly black. The carb that was on it had a 142 main. I replaced it because every time I gave it gas the needle slide would twist slightly leaving the throttle open. Any advice. And yeah I read the jetting thread up top. I'm over my head with two strokes

[Bren_downe]

Hmmm… ok… there's a lot going on here. The smoke could just be your mixture, which is what btw? A black and oily plug is rich. But 120 sounds wayyy too lean. I can't see how the 142 would make your throttle stick open. I would try the 142 again. Take it for a ride. Clean 'er out a bit. Any backfiring is BAD. Stop and check your plug. Also I would go back to the NGK BR8es plug. That is stock, if your bike is mostly stock that's what I would run.
Other things to check
Did you change your tranny fluid
Head gasket leak/leak down test

[joenovosel]

I am running about 40:1,mix. The original carb had a 142 in it. The jet wasnt causing the throttle to stay open. With the airbox removed i could see as i pushed the throttle in as soon as the needle slide came above the idle screw it would twist and not allow it to close fully back down to idle. I have another bike i got at the same time as this one and pulled that carb and throttle and put it on this bike. While cleaning this carb i noticed it had a 120 jet. This carb has been ran in utah around 4500-5300 ft. The original was in arizona, not sure of elevation. I havent been able to keep it running enoug to ride it. The other bike i have had the 7 plug in it, its an 83. Ill try switching them back today and see what hwppens. Im not worried about the smoke too much for now. I did notice when i give it gas it will kind of puff out a little more whitish/grey smoke? Havent touched tranny fluid yet, not too sure how. Im reading up on it.

[Bren_downe]

Get the owners manual from kbonly . They oil drain is on the very bottom of the case. The small bolt/ screw is on the side. Both R carbs I've seen had 142 main jets, so if you assume that's stock and works well for seal level you would need to go even bigger for higher elevation. Try the 142 and let us know. It's possible you coul be way rich on the pilot but still lean on the main/ needle circuit and never know. Good luck

[joenovosel]

Now m yproblem is at idle with the 142 its running fine. As soon as i give throttle it dies. I tried holding throttle maybe 1/4 in and it backfired and died. What would cause backfiring, but idling is great.

[barnett468]

Stock 83-84 250r carb is 30 mill Keihin 130 main jet 50 pilot jet.Pilot screw about 1 1/2 turns out. 142 jet is stock for the 85 liquid r carb wich is a 34 mill Keihin.



This bike was non running. New gas cleaned carb and it fired up.

…when its idling it seems ok. I tried giving it some gas and it seemed to slowly bog down and due out. Then it would take a minute till it restarted.

...has a 120 main jet in it.

It seems to smoke quite a bit when giving it gas but not at idle. ] I am running about 40:1,mix.

… at idle with the 142 its running fine. As soon as i give throttle it dies. I tried holding throttle maybe 1/4 in and it backfired and died.

What would cause backfiring, but idling is great.

Ok, it idles with a 120 and 142. it dies ooening throttle but backfires with the 142.

It is likely too rich now with the 132, it was likely too lean before with the 120. Try putting a 128 - 132 main jet in it then look at the plug if it dues and see if it is wet.

Float level might be incorrect or the needle and seat might be leaking causing it to run rich or flood. Set float level to spec in manual if it continues to have probs with the 128 - 132 jets or set anyway if you want.

Smoke might be a bad crank seal. It might be beneficial to do a leak down test. Light color is oil, dark is excessive gas and possibly oil.

Make sure the air cleaner is clean.


Free online manual, takes up to 7 minutes to load.

http://www.oscarmayer.net/atc/manuals/honda/atc250r_81-84_servicemanual.pdf

[joenovosel]

i cant seem to find how to do the leak down test. Sorry.

[barnett468]

i'll post it in a minute. you need to buy special tools.

[barnett468]

http://www.youtube.com/watch?v=zdq7NRcUIp8

[joenovosel]

How do you figure tdc on the 250r?

[joenovosel]

The laek down test was good. Held 81/2 lbs for 15 min. Soaped it up to be sure. No leaks. Now to find a 130 main jet and see what happens.

[Bren_downe]

JetsRus.com has everything you need. Always buy Kehin jets for a Kehin carb, after markets will end up giving you a headache.

[joenovosel]

The local shop had a 130-135 jet. Put in the 130 seemed like it wasnt right. Swapped the 135 in. Runs good except on the top end. In 1st and 2nd on the top end of the gears it sputters and runs rough. Would it be getting too much gas and cause the sputter or not enough? I think ill try a 132 jet and see if it runs better on the top end. Low end and idle are wonderful. Maybe the float level is too low and im not getting enoug fuel with it wide open.

[HondaRidr]

Have you done a plug chop to see what color your plug is? It sounds like its just a little to rich on the main.

[beets442]

A backfire means that there might be an air leak. Between the carb & cyl or cyl & pipe.
Check inside exhaust make sure nothings in there.

[barnett468]

How do you figure tdc on the 250r?download the manual i posted for you and follow the instructions. basically just line up the timing marks on T for top. F is for fire.

[barnett468]

The local shop had a 130-135 jet. Put in the 130 seemed like it wasnt right. Swapped the 135 in. Runs good except on the top end. In 1st and 2nd on the top end of the gears it sputters and runs rough. Would it be getting too much gas and cause the sputter or not enough? I think ill try a 132 jet and see if it runs better on the top end. Low end and idle are wonderful. Maybe the float level is too low and im not getting enoug fuel with it wide open.

What exactly do you mean by wasn’t running right with the 130?

Float levels should be properly set first.

Did it have a hesitation/flat spot upon opening the throttle?

Sputtering/burbling = too rich.

I suggested you check the float level earlier. If it is sufficiently off, there is no point in jetting it. Float levels should be properly set first.

Bikes are rarely that sensitive to such small changes in jetting, that is a bit strange imo.



GAS LEVEL TEST

Get a 10” long piece of plastic tube.

Stick it on the float bowl drain fitting.

Hold it close to the carb with the open end even with the top of the carb.

Open the gas valve on tank and bowl drain screw.

The gas level should be from even with the bottom of the carb base to 1/8” below it.

[joenovosel]

I didn't bother adjusting the float level at first since it wasn't even staying running and the guy I ot it from said it was rebuilt. With the 130 jet it seemed to lack throttle response when taking off. Not hesitating or stalling just slow to take off. With the 135 it takes off great no hesitating. Nothing but pulling the front tire up performance. Once I hit the too end or close to it it sputters almost like a car hitting the rev limiter. Now I'm off for a couple days I'll set the float height.

Its not backfiring at all now. And I figured the tdc thing out just never posted it. Other than the sputtering its running great. Hardly smokes. Idles and takes off like crazy.