Yamaha Moto 4 250 Won't Start - Help Appreciated

[Azulom]

Bought an old Yamaha (Moto 4 250) and the thing won't start. 

It will start with choke full on - but close choke and it'll die. If you give it gas - it dies.

It will take throttle with choke on (and smoke like a chimney).

When I first got it the thing would start periodically - but again soon as you give it throttle it died.

I took the carburetor off and cleaned it all with carb cleaner and a tiny piece of wire (to get into the holes) I checked the float levels (good). Has spark.

What else could be the issue? I can safely say the carburetor is 100% clean - the pilot mix screw is set where it's supposed to be set (1 3/4 turns).

Driving me nuts. 

I took the air filter off and cleaned and oiled it (would over-oiling the filter choke it from getting air?)

[davefrombc]

Sounds to me  like  either  there  is still some  blockage  in the  fuel  passages of the  carb making it run lean without the  choke on, or possibly  the  throttle  slide needle  is set  wrong .. This video  on rebuilding  the  carb might help:

 

[Azulom]

I actually thought it was still a carb being dirty issue myself - which is why I've cleaned it three times. It's definitely clean - and when I cleaned it the two extra times there was no blockages.

Slide needle clip is set in the middle.

 

[Azulom]

Just an update - shaking the bike for a second or two will make it start and run. It'll eventually die if you don't shake it while riding.

Would the needle valve sticking cause this?

Edited June 18, 2017 by Azulom

[davefrombc]

That sounds like  the  float  or  needle valve in the  float  bowl  is  sticking  and  not  letting the fuel  into the  float bowl. . You  might als try  disconecting the fuel  line  and asee  if  fuel  flows  freely  from  it .. There  could  be  an  obstruction  in the  line  or fuel  petcock.

[wjb228]

I also have a yama 4 but an 200. had same problem. I replaced the gas valve in the tank. rebuilt the carb reworked the choke and it has been a champ since. I do not run it much as it is like my little old toy from the 80's

Edited June 19, 2017 by wjb228

[Azulom]

Did a thorough cleaning of the float needle valve (where it sits) it sometimes sticks in and doesn't fall out. Just a tiny movement will make it fall though. There seems to be needle wear on the thing it sits in.

Gas is flowing freely from the gas valve.

I was leaning toward it being the float needle valve because I can get it to idle now and even run - but it bogs down sometimes like it's going to die (happens more when going in reverse).

And the idle is the same thing - idle sounds real good and then all of a sudden RPMs will drop and it'll start bogging.

When I checked took the carb off after that - gas was in the float bowl.

From my understanding the needle would stop gas from getting into the carb if it was sticking, right?

Will buy a carb rebuild kit anyway - but is there anything else that can cause this issue? (Valves or something?)

 

 

[davefrombc]

The symptoms  you describe all  point to  fuel  problems , and  a stcking float  needle valve is the most likely   culprit .

 

[joshmedley88]

My money is on float needle valve or possibly bad needle on slide

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[Azulom]

Went in and cleaned the float needle seat as best I could (mirror like now) - noticed notches on the side from the needle valve wearing in. It still sticks in my hand (doesn't fall out) - I don't think it's sticking enough with the floats pushing down on it though. 

Unfortunately I have to wait a week+ for the Carb repair kit to replace everything.

She's working a lot better (Starts now first time, idles nice for the most part) but she does have a bogging issue which is most prevalent in reverse (but also happens intermittently at idle and going forward).

If it's the float needle it seems the carb is filling with gas but once the needle is fully sat closed it doesn't come out resulting in not enough gas in the carb to make it into the jets to keep it running right.

Another thing I noticed is smoke - but it's not really bluish. More white. It gets really thick if the mess with the idle screw and have it revving real high.

Could that be a gas issue?

if it's oil - how can you tell if it's the rings/valves? Is there a certain time it'll smoke if it's one of the other (Idle, Revving, Derevving)?

[joshmedley88]

Compression test the cylinder

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[Ajmboy]

I've had float pin sticking issues on my Yamaha Kodiak and Kawasaki bayou after sitting too long. 

Moved topic to Yamaha forum and added ATV info into title. 😁

[awyelton]

Had a lot of the same problems you're describing. Picked up a carb for about the same price as a rebuild kit, now sure where, but i could check. Other than a little adjustment, that had me running the same day i replaced the carb.

[Splitty]

Im new here so i just wanted to say hi to everyone first. awyelton where did you find a carb for the 250 moto 4.  

[SirMaxwell]

On 7/3/2017 at 7:56 PM, awyelton said:

Had a lot of the same problems you're describing. Picked up a carb for about the same price as a rebuild kit, now sure where, but i could check. Other than a little adjustment, that had me running the same day i replaced the carb.

PM'd you. Thanks

[Kelly Rose]

If it’s smoking that bad, it’s probably a ring or valve seal. Check your oil immediately after shutting it off. If you have smoke coming from your crankcase..... scratch everything else, you’ve got a blown head gasket.