Intermittent power loss 250es Big Red

[prometheus]

Ok I have a 1985 250es that is sometimes hard to start and sometimes not. It will just start bogging like I've lost power and then as quick as it went away it all of the sudden will hit amd I'm back to full power. Now also if I'm in neutral and hammer the throttle it will die. I have to slowly progress the throttle. I'm not a carb guy but this seems lile a fuel issue. Dirty carb maybe or does the carb need to be adjusted?

[Flyingw]

I can rebuild your carb for you for 90.00. It sounds like it needs a little TLC. Option B is to do it yourself. Here is a tutorial I did on the ES/SX carbs.

http://www.3wheelerworld.com/showthread.php/161746-ES-SX-350X-Carb-rebuild-Tutoral?p=1257154#post1257154

You will need to order an 85 kit. Don't pay more than 20.00 for the kit. Shindy kits are the ones I buy.

[Flyingw]

Also, Be sure your tank is clean (no debris in the bottom). Pull your fuel line off the petcock and open the valve and ensure you have good flow. Check it with cap on and off. Those caps are known for corroded vents which can prevent good fuel flow.

[prometheus]

I've been wondering about my fuel cap. Even with vent open all day I will come out and check my fuel level and when I pull the cap off it releases pressure. But I do think the carb needs some work. What do I do about the cap? Can I take it apart amd clean it or is it throw away and get a new one?

[Flyingw]

Pressure relief is a clear sign the vent is blocked. Nothing you can do with the cap but replace it. With a blocked vent, as the fuel drains front he tank, the pressure in the tank will go negative and when it reaches a point will actually pull fuel from the bowl back in to the tank. You have to have air above liquid for good flow. The caps are still available from Honda. Service Honda has good prices but you may find one cheaper if you shop around. I think I paid 35.00 for a new cap a couple of years ago. Don't buy a used one as you may end up with the same problem.

http://www.servicehondapsn.com/fiche_section_detail.asp?section=2461307&category=ATVs&make=Honda&year=1985&fveh=131327

[prometheus]

Awesome thank you for the info on the gas cap. I had been checking ebay finding used crap. I did not know Honda still sold them. I will order one from my local Honda powersports shop. I'll see if that solves my prob.

[Flyingw]

Keep us posted.

[dakotab]

you can drill out the top of the cap and weld a nipple in and hook a hose to it

[prometheus]

OK I rebuilt the carb. Thank you for the tutorial flyingw. It was a great help but I am still thinking I should have had you rebuild it. Its my first carb rebuild. I can tear a 350 down to the bearing caps and back again but carbs have always been trouble for me. I didn't have much time last night to test it out but it ran much better and started easier. It still falls flat and almost dies if I rev it from idle. Any suggestions?

[dakotab]

did you ever get a new gas cap?

[prometheus]

Not yet but I am leaving the gas cap loose while testing carb.

[dakotab]

ah, ok then

[dakotab]

clean air filter? air box lid on? checked for cracks in carb boot?

[Flyingw]

When it falls flat at high rev, are you stabbing the throttle right off idle or working the throttle normally as if you were riding it?

[Flyingw]

Also, did you do the linkage adjustment (Synchronization Adjustment)?

[prometheus]

Yes did the linkage adjustment per your instructions. It only falls flat when I stab throttle at idle. Once I get above idle its fine. I'm not in gear just sitting at idle it will stumble and die if I don't let off. Now I was not able to change the main jet and needle because I coiud not get the screws out. They were siezed stuck.

[Flyingw]

This type of carb is notorious for this very problem. Some are mild, some are extreme like yours. I have yet to figure out why they do that but about 75% of the carbs I've rebuilt have this problem in varying degrees. I will say that sometimes messing with the pilot screw at the bottom of the bowl will have an effect on the problem but not always. Try turning that screw IN going 1/4 turn at a time and see if that has an effect on the problem otherwise just don't stab the throttle right off idle.

If you want to get those screws out of the slide to change the needle, place the carb on a solid surface. Use a #2 screwdriver and push down with some weight and gently twist the screwdriver while pushing down. I have yet to drill those screws using this method. Always replace the needle and the needle jet (brass barrel the needle passed through) together. Never do just one or the other. Do both or leave the old ones in there. Those two parts are matched and I have seen similar problems like yours when both parts aren't changed together. Perhaps somebody has done exactly that and this might be causing your problem.

[prometheus]

That is a possibility. I just took her out and ran around for about a half hour or so and she runs really well. I don't really ever hammer the throttle off idle anyway. Its a 250es not a 250r. Lol. Its used here on my farm so slow starts are normal with either pulling trailers or my kids on the back. Only reason I noticed it was because I was testing it out after I just did the rebuild. Normal day to day this will not affect me. Now I am working on a 185s that is going to be hotrodded and that would greatly bother me because I want wheel spin. I may have you do the carb on that when I get ready as I will probably be putting a 200x carb or something bigger on it. Thank you Flyingw for the help and tutorial. It was a great help. I also did not change the startup jet for cold starts but in Texas that's not really an issue.