85 Big Red won't run right

[UncleBubbles]

So I'll tell my story so you guys have idea of the history on this trike. It always started great and ran great, never a miss or stumble. Last winter the engine puked because of my mistake (long story) and needed a new top end. Ordered a kit for it had the cylinder honed out everything looked great. I knew my carb needed a gasket for the bowl as it was starting to leak on occasion, so I ordered a carb kit for it. Threw engine back together and put the carb kit into the carb thinking it could only help it, right? This is where my trouble began. It would start and idle ok but it wouldn't go past 1/8 throttle without and stumbling and missing. At first I thought I had it out of time but I've checked and it seems to be in time. So I spent a day tinkering with the carb and anything else I thought could be even remotely responsible hoping to get it to run but no sir. Then it sat all summer buried under stuff in dads shop until few days ago. So now I have everything original back in the carb after much tinkering and it will run decent now, but in the mid throttle it still stumbles and misses. I don't know what to do now, everything is as it was before the rebuild and it still wont run right. Its getting filtered fuel, the carb is so clean by now it literally shines. Does anybody have any suggestions for me? Thanks.

[yaegerb]

You blew the jets out with compressed air? A mid-WOT problem is likely your main jet. It may have garbage in it.

[badass350x]

Did you use the needle from the kit? Just went through the same problem on a friends 350x it was the needle that came in the kit was wrong size, put the stock assembly back in it ran perfect.

[atc007]

It very well could be carb. But per your story,it hasn't ran right since engine work? Recheck timing,valve lash etc.. Tight valves would be hard starting,so I would suspect timing. All after carb of course,it probably is in your carb,but you have a lot to recheck. Also sounds like text book CDI,,but i've never replaced one on a 250.. Let us know what you found.

[UncleBubbles]

The carb has been taken apart and all the jets blown out 7 times today, so they HAVE to be clean. Idles fine, will run at mid throttle but stumbles and misses, wide open it runs pretty good a wee bit lean maybe. I had the new needle in right after the rebuild but now I'm back to the original Honda one. I thought spark maybe too but I really don't know how to go about checking for spark at mid throttle? I have replaced the CDI, last summer when I drowned it by accident.

[Flyingw]

The aircraft troubleshooter in me is saying to backup. First of all, it the timing was off even one tooth on the cam, you would know it. You said it ran good before the "mistake". You swapped out the top end and rebuilt the carb and your troubles began. You stated that it started and idled fine but would stumble off idle at about 1/8 throttle. With that, you can eliminate the startup and idle circuits of the carb. From idle to about 1/8 throttle is controlled by the pilot screw and jet. Above that the carb is transitioning over to the slide cutaway and needle jet. At this point the pilot screw adjustment/jet is suspect. I encountered the same exact thing a couple of weeks ago on one of the SX carbs I rebuilt. I turned in the pilot screw 1/2 turn and the problem went away.

Now, you said you backed up and reinstalled the old components back in to the carb and the problem changed. Ahhh Haaaa!!!!!! You said now at mid throttle stumbles and misses. At mid throttle the carb is half on the needle and just coming in to the main jet so there are the two circuits you need to look at.

Pull your carb again and disassemble it again. Pull the main jet and the brass stack it screws in to. Hold the jet up to the light and look if you can see if there's light coming through the main hole of the jet. Inspect the jet stack and ensure all the holes are clear. Shoot carb cleaner through all holes in the carb. Ensure if you shoot carb cleaner in a hole that it comes through somewhere else. Put it all back together.

Set your pilot screw at 2 turns. Under the throttle cable cover, there is a split lever thats hooked to the butterfly. It contacts a tab that moves the slide. With the linkage relaxed, that split lever should just barely touch the tab. The slide and butterfly are supposed to move at the same time. If theres a gap between the two, it causes problems in throttle response. See page 4-15 of the Honda manual for this adjustment.

I hope this helps.

[kb0nly]

Sounds like the CDI isn't advancing the spark so it stumbles, but still could be a carb jet problem, although it sounds like you worked that carb over really good.

[UncleBubbles]

Flyingw- Thank you! That is something I haven't done yet, is set the pilot screw, I was always putting it back in as far is it was the very first time. And yes I understand the two valves need to be timed quite well, which is also something I haven't really touched - ever. I figured if I left them alone they would be alright. Once I finish this shift at work (9 days) I will try those two ideas and report back. If all else fails I guess I will look into the ignition as others have suggested, really hope I don't have to because I know less than nothing about it.

[Flyingw]

I have rebuilt many of the ES/SX carbs and more times than not, I find the tab on the slide bent up. I'm not really sure why this is happening but I bend them back down then reset the split lever.

[UncleBubbles]

Reviving my ol dead thread. I opened my carb up again today, and yes the tab is bent up, BUT there are clear machine marks on it. It looks like it was bent that way for a reason. So I dont really know what to do? My battery died on me and wont take a charge so I havent been able to play with the piolt screw yet, but I will get another battery tomorrow for it and try that.

[Lil Earl]

so its not running right. which means it is running left? right?