Honda 250sx still bogging

[mmiguy2103]

Ok guys another notorious 250sx carb issue here. So i have a 87 250sx that i have completely rebuilt, I am talking everything was dissembled and cleaned or replaced. all new bearing through out the entire machine. Started right up with the carburetor that i had cleaned with a 48 hour soak in a ultrasonic cleaner all new jets. cleaned every orifice and blew it out etc. So it idled great.. but if i gave the throttle a bump at all or a full throttle shot it would bog and die. If i kept the choke on it would idle high and would rev up way better when slamming on the gas. so i cleaned the carburetor again with another 48 hour ultra sonic soak and manual cleaning of the entire thing.. again new jets were installed. Installed this again and still the same issue.

So upon great reviews i decided to send my carburetor out to Flyinfw as he seemed to know a lot about these carbs. my experience with him was great I got my Carburetor back and installed it. it seemed to run better.. but i wasn't able to get out and ride. I am finally getting more time now to ride and started her up.. she started up great and idled perfect.. but now the bog is back 100% it almost cuts out whenever i press the throttle..again if i pull the choke and have it idle higher with the choke it seems to want to rev up way better when smashing the throttle. its to the point where its completely not rid able. its either idling or full throttle after 10 seconds of slowly easing the throttle .

So what gives? what am i doing wrong here.. would a faulty CDI cause this ? i have checked spark, and its great and powerful when cranking. coils tests perfect.

i know ALOT of 250sx and big reds seem to always run like crap. I owned one brand new back in 86 and i remember it running amazing with absolutely no bog whatsoever.

So any input is welcomed


Chris

[Baba Yaga]

Pilot jet/circuit, or the carb was not reassembled correctly.

[mmiguy2103]

Pilot jet/circuit, or the carb was not reassembled correctly.

I am 100% sure the pilot circuit has been assembled correctly and is fully clean and clear. everything is to Honda specs as far as jets go and adjustments

[mmiguy2103]

Tomorrow i will upload a video to help show my problems i am having

[ps2fixer]

Maybe adjust the needle clip location down a slot and see if it's better or worse. One tuning doesn't work for all locations and elevations, sounds to me the main/needle is too lean. Also doesn't hurt to do a plug check, white powder is lean, black is rich, light brown is normal. The choke testing supports the idea that the main is too lean (or possible plugged/restricted, but I'm sure FlyingW checked it out well).

Also, an intake leak could cause issues too, is your carb boot good, good O-ring etc? Is the compression up to par?

I have an 85 250es, ugliest machine I have, but it always starts first kick, revs out great, it's not inherently a 250es/sx problem. I've heard the 85's were "hard starting", either this one has a later carb, or the jetting has been adjusted for easier starting. It's been sitting for a bit so I get to check what's in it pretty soon, hopefully jets were replaced, not drilled out.

[MrConcdid]

Is your choke hooked up, My 250sx is cold natured, while cold you can't rev it. once warm its perfect.
Does your choke hang up?
MrC.

[350for350]

I am 100% sure the pilot circuit has been assembled correctly and is fully clean and clear. everything is to Honda specs as far as jets go and adjustments

Yes, but you said that it seemed to run better (after Flying W did his thing) and then you couldn't get out and ride it. How long did it sit? It's possible that the pilot jet is partially or fully plugged up.

[shortline10]

Make sure your choke assembly is installed correctly , seating all the way down , if not it will have your symptoms .
As far as I know Jim test all his carburetor rebuilds on a running test motor before he ships them out .

Also 2 or 3+ month old corn fuel will have your symptoms . Try fresh fuel .

[mmiguy2103]

Thanks everyone for the ideas.

So the fuel is Fresh non ethanol fuel. I didn't store it with fuel in either the tank of the carb.

I did make sure it was warmed up.. I always remembered how cold blooded these guys were lol it ran for about 15 min idling with a box fan on it then i tried to take it around the block a few times.. sputtering.


I am very confident that there is no obstruction in the carb as both me and flying did our thing.. and he said he had it fully running great on his test bench engine.. so that leads me to confirm that.

I am leaning towards the choke maybe.. it is a new choke rebuild kit. it does feel like it is fully seated as far as i can tell.

I think i will get to my shop today to take a quick video to help show you guys what its exactly doing. of course carb issues are hard to explain in a written way.

also does anyone think a bad CDI or partly failing CDI would produce this issue?

[shortline10]

I have seen plenty of bad CDI boxes were the motor would not rev up , only idle but not on this model .
Try wiggling the ignition switch with the key back and forth while it’s acting up , could be a poor connection their , same with the handle bar switch .

[ps2fixer]

FYI, the kill switch and ignition switch should have NO CONNECTION for the ignition system on those machines. Completely disconnect the wiring if those parts are suspected. On a DC based CDI that can be an issue because the power supply comes through the switches, but on an AC CDI system the kill wire is shorted to ground to kill the engine. All Honda 3 wheelers have AC based CDI's or are points engines (effectively the same thing, just uses a mechanical switch instead of an electric one).

The lighting system has nothing to do with the ignition for AC CDI systems, can completely disconnect the lighting wires and have no effect on ignition. Some DC systems uses the AC power from the stator's lighting coils to detect the engine running/spinning like on a TRX300/FW.

[mmiguy2103]

ok guys i was able to get to my shop today and get the 250sx all warmed up and take a video of whats going on.. now i also want to state that when i am actually driving this guy around the symptoms seem to get worse.. hard to tell

here is a link to my you tube video of it .

https://youtu.be/rs5bcB5vbYk

[MrConcdid]

That hanging Idle may be the culprit, I think its going lean and diying.
Check the float height and the choke circuit.
P.S. Beautiful SX

MrC.

[ps2fixer]

That machine really did turn out nice, best 200x front end conversion I've seen, it actually looks natural on the machine. I might have to copy the parts list you use =).

The hanging idle is defo something to check into, I have a 250es that does that, and it's also lean on the high end, does the same thing, floor it fast and it dies. I haven't messed with it though, pretty sure in my case it's the needle jet adjustment but haven't done it to solve that exact problem.

All of my 3 wheelers if you really stab the gas, they all stumble. None of them have an accelerator pump which off sets that issue. For the 350x, the 400ex carb is known as an upgrade, but the biggest reason people go for it is the accelerator pump feature. Basically if you stab it too fast, it doesn't have enough vacuum to pull fuel from the carb and it goes lean for a bit then ramps up once the fuel gets to the engine. Your machine seems to run about the same as my best runners, but it's hard to judge how fast you're hitting the throttle.

If the stabbing the gas and not having it stumble is what it should do, I'd like to see a video of a Honda 3 wheeler showing that off with out a carb swap. I don't think any honda 3 wheeler had an accelerator pump.

Anyway, seems to me your carb is dialed in pretty close. I'd check the throttle cable routing and make sure it's returning freely (good spring etc). That hanging isn't normal for sure but I can't think off the top of my head what causes that besides the cable holding it open.

[yaegerb]

I would try the following.
1. Check fuel flows freely into carb
2. Ensure nothing is clogging the air filter or pathway
3. Ensure your muffler isn’t clogged somewhere
4. Try revving with fuel cap removed. Your vent may not be working.

Let us know if those have all been checked.