Honda 250sx still bogging

[ps2fixer]

I suspect a 400ex carb could be used on a 250es/sx then.

I should start a build thread (a very slow one). Going to attempt a 350d engine swap into a 250sx frame with some mods. Should be a fun build and the 350D uses a QA series carb too, so probably switch to the QB series like the 400ex carb.

[yaegerb]

Here's my second YouTube video upload of how I raise the lid. https://www.youtube.com/watch?v=Z7IMxK5F87E

That whole setup is so cool

[ATC King]

Flyingw, it'll be interesting to see what you find out.


There's always a chance for something out of left field.

[Flyingw]

Ya King, I'm curious too. I have changed every part in a few carbs and the problem went unchanged so it left me scratching my head. I will certainly post up the results.

[MrConcdid]

Yes, I think we all stand to learn something.
MrC.

[MrConcdid]

Any Updates?
MrC.

[Flyingw]

I got the carb back from MMIGUY but haven't had to look at it but I will this weekend. My plan is to run it then seal up all the seal balls (Brass BBs) with a two part epoxy then run it again to see if there is any difference. I'll report my results sometime this weekend.

[MrConcdid]

I have one, that I have gone through many times, I am ashamed to say, it just wont act right, each time I try it on different bikes, I end up taking it back off, putting a different one on, and they run great. I think there is a casting that fails with age or heat cycles, that cause a lean issue, but that just a guess.
I hope you find the issue.

MrC.

[Baba Yaga]

I am sending MMIGUY a Chinese carb I bought years ago that runs great. This carb is an 86/87 clone and when I got it, there were a few minor discrepancies but its always ran good. I asked Chris if he would send back his carb and I am going to explore the sealing ball suggestion made by ATC King to see if it makes any difference. That's one thing I never thought of. Over the years people have asked a lot of questions about my test stand so here is my very first You Tube upload of the test of the Chinese carb for you motor heads. This test stand has been an invaluable tool for me over the years. https://www.youtube.com/watch?v=YGnuNSzyfr4

That initial bog when snapping the throttle, is like pretty much every ATC I've seen.

[mmiguy2103]

Hey everyone havent been able to get on here in a bit .. a update from my end.
I got the chinese clone carb from Flying and swapped it out.. this is a night an day difference. from a dead idle i can completely go full throttle instantly and there is almost no bog. the bike also does not die like it was doing with the stock carb ever. I went out and ran the hell out of it for about 3 hours.. and never had one bog or issue with it.

So i am curious what you will find flying. I had multiple times sprayed cleaner around the carb while running to check for and change in idle for air leaks.

[mmiguy2103]

see I have a completely different view.. I have owned 12 different honda atcs. some brand new from the factory back in the 80's and some used. i never had a bog like that. maybe one out of every 100 times you chopped full throttle. but now that i see a huge diffence in swapping out my stock carb to the chinese clone and its running perfect i am curious what flying finds

[Baba Yaga]

Glad it's working better. Even in the YouTube video on his running setup, you can see the hesitation when the throttle is ed, which is normal. Of course, if it's much worse than that, it needs attention.

[Flyingw]

I had a busy weekend rebuilding six carbs. I had two 85 SX carbs, one 86/87 SX carb, and three 85 350X carbs and every single one of them had the same stall on throttle stab off idle. Every one of them. Unfortunately I did not have time this past weekend to work on MMIguy's carb but I will get the brass balls sealed up this week sometime. More to follow.

[Flyingw]

UPDATE: I sealed off each sealing ball with some two part epoxy and ran it. No change to the stalling problem. I was really hoping the carb would have improved but as I said, no change so back to the drawing board.

[ps2fixer]

Maybe it's a small air leak in another area, like the shift the butterfly is on or the plunger for the main jet? Just random ideas to give a shot. Erosion could be a possible thing on the machined passages in the carb, I would think if that was the case it would be too rich if anything. There has to be something to put the blame on.