HELP; 1980 XS250 air box to pod conversion

[jamesmoni]

[Aware this is a XS400 website, however 250 is similar in minor way and has no website]
[New development on the end!!!!!]
Symptoms
1. Only starts with choke on, even when its a warm day. (Pretty normal)
2. Can rev the engine with throttle with choke on
3. If I continusly rev the engine and turn choke off at same time continues to rev
4. Engine will die if I dont consistently apply revvs with choke off.

Videos;
Shows idle and revving with choke on/off

If you go to my youtube channel you can see more videos I took.

Ive taken my carbs apart entirely including the choke etc etc gave it a super good throttle body spray clean and compressed air charge.
Ive done things like restrict my pods with washer inserts and sponges etc.

Ive rejetted pilot/main from 20/117.5 to 30/130

NEW DEVELOPMENT!
Set my needle to richest position, started bike with choke off (was warmish) pulling the throttle revved the engine. FINALLY!! Before this just made it cut off. Now it goes into high idle so need to step down the needle one notch etc.
I think Im getting somewhere.

 

[member11511]

I had the same problem with my xs400. While searching i found another xs help site that talked about cutting the air pod in half. Basically these bikes are really hard to tune in with air pods. So when this user cut the pods in half, only half the amount of air came in, thus giving him the correct mixture. I'll post the link if I can find it.

 

[jamesmoni]

new development today. I put the needle in the most rich setting. Now my bike starts off and can rev well off choke but goes into high idle eventually.
Will try 1 step down and one more step down tomorrow

 

[xschris]

Those are the worst type of "pods" to use. Either use the stock setup or get a set of uni's. Real K&N filters are ok too. Also you can use the stock H-pipe with pods on the ends. There are many threads on these subjects in the forum. You will still need to jet and or adjust the carbs with what ever you do. Remember to sync them with a manometer. Also a non-stock exhaust will cause issue.

 

[jamesmoni]

Those are the worst type of "pods" to use. Either use the stock setup or get a set of uni's. Real K&N filters are ok too. Also you can use the stock H-pipe with pods on the ends. There are many threads on these subjects in the forum. You will still need to jet and or adjust the carbs with what ever you do. Remember to sync them with a manometer. Also a non-stock exhaust will cause issue.

Thanks buddy. Im using the stock h-pipe which is great as it doesnt block any of the holes with my pods.
I have no idea if my exhaust is stock.... but its super shiny so probably not stock

 

[xschris]

I would remove all the stuff from the filters because that won't help. Check the plugs and see what they look like. Also make sure the floats are set to spec and all the o-ring and diaphragms and in good shape. Also if your bike is a points model bike make sure all of those things are adjusted well. Lots of other things can cause you issues.

 

[jamesmoni]

If I just chucked my CV carbs in the bin and bought a flat slide carb would that just make everything work? I assume yes!

 

[16VGTIDave]

If you keep on assuming, I'm fairly certain that you will find someone close to you, with a trailer, who would be willing to buy your non-running bike (for next to nothing) once you give up in frustration. Or you can clean and adjust your carbs properly, replace the crap pod filters, and have a nice bike to ride once you get it back together. There are many threads here about similar issues, feel free to read them while you have your carbs soaking.

And no, your exhaust does not appear to be stock.

 

[BBS360]

If I just chucked my CV carbs in the bin and bought a flat slide carb would that just make everything work? I assume yes!

At least with the stock carbs you have a good starting point to go up or down from, you also have all the past inquiries on the subject on this forum, other forums, service manuals, and people knowledgeable about the stock carbs.
By switching to some random carb you still have to figure out the correct jetting, but now you don't know have a good starting point or any else's experience to draw from.
Figuring out how to even choose the correct size carb would be a challenge.

It's certainly possible to use other carbs but you're looking at more work, not less, and with no way to know that it'll ever work well.

 

[jamesmoni]

I have a contact who converted his cv carbs to round slide carbs with all the necessary jetting information for the same bike. And it works perfectly apparently for 600km and still going.
I find my carb cylinder isn't responding well with any range of pods, and Ive tried several peoples different ones on their working bikes.

I assume the change will work... because well.. it worked undoubtedly on the same bike with similar modifications.

 

[16VGTIDave]

600km is barely a proof of concept. 6,000km trouble free and they might be onto something. 60,000km and no complaints, now they are onto something!

I'd suggest you stop looking for modifications to fix what (to me) sounds like dirty carbs. Clean the carbs. Then clean them again. And when you think they can't get any cleaner, do them again. No, I'm not kidding. I just did the carbs on another bike that had sat for 10 years. It took 3 extensive trips through my ultrasonic cleaner with a citric acid solution to get them functional. They looked fine after the first cleaning, but passages were plugged internally.

 

[jamesmoni]

Not sure if cleaning the carbs would do anything at all, but I have cleaned each jet and checked to see light on the other side.. Perhaps my diaphragm bunny ear being bent is causing a problem with the vacuum.
Still need to investigate my exhaust system. 0 back pressure.. not sure if legal.
I honestly don't like soft flaccid moving parts and would prefer the concept of the flat/round slides.

 

[16VGTIDave]

Not sure if cleaning the carbs would do anything at all, but I have cleaned each jet and checked to see light on the other side.. Perhaps my diaphragm bunny ear being bent is causing a problem with the vacuum.
Still need to investigate my exhaust system. 0 back pressure.. not sure if legal.
I honestly don't like soft flaccid moving parts and would prefer the concept of the flat/round slides.

Yeah. I stopped reading half way through the first sentence. Typical answer from those who don't know. Dirty carbs are so common that we had T-Shirts made a few years ago. I'm not going to waste any more of my time with this.

Have you ever heard the saying "You can lead a horse to water, but you can't make it drink."?
You are the horse.

 

[NewHavenMike]

I went through a lot of frustration getting my engine to run after a complete rebuild, specifically with the carbs..
I cleaned them and again and again to get nothing.

I bought rebuild kits that included new float needles and seats. This was very important, the springs that are in the needles were worn out. The float tang would sit on the needle pin and compress the spring.. The tang should stop on the pin without compressing the spring.. I did not know this until I bought one rebuild kit because one of my carbs was missing a jet, Then I had to buy the other to have matching jets

Then I was able to set my float height properly to factory specs. Then I was able to bench sync the carbs...

After that, I was also suspecting timing problems, I adjusted the points and set the timing by static method...

Bike fired up and was ready to go...

Youll just build more frustration when you throw all random aftermarket crap and "solutions" at it... Get the carbs back to stock settings and get it running the right way first, then start your tweaking... I bet youll just be happy with the way it runs and you wont want to touch it...

This isnt a modern computerized vehicle were you can practically do whatever you want to it and it will still run fine... These engines are 100% mechanical where ONE spec of dirt can greatly alter performance.