Carb settings etc.

[johnD]

OK. Started to look her over.
More in hope than..... Charged battery, removed and inspected plugs, a bit dirty but.... Gave it some fuel via a slave tank, churned away, got a backfire.
Took plugs out sonic cleaned them within an inch of their lives, ordered some new off the Wemoto, replaced them.
Gave the airbox a good warming with the heat gun, pulled choke on, pressed starter and she limped into life.... very ragged, as if misfiring but revved up quite cleanly.
Left it at about 3000 rpm on the throttle adjuster for a short while to warm up / clean up...
Started gasping as the rich fuel black smoke filled the garage.
Checked the mixture screws.... All about 3 -4 turns out. Guessing, but set them at 1 1/2 out.
Started up OK, still very ragged below 3000 rpm, but no black fumes.
Inspected plugs, very sooty.
It also seems to consume fuel at a heck of a rate!
Guessing its carbs out and see what indignaties have been done.
Am I right in the mixture screw settings? I'm guessing the floats are incorrect or the wrong jets. Anyone have those settings to pass on.
Cheers.

[johnD]

Woah!!! Just doing some read ups and it would appear the pilot jets should have a plastic plug over them.... No plugs anywhere on my carbs.
Any photos of the item in question and its position please.....

[Uncle Bob]

Sure there isn't, never had any on my 250 or 400. Just looking at the parts list and nothing shown there (Item 26 pilot jet and 29 main jet).

carb.JPG (25.12 KiB) Viewed 2330 times

I would strongly recommend you get Service Kit A and Service Kit B from https://litetek.co/Carb_Kit_Suzuki_GSX400_Katana.html The O rings are the main issue and these are the correct size and Viton. I think all of us on here have bought those for our 400's and also the 250 kits as well for those that have them.

I would possibly look at replacing the fuel tap rubber bits as well for the cost
https://nrp-carbs.co.uk/shop/index.php? ... =gsx400ssn

UB

[fossie]

The plastic blanking caps in the carbs are the earlier Kat carbs ...( not water cooled) .
The water cooled ones are a cage system with the float hanging a a thin bit of wire which is easily bent.

The mixture screw is 1.75 t/o ...1 & three quarter turns out...you are correct.....but if they were 3 to 4 out ..yep someone with errrrr limited knowledge has been in . So yep rip of off and strip , ultra sonic reassemble with new o rings . Get a copy of the bible , Koran, chrisna, Buddha , and of course Shinto . Put then back on & don't press the starter button ... As you still have hope !

[Smallkat]

Is it N588 HFS?

[Smallkat]

Woah!!! Just doing some read ups and it would appear the pilot jets should have a plastic plug over them.... No plugs anywhere on my carbs.
Any photos of the item in question and its position please.....

No plastic plug on either the 250 I had or the current 400. I would guess the pilots are set so badly to compensate for some other problem in the carb. Check they are in good condition.

As previously mentioned, take the carbs all apart, do a massive long clean of all parts in an ultrasonic bath, re-assemble with Litetek O rings. That's a start. To your problems

[johnD]

Hi all, thanks for the replies.
So.... No pilot jet plugs on these, damn, thought I'd nailed it.
Yes, had a good peer inside the galleries and there is no connecting port between main and pilot jet housing....
Bit of background. it's a 10,000 Km miler, very clean, so no reason to doubt. The PO could never get it to run properly, laterly, it wouldn't start at all. He had the carbs sonic cleaned and rebuilt, which I can confirm. All new o rings and gaskets.
He replaced the battery and, the starter motor..... probably because of all the churning trying to start it.
Once I reset the pilot airscrews, it will start quite easily. I have found that it needs full choke, but no throttle, maybe he was flooding it when starting?
Choke plungers are returning home fully, but I will strip and inspect, but have no reason to suspect.
Once warm, it will rev very cleanly from 3,000 up, but is very grumpy below, almost as if its misfiring.
The ignitor is a Chinese aftermarket item, with the side mounting lugs. It seems to be working fine.
I am convinced it is a prolem with the pilot jet area. On inspection, I can find no markings on the pilots, but all look the same and do not appear to be aftermarket.
Main jets are 85.

That's where I'm at. Keep the info flowing gents and thank you!

[Smallkat]

So it's Bill's (William.sn032 on here) bike!

I don't think the Igniter is the correct one. It shouldn't have side lugs.

85 is the correct main jet size.

Are the carb rubbers in good condition?

[johnD]

Hi Smallcat.
Yes, this is Bill's..... Sounds like it has history?
So.... This is in excellent condition, all my usual suspects check out good to perfect, carb rubbers, fuel flow, float height, diaphrams, airfilter, airbox rubbers, airbox sealing etc.
The ignitor is the one commonly offered and seems to have good reports.... but.....
I am waiting on a set of new plugs, just to eliminate.
Whilst the carbs are out, I need to eliminate anything that might have ben inadvertantly done. But I can't see anything untoward. As a last resort, I might try changing for smaller pilot jets....? If I had any idea of the pilots sizes.
I'm just sitting and ruminating over a cuppa, might put it all back together and try again.
One thing has occured. I didn't check the alternator reg/rec performance. I might, just, have an electrical problem.... Just a clutching at straws thought.

[Smallkat]

Yes, Bill has been on here for advice. You can see it all on another thread. I tried to buy it and although we agreed a price, we couldn't agree a payment/delivery solution.

Pilot air jets should be 32.5. Although I can see why you want to weaken the initial fuel flow, it should work with stock jets. Maybe it would be easier to progressively wind in the pilot air screws to achieve the same effect? And then you don't have to keep getting the carbs on and off. And god knows, that's a struggle we can all do without.