Tuning pilot screws

Thanks JR, very helpful as I was expecting significant changes in the height of the pilot screws. Knowing that it's subtle will make sorting this out easier.

Nessim, I agree that the OEM kits are better, and I would have gone with them knowing what I know now. The kit I bought is japanese made and pretty good, but there are some small changes. The main nozzle was slightly too big to fit - the old ones were tight but moved with a small amount of weight, these would have required press-fitting. And the pilot screws are tighter too, but not overly so. The main reason I replaced instead of reusing is that the needle jet holder was pretty caked with brown gunk - probably rust from the tank - and while it was easily removed with a light scrub, a clean in the ultrasonic cleaner didn't completely remove the gunk from the tiny holes, I was worried that they might not be clean enough on the inside. I replaced the pilot screws because the old ones were pretty bad, and one completely destroyed.

With the bowls having been removed once it probably won't hurt to take them off again with the carbs in situ, and try with the old jets again.

Pics of the plugs?
Steve

When I get home (I'm in Australia, it's before lunch here) I'll check the plugs, and if that's all good I'll do a spray-down test on the carbs, and then maybe I'll take the bowls off and switch back to the old jets.

I do have a colourtune somewhere that I used to use on my mini, that will probably be useful if the threads are the right size.

Pics of the plugs can help us help you.
Steve

I changed the jets back to the keihin ones that were in there. I made a solution out of carb cleaner and degreaser and put them all in the ultrasonic cleaner. The carb cleaner usually don't dissolve with water, so that combined with the degreaser seemed to work well to clean them up.

Changed them all out, and it ran exactly the same as before. I then checked the plugs:





They look a bit uneven, but really they all have black soot that has started to burn off. Since I turned the pilots really far out and then back in again, I'm not really surprised, since that would have meant it was running really rich for a while, then I backed the screws back. One of them has obvious corrosion - probably running quite lean before the carbs were cleaned.

I also took this video to show the problem I have:



After the video I took out the spark plugs to check them again. They looked much the same. But when I put them back in the bike ran awful. I didn't do anything apart from taking the plugs out and putting them back in again. I think I might buy some new plugs to rule that out, they're pretty old. And I need to find my colourtune, it should help me get the right mixture at least at idle.

But everything to me still says air leak - but I can't find anything. I tried spraying around the butterfly shafts and everywhere else for good measure, no change.

The idle is hanging a little which means some air leakage. Most likely at the carb boots. I always change the boots at the head as a mater of course since even if they aren't leaking they always seem to be hard and aged. The airbox boots are subject to less heat so reusing those is typically less problematic. They do need to be full sealed to the carbs and airbox (no gaps).

You didn't answer the question about removing the bleed pipes and pilot jets and making sure they are properly open. The orifice is very small on these and subject to clogging.

I agree that the idle is hanging a little - and that's why I think it's an air leak. But I simply can't find the source. I doubt it's the boots, they're less than a year old and pliable, and I've disconnected and reconnected them to make sure and tried all sorts of things to 'seal' them. In my experience they're usually the culprit.. The airbox boots are a little harder, but no cracking or damage, and I wouldn't expect those to cause this issue anyway.

I'm not sure what part you mean by 'bleed pipes'. The pilot jets and the passages they were in were cleaned pretty thoroughly , and I did switch back to the old pilots to make sure it wasn't those that were the issue.

A carb vaccum sync/check would be necessary after a carb rebuild.

I do have a carb sync tool that I loaned to my cousin, so I'll get that back from him. I'm hoping I can use it to help track any air leaks too - if one or more carbs loses its vacuum after revving that would indicate that it's leaking.

Irish Yobbo wrote: I'm not sure what part you mean by 'bleed pipes'. The pilot jets and the passages they were in were cleaned pretty thoroughly , and I did switch back to the old pilots to make sure it wasn't those that were the issue.

Searched and found this thread for you about bleed pipes... www.kzrider.com/forum/3-carburetor/608501-rebuild

BTW, I put the phrase below into google in order to search the site. It works much better than using the forums search function

site:kzrider.com bleed pipe

Thanks Nessism. The 'bleed pipes' are what I've referred to as the 'main nozzle' at the start of the thread - I thought it was a strange name for something that goes under the primary jet, but that's what it was referred to as on partzilla.

I did make sure that they, the pilot jets, and the passages were very clean. The old bleed nozzles were snug and took a bit of pressure to remove, but I didn't install the new ones as they would have been press-fit, and I was worried about damaging them on install. So I made sure the old ones were very clean, and re-installed them.

All I can suggest at this point is doing all the basic checks like checking fuel level in the carbs with the clear tube test and doing a vacuum sync. Another thing is to start the bike from cold and then carefully touch the exhaust headers before they get to hot to verify each cylinder is firing properly. I'd also set the pilot screws to 2.5 turns open from lightly seated. That's a good all around setting. Once the bike is warm tweak the screws until the highest idle speed is achieved. If turning the screws doesn't seem to affect much, don't worry. Just set them at 2.5 turns open and leave them there.