86 Tri-Z carb tuning

[keith-z250]

Can someone throw some suggestions at me about tuning my carb? Mine is an 86 Z with a stock 320 main jet. I have installed full DG exhaust, uni air filter, boyesen reeds, .20 bore, and weisco pro-lite piston. Well I jetted from stock 320 all the way to 400. I got the clip all the way to the bottom of the needle but I am going to bump it back up one to the recommended setting. I run my bike for about 20 seconds and open it up in 6th gear. I take the plug out and it is just a dirty white with a light brown tint. But it isn't brown like a paper bag. I am running a B8ES plug and my engine gets hot and drinks coolant fast. Also, should I adjust the screw w/ a nut(pilot screw???) on the carb that is on the opposite side of the idle screw? I know I will have to jet higher but didn't know this high. But from 320, 350, 380, 400, it is starting to brown better. Could there be something else wrong or should I just keep messing with the jetting?


I almost forgot to say, that it does sputter when I opened it up in 5th and 6th gear like it was wanting more fuel or power. Other than that, the power is great till it is opened up 3/4 throttle and past that in 5th and 6th gear. Any help would be appreciated.

[twgranger]

mine use to spit and sputter because the main jet was to big. If it starts poping then it's to lean. Mine is and 85 so the setting are way diffrent from 86.

[keith-z250]

But should I just go by the plug and go for a bigger jet?

[twgranger]

But should I just go by the plug and go for a bigger jet?

It sounds like to me your main jet is to big. I did the same mods to mine and went up 1 size in the main jet and left everything else stock and works great. I would wait for some more replies and see what other people say first. Just make shure your plug is not dead white then you are lean. For your coolant going somewere did you ckeck your oil to see if it white?

[keith-z250]

Copy and paste this link to check out my spark plug. Quality isn't best but shows my plug after a 20 second test run with a wide open pull on 6th gear and killin it with the 400 main jet. http://www.fidnet.com/~sideshow/images/plug.jpg

[keith-z250]

Looks tan more than anything like skin color. I am lost and don't want to keep jetting to high. The oil is brown and only about 1 week old with a few plug checks on it. I just checked it again like 30 minutes ago when looking a the carb and still brown oil

[twgranger]

Copy and paste this link to check out my spark plug. Quality isn't best but shows my plug after a 20 second test run with a wide open pull on 6th gear and killin it with the 400 main jet. http://www.fidnet.com/~sideshow/images/plug.jpg

Did you warm the bike up to normal temp before testing? Warm it up with an old plug and then test with a new one.

[keith-z250]

Maybe that is where my mistakes are. I just thought you were only suppose to let the trike run no more than 30 seconds when doin a plug check? I only let it sit for like 10-15 seconds then take off when doin the plug check. That is why I was confused when reading the plug checks since your always suppose to let a 2-stroke warm up before hitting the . That is prolly why it is sputtering at me right now, could be cold engine since the temp. in Missouri has dropped crazy in the past few days.

[twgranger]

ride around for alittle to warm up the engine with a old plug and then put in a new plug and then do a ckeck.

[keith-z250]

Did what you said, it is tan like the picture above.

This is confusing me, since I have never had a problem rejetting a 2-stroke. ANd about the coolant, When I was riding around warming it up. I seen it coming out of the coolant bottle through the overflow hose that drops down by the swingarm. I guess I had to much in there but I always kept it half full.

[Derrick Adams]

I'm sure TimSr. will jump in on this thread as well, but IMO you should not be jetting much at all with those mods. You need to let the bike warm up at least a few minutes before running it out, especially with the weather changing.

My 85 has the exact same mods done to it, with no jetting changes at all. It was brought to my attention that most 2 strokes are a tad rich to begin with, which gives you some margin. So far the only thing i've done is drop the needle to lean out the mix part throttle and leaned out the idle mixture. Never did any jetting changes.

I would recommend that you put it all back to stock settings and start over. Make sure that you warm it up enough that the radiators are warming. Then start your testing.

If it feels like its bogging down at low rpm's, lower your needle in the seat to lean it out, if it is real poppy down low, raise the needle. Also keep an eye on your exhaust, if it's smoking excessively at idle or part throttle AFTER it's warmed up, that's a general indication it's rich. (or needs rebuilt lol). When your riding the bike full throttle you should be able to feel if the bike starts laying over, way up in the normal rpm range, if it's lean. But checking your plug is a always a better option.

If the top end is fresh, it wouldn't hurt to leave a little bigger main jet in it, until it's broken in.

One last thing, If your getting water in your oil, which it sounds like you are, check your water pump seal to the crank case. This is the seal located right behind the shaft, inside your water pump housing. They are known for going bad and share the same seal as the Banshee. Also inspect your water pump shaft for wear. These seals are real easy to change.


Hope this helps you. Let us know how it runs.

[keith-z250]

Thanks guys. I will try that out what you said Derrick. It does smoke when it first starts up for a few seconds but then lets out enough to smell but nothin to leave a trail behind me. It doesn't bog down at all that I can tell, but sounds like it is coughing when the powerband is opening up in 5th and 6th, but it still opens up fast with no problems. I have a used DG silencer that probably needs repacked, from what I am guessing.

Also when I reset the needle from 2nd to the bottom(stock is middle right?) to get it alittle richer, I see when screwing them 2 small screws in, there is a 3rd hole that nothing goes in, should that plate(2 small screws hold it to secure needle) cover the hole or should I turn it 180 degree to let it stay open?

I will probably go to the local dealer and order the water pump seal for a Banshee but for what years? Any year?

Thanks for all the help and keep the suggestions coming because I am stumped. I got this bike for free and it wasn't running at all. So I know there is small things that need replaced that I must be looking over.

[keith-z250]

Ok, I messed with the air screw while having the 400 main jet in there and actually closed it all the way and opened it up 1 and 1/2 turns and now I got dark spots on the porcelain(sp?) part where it should be brown. This is on a new plug. I guess I do have it jetted to high maybe?? I am going back to the 380 main jet and check it out.

Also, on the right side of my Z, on the cylinder, there is a hose attached with a L shaped piece attached to it. It comes from the Mikuni fuel petcock where you turn the fuel on. I don't know what this does and it keeps popping out when hitting the throttle and revving my engine hard on its own till i can hurry up and put it back in. Does this adjust the air/fuel that goes into my cylinder? Well I just want to know of a way to keep it in.

[Derrick Adams]

That is a vacuum line that runs your fuel pump. You need to secure that in some way. That is VERY important. I need to check something, I'll get back to you in just one minute.

[keith-z250]

Yeah, I just went out and put the 380 jet in it and going to try that one after I find out how to secure that vaccum line. Should I keep the needle 2nd from bottom or in the middle for stock? I was thinking 2nd from bottom to make up for the aftermarket parts.

Anyone know of anything about that plate that sits over the needle? Should it block that third hole because the other 2 holes have screws in them(This is when your taking the carb apart to reset the needle).