carb troubles

I am sure there is info somewhere on this site but after about a full day I still have not found the info I need. I have a 78 kz650 with pods and open pipes. I did weld some washers in the pipes to quite them down and give me a little back pressure. I had it running great with the open pipes but since I have put the washers in I can't get it tunned in so that it will run off choke. I have 102 main jets I think stock were 90 and the other jet is I think 50 but that doesn't seem right after what I have been reading. I would be greatful for any advice to help me getting it back in shape. I don't really want to take the washers out but thought that maybe I needed to open the holes a little more or putting more holes in it. thanks

Lordy... went from running great to not running at all off choke. That makes little sense since the welded in "washers" should have restricted exhaust flow and richened your air:fuel mixture... I think somehow you buggered up your exhaust with the mod. I would start looking for a new exhaust system...

Anyway, to the jetting... the #102 is a bit lean on the top. Suggest you bump to #107.5 or #110. leave the jet needle be. Should be on 3rd slot for your lean 78 carbs. The #50 jet is no mistake. Unscrew them and put them in your pocket... they are restrictors for the pilot jets beneath. Get some #17.5 pilots to replace your #15s. Again, the exhaust mods make it hard to say what is going on now...

What is the purpose of those restrictors if you dont need them? Spare parts?:woohoo:

I emailed jeff at z1 and I am waiting to see if he can get the jets for me. I puled the 50's but I am confussed on that too, what are they for I mean I am sure they did something right? I also wanted to know why when it was running if I gave it any throttle at all it would kind of cough and want to die. I assume the jets are to small for the pods and pipes. I wish I had a good kaw dealer near but I don't even know if there is a good kaw dealer, everyone I have been too in St. Louis, MO. sucks. I am greatful for jeff at z1 he has always been good to me and helped with super fast shipping and great products, so I am hoping he can come through again. I will let you know how this goes thanks b

The restrictor jets? I guess they keep the normal pilots from gobbling up gas... who knows? I can only guess... they were used in 78/79 I think when Kaw was using the LEANEST carbs they could get away with and have the bike still run... suspect it has something to do with making them lean. They really serve little purpose. Take them out and after installing the larger pilots, see how it runs. If you want to put them back in, its your bike... the bike will run OK (with the larger pilots which actually are the mechanism the bike uses to meter gas at idle and just off idle.)

Thanks for your advice. I ordered some jets from z1e today. I can't wait to get them, and see how they do. thanks again and I will reply back to let you know how they work. b

Billy, You hit on a point that was discussed elsewhere... lots of questions, lots of advice and then the person goes off and does "whatever". You hardly ever hear back on how good the tips were. It is important to close up a thread by providing feedback on how the tips worked... If someone comes upon this thread in search a year from now, his most important question will be "HOW DID WHATEVER BILLY DID WORK?"... hope you come back and let us know for that reason... too many unresolved and open threads... (off soapbox!)

I have run across many threads like that. I will let you know what happens and thanks again for you advise I have noticed from my searches that you always help us out when we need it. I will be back I love this site. billy

YOU ARE MY HERO!! really it runs really good, better than ever. I ordered the jets from z1 on monday morning and they got here to st. louis this morning wed. I think he heard me wrong cause I asked for the 17.5 piolets and 105, and 110 main jets. I got the 17.5's and the 110's but then I got the 115's instead of the 105's but the 110's worked like a charm so no worries now I have the 115's for later or another app. so no big deal. I really want to thank you for your help you are awesome. billy

I did end up putting the 50's back in place too.

Post edited by: KZbilly, at: 2007/06/27 21:54

Main jets, when just a tad large, make no great difference in performance. When they are way too large, it is hard to feel the difference from when the bike is running lean on top. The #110 mains should be fine... try and pull redline and if it pulls up to redline cleanly, you are good. It would have done it with the #105s probably as well. I think if you put the #115s in, at about 6 to 7K rpm, the bike would start to feel like it was running out of gas... it would likely be too rich and is actually running out of air. You can also try leaving out the #50 barrels over the pilots and see what difference it makes. I think you would be surprised to find it makes no difference at all.

The redline is good, like I said she runs great now. I wish I would have asked for help earlier but it is hard to admit defeat and ask for help sometimes. Thanks again I hope this thread can help someone else in the future. thanks again for your help. billy

I read that bike was running fine with open exhaust and the smaller mains. When restriction added to exhaust it required larger jets...

what gives here WG?