Wide Open

I just rebuilt my bike an 1978 kz1000 rings,hone,valve job,new cam chain. It has an 4into 1 exhaust kn air pods. The problem I'm haveing is banging bad when running through the gears 1st and second is as much as I went it was so bad. It has 107.5 mains and 17.5 secondary jets. It ran good before the rebuild with this set up. Any suggestions? Oh yes this is a great site

Clarify please. Banging = popping? lurching? mechanical knocking? backfiring? etc. etc.

The likely cause of the banging (backfiring?) is the intake manifolds which came off while the top end was being rebuilt. If you didn't replace them, it is time to do so probably. A leaky intake manifold can surely hole a piston... other potential backfire causes are leaking vacuum plugs on your intake manifolds and bad copper exhaust gaskets. I hope you didn't reuse your old ones!

I guess banging would tranlate missing. Not backfireing.I put some octane boost in the gas and it helped some. I did use new brass gaskests on head but it could be the manfold and or the plugs on the vacum ports. I think I'll replace them first. Then I'll post the results.
Thank you

Ron, Please describe your ignition system as well... Don't want to leave any stone unturned!

I put an Dyna-1 on it just before the rebuild.What brought all this about was an pluged jet in no.1 carb. Because of that I found a worn timing chain and leaky valves.Since I had it so far down I did the rings too.

Gonna assume you adjusted the valve clearance... I would recheck since the bike likely hasn't been run in yet. How did you set the timing on the Dyna S? Did you replace wires, caps or coils? Did you measure voltage going TO your coils?

Yep I set the valves when I put it togeather. Rode it for about 500 mi. and rechecked them. I have about 1000 mi on it since the rebuild. It has new dyna coils wires and the ignition. I set it with a timing light it starts fine idles good. I checked the float levels and 2 were a little low and 1 was too high. I adjusted them and put new caps on the vacum ports. Took it out and ran sweet. I still need to sync the carbs though,but don't have an vacum gage set to do it with yet. Also do you know where I can get new intake manifolds? I have 1 new one on it and 3 cracked ones. I bought the bike on ebay 2yrs ago.

Ron,

Before you spend money on vacuum gauges, you might consider checking out my writeup on making a low-cost differential manometer (vacuum gauge). You can use a $3 section of tubing, some transmission fluid, tape, and a stick to build an assembly that will help you to synchronize two carbs. You synch two at a time, for instance 1-2, then 2-3, then 3-4, then 1-4 (just to be sure that error didn't get carried through).

It's easy, cheap, and surprisingly very accurate (it'll show a difference in very tiny adjustments quite easily). The only disadvantage as I see it is that you can't have it connected to four carbs at once, but if you don't mind going two at a time it's much cheaper than a gauge set.

Anywho, that's enough off-topic rambling from me. If you're interested, check out Community->Filebase->Non model-specific and search for "manometer" (or just browse for it -- the title is "differential manometer". Please feel free to contact me if you have any questions or concerns or just any feedback you have about the writeup.

I would not recommend attempting to sync in the manner you described. The slides are mechanical and the #1 slide can be keeping the #4 slide up. When you sync 1 to 2 to 3 to 4 the "reference" will be lost... I strongly suggest using a 4 tube manometer. I guess if you don't have the "keeping slide up" issue, this system would work OK but invest in a real tool if you plan on keeping that KZ or any bike with four carburetors. The economy Motion Pro unit works fine and is inexpensive. I bought my last one from Jeff at www.z1enterprises.com . I will probably buy the upscale version the next time as I use mine several times a day and the tubes/hoses take a beating being installed and removed so many times. I have also burnt the plastic hoses a bit allowing them to touch my pipes so will be in the market for another tool soon. I am also looking at non-mercury tools which are more expensive but you don't have to fuss with mercury... Jeff sells one via K&L and I am also interested in Morgan Carbtune, a Brit company that makes a non-merc tool.

Phew! I'm glad there are cheaper sets out there. The only time I priced a set was when I saw the $150 pro set on Jeff's site, which sort of scared me off given my present meager budget.

I eventually need to decide that it's cold enough to stop riding for the year so I can shim the valves before considering carb sync issues anyway, but it's good to have some feedback and advice for when the need arises. It sounds like it might require a lot of trial and error to sync two at a time if one hits the hanging issue while trying to work.

Good tools treated well can last a long time, so I'm sure that a real gauge set will eventually reach the top of my list of things to spend money on, right after a torque wrench.

(I have a long Christmas wish list...)

Hey Chet,
Couldn't your differential manamometer be hooked up 1-2, 1-3, 1-4 to get around WG's concern about #1 keeping #4 up? Seems like a simple adjustment in your plan puts you back in the thick of it.
KZCSI