TOPIC:

Well I just installed the dyna III today, very easy install and works great. Did carb sync, all respond nicely and level right out very smooth. Just when I crack the throttle she bogs really bad. An easy and a little slower roll on the throttle she runs great. Just when I crack it open fast. Is this jet size ? or needle position. Thanks for the help.

Post edited by: woodyskz, at: 2006/09/16 20:58

First what type of carbs are on your bike? When you say you crack the throttle open fast does mean you snap it open from idle to full throttle? If you are running Mikuni slide cars then that is normal. I have a 78 KZ650 with VM26's and my engine will simply die if I snap the throttle from idle to wide open really fast.

If you snap the throttle open, the VM carbs SHOULD react immdediately and rev cleanly; no fall on their face. What carbs? What jets? What airbox/pipe set up?

I'm running the stock VM24ss carbs for a '77 KZ650c, The jets are 17.5 pilots & 107.5 mains, the carbs have pods instead of stock air box. The Pipes are OEM stock 4/2. I'm open for sugestions. Runs great, just wont take the snap of the throttle like it should. Thanks again.

Post edited by: woodyskz, at: 2006/09/17 19:35

I am thinking those carbs should have air screws (up on the sides) rather than pilot fuel mixture screws... is that correct? What jet needles are in the carbs and how are they clipped. The pilot and main jets are good I think.

Has the mechanical ignition advance been cleaned and lubed recently? Do you have points or electronic ignition... in other words, has the timing been set? Are the valves adjusted?

Post edited by: wiredgeorge, at: 2006/09/18 08:54

So what your saying wiredgeorge is when I quickly snap the throttle from idle to full throttle my bike should not stall but rev cleanly? I have never been able to get any VM carb to do that. I have noticed diaphram carbs will not stall and die when snapped to full throttle.
My bike is jetted spot on, VM26 and will stall and die everytime I do that. Am I missing something here?

Hey,
thought I'd chime in since I also have a Kz650 with similar setup. Stock pipes, emgo pods but dyna2 ignition and dyna (3ohm) coils.

My guess, and everything always is a guess until you try it, is that your pilot jets are too large and you have to move your needle clip up a notch or two from stock position. Try 15's pilots out. I had the same problem with 17.5 pilots. I went to 15's got my needle clipped in 2nd position (from top) and have 112 main jets. That's the only combo that really works for mine anyway.

She's running pretty damn good like that and no choking with full throttle wacking. Just a nice loud broooooaaaa and hold on!
Sounds like your rich to me but check your plugs first and save yourself some headaches.

Baldy: That just don't sound right man - she should just roar like wg said.

Steve.

Post edited by: saszta, at: 2006/09/18 16:03

Baldy, I don't mean to hijack this guys thread but the reason folks put mechanical slide carbs on turbo bikes is that there is no lag... If the throttle is open, the bike should cleanly gain rpms with no stutters, lags or bogging. If it does do this, there is an issue somewhere... might not be the carburetors... valves, ignition, timing, etc but it may be the carbs. Start a separate thread and we can look at it. By the way, folks with turbos won't use CV carbs as the vacuum must build a bit creating a slight lag. that is a reason that there are plenty of tuning tricks to increase "throttle response" for CV carbs... like opening up the return hole on the base of the slide from its 3mm to 1/8" size. Dynajet even gives you the drill bit to do this. This drilling of the hole supposedly gives you more immediate throttle response. You can also stretch the return spring and clip it a bit shorter... some have done this as well to get the throttle to react more directly. I personally haven't seen a bit of difference when doing this stuff but you won't find CV carbs on many turbo bikes. Lag is usually the result of too lean or too rich pilot mixture... or perhaps the jet needle clip position or length/taper.