Kz650 best head

My kz650 has the Wiseco 810 cc 10.5-1 comp pistons, 82 GPZ750 cams, ported head and a 4 into 1 exhaust. I have used 4 different carbs on it from the stock VM24 to 29mm smoothbores. I found ouf after spending some serious $$$ the stock VM24 carbs were the best all around setup. Put in the Dynojet kit and be done with it. My bike starts easy, idles smooth, pulls hard and clean from idle to redline even with K&N pod filters. No carb issues from sea level to 12,000 ft.. It runs perfect and it's for sale.

Thanks for that Baldy. Will do.

Read Echelons first post on the vm28mm carbs he recently installed...... he picked up a good 3 plus hp (over the 24s) and pulls harder and longer on the top end. He also has the jetting he's going with.

KZB2 650 wrote: Read Echelons first post on the vm28mm carbs he recently installed...... he picked up a good 3 plus hp (over the 24s) and pulls harder and longer on the top end. He also has the jetting he's going with.

ok...I read Echelon's thread....he has vm28sc. I have vm28ss. Big difference in the needle probably because of the ss's used an accelerator pump system....so anybody got a set of vm28sc needles and needle jets...or at least can tell me what ones to order?

Also my problem is not with the top end, it's small throttle openings. Street bikes have to stay under the speed limit occasionally. Mine just bogs at those throttle positions making it very unfun to ride.

By going to larger carbs you gain top end but lose the low and midrange. That is where you spend 99% of your time. My bike pulls harder with the smaller carbs down low. The smaller ones are also WAY easier to tune correctly. I am skeptical on a 3 hp increase with bigger carbs. I would like to see the dyno sheet on that. I could see maybe 1 hp at full throttls but less HP down lower where you need it. I spent a lot of time and money hopping mine up and based on my experience bigger is not always better especially on small displacement engines.

Echelon has the dyno chart in his thread (near the end)........ Larry C and Dale Walker along with another engine builder told me I could probably expect a 3 to 4 HP gain with the 29s over the 24s and a stronger mid range. I honestly feel the diff from 6,000 up.... not a huge diff but it pulls a little harder and hits 500 in the red easier. I'll admit and won't argue for a minute the 24s are smooth start very good (a better idle), runs strong and are a exc choice but I'm always looking for that little bit extra.

The 29s need to idle at 1,500 vs 1,100 on the 24s but it starts instantly and has no hick ups off idle or putting around. I always had that off idle hesitation they talk about with these carbs (since buying then new) till I went with the 700cc and cams then went through them cleaning replaced o rings and gaskets and added new carb holders and it finally went away)..... (can't really say what cured that)...........Wish I could help you Sean Might be more in the pilot, air screw setting (mine is best at 3/4 turn out now and set at 1/2 or 1 out it runs defently worse) carb holders leaking air or a sticky timing advancer ??? Maybe like you say it needs the acc pump to make up for the needle design.

Also just realized am getting a little off subject sorry mods and Vict182.

Going through the same thing with my 33's. Too rich or too lean. With the stock carbs it was set it and forget it.
The 33's, basically the same as the 29's only larger, it's open it up and GO.:woohoo:
Steve

No problems about hijacking guys it is all interesting

So that's new for me. I have always read everywhere that when you want some more performance you should go for bigger carbs. Now i am confused.

But here you go, getting back to my question. Does bigger valves mean more performance or not? So is it better a kz650 head or a kz750?

I fogot to thank all of you for the info. I am now aware that the route of a zr7 head will take me nowhere good

Maybe.
It depends on the combination of port size and design, displacement, cam specs and carbs. They all need to be optimized for each other, based on the desired outcome.

I think it's a matter of question you have to ask yourself. What kind of riding are you building this bike for and where do you want the performance? Low range? Mid or high RPM? There is always the trade off too. Like race cars and large aircraft recip engine have lousy idles but throttle up and they smooth out. The old stationary engine that put all day at low RPM for water pumps and other low rpm arm machinery They don't throttle up very much.. It can be too easy to over carburate any engine.

Will be a street bike, everyday ride, and some traveling too. So no sport or track riding. I guess i want it to be smooth and strong at low and mid range. No need of high rpm performance