Help needed. 81 KZ650-D4 w 81 KZ750-4 (Wiensco 810 big bore) engine & VM24

SWest wrote: One thing at a time. Install the jets then if you feel you need a little more at midrange, raise the needle one notch and bench sync. Each time adjust the air screws for best idle. Once you're satisfied, sync the carbs.
Steve

Ahh so no point using time on carb sync before I’m happy! I learn so much from you all

I have needle in 4th place now (had it there all time) I go back to mid 3th when I install the 20 jet pilot or shall only change the pilot jet adjust the screw and take the bike out for a spinn?

I would start with the center position. The needles are for elevation changes normally. 4th place? from the top or the bottom? From the top it's richer, from the bottom, it's leaner. If you disturb the slides you must bench sync them. Vacuum sync is the final step once you know you have it right.
Steve

SWest wrote: I would start with the center position. The needles are for elevation changes normally. 4th place? from the top or the bottom? From the top it's richer, from the bottom, it's leaner. If you disturb the slides you must bench sync them. Vacuum sync is the final step once you know you have it right.
Steve

I’m running at 4th (richer) I have one step left for even richer. I have had these 4th when I was using 750cc stock piston and now for the 810cc.
When I got the bike 2 years ago, I needed to re jet. Then I started with the needle in 3th (middle) and increase it to 4th because of some load alternation, but it was not improve a lot,
but it was so close to perfect I was not playing more with it.

So what I wondering about is, should leave the needle in 4th and only replace the pilot or should set the needle to mindle posistion at the same time I replace the pilot jet?

Just replace the jets first.
Steve

The 4th position is "stock"..... from the factory (1 up from the bottom) for a 650 with a air box and a stock exhaust..... sorry Steve but I don't think you would not want to go leaner a step after boring 160cc putting in a step hotter cam, headers and pods. Like Steve said try the pilots first and see what happens. Idle sounded good on your video at 1,100 rs maybe you could try slightly higher 1,200 or so to see in that helps leaving too but play with the jets and air screws first.

I was talking about going one step richer. Most important is ONE THING AT A TIME. Every time I do more it bites me in the pooper. :pinch:
Steve

Today have I installed the 20 jets. It started up great, I run the engine warm and then adjusted the air screw, fin the point where engine was not going fine and then turn 1/4 out.

I have been out driven for a hour in different condition, and I cannot feel big difference after the upgrade to 20 from 17,5m
I don`t think anything is worse, but I cannot feel improvement either, maybe some but not much.

Should drive the bike more with these setup just to "learn" more how its behave, or should I just try to install the old pilot and then raise the needle to 5th?

I recorded a video when it comes to the "problem" where you go off the idle, where you need to give some throttle quick if not kill the engine,
or take the throttle back and forth to come over the point if you don`t want a lot of RPM. It sound like the engine need some carb sync, so
maybe these is the reason also?

ufile.io/0imbs

Turn the screws to best idle. 1/4 turn more will make it lean. You may have to go one step up on the mains. Before doing the needles put 100 miles on it to "settle in." Sounds like a air leak.
Steve

SWest wrote: Turn the screws to best idle. 1/4 turn more will make it lean. You may have to go one step up on the mains. Before doing the needles put 100 miles on it to "settle in." Sounds like a air leak.
Steve

I found the point where you can hear it start to get problem and Then I turner 1/4 out.

Shall I step up main jet one size now? And then see how the engine perfomance are?

«Settel in» what do mean? So I get better experience with the problem or is it gonne happening something with the engine the next 100 miles?

You are sure we are on the right track?
I mean why are we not going back to the old pilot and then try new one step larger main jet?
Is it because the new pilot jet maybe need to stand in reletation with a larger main jet?

Air leak between the carb and cylinder?
Use some start gas and see If I find something?

Wow that sounds pretty rough....... forget the needle and main for now you need to figure out the idle and off idle problem first.

Did anyone else listen to the video? Sounds like your missing a cyl or 2 ....... you got new carb holders if I remember right........ did you use blue locktite on the thread and tighten the hell out of em....... like Steve said maybe a air leak........ I know you went through the low end jet cleaning but maybe still plugged ?? Run it for a few min then take out the plugs keeping them in order betting one or two are wet and not firing. Could maybe try a new plug in that hole if they are soaked with gas to see if it fires. What do you think Steve maybe go back to the 17.5 pilots? Don't think the jetting size is the problem after hearing that. My 24mm carbs were set at 1 and 1/4 turns out from the factory maybe go with that to get close at least ??? When you first started it the video showed it running perfect at idle so something happened since then.

See what Steve says and hopefully a few others.

20 from 17.5 isn't that large a step. The air screws should be able to handle the overlap. If you have to go over the 1 1/4-1/2 turns out, the pilots are too big. 100 miles is enough time for the engine to clean up and things to settle in. Yes, I would put off the needles for now. After the run in time of 100 miles, I'd do a WOT test to see if it runs out of gas under load. It can run great sitting but under load it can crap out. Right now it's about finding and fixing that "flat spot" just off idle. Could be a lot of things, low float level, bad plug, weak spark (bad lead connections) or something else. The plugs should tell the story.
How is the spark advance?
It's the little things that make you chase your tail. :whistle:
Steve

Thank you for your feedback!

I don`t think I`m missing any cylinders, I will take out the plugs today and take some photos.
When I installed the carb holders was I using Three Bond Case Sealant Liquid Gasket one the surface against the block.

I will check up and come back to you.