More info on Z650

[crossy2425]

Also I'm running with a Marshall Deeptone that was on the bike (I've read previous posts about these!!) and individual K+N filters. Would I need to change pilot jet from standard? Shes got Boyer digital ignition and micro digital coils.
Pilot standard is 15
Main jets are 100 or 102.5 (depending on model and whichever manual you are reading!!)
Dynojets offer 118 as standard and 122 for stage 3.
Carbs are Mikuni vm24ss slides.
Problems show up throughout the rev range as lurching on acceleration. Plugs were quite sooty. (too rich ??)and the jets that were in were 127.5
I've cleaned the carbs, pilots and emulsion tubes. New plugs, will replace and balance carbs tonight and see what happens.
Many thanks.

[chrisNI]

Main jet sounds very big based on what you say is standard and a Marshall wouldn't flow that much extra gas. It's very hard to get a bike with individual filters to run properly low down without Ledar air corrector screws which no longer exist, and I'm assuming they aren't already there. The Dynojet 118 would be a start and go from there. If you haven't got air corrector screws you could try going down a size at least on the pilots - 12.5? -if you can get them and it's still not good low down.

[Rich]

Check all your ignition and charging system as well, Boyers can suffer from low voltage levels causing a missfire. As Chris says the mains do seem a little large, but if it's missing when you're accelerating overly big mainjets won't affect this much.

[crossy2425]

Thanks for the replies.

I dont actually think it is missing, it feels more like surging, as though she wants to go but is being held back. When you say try and get 12.5 jets are they not smaller? Please forgive my ignorance here!
They dont have the air corrector screws.
Do you think its worth scrapping the K+N's and going back to standard set up then? Do they make a big difference or not..
I forgot she has been bored to 720 cc using the wiseco kit. Would this effect things?

Sorry for all the questions but the sun is shining and I want to get out!!!

[chrisNI]

Yeah you're right you need to go up on the pilots it's too much air you'll get low down not too much gas. The Ledar corrector screws blocked off part of the pilot air passage to compensate for the increased flow through the filters. That would be 17.5 to richen it up based on a 15. If you've still got the standard setup it might be easier to get it to work on that - as you say the bore will make some difference but possibly not that much on the jetting. The more you change the more complicated it gets... I would try the standard airbox if you have it with a 110 mainjet to allow a bit for the exhaust and bore and see what that does. If it works you can stick the filters back on and at least you'll know what they're doing to it it'll be easier to address.

My brother has a Z650 with a Z750 engine in it but I think there's 26mm carbs off a Z1000 on it. I'll check later and see what the setup is on that.

[crossy2425]

Thanks Chris, I put a Gunsons colourtune on it this afternoon.
Got her going and the flame colour was yellow throughout the range so this shows shes too rich. Didnt need any choke either, although it is warm.
This makes me think I should try a smaller pilot??
I'm, getting confused now as 15 is the standard size for these bikes but now more air is geting in. Or does the air not really matter at low revs?

[chrisNI]

The first thing is the main is way too big. Try and get hold of 115 mains and then see what's happening.

My brother's bike has 26mm Z1000 carbs on it and he thinks there's 115's in it with filters and a Yoshi pipe. The 750 engine was just a bored 650 but you'll have more compression with the Wiseco kit. If you've got standard carbs they're probably a bit small for the 720 but change one thing at a time - it should still be possible to get it running properly to some extent.