Well that was a really valuable learning curve for me today. Got the Keihin jets #110 and the slow idle jets #40 ordered from a company in Adelaide that stock all the original new Keihin, Mikuni and other carb brands (Show N Go Motorcycles).
The slow jets are not made anymore but they are replace by ones that are almost identical except 3mm longer. Originally they were 29mm and these are 32mm. They said that is what the CB guys are replacing with and it has no difference in performance. The non labelled ones in the bike were 28mm. Also the kit air screws are hollow in the middle with side holes. Thread is less as well.
There is heaps of difference with the air screws and springs. Different shape, thickness and length. I am putting back the originals because they are K stamped. Springs are different as well.
I am going to use the float valve seats and floats from the kit as I have had no problems with flooding or anything. Also the float valve seats had 2 different types in the bike both originals and non originals. Heaps of different in height hole dimensions, thickness and everything. The floats are toast.
Original needles back in. Heaps of difference in thickness and shape to the two needles. Also on the kit needles the circling is different and flops around because it's so loose.
So everything original bar the float valves and float valve seats.
I solemnly share never to buy another rubbish kit for a carby. Just posting the pics as a reference for people to have a look at if they ever want to go down the cheap kit road.
I've long been amazed at the carb parts that have appeared for the 750. Sometime during the 1990s the [in]famous Keyster parts started appearing, with things like needles that were 1/4"longer, and would jam in the needle jet, holding the slide partly open, which caused the idle mix to be so lean the bikes would not idle without the choke. Then they introduced their version of the idle air screws, which had a sideways hole drilled across the tip, but none in the tip, which doesn't even make sense: it either has to have the holey tip with the cross-drill, or none at all, to work. For a while in 2005-6 they made float bowl gaskets that dissolved when in contact with gas, which they replaced with a sandwiched version that delaminated instead, in 2007-8. In 2009-10 season they came out with their new, thicker needles that we see today: with the stock #105 mainjet these ran so lean the engines would not rev up past about 6000 RPM, at all. It did keep the sparkplugs cleaner...in 2011 they came out with the float valve that had springs so stiff that you had to set the float level to 24mm to get the bowls deep enough for the idle jets to stay wet. Those seem to be fading out, now, thankfully. The ones we are now seeing "Made in Japan" are sometimes marked Keyster, sometimes not, and have a somewhat softer float valve spring, stiff stiffer than OEM versions. I have had pretty good luck setting them in the 25mm float level range, with staggered floats (one at 24mm, one at 25mm) to help keep things loose. Honda did this with the K0-K1 carbs, quit doing it somewhere along the K3 or so: they usually had one set to 25mm and the other at 26mm heights.
