Jetting questions

[Guest]

Hey guys, I recently finished up my 550 to 673 conversion on my 82 550 Katana. I have a mac 4:1 and K&N twin filters. After I got the engine in, I put my stock carbs back on but upped my pilot to match the 650 spec, 42.5 and my main to a 100. Bike ran horrible. I ordered the Dynojet Stage 3 for the 82 650G. To make a long story short, I fiddled with a ton of combinations with the main problem being the mid and up range. It just stumbles and would not pull anything past 6500 rpm. Plugs were black so I assumed it was running way to rich.

The other day I realized someone else had jetted the original 550 carbs because the little plastic washer was missing above the needles. Since I don't have any of those washers, I put the clip on the 1st position along with a thin washer I had that would fit, and now it finally runs great at idle, 1/4 throttle and WOT above 5Krpm. This is using the 160 main dynojet, and a 40 pilot at 3.5 turns out. Unfortunately, it's still stumbling in the midrange. So, I have some BS32's coming in the mail. Hopefully they will have the little washers in them.

So, my plan is to replace the 160 main with the 155 from the kit, put the spacer in, and then set the needle on the 2nd position (dynojet says start with 3rd position). I am also running a 40 pilot at 3.5 turns out. The 42.5 was too rich. I think that will take care of the midrange issues.

Any thoughts on the above plan or suggestions? I want to get the collectives feedback because I've already ruined one float bowl drain plug installing and removing the carbs so many times lately.

Thanks for the input.

 

[Steve]

Don't have the time right now to review all the jet sizes, but if all you needed was the spacer, you should have asked.

I am sure I'm not the only one with a few of them sitting in the parts box.

And that would have been a LOT cheaper than a new set of carbs. :-\\\

.

 

[Guest]

Yeah Steve, you're right, I should have asked. But I needed a few other parts as well (the aforementioned drain bowl for one) so having an extra set has always been a desire. This was just the impetus to get it done.

One thing I found interesting in all this trial and error I've been through is the effect the needle has on the overall operation of these CV carbs. When I initially installed the dynojet kit, I put the new needle in without the stock washer that sits on top of the needle and in the recommended 3rd slot of 6 which meant the needle was sitting way higher than it should have been making the mixture very rich. I was always led to believe that at WOT, only the main jet is responsible for the mixture. Well, using the same 160 main jet as before but moving the clip to the 1st position on the needle to lean it out as much as I could, the bike would take WOT above 5000rpm whereas before it would stumble and not rev past 6k. Now, it's still too rich in the middle, and probably too rich at WOT as well, but it will at least run to redline without stumbling at WOT just by changing the needle position. Interesting.

I'm hoping that by dropping the main down to 155 and fitting the washer on, I will be close enough that I may only need to raise the clip to get it perfect.