Judging by the PAJ and Fuel screws wanting to be at 3/4 and 1-1/2 respectively you have the right brass in it for that needle. To fix the problem you will have to make the needle smaller where you are having the problem. I’d bet a hundred to the AFF the 42 pilots make it worse...
I'll say again it doesn't hurt to try higher fuel level in the float bowl. The higher the fuel is around the needle jet the quicker it will pull up an into the air in venture. That might be causing a stumble
Those are downdraft carbs, they should be tilting forward! The way they are sitting on your bike is changing what the float height should be?I was a motorcycle mechanic for more than 20 years. Doesn’t mean I know how to fix everything but I do know where to start!? And first and foremost you have to have the float height set first before you go to ALL OF THE OTHER ADJUSTMENTS YOU HAVE DONEjust saying
A good day tuning is a hot spring day at mx practice. All good except for the yz85 kid with fouled plug, nobody has one, dad says it just started doing it. I cleaned the plug with knife tip and leaned the air screw 1/2 turn. Ran the rest of the day. A bad day tuning is getting a handfull of expensive pilot and main jets then a week later its no better. Well I tried richer needle jets with no joy so I guess I need to spend a bunch more money on leaner needle jets. First set you put in and all the sudden the pilot circuit is responding to adjustment. VTEC, rule 1 in carb tuning is most everything you do will be wrong its just information gathering to get headed in the right direction. Keep notes. Factory Pro has a tuning manual http://www.factorypro.com/tech/tech_tuning_procedures/tuning_FCR_Burns,Pat.html Did you buy the carbs new, for your bike, from who?
Bought them new from Web Bike in Japan since Sudco no longer sells a set for a "J" engine in the US. This is the Keihin set for my bike. Factory jetted for a fairly-stock engine with somewhat open exhaust and stacks. I'm using a Kerker exhaust with a 2" performance baffle, and K&N pods. The stacks make a big difference at high rpm, but I've already proven slim to no effect at off-idle where my problem is after running it with the stacks instead of the adapters and filters.
Hey Guys, Been gone for a while. Working way too much. Today I eliminated the fuel level theory. Went a mm higher on fuel level (lower on float height) and no change. While running, holding at 2k rpm where it's breaking up, I used a piece of cardboard to slowly block off the intake side of the carbs. Wanting to see if choking it at the problem spot made an improvement. But it didn't. Next I'm going to install the OEM Mikunis to see if that corrects the problem. This way I'll be sure it's the carbs, and the problem doesn't lie elsewhere. If that does fix the problem I'll go more aggressive on the needles as turner38 suggested.
if you can, try and fit an airbox, those old inline 4s like stable air. even if it does not seal well try it, you will notice a big difference without those pod filters.
No box. Cut it up and used the back to shield the battery, wiring, etc. Wish I spoke Japanese? Bull Dock in Japan uses FCRs with stacks or pods on every bike they build. http://www.bulldock.jp/ They do some serious classic Kawi hypo-restorations. All these are running my "J" engine. http://www.bulldock.jp/gtm/z1000jr/
We had a big bore kit with a set of FCRs and struggled with a flat spot. It ended up that the combination of the collector on the header combined with the cams, pistons and port work just did not gel. We took the baffle out and it got better in the end we swapped out the header.
Interesting! That's what I'm starting to think. That these carbs just don't mesh with my setup. I guess I can pull the baffle to test (it will be real loud). But I have a beautiful chrome Kerker that they don't make anymore. I'm using the 2" hp baffle, but I do have the original 1 1/2" long baffle that I can experiment with in the other direction.
Wonder if the added back pressure may help. Should be considerable difference between the 2 baffles. This is my 2"comp. This is the original 1 1/2" standard Either way it's a good test running it with baffle out and original baffle in.
Do you have any more specifics on that engine, and what exhaust didn't work, and what exhaust did? Thanks.
, It was a while ago. Big bore with pistons and cams and a ported head. It was a Kerker which did not work well with it, if I remember right the header pipes were bigger and the collector was smaller on the Kerker.
