carbs are fussy, period. carbs are fussy with exhausts. they bolt on, they work but they wont necessarily run optimally. people don't appreciate just how much they effect things and people who throw exhausts on and say they run fine typically havent felt carbs tuned to suit.

to address it, there's nothing wrong with the exhaust and it'll be fine enough to ride as is too, it probably has more top end from being leaned out but it'll need tuned if you want the most out of it.

need to look at it in terms of throttle position not rpm. this is a fair example https://www.google.com/url?sa=i&url=...AAAAAdAAAAABAE

first identify where in the throttle range youre having issue and got to remember theres slight overlap in the circuits. so if you raise the needle a clip and richen the 1/4 to 3/4 throttle you might need to turn the mix screws in slightly. take good notes if in case you need to revert settings.

so yeah either tweak it to suit as is or throw in one size larger main jets (stage1 is considered 138 -140 - 140 -138), see what like and tune as necessary making one change at a time.

hope that helps

 

the stator and regulator/rectifier plugs are pretty much all burnt on these bikes. like all 90s hondas they're notorious for burning out R/Rs so at some point it will have been replaced but stators rarely die. word of warning, dont mess around with cheap R/R replacements if/when the time comes, just upgrade it to the likes of a mid 2000s gsxr 600/750/1000 or mosfet, change the plugs and make it fit.

 

Idodirt & Iamhiding- this is gold! Thankyou so much for this information, these charts and wee bits of information are absolutely invaluable.

its 3/4 I think, just no power and feels like it’s starving so it seems to screw up the fuel/air mixture right there, is there anywhere you can just get jets and not the whole lot? The plugs show a very rich mix.. what range would that likely be from?

They're (Black Widow) very defensive over their product “needing no further tuning” and just won’t entertain it. They won’t suggest any jet sizes so this is brilliant

 

I replaced it with a cheapy one and the connectors were both toast. Have noticed the GSXR R/R have the 3 "yellow wires" and the +/- are in a separate plug. These would just wire into the existing male plug I assume.

 

Yup, typical 5 wire set up.

 

Glad to help, this forum has been invaluable for me over the years.

To be honest black widow will be right in their claims. The stuff bolts on and works, they dont require tuning as per say but... On the other hand Any change to how the engine breathes will likely need a carb tweak. Most folk would think its quicker because it sounds quicker and live with tge flat spot. But yeah it's in no way black widow's fault. Also no two bikes will respond identically to the same changes.

If you're going down the carb tuning route, ideally you want to clean them, inspect everything, make sure no ones monkey'd them by not applying equal settings across all 4 carbs, that the airbox is sealed properly and maybe balance them before starting to make changes. Tunings not a big deal but you need to be methodical, take notes and it can be time consuming, especially if its your first venture into setting them up.

Its a case of raise the needle, see if it helps the half throttle issue. If it helps then raise it again, if its worse then go back down a clip. Once happy Then address any changes you need to make to off idle and 1/8 throttle with the air mix screws, i like to make 1/2 turn mix adjustments to get it in the ball park then 1/4 turn if need be and tweak it down 1/8 turn adjustments on the mix screws to totally dial it. But... I enjoy tinkering with them.

​​​​Standard main jetting is 135 on cyl 1&4 and 138 on cyl 2&3.

As for upgrading r/r. 5 wire setup on the gsxr k5 etc for example the 3 blacks are for stator input, red/black is positive and black/white is ground. Pretty straight forward to do, you can either depin the plugs and swap them to suit, splice and solder or even bullet connector them. Think i went through 5 or 6 used oem and cheapie r/r's some of the new ones had failed before i even fitted them. Hence best to just upgrade when needed. Can show you a pic of the wiring if its helpful.

 

I'm definitely not in agreement with this statement at all, but mind you it's my opinion. It does affect the flow of air though the engine/carburetors. They don't work "properly" out of the box for that reason. They do require tuning for it to work efficiently and because of that, it is Black Widow's fault. The needles from Honda don't have grooves with an E-clip that you can move up and down to tune it, so you have to buy aftermarket needles. From that point, how do you know that the taper of the needle is the same as the factory. You don't. There are a number of variables that need to be taken into consideration when you put a full header on. Truthfully, how much design time/money do you think that Black Widow did in 2021 (that's their claim) for an exhaust on a 23 year old motorcycle?

Be realistic here.

 

The jets are all stock, I shimmed the needles with washers and the problem seemed to be worse! The complex nature of throttle position and fuel delivery at intervals from certain jets makes this all so hard to keep track of!

The flat spot feels like it’s a lean problem and the engine is starving of fuel, releasing the throttle gives a little ‘bump’ in power but the spark plugs are carbon fouled, this all seems like a mammoth task done with toothpicks! Have ordered a GSXR reg/rec, no doubt this cheapy one will fade soon enough!

The Black Widow headers were relatively cheap so can’t imagine they’re going to run absolutely perfect or ‘plug and play’. Would a dyno run show me where the lean and rich occurs or am I barking up the wrong tree?

Have the newer coils here and fresh plugs so will try fit them tonight and let y’all know.

Appreciate the quick replies!

 

Ok.. compression was 55-55-57-70psi across the cylinders.

Tried pouring a wee bit of oil into the cylinder and very little change. Don’t know where I’m leaking from but I’m surprised it even runs at all! This thing needs to be burned down I swear..

my valves are all within clearance spec, at least it isn’t the piston rings and hopefully something valve related. I replaced the head gasket a while back as I had oil in my coolant (turned out to be the oil cooler had a nick in it and let oil pass through and not the cylinder head!) and maybe I didn’t torque the head down properly or maybe the head is slightly warped?

This would surely explain the mid range flat spot wouldn’t it? A leak causing the plugs to foul from too much fuel not being burnt?

Man this sucks massive donkey b****

 

I'm surprised it runs too. That's really low, but surprisingly even.