TJS Posted August 1, 2022 Posted August 1, 2022 My year long and maybe longer battles with tuning 33mm FCR carbs on a 1991 Bandit 400. I have learned much on the relationship between the air jet, air mix screw, and fuel mix. Still some tuning to go as I wait for a few different air jet sizes to come in. I never had such fine tuning issue with my 1994 GSXR 750! Smaller motor with big carbs; I guess. Quote
Safra Posted August 7, 2022 Posted August 7, 2022 Been following you on the tube love your projects 1 Quote
wraith Posted August 7, 2022 Posted August 7, 2022 Never seen anybody do much with the b4. Good on you 1 Quote
TJS Posted August 12, 2022 Author Posted August 12, 2022 Frustrations never end! Flooding! Time to check floats and needle valves! Quote
Panos Posted August 13, 2022 Posted August 13, 2022 On 8/12/2022 at 7:52 PM, TJS said: Frustrations never end! Flooding! Time to check floats and needle valves! If your bandit has a vacuum membrane at the fuel tap like oilcooled gsxr has , check it to see if gas is leaking through that . Thats a lot of leaking though . Quote
bluedog59 Posted August 15, 2022 Posted August 15, 2022 I think the base problem is that they're just too big, you're running a 33mm carb on a 100cc cylinder. Quote
TJS Posted August 16, 2022 Author Posted August 16, 2022 Hope not too big! They pull like a freight train on the main jet! Quote
bluedog59 Posted August 16, 2022 Posted August 16, 2022 30 minutes ago, TJS said: Hope not too big! They pull like a freight train on the main jet! At the top end when you finally get enough gas speed to make them work. Quote
TJS Posted August 19, 2022 Author Posted August 19, 2022 Quick clean with kerosene, carb cleaner, and air. Quote
TJS Posted August 31, 2022 Author Posted August 31, 2022 (edited) Is suppose to be brown?...workn a fix and trying these filters. http://pjmotorsports.com/ Edited August 31, 2022 by TJS Quote
bluedog59 Posted August 31, 2022 Posted August 31, 2022 Just out of interest, have you set the float heights and by what method ? I've just done the FCR on my DR650 properly and it does make a difference. Quote
Gixer1460 Posted August 31, 2022 Posted August 31, 2022 Those 'filters' will lose you a few hp - Dyno proven. Might keep bugs out but do no good for airflow unfortunately! Quote
bluedog59 Posted August 31, 2022 Posted August 31, 2022 16 minutes ago, Gixer1460 said: Those 'filters' will lose you a few hp - Dyno proven. Might keep bugs out but do no good for airflow unfortunately! +1. If you're trying to run a 33mm carb on a 100cc cylinder you're going to need every bit of help you can get and those "filters" will only make things worse. I think the root problem is a lack of gas speed through the carbs at low rpm leading to very little depression over the jets making it difficult for the engine to lift enough fuel. Quote
TJS Posted September 1, 2022 Author Posted September 1, 2022 On 8/31/2022 at 10:23 AM, bluedog59 said: Just out of interest, have you set the float heights and by what method ? I've just done the FCR on my DR650 properly and it does make a difference. Set to 9mm with this: https://a.co/d/c7QiVJ1 Quote
bluedog59 Posted September 1, 2022 Posted September 1, 2022 What angle did you have the carbs at when you set them ? On my FCR39mx the carb has to be angled so the float tab is just touching, but not compressing, the sprung plunger on the float valve. Your carbs are slightly different but of the same "family" so it could be worth checking what the official method is for them. 1 Quote
TJS Posted September 6, 2022 Author Posted September 6, 2022 It was tricky...but yes checked and double checked all floats! All were in spec. Quote
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