|
Author |
Message |
Downunder Wonder |
This post is not being displayed .
|
Downunder Wonder L Plate Warrior
Joined: 03 Jul 2023 Karma :
|
Posted: 01:39 - 05 Sep 2023 Post subject: 1982 CB900F KEIHIN Tuning |
|
|
Chasing some advice on tuning the 4 KEIHIN Carbs on my CB900.
It was in storage for 5 years, and not running when I got it.
Carbs needed cleaning, to get rid of the old dried up fuel. After that it ran, sort of.
Below 4500 RPM it coughs, misfires and splutters and has poor acceleration.
1000 RPM idle is lumpy and most time dies after a few seconds. Stays running if I set the idle up to about 2000 RPM
Hit 4500 RPM and it comes alive and pulls like a freight train.
Would appreciate any advice and how to tune for good bottom end performance |
|
Back to top |
|
You must be logged in to rate posts |
|
|
Easy-X |
This post is not being displayed .
|
Easy-X Super Spammer
Joined: 08 Mar 2019 Karma :
|
Posted: 08:45 - 05 Sep 2023 Post subject: |
|
|
For starters the baseline you want to be using is what's the engine like when warmed up. And while you're heading to that point monitor the temperature of each cylinder i.e. are all of them firing? In my experience if it's really running rough you might miss you're down on one cylinder.
Low RPM rough points to the idle circuit - blocked pilot jets and/or wrong mixture screw settings. Did you do a complete carb strip down, new gaskets, etc? If so did you note the turns on the mixture screws (maybe you never touched them and they're factory set and blanked off.)
After that make sure you have proper carb cleaner, not just a can of WD40, and clean again paying special attention to the idle circuit. ____________________ Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter |
|
Back to top |
|
You must be logged in to rate posts |
|
|
A100man |
This post is not being displayed .
|
A100man World Chat Champion
Joined: 19 Aug 2013 Karma :
|
Posted: 11:59 - 05 Sep 2023 Post subject: |
|
|
Easy-X wrote: |
Low RPM rough points to the idle circuit - blocked pilot jets and/or wrong mixture screw settings. Did you do a complete carb strip down, new gaskets, etc? If so did you note the turns on the mixture screws (maybe you never touched them and they're factory set and blanked off.)
After that make sure you have proper carb cleaner, not just a can of WD40, and clean again paying special attention to the idle circuit. |
Yep this^^ pretty all old UJMs are the same - you didn't clean the carbs properly.
Do this first then set the valve clearances then report back. ____________________ Now: A100, GT250A, XJ598, FZ750
Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600 |
|
Back to top |
|
You must be logged in to rate posts |
|
|
WD Forte |
This post is not being displayed .
|
WD Forte World Chat Champion
Joined: 17 Jun 2010 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
stinkwheel |
This post is not being displayed .
|
stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
|
Posted: 21:30 - 05 Sep 2023 Post subject: |
|
|
Replace all the jets you can remove with stock standard ones. Replace the needle valves with viton tipped ones.
It'll be quicker in the end.
Drop Allens performance a line, they stock most genuine kehin jets and at a fraction of the cost of OEM ones. Most jets are less than a fiver each. ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
|
Back to top |
|
You must be logged in to rate posts |
|
|
|