FCR Specialist?

[TJS]

I have a Bandit 400 with FCR carbs. It has a super hard time with starting when the motor is cold. Once I practically kill the battery and it starts; then it's okay when the motor is warm. Here is a video of it finally starting and warmed up. Where should I focus my attention for cold starting adjustments? The video has a description of current settings and I have a video series of 6 different attempts to tune the carbs. I usually focus on the air jet on the air box side of the carb and fuel mix on the bottom of the carb.

 

[TJS]

 

[Jaydee]

First thing I noticed. You are trying to sort out the fueling with no air box or filters fitted!!!

All that tweeking you are doing will be gone out the window as soon as you fit them as now the air flow will now be restricted, thus changing air/fuel ratio. 

You mentioned that you turn up the air screw a quarter turn, it's actually a mixture screw. If you have unrestricted air flowing in to the carbs it make the ratio lean. You are richening up the mixture screw to compensate for this. Same story with your upjetting. Your main jet choice might suit the carbs running unrestricted, not with air box/filters. 

Start by putting back on the air box or filters, go back to base setting on the mixture screws and mains and then tackle your fueling.

[TJS]

Thank you, I run these carbs without the air box or filters. I will use metal screens like the following. It's the same I have used on my track bike with FCR carbs.

http://www.pjmotorsports.com/velocity-stacks-with-flanges.html#HD CV Carbs

 

[TJS]

My main focus is helping to cure the cold start issue. The other tuning will be done with a dyno.

[Jaydee]

9 minutes ago, TJS said:

Thank you, I run these carbs without the air box or filters. I will use metal screens like the following. It's the same I have used on my track bike with FCR carbs.

http://www.pjmotorsports.com/velocity-stacks-with-flanges.html#HD CV Carbs

 

Ah, now it makes sense. 

[dupersunc]

Throw the screens away.  Fit proper bell mouths and either run them open or proper filters.  

Cold starting, give the throttle 3 or for sharp full twists, so the accelerator pumps wet the inlet ports. Spin it over with no throttle then crack it open stightly as soon as it catches. might take a couple of attempts if it's really cold.

[bluedog59]

1 hour ago, dupersunc said:

Throw the screens away.  Fit proper bell mouths and either run them open or proper filters.

With the emphasis on "proper".  I wouldn't fit those on my lawnmower, and that's a f**king H**da ! 

Edited April 11, 2022 by bluedog59

[Gixer1460]

14 hours ago, TJS said:

Thank you, I run these carbs without the air box or filters. I will use metal screens like the following. It's the same I have used on my track bike with FCR carbs.

http://www.pjmotorsports.com/velocity-stacks-with-flanges.html#HD CV Carbs

 

Easy way to 'throw away' horsepower - been proven. The gauze may filter rocks and gravel but sand and smaller - straight in! A good filter loses nothing and gains engine life. They probably make no difference on the HD application and hard to lose what you ain't got in the first place LOL!

The throttle pump exercise is about the std. way for carbs without choke's - even works with RS flatties & they have a choke !

[djayedot]

Hold on a second... Forgive my ignorance here, and I don't mean to threadjack, but I'm honestly intrigued... What the hell is a Bandit 400!?

I'm looking at the motor in your pics and am completely baffled. The cylinder looks sort of like an O/C motor but it's watercooled? What head architecture is that motor based off of? Doesn't look like any WC or OC I've seen before... And the bottom end almost looks like a GS twin in shape... Totally unlike the other 4cyl Suzukis that I'm aware of.

Nonetheless, cool as shit man.

[Jaydee]

27 minutes ago, djayedot said:

Hold on a second... Forgive my ignorance here, and I don't mean to threadjack, but I'm honestly intrigued... What the hell is a Bandit 400!?

They were available to the Japanese domestic market. Sold as grey imports around Europe and rest of the World. There's also a bandit 250 that resembles the 400. 

[TJS]

Some of the motor design comes from the later gsxr 400.

[Joseph]

Also did a GSXR 250 with that WC engine and it does 45HP with a 17000 rpm redline, which all things considered must be quite a whip of an engine

Edited April 13, 2022 by Joseph

[djayedot]

As soon I saw this thread I went off on a little tangent about these things.. WOW what an interesting bike!

Definitely different motor architecture compared to any other common US-market Suzukis. And variable valve timing in 1991?! You gotta be kidding me lmao

An employee of mine just recently purchased his first bike. I recommended he buy a GS500F (and he did) but damn, after learning about these I kind of wish I sent him on the hunt for one!!!

-Austin

PS: I was aware of the GSXR400 however I guess I just assumed that it was a super sleeved-down version of the 600, lol.

Edited April 13, 2022 by djayedot