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post #1 of 16 (permalink) Old May 22nd, 2019, 8:44 pm Thread Starter
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Help fine tuning factorypro jet kit

on my 1995 900ss/cr!

I feel like I'm getting close with the settings but I have an annoying issue on warm up that I'm struggling to debug as I learn about carbs. The bike as it sits today has...
- stock exhaust header pipes with spark slip on mufflers, baffles removed
- CA cycleworks coils, plugwires
- air filter is a K&N with airbox lid removed
- carbs cleaned and rebuilt by me this past winter. New gaskets, o-rings, all jets and emulsion tubes replaced
- Factorypro kit CRB-D09-3.1-TI installed. Started with 150 main jet and 40 pilot jet. After some testing moved to the 145 main jet and the 42.5 pilot jet in there now
- Floats set to 14mm measured on the diamond shaped float as per Factorypro instructions
- Both mixture screws set to 1.5 turns out. Factorypro needle clip on slot 2 as per their instructions.
- I've balanced the carbs a few times after adjustments so they are balanced if not very close.

When fully warmed up after about 15 minutes of riding the bike is fantastic. Starts, idles fine, smooth power at all throttle settings from idle to redline. Can even lift the front wheel slightly on a solid 1/2 shift. Plugs look great, really a fantastic fun ride.

But warmup is horrible. The bike starts fine with some choke but won't idle without choke for at least several minutes. Idle will seem to load up and require clearing with a throttle blip which may generate a pop through the airbox and hesitation. Then during the first minutes of riding it bucks, misses and will even pop through the airbox. After about 10-15 minutes of riding it eventually smooths out and behaves, but occasionally it will foul the plugs if I've done a few shorter rides back to back. Opening the mixture screws a 1/4 turn causes fouling sooner. Closing up the mixture screws a 1/4 turn seems subjectively to make the popping and hesitation worse.

Thoughts? Based on how the bike runs when fully warm I'm hesitant to mess with the mains or needles. Go back to the 40 pilot and give it a try? I went to the 42.5 because the 40 seemed to need about 4.5 turns out to idle, but that was over the winter in the garage, no real test runs done.

Hoping to find a magic bullet here!!! This is the only issue with what is otherwise a great little machine.

Cheers

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post #2 of 16 (permalink) Old May 22nd, 2019, 9:54 pm
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wind the mixture screws out to 4 turns or so.

know all wanker
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post #3 of 16 (permalink) Old May 23rd, 2019, 12:26 am
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Air/mixture screw at 1,5 turns out seems way too little to me.
I've got basically the same set-up (K&N, 42,5 pilot, open mufflers, stock headers) but I'm using the stock airbox with lid and snorkels. And I'm using a Dynojet stage 1 kit but that doesn't matter as our pilot jet is the same.
So if you got the same pilot, air filter and exhaust but an open airbox I would think that your air/mixture screws would be at least at the same point as mine (or even further out due to your open airbox).

Right now I'm finetuning the air/mixture screws and I'm very close to the perfect setting at 3,75 turns out.
I started at 2 turns out as dynojet recommends but that was way off. White spark plugs, backfiring at declaration, hanging throttle,...
So I started turning the screws out by 1/2 turns, made a testrun each time and ended up at 3,75. I might try another 1/8 turn out but I don't think that's necessary.

I would advice you to go with belters opinion. Wind them out and see. Go for at least 3,5 which is the often suggested ideal starting point

P.s. Although my bike is now almost at the perfect spot I do need a tiny bit of choke for the first 5 km in the morning (+/- 5 Celsius). I can turn it off sooner but then I have to play with the throttle when idling to keep her from stalling. In summer (+/- 20 Celsius) I can turn the choke off after 500m.
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post #4 of 16 (permalink) Old May 23rd, 2019, 6:50 am Thread Starter
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Thanks much for the advice. I'll give it a shot starting at about 3.5 turns out and see how it responds.

Cheers
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post #5 of 16 (permalink) Old May 23rd, 2019, 7:01 am
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Keep in mind also a good point brought up in another thread.

What carbs do you have?
US models will be different from the rest of the world so in some cases the 42.5 are correct but others not so much and should be 37.5 . The US models did use the richer pilot on early models but not later ones and there is a different designation for the carbs so there may be internal differences.

Where are you located?

I do not use factory jet kits much so jetting will be different but 1.5 turns out on the fuel screw along with your description of fouling plugs makes it sound rich. Keep in mind these bikes are not the fastest bikes to warm up (carburetors) If it runs well when warm I would not worry much about it. If you start fouling plugs thats different and it is telling you you are feeding it too much fuel from somewhere.

If you completely close the fuel screws does it still run?
It shouldn't.
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post #6 of 16 (permalink) Old May 23rd, 2019, 7:17 am
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For whatever reason I found 40 pilot jets, screws out 4 1/2 turns to work better than 42.5 in my bike too. The screws are still influencing mixture past 5 turns out on my bike. I also thought this seemed like the screws were too far out so I went to a 42.5 but had to switch back. Do what works.
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post #7 of 16 (permalink) Old May 23rd, 2019, 7:25 am
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My setup is similar to yours. Mine starts better with choke but you can cut that back to a high idle very quickly. My normal riding altitude varies from sea level to 500 ft.
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post #8 of 16 (permalink) Old May 23rd, 2019, 9:30 am Thread Starter
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Quote:
Originally Posted by ducvet View Post
Keep in mind also a good point brought up in another thread.

What carbs do you have?
US models will be different from the rest of the world so in some cases the 42.5 are correct but others not so much and should be 37.5 . The US models did use the richer pilot on early models but not later ones and there is a different designation for the carbs so there may be internal differences.

Where are you located?

I do not use factory jet kits much so jetting will be different but 1.5 turns out on the fuel screw along with your description of fouling plugs makes it sound rich. Keep in mind these bikes are not the fastest bikes to warm up (carburetors) If it runs well when warm I would not worry much about it. If you start fouling plugs thats different and it is telling you you are feeding it too much fuel from somewhere.

If you completely close the fuel screws does it still run?
It shouldn't.
Great points. I'm in Alberta Canada, around 2600 ft altitude. Carbs are the stock mikuni's, I would assume an NA spec, the pilots I took out when I rebuilt were 37.5. I just tried closing both mixtures screws completely. Bike started with full choke but died immediately when I closed the choke. Would not restart or even sputter with the choke closed.

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post #9 of 16 (permalink) Old May 23rd, 2019, 10:17 am Thread Starter
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Quote:
Originally Posted by duc96cr View Post
For whatever reason I found 40 pilot jets, screws out 4 1/2 turns to work better than 42.5 in my bike too. The screws are still influencing mixture past 5 turns out on my bike. I also thought this seemed like the screws were too far out so I went to a 42.5 but had to switch back. Do what works.
Thanks, that was exactly my reasoning as well. I'm wondering if the plug fouling part, perhaps as a result of having to run with choke open for so long on repeated short rides, threw me off and I was adjusting leaner when I should have been going richer.

Learning as I go I suppose.

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post #10 of 16 (permalink) Old May 23rd, 2019, 11:07 am
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ditto...experimented with 42.5 ....went back to 40. Stock airbox with cover and K&N drop in, GPR up exhaust with db killers intact....pilot screws around 3 1/2 to four out...but putzed to find each cylinders "sweet spot" o' course, synched with mercury manometer.

Delivering near 50mpg, fairly quiet (I like) with more than adequate street performance throttle closed to WFO. I frequent slow, winding back roads...off/on throttle response and low RPM cruise quite friendly.

As an older, retired bum I'm setting no world speed records, incredibly happy with my super reliable, 24 year old, 35,000 mile 900SS/SP as is, Mikuni carbs and all.

'95 900SS/SP , '07 SS800 . '98 VFR800

Last edited by bigbadbass2; May 23rd, 2019 at 9:25 pm.
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