Trouble Getting Going

[koko64]

At least you have a range of tuning parts to throw in the tackle box for your future mods.

[ChrisK]

lol, I literally have them in a tackle box too.

[koko64]

Yep, a 8x12 for FCR jets, a 6x4 for CV carb jets, a 6x4 for Mikuni flatslide jets, etc

[krista]

Those compression numbers are pretty awesome.

[ChrisK]

Those compression numbers are pretty awesome.

That's good to hear. Now hopefully I can get it tuned right.

[caferacermike]

Subscribed

Chris at CA-Cycleworks sent me this link. I too just installed a set of 41mm FCR's on my '97 900SS and I am having similar issues.

Baseline.

Bought the bike about 2 months ago
Was having some strange running problems when holding a steady highway speed as well as some lugging/popping/backfire when pulling away from stops. Figured it was time for emulsion tubes. Previous owner had said it had a Factory Pro jet kit installed a couple of hundred miles back. That always scares me to hear. I actually prefer stock jets in stock bikes. A lot of "kits" just don't get it right. I also have to ask, "why did you do the kit years after you bought the bike".  Was about to plop down the $200 or so and order all new jets and tubes when I found a great set of FCR41's used at a great price. As always, ad said used less than 50 miles. Another red flag. When I removed the airbox, I found a missing screw in the CV cover. Guess why it ran poorly?  Lol. So I spent $700 on new carbs instead of a 15 cent screw.


Got the carbs installed. Put the filter I got from Cycleworks right in front of the carbs.  Tried to fire up bike. Spin the engine over several different times and it just wouldn't catch. A quick spray of ether and it fired right up and idled around 1,000. Seems really nice.

Next day I put everything else back together and get it fired up. Warm up the bike. Twist the throttle, instant death. Hit start button, it fires right up. Twist the throttle open, I hear a small pop and the motor stops dead. What I find is that if I crack open the throttle, at exactly 2,300 the engine just quits. If I feather up the throttle it gets to 3k and just screams all the way to the end as it should.

Rolled to the street and I can't just roll away. I can hold in the clutch, feather up the throttle, and double clutch away. Once I'm up and running the thing pulls clean and like a freight train. First time around the block it was trying to pull the front wheel. At stop signs it would die if I didn't feather it coming up to the sign and hold it at 4k hole shot starting position. 

Got home and double checked all previous settings. Slow screw was at 2 and fuel was at around 31/2 to 4 ( I quit counting when it was that many) set fuel to 3/4 and air to 11/2 as ducatitech and Cycleworks paper said to do. Not really a change.

Read some thoughts on the pages here, set it to 1 on the slow and 2 on fuel, not any different.

I can tell you the bike will not idle higher than 1,200. I've checked that my return line has fuel flowing back to the tank. I've watched fuel flowing through the new clear filter without it running dry.

Bike is set up with an older K&N filter without a lid. Has the aftermarket alloy frame. Battery is holding 13v. Spark at both plugs. staintune exhaust cans. Was running a week ago. I can see the potential. I just need the very bottom end sorted. At this point I do not know what jets are installed but previous owner mentioned not having changed them from Sudco. Unless Sudco installed custom jetting from a customer profile.  There is a backfire in the carbs at 2,300-2,500 when it kills. I can kill it every time cracking open the throttle. I've read that this is possible due to the pumping action of the diaphragm but mine would get you killed on the road so I don't think it's quite as the write up described.

[Speeddog]

Make sure that alloy filter frame is actually holding the filter down firmly to the airbox.

If it's floating around leaking air one second then sealing up the next second, you'll drive yourself crazy trying to jet it.

Open up the carbs and find out what jets are in it.

And confirm that all jets are clean and clear, especially the pilot jet.
Make sure there's no ring of gummy varnish on the needle.
If the carbs were used once, then left sitting on a shelf with half a bowl full of gas for 6 months, they could be gummed up.

As an FYI to all readers, in this context of carburetors, "confirm clean and clear" means remove the jet, visually inspect with a magnifying glass if necessary.

It does not mean remove the float bowl, spray with carb cleaner, and call it good.

[caferacermike]

And of course because its today and not yesterday, and probably because I complained in a thread, the bike runs much better.

If I whack the throttle open it kills immediately. If I roll it on smoothly, which in reality is how it will be used when riding, it seems to do well. Took it around the block and no hesitation and no stalling.

I'm on call for work until this weekend so no riding it long distance for a couple of more days.

[caferacermike]

Is the OP having any better luck?

I was able to put 50 miles on the 900SS today. It ran really really smooth and accelerated quite nicely.

One thing though, if I whack open the throttle I can kill the engine. I can do it under load as well. Trust me I tried several different ways and getting more than a half twist in one handful will kill the bike.  Thankfully when I release the throttle the moving bike will cause it to fire right back up. I don't guess I get to use the pumper portion of my carbs no 1/4 turn throttle for me yet.

Is this normal?

[ChrisK]

Hey I'm back! With good news too.

Got the jets in from CCW today and finally got time to throw the 58 slows in. So here's my setup now: 58 slow fuel, 165 main fuel, 5th needle clip on stock EMT needles, and I went back to what I'll call baseline settings of one turn out on both fuel and air screws.

The bike idled much better, transition from no throttle to on was MUCH better, and it was very smooth at what I've been calling cruising speed. I was kind of disappointed with acceleration from say 1/4 to 1/2 throttle. After that it pulled immensely harder than the Mikunis. I still felt that sharp vibration at takeoff, but not as bad. I don't like that feeling.

It is 37 degrees outside right now. I'm going to table it for the night and ride again tomorrow when it's hopefully 47. After I take notes then I think i try the EMS needles, to hopefully cure that lag from 1/4 to 1/2 throttle.

Sound like a plan?

[koko64]

Why not.
Consider the effect of the SAJ screw on response off a closed throttle. Fine tune that and your IMS, then start playing with the needles. Try #4 notch on the EMT, just so you know, and if that don't help then try the EMS on say, #4 to start with, and try that with acceleration and plug tests.

[ChrisK]

Very similar performance today, mid-40's. I just tried a half turn out on the fuel and I don't know if I really noticed much, so I'm going to go back a half turn the other direction and see if I notice something.

[ChrisK]

Fuel screw at half turn out I didn't notice much of a performance bump and I even felt two or three stumbles during a 10 minute ride.

Going to go back to 1 turn out, and start tweaking air screw, 1/4 turn at a time.

[koko64]

With the SAJ screw you will find a setting for how it interacts with the slow fuel jets and IMS, and a setting for how the power comes on from a closed throttle at lower revs. They might be the same, might not, if not then you can go for the compromise setting.
I found that a richer needle root diameter made me go down a size in the slow jet, and then I had to tune the slow circuit all over again!

[ducpainter]

Having fun....

yet?