WAYWARD 1998 944SS - NEEDS HELP

[Brid]

SMALL UPDATE
Got into the valves yesterday - and found quite a bit that needed addressing. Remember, this engine has done so little since it had the big bore kit installed, I wasn't really expecting to find anything much to do. Both Exhaust openers had non-measurable gaps (less than 0.0015" - but shims still turning) and the vertical Ex closer shim was about 0.004" out of whack. Bless the top of that valve being a little mushroomed, which took forever to get to where I could get the shim off! So, all done, and am going to try some EMR needles on this excursion into the carbs. More to follow  
PS - Tony? Going to the 165 mains you suggested, and - with the 50 pilots, what do you suggest as a starting position for the mixture screws?

[koko64]

In theory if the slow jet is correct then between 1-2 turns out is the theoretical range. I have had to run the IMScrews at about 1/2 a turn with our pooey fuel down here. Curious how many turns causes the motor to stall or falter as the slow jets should be good if you can get the motor to falter when going less than half a turn and more than two.

[Brid]

Didn't get it buttoned up until late, so just got time to fire it up briefly. I set the idle screws at 3/4, and noticed it is is a bit lean off the bottom (where it wasn't before!!) so, I'll put the sync on tomorrow, and see where they feel happy. Then - it's 'show time' for a quick road test, with the different jetting - with fingers firmly crossed. The customer thinks the bike has made a little bed for itself in the corner of the shop -- I have had it that long!! 

[koko64]

1 to 1 1/2 turns could be good according to the theory. Should be a little cold blooded with non existent choke which means it's close. The 60 slow jets in 41s start too well if you know what I mean.

[clubhousemotorsports]

Does it feel like you are hitting a rev limiter?
I have seen aftermarket ignition boxes cut power as a rev limiter way too early. They ran great until the same rpm and then killed it. In our case we popped on some oem boxes and all was good again. Know that some of the Ducati performance boxes also had built in limiters.

I have also seen kits to run non-resistor plugs and wires that caused all kinds of issues as the noise messed with the ignition.

Best thing you could do would be to get the bike to a Dyno and pull air fuel. I had a customer trying to jet a bike that had bad boxes so until you see what air fuel and what happens when it falls on its face you might be spinning your wheels.

[Brid]

Clubhouse, If you read the whole thread, you'll get a better feel for what's going on, but - yes, it's just like it's hitting a rev limiter. After all that's been done, it's really getting sillier than better though! Unfortunately, we don't have a Dyno facility anywhere close by, and even if we did - it's such a bear getting to the carbs to make adjustments, that we'd need a big fist full of smackeroos to make it all work!! Takes me about 1 1/2hrs to R&R the carbs, to make jet changes  (stock airbox base & all coils/igniter modules mounted to it)
Tony - you looking in? 50 pilots, with mixture screws at 1-1/2 turns, and it sounds happy off the bottom. EMR needles in 4, with 165 mains - AND, our 'gremilns' are still having a field day - YET, it seemed on the quick road test I did, the problem may have shifted a bit - to a little more than 1/4 throttle. However, we aren't supping champagne today 

[clubhousemotorsports]

Carbs do not usually act like a limiter, the point I was trying to make is you may be heading in the wrong direction with the carbs (electrical not fuel) . If the carbs were off as little it would not run great but not shut off like a limiter. Too lean a main and it should feel flat, too rich a bit choppy but if you are within 10  jet size it should be good but not great.

Were the heads ported? If so then go leaner on the mains.
What RPM does it happen at and is it consistant regardless of throttle position? can to hold 1/2 throttle to the same RPM and re-create the problem?  1/4 throttle etc.

The bike with the bad aftermarket boxes worked just as you describe but without a dyno it is hard to see what is happening.
What order are the pick up wires in where they enter the ignition boxes ?
What color wire enters the  box as you have the connectors at the top and facing you

  Two pin                          Three pin                                         Box #2                     Two pin                                            Three pin
  Black       yellow            Black      Brown/green          red                                                        White             Red                             Black           Gray           Red

What do you have?

[koko64]

FCRs are pretty good at taking an over rich main jet when asking for it so it could still be an ignition pick up or ignitor issue Eric suggested. The 185 mains I understand killing the motor but a jet or two must be something else. With an unported motor and open but stock airbox I would have even tried the stock needles first. Sudden killing of power might still be electrickery.

[Brid]

Carbs do not usually act like a limiter, the point I was trying to make is you may be heading in the wrong direction with the carbs (electrical not fuel) . If the carbs were off as little it would not run great but not shut off like a limiter. Too lean a main and it should feel flat, too rich a bit choppy but if you are within 10  jet size it should be good but not great.

Were the heads ported? If so then go leaner on the mains.
What RPM does it happen at and is it consistant regardless of throttle position? can to hold 1/2 throttle to the same RPM and re-create the problem?  1/4 throttle etc.

The bike with the bad aftermarket boxes worked just as you describe but without a dyno it is hard to see what is happening.
What order are the pick up wires in where they enter the ignition boxes ?
What color wire enters the  box as you have the connectors at the top and facing you

  Two pin                          Three pin                                         Box #2                     Two pin                                            Three pin
  Black       yellow            Black      Brown/green          red                                                        White             Red                             Black           Gray           Red

What do you have?

Looking from back of bike - LHS 2 pin White/Red, 3 pin Black/Green & Brown/Red    RHS 2 pin Black/Yellow, 3 pin Black/Grey/Red

[Brid]

FCRs are pretty good at taking an over rich main jet when asking for it so it could still be an ignition pick up or ignitor issue Eric suggested. The 185 mains I understand killing the motor but a jet or two must be something else. With an unported motor and open but stock airbox I would have even tried the stock needles first. Sudden killing of power might still be electrickery.

Hey Tony - Who knows if the heads have been fiddled with? It really feels like it is starving for fuel, when the needles come into play, so I ordered some really rich ones - GJM's, and some basically between them and the EMR's I have in it - FHN's. At least I can get a better feel for what it's asking for, by having a better selection of needles. Sure, a dyno would be great - but, at $100 an hour, I'd be a poor man just doing 3 or 4 jet changes -- plus, I'd maybe need more jets/needles than I have!

[ducpainter]

I never saw Eric suggest that you jet it on a dyno. He suggested to do a dyno run with an EGA to see if the air/fuel ratio is close when this thing acts like, in your words, it hit a rev limiter.

...and when he say's...

Does it feel like you are hitting a rev limiter?
I have seen aftermarket ignition boxes cut power as a rev limiter way too early. They ran great until the same rpm and then killed it. In our case we popped on some oem boxes and all was good again. Know that some of the Ducati performance boxes also had built in limiters.

I have also seen kits to run non-resistor plugs and wires that caused all kinds of issues as the noise messed with the ignition.

Best thing you could do would be to get the bike to a Dyno and pull air fuel. I had a customer trying to jet a bike that had bad boxes so until you see what air fuel and what happens when it falls on its face you might be spinning your wheels.

It's because he's seen it.

[Brid]

I never saw Eric suggest that you jet it on a dyno. He suggested to do a dyno run with an EGA to see if the air/fuel ratio is close when this thing acts like, in your words, it hit a rev limiter.

...and when he say's...
It's because he's seen it.

Ducpainter - Yes, I understand what Eric is saying - but, as I replied, we don't have an accessible dyno locally -- period, so that's ruled out. I did more than my fair share of dyno runs when I was building/racing bikes, and fully understand the huge benefits of having a smooth fuel curve. In this case, it is unfortunately the 'seat of the pants' dyno, and I am sincerely thankful for all the help so far.

[Brid]

Eric - thanks for the sensible suggestions, I really do appreciate the help here. The wiring I have does seem to be reversed from what you wrote?

[ducpainter]

Ducpainter - Yes, I understand what Eric is saying - but, as I replied, we don't have an accessible dyno locally -- period, so that's ruled out. I did more than my fair share of dyno runs when I was building/racing bikes, and fully understand the huge benefits of having a smooth fuel curve. In this case, it is unfortunately the 'seat of the pants' dyno, and I am sincerely thankful for all the help so far.

I think you're missing the point.

I have to admit that I know Eric, and without a dyno or EGA to prove it, my gut feeling is he's telling you to stop chasing jetting, and look at ignition, if in fact this bike acts like it's hitting a limiter.

I certainly know I'd trust him, and his many years of Ducati experience...don't want to date him but I met him in '00 and he had been at the shop a while...more than an ebay vendor that assures you his ignition boxes are the ticket.

Now if the bike is just a little flat at a certain throttle position/rpm, then jet away.

Which is it?

[Brid]

I think you're missing the point.

I have to admit that I know Eric, and without a dyno or EGA to prove it, my gut feeling is he's telling you to stop chasing jetting, and look at ignition, if in fact this bike acts like it's hitting a limiter.

I certainly know I'd trust him, and his many years of Ducati experience...don't want to date him but I met him in '00 and he had been at the shop a while...more than an ebay vendor that assures you his ignition boxes are the ticket.

Now if the bike is just a little flat at a certain throttle position/rpm, then jet away.

Which is it?

Going back to when this thread started - yes, it feels like it's hitting a limiter, and that's why I changed out boxes/coils/wires (the spark was weak), went back & double checked the air gap/timing, checked cam belt timing, and just did a valve adjustment. It was doing this with the OLD Kokusan boxes/coils/wires, and first advice given, was that the FCR's must be correct in all stages, or they will give this condition. Everything mechanical is now addressed, so it's either 'lecktrickery' or jetting. There have been a couple of times when (on the road) I just twisted on, and tried to get it through 'the bog' - which is consistently at 1/4 throttle, and when it starts to clear, it wants to take off big style. the bike doesn't have current license tags, so I can't go too far from the shop, and my 'test run' street isn't too long! Would bad boxes clear up at higher revs?