Topic: Carb tuning noob..what's needed

[RRBuGGz]

So I've "finished" my project a few months ago but it's never quite ran right.  I built the bike but never felt comfortable with tuning the carbs and didn't have all the necessary tools ie sync gauges, etc.  I can't seem to find a decent shop out in NY that will a) spend the time to tune it right b) cause damage while working on the bike, or c) just sitting on the bike for weeks.  I've come this far and with it and would like to getting it running as best as it can with using a Steel Dragon Dual air box.  I don't have the option of going back to the stock airbox without relocating my battery which means re-welding my battery box and a couple of other modifications that will damage a good bit of powder coating.  I'm running a Steel Dragon dual breadbox style airbox and a Delkevic 4 into 1 exhaust.  The last mechanic should have installed 120 main jets and 40 or 42 pilot/idle jets..I'm not too sure what's in there now.  When I first got it back from the shop he said the idle was set high around 1500 rpm.  It rode ok but seemed to struggle in the mid to upper rpm range over 5k.  It also struggled to get past 40/50 mph.  I've only taken it around the neighborhood so I haven't gotten it past 3rd gear and it would sometime shut off so I was nervous to take it it out further on open roads and get stranded.  Now it doesn't want to hold idle without a little choke.  I decided to tape up some of the opening on the airbox, but feel like it might have made it a little worse.  I also got it back with some clutch drag that improved after I readjusted the clutch and changed to different oil, but it's not 100% gone.  I've only put about 25 miles on the new oil and clutch plates though.  I'm tired of wasting cash and time behind more shops, so I started researching DIY'ing the tuning and picked up some various size main/pilot jets.  Also going to pick up a motion pro sync tool and a float gauge tool.  Anything else I should look into getting or will need?

Dre

[PeWe]

Be 110% sure that ignition is right before carb tune.

 I have wasted much time and jets hunting a problem caused by a bad (new) HT wire with intermittent conductivity issue that could make engine to sound lean or rich depending on when it occurred.

[RRBuGGz]

Yea I checked before I dropped it to the shop but I will definitely check again just to cover all avenues.

[ekpent]

  Looks like maybe an aftermarket ignition set-up so we can eliminate points and condenser problems ?  You need to open the carbs up sometime to see what you really have in there so you can get a baseline for where you are at. Also since those look like they are 'pumper' carbs you need to verify that circuit is working.  Fun stuff !

[evinrude7]

I would start by pulling the carbs off and bench syncing.

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[pjlogue]

What PeWe said.  Make sure everything with the ignition system is in good order as well as the compression and timing chain and valve clearance.  I would start with valve timing chain adjust.  Then valve lash adjust.  Then check compression. I would be sure your intake rubbers are not leaking as well.  Then you can begin tuning the carbs.  I would first double check the float bowl fuel height and then do a carb sync.   Then adjust mixtures starting with high speed jet and doing a WOT and plug chop and check plug color.  Once you get the main jet go to the needle height mid throttle, then on to the slow jet and finally the idle mix adjust.  Then check your carb sync again.  It is a painstaking process but worth the time in the end.

I doubt there are many modern bike shops that will be willing to do this job the correct way. (or even know how to do it)  Most dealers don't have mechanics.  They have service technicians which is a fancy word for saying their technicians can only follow a flow chart that we give them.  Your best investment (aside from good tools) is a good shop manual. 

-P.

[Mark1976]

Where in NY are you?

[WhyNot2]

In the same boat with my 750.

You have a nice looking bike.

[RRBuGGz]

Where in NY are you?

I'm in Long Island.  The bike was a low mileage bike purchased from a shop (about 8500 orig miles).  It was running fine stock but I couldn't leave well alone.  I've changed ignition to a Dyna S, new coils/wires, sold the stock carbs and purchased a rebuilt/polished one, new clutch plates.  I checked compression before taking it to the shop for carb tuning and all 4 cyl were pretty close.  Ill redo a compression check this week and recheck the timing.  Is it worth getting a timing light tool or is static timing going to get me close enough?

[SohcCBs]

Go here and download the 2nd pdf for the DS1-1.

http://www.dynaonline.com/support/downloads.aspx?p_v=DYNA%20S

There a section on timing the Dyna-S

Static timing requires it to be timed at full advance.  I always did it that way.

.

[Bankerdanny]

Static timing should do fine. All 4 cylinders with similar compression is good, as long as the compression level they all have is within spec. The downloadable manuals available here at the Forum will have that data.

Have you pulled your plugs to check for color? That will give you some clues.

If you decide to confirm the jet sizes and bench synch, if the 750 PD series carbs are similar to the 550 PD series carbs, the #2 slide is non-adjustable, so you use it as a reference to set the baseline heights.

My understanding is that the exhaust and filter setup you have shouldn't require a big change in jet sizes over stock.

be systematic, don't just start throwing parts randomly at it. That is a recipe for major frustration.

[RRBuGGz]

So got around to checking compression and pulling the plugs.  I did notice plug #2 was a little loose.
 Cyl 1 - 145,  Cyl 2 - 135, Cyl 3 - 130, Cyl 4 - 145

Comparing the plugs to pics online am I right to assume they are reading lean?  These plugs only have about 25 miles on them.  I swapped to some new NGK iridium plugs. The bike started up fine and I was able to get it to idle without any choke. I had to adjust the idle to 1500 because any lower than that and the throttle would hesitate and sputter before revving normally. With 1500 rpm it revs fine. I will run the bike again tomorrow as it was late and see if it holds idle.  I will check/adjust the valve clearances, check cam chain tension, and check timing next.

[RRBuGGz]

Here are of a couple of vids showing idle under 1500rpm and idle at 1500rpm

[Bankerdanny]

I found that my bikes are happy with idles in the 1000-1100 rpm range, so you aren't far off. You really shouldn't worry too much about dialing in the idle until you have the mixture and balance correct. The idle is the last thing you set.

[RRBuGGz]

I found that my bikes are happy with idles in the 1000-1100 rpm range, so you aren't far off. You really shouldn't worry too much about dialing in the idle until you have the mixture and balance correct. The idle is the last thing you set.

Understood, I was just trying to get it to a point where it stays on long enough to be rideable to test out and not shut off at every stop sign.  Had a few minutes to spare so took it out for a quick ride.  Idle was holding up but the bike doesnt want to get past 4500rpm in any gear.  It feels like its maxxed out.

[Bankerdanny]

It should be pulling hard at that point.

[RRBuGGz]

Checked out the timing and everything looked good.  Still only pulling up to 4500/5000rpm then maxes out.  I need to pick up a new set of feeler gauges tomorrow and check the valve clearances.  Last time I checked the boots looked ok but I'll check that again as well.

[RRBuGGz]

So figured out why the bike couldn't get past 4500rpm.  I had taped up some of the holes around the perimeter of the air box and left the bottom of the box open.  I removed the tape and now the bike is accelerating much better now.  Still have to figure out the clutch drag issue.