Bike breaks up at ~5500 rpm (long but questions at end)

[rdsarefun]

I had some time today to install my Dyna S ignition.  I determined timing with a dial indicator and roughly set timing, then once running fine tuned with a light at zero degrees advance, dynamically set the timing.  I am almost out of adjustment slot but have this now set to 1.8mm.  To rehash, bike is as follows:

Stock bore 75 350 with DG pipes. Bike has a K&N with a new Y boot.  I have the carb currently (set up with Dave F mod)5DP7 jet needle, 169P0 primary needle jet, 27.5 pilot, with 200 mains and the needle clip in center position, air screw 1 turn out from seated. I took the bike for a ride and is crisp but breaks up at around 5500 rpm really bad and I cannot rev thru this.  I then installed new coils today and BH8S Resistor plugs per below (John from Economy)

Replacement Ignition Coil Kit - for Yamaha RD/R5/YDS6/7. Every thing you need to replace your coils, plug caps and ignition coil wires. Kit Includes the following:
2 Replacement Coils, same dimensions as stock coils, same bolt spacing. Easy to mount and install.
2 NGK 5K Resistor Spark Plug Caps
2 Feet of high quality Ignition Coil Wire[/b]

 With the new coils, it still breaks up at same point.  I did have to repin the gender of the yellow and black wires from the kit as the black was a female connector and the yellow was a male connector as opened from box.  The kit came with crimp on connectors and I replaced, these are now pinned to hook up.  I have changed every ignition part, plugs and coils and have a solid battery that charges around 14.2 volts at 2kRPM.  it seems electrical and does not appear to be running out of gas (just a guess), but just getting bike sorted and don't want to change too many items at once.  Was wondering if my pilot jet needs to go to a 30, would this help the mid transition range?  At a loss for now.  Also, had a question regarding plugs.  With the new coils is a 5K ohm cap.  I am running resistor plugs, I am assuming this is the correct setup. Bike starts first or second kick , idles at 1500 rpm consistently but cannot rev past this point, can only swap gears to drop RPM and then rev to this point where it breaks up. 

[rded]

B8HS are not resistor plugs. BR8HS are resistor plugs

Others more knowledgable than I will chime in but it sounds like you need to lower the needle clip and with chambers and boot intake, your mains would probably need to be like 230.

[m in sc]

try your coil & ignition power (temporarily) straight to the battery. see if that cleans up the running. if so, its a connector or internally corroded wire int he harness, or the key or kill switch. I think you are chasing a symptom of another issue.

[rdsarefun]

Correction, I installed BR8HS plugs within bike.  Most likely will cobble together a plug/switch combo at work this week and test next weekend powering coil directly from battery

[rdsarefun]

07/22/23 update.  I ended up putting on banshee intakes and a crossover tube, 3/8" thick reed spacers and upped my pilot to a 30 and main jet to a 220 (from a 27.5 and 200's, clip still in middle position). With the spacers, I did not need to cut the ears off the banshee intake, just cleared. Upon startup, idled higher so set this back to 1500 rpm and took it for a rip.  This time it broke up at 6K rpm (from 5500) but made it thru and pulled hard until I dropped out near 9K.It could never pull past 5500 before.  To me sounds like it was starving for fuel and I must have been experiencing the mid range stumbles I read about.  My 73 with stage 1 top end from Chuck Q never missed a beat all the way to redline.  wondering if I should go up on main again or move needle clip, wanted to get some ideas.  Thanks, Brian

[m in sc]

where waqs throttle at 6k when it broke up? if 3/4 to wide open might be main? but?

[rdsarefun]

Throttle was roughly at ~3/4+ when this occurred. I have a 220 main in it now, may go to a 230 , but need to buy some more as 220 is largest I have at present.  Thanks for the input.

[m in sc]

do you have 190s? try those 1st. 

[Striker1423]

Honestly, break up at high RPM for me always occurs from 3/4 throttle up when the main jet is too large. I'm on 210's now, and the bike really needs 200's or even 190's.

[m in sc]

Honestly, break up at high RPM for me always occurs from 3/4 throttle up when the main jet is too large. I'm on 210's now, and the bike really needs 200's or even 190's.

that was my point (190s) after eliminating the ign as an issue.

[Jspooner]

do you have 190s? try those 1st. 

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