Help Dialing in Engine

[ScottyShy]

I've got a 1983 with an electronic Boyer ignition, Hugh's PMA, and stock Bikuni bs34 carbs. I recently had a leakdown done and i've got 4% on the left, and 12% on the right. So, I know I won't be able to get her running perfectly, but I feel like I can still dial it in better than it is now.

It starts right up, (kick only) and idles fine. My main problem seems to be after i get to about 3000rpms and up. (I'm not 100% sure on the rpms because I removed the tacometer). But i have good power in the lower part of my gears. I adjusted my valve clearance at the end of last year, have checked the cam adjustment, and have been tinkering with the carbs to try and get it running better, but i seem to be stuck. It kind of sputters around 3000rpm like it's struggling, but i can't tell if it's struggling for gas/air mixture, or if my timing could be the issue. (i don't have a timing gun).

I know this is a broad and vague question, but any tips are appreciated.. thanks!

 

[grizld1]

First off, your leakdown numbers aren't too bad at all. 4% pressure loss is exceptionally good, 12% is only 2% over the 10% loss that's acceptable in a street engine, and loss may decrease with use if the bike has been sitting. Based on the information you've given, I can offer only two bits of advice. First, buy a strobe and and a multimeter. Second, use them. Find out where the ignition timing is at idle. Then find out if the ignition is advancing as rpms rise. If not, check power supply to the ignition. If the Boyer isn't getting adequate power, it won't advance correctly. Don't just check battery voltage (you do use one, don't you?), check voltage at the wire that sends power to the Boyer control box.

 

[ScottyShy]

First off, your leakdown numbers aren't too bad at all. 4% pressure loss is exceptionally good, 12% is only 2% over the 10% loss that's acceptable in a street engine, and loss may decrease with use if the bike has been sitting. Based on the information you've given, I can offer only two bits of advice. First, buy a strobe and and a multimeter. Second, use them. Find out where the ignition timing is at idle. Then find out if the ignition is advancing as rpms rise. If not, check power supply to the ignition. If the Boyer isn't getting adequate power, it won't advance correctly. Don't just check battery voltage (you do use one, don't you?), check voltage at the wire that sends power to the Boyer control box.

I don't have a traditional battery. I have a tiny battery and a sparx capacitor that basically help the kick start. I was under the impression that the hugh's pma would give me the power I need without a battery.

I already own a multimeter, but i'm not sure how to use it to check the voltage on the bike. (i uploaded a pic, will this one work?) What setting, and how much voltage am i looking for? Also, if i find out that i'm not getting enough voltage, am i out of luck with my current set up?

 

[figure8]

Battery load test, 12v setting. When reving to 3000 rpm you want to see around low 14.xx volts. If it's spiking up over 15 or more it's likely the regulator. You are definitely not shit out of luck though. I would invest in a strobe light and see where things are in that regard. A bigger battery might need be a bad idea as well.

 

[ScottyShy]

Ok, I got a timing gun. I've tried watching a few videos, but i'm still a bit confused on how to use it and what i'm looking for. I understand that i need to take the plates off to see my boyer ignition and the fly wheel to see the TDC mark. Then I shoot the light at the TDC mark while its idling and while revving the engine, but what am i looking for with the gun?

 

[weekendrider]

The mark on the rotor in relation to the mark at the fixed point. In this case marks cast into the stator housing. At idle you would want the rotor mark to between the lines around the F. At a higher rpm it should move to the left but not go past the mark about an inch to the left of the F. That is the full advance mark.

 

[grizld1]

It's an '83 WR; no cast marks, just a movable timing plate marked for F (Fire) and TDC. Scotty, when you aim the timing light at the alternator rotor, the line on the rotor will appear to stop. With the motor idling, the rotor mark should not appear to stop at the TDC mark on your timing plate! It should appear to stop in the range bracketed by the U-shaped F mark. When rpms increase, the rotor mark should appear to move to the left. See the notch in the case below the leftmost stator mark in WR's photo? The rotor mark should appear to stop at the right hand side of the notch, and should not move farther to the left. If the mark does not appear to move as rpm rises, you probably have a power supply problem.

 

[ScottyShy]

Ok, thanks guys. I put the Hugh's PMA on my bike, so it's a little different than the stock set up, but I do have a sticker that marks the Fire, TDC, and Advance positions. So to be clear, while idling, the line should hover around the Fire mark, and then when I give it gas it should move left towards, but not past the Advance position?

Will I need to adjust any settings on the timing light between the idling test and the higher rmp test? Also, will I want to adjust my timing based off when it's idling or when i'm giving it gas? Or should it be one in the same?

 

[DirtyErnie]

Big question: what air filters are you running? can you post a pic?

BS34's HATE the K&N/XSPerformance style pods (I think it's an intake resonance/double carbureting issue)

 

[ScottyShy]

Ok.. here's the update. My power supply seemed to check out with the multimeter. Peaked around 14 volts like you said when revving. I then got my timing gun and dialed in the boyer, but after a quick test ride it was still bogging. I was curious about @DirtyErnie's question about my air filters because mine are pretty shot. (Pic attached. Even though they're relatively new, I had a float issue and gas got into them.) So, I took off my air filters for a quick ride down the street and I had way more power! But it was reverse from before. Instead of having good power at low RPM's then losing power when accelerating, I had great power when accelerating, but there was a bit of a sputter right at the start of each gear. Keep in mind this was with no air filters on.

So, question #1: What are some good air filter recommendations for the Bikuni BS34 carbs?
And, question #2: After I replace my air filters, what adjustments will i have to make?

Thanks again for all the help here.

 

[ScottyShy]

Oh, I had one more question. When i was using the timing gun, the line stayed at the Fire mark while idling, and moved left to the Advance mark when accelerating, but then the line would disappear for a quick second after it reached the Advance mark, like the plug stopped firing. Then it would re-appear as it went back down towards the Fire mark. Is this normal?

 

[5twins]

Yes, those are the bad air filters. Set them upright on your desk and use them for pencil holders, that's all they're good for, lol. Get UNI foam pods, the longer 4" ones. The stubby ones don't flow much more, if any more, than a stock airbox.

 

[ihaxs650]

Oh, I had one more question. When i was using the timing gun, the line stayed at the Fire mark while idling, and moved left to the Advance mark when accelerating, but then the line would disappear for a quick second after it reached the Advance mark, like the plug stopped firing. Then it would re-appear as it went back down towards the Fire mark. Is this normal?

I checked my timing the other day and the line never disappeared from idle to full advance and back to idle.

 

[grizld1]

Good catch, Ernie!

 

[ScottyShy]

Yes, those are the bad air filters. Set them upright on your desk and use them for pencil holders, that's all they're good for, lol. Get UNI foam pods, the longer 4" ones. The stubby ones don't flow much more, if any more, than a stock airbox.

Can I just pop those UNI filters on, or do i need to spray them with the filter oil stuff? i'm trying to read up on them. Also, will i have to re-jet the carbs? I just had my carbs cleaned.

 

[ScottyShy]

I checked my timing the other day and the line never disappeared from idle to full advance and back to idle.

What do you think that means? The white line that is drawn on my alternator is somewhat faded, but i could see it fine at the Fire mark. Is it possible I wasn't aiming the gun at the right place? What are some other problems that could cause this?

 

[5twins]

If you use the black foam UNI pods, you don't need any special oil. Just use a 50-50 mix of gas and motor oil. The black foam is very fine and the regular foam filter oil is too thick for it, it will clog them.

The BS34 carbs on your later model are pretty heavily E.P.A. strangled. Just about any change to intake and/or exhaust will require some re-jetting and carb tuning. But the changes required aren't much really. Maybe one size larger pilot jet and 2 to 3 sizes larger on the mains. Check what you've got in there now. Chances are good they may have been changed already. Your off-idle stumbles indicate that maybe the pilots weren't changed but the decent running at higher RPMs means the mains could have been.

 

[ScottyShy]

If you use the black foam UNI pods, you don't need any special oil. Just use a 50-50 mix of gas and motor oil. The black foam is very fine and the regular foam filter oil is too thick for it, it will clog them.

The BS34 carbs on your later model are pretty heavily E.P.A. strangled. Just about any change to intake and/or exhaust will require some re-jetting and carb tuning. But the changes required aren't much really. Maybe one size larger pilot jet and 2 to 3 sizes larger on the mains. Check what you've got in there now. Chances are good they may have been changed already. Your off-idle stumbles indicate that maybe the pilots weren't changed but the decent running at higher RPMs means the mains could have been.

I remember replacing the main jets last year sometime, but i can't remember if i went up a size. How can I tell? Will it say on the actual jet?

 

[figure8]

I remember replacing the main jets last year sometime, but i can't remember if i went up a size. How can I tell? Will it say on the actual jet?

Yes. Look up the carb guide and you'll see what stock sizes were through out the years.

 

[ihaxs650]

What do you think that means? The white line that is drawn on my alternator is somewhat faded, but i could see it fine at the Fire mark. Is it possible I wasn't aiming the gun at the right place? What are some other problems that could cause this?

I do not have the experience on these XS650 as the other souls that post on this forum. I was checking my timing because of no power in 3rd gear and up. This was after a shop install of Mikes Big Fin 650 kit. The shop says break the bike in! But I do not believe that will take care of this no power. However, I am breaking the motor in!