CB360 missing on one cylinder after 1/2 throttle

Swapped coils, same problem. Thought it might've been a ground connection on that side since the ground is through the bolts, and the tab on the aluminum plate that I made to fit the MikesXS coils to the stock 360 bracket broke when I swapped coils. However after fixing it, the problem persisted.

I'm going to pull the hats and check the diaphragms, and email Dyna to see if I can bench test the Ignition Booster.

-MK
 
mktsc said:
Swapped coils, same problem. Thought it might've been a ground connection on that side since the ground is through the bolts, and the tab on the aluminum plate that I made to fit the MikesXS coils to the stock 360 bracket broke when I swapped coils. However after fixing it, the problem persisted.

I'm going to pull the hats and check the diaphragms, and email Dyna to see if I can bench test the Ignition Booster.

-MK
Click to expand...

Look REAL close and use a light from behind...it could just be a pin hole. I got lucky when mine tore...it was a 1/2 inch hole. very easy to spot.
 
Verified float height, both carbs are spot on. Diaphragm looks brand new.

It's looking more and more like a fault with the Ignition Booster.

-MK
 
Probably the dumbest thing anybody could ever suggest, but....could you test the bike without the added "booster?"
 
I had thought of that, but instead of being an add-on piece when I did the harness, it's part of the system. I could probably rig it up, but I'm going to wait to hear from Dyna to see if there's a definitive bench test that will allow me to evaluate it. At this point, there's not much more it could be.

-MK
 
Yep, Im sorry bud, I thought for sure it would be diaphragm.
Your battery voltage was good at 5000rpms? under 15v
 
I think you can get on Dyna web site and find troubleshooting instructions for some of the stuff.
Mostly though, they want you to send it back and let them tell you there is nothing wrong with it (after they fix it probably?)
 
Finally got some time to wrench on the bike. I completely removed the Ignition Booster from the bike and ran the wiring stock way.

AAAAND it didn't fix it. I pulled my points plate AGAIN and verified that the advancer was functioning properly (it is). The only significant thing I found was that the points were a little dirty. I cleaned them with a business card and there was some junk that came off of them, but both of them were dirty and I can't get my head around this being the sole source of my issues.

Not sure where to go next...

-MK
 
As I said, swap coils from left and right. You shouldn't have to unbolt anything, just swap the four wires I mentioned.
 
Swapping the coils isn't intended to fix it, but to see if the problem swaps cylinders.

Pull the plugs. With the plugs inside the insulator boot and the threads resting on a good solid frame or engine ground you can test the spark quite easily.

Open your points cover. Rotate the engine via the crank bolt or kick start until the yellow point breaker is closed and the dot on your points cam is at the point where the breaker-arm contacts the points cam. Switch the ignition to ON and with a flat-head screwdriver, repeatedly open and close that breaker point. Then rotate the engine to the appropriate angle for the other side and repeat. Never leave the ignition on for more than a minute.

Post the condition of your spark. Better yet, try to snap pictures of it. It is possible, opening and closing rapidly.

Finally, we need to insure that your coils are using the ground electrode as a ground, and not the other way around. Polarity effects performance as these coils are intended to work one way.

After you look at the condition of your spark, pull the insulator/boot off of your high-tension lead. Return the spark plug to its hole. You may need an extra hand with this.

Try not to make contact with any ground! A good 15,000v won't kill you but it will make you back away and summon a string of words that would reprimand a Marine.

Grab a sharpened graphite pencil. Hold the high-tension lead about an inch from the post on the spark plug. Now place the pencil in between these two points and use a screwdriver to open the breaker point. A long white spark should jump to the pencil and then might jump to the spark plug. Move the pencil closer to one point and the other. At no point should there be a spark between the spark plug and the pencil. The spark should always originate from the high-tension lead. If a spark originates from the spark plug, your poles are reversed...
 
Since the bike starts, idles, and runs fine until I open the throttle, I'm not sure what this would show me. I've pulled the plugs and verified that I'm getting a decent spark. I've switched the coils and the issue stayed on the same side, so the coils are performing correctly. I'm just not sure where to go from here.

The plug is dry and sooty when I pull it, not oily and wet. I'm not sure what that tells me, but it's definitely repeatable.

Is there any way to definitively determine whether it's carburetion or ignition?
 
mktsc said:
Is there any way to definitively determine whether it's carburetion or ignition?
Click to expand...

Process of elimination. It's one of these three: electrical/ignition, mechanical/compression, or fuel delivery.

If you will test the polarity of the coils as described, then we eliminate the ignition and electrical, assuming the spark is good.

Next you need to compare compression (when hot) between the two cylinders.
 
I guess my point is that the bike ran perfectly for 4 months and a lot of miles with the coils wired the way they are now. Plus if one of them was on the fritz, it would've showed up when I swapped them.

I'm going to check compression and valve clearance tomorrow.

-MK
 
If you don't want to have to buy new coils sooner, I suggest you double-check the polarity. Wired incorrectly, they'll run fine, but cook faster.

Continue in this order:

Adjust cam-chain tension.

Check timing mark on camshaft.

Adjust valves.

Then check compression. If the difference is no more than about 5lbs maximum on this engine, fire it up and see if the adjusted clearance and cam-chain helped.
 
I pulled the carb hat back off of that carb, and found a small tear in the diaphragm that I must've missed before...
 
mktsc said:
I pulled the carb hat back off of that carb, and found a small tear in the diaphragm that I must've missed before...
Click to expand...

I didnt want to sound like an a-hole but I was gonna tell you to check it again.

that sucks...but I am glad you found it!
 
I appreciate it. I was just racking my brain thinking what I changed since the bike ran. Decided to start rechecking the obvious. The comment you made about a pinhole had me doubting myself. Which is good, because that's what it was. I'm going to pull the tank and reinstall the Ignition Booster again before the diaphragms show up.

I've already emailed JBM to get a pair of them. Thanks for all the advice.

-MK
 
mktsc said:
I appreciate it. I was just racking my brain thinking what I changed since the bike ran. Decided to start rechecking the obvious. The comment you made about a pinhole had me doubting myself. Which is good, because that's what it was. I'm going to pull the tank and reinstall the Ignition Booster again before the diaphragms show up.

I've already emailed JBM to get a pair of them. Thanks for all the advice.

-MK
Click to expand...
Anytime bubba, I am delighted I could actually help out this time.
Also, I understand it can be hard to find. But if you can find 90 octane fuel OR fuel labeled as "recreational 90" rather than "unleaded 87" or "premium 93", chances may be good it doesnt contain alcohol or ethanol. Be sure to ask the owner, though. Anyways 90 recreational is pure gas. Ethanol and alcohol both detroy the o-rings and diaphragms in carbs. I am lucky all the rich farmers around me insist Don keeps it in stock, for their antique tractors.
Most gas starts out at 90 and they cut it w ethanol to make 87, or add alcohol to boost it up to 93.

gas_zpscf120d3d.jpg
 
We have a local marina that carries 89 octane with no ethanol. I usually get a 5gal can filled every year for the mower and all the yard equipment. Unfortunately the pump is on a dock, so you can't just drive up and fill up.

I'll have to keep an eye out for recreational, although I can't say I've ever seen it here in Ohio...

-MK
 
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