74 CB360 cranks, backfires, but won't run

[dlogreen]

I have a Harbor Freight dynamic light. Works fine and didn't break the bank.

Ethanol can clog up little jets fast if the carbs are left with fuel in the bowls.

I don't *think* a leak at the headers would cause a hang, but improper timing, air leaks, or issues with the advancer could. Carb balance also, but you've not changed the carb synch since it was running good.

Yeah I don't run anything but 89 or 90 Ethanol-Free, so there shouldn't be any sludge in the bowls, but I suppose it could still dry up and create some blockages even without ethanol? I might throw some fuel treatment in there too just in case, while I look around the other stuff.

I have a HF right by me, like 2 miles, so i'll swing by tomorrow first thing and check. I didn't adjust anything else on the exhaust other than the elbow section and it welded right up earlier today. I'll go back over everything again... double check timing, valves, mixture screws (which I assume could be affected by new better seated exhaust valves), pilots and other carb circuits, throttle idle screw, etc.

Also, never used a dynamic timing light, so i'll be learning that tonight lol while I grill chicken and porkchops on the back porch

 

[stl360+450]

Also, never used a dynamic timing light, so i'll be learning that tonight lol while I grill chicken and porkchops on the back porch

It's pretty simple. I tend to use a spare battery to power it, but it can be powered by the battery on the bike.

Clip the pickup over one or the other spark plug wire and then point the light at the rotor and squeeze the trigger. The strobe light will help you see the point at which the corresponding cylinder is firing.

Mine has a dial on the back that allows you to adjust the the timing of the light itself. I suppose it could be used to determine the actual advance angle, but sometimes I accidentally bump that dial, which is annoying because it throws things off. Helps me understand why many performing guitarists put tape over pickup selectors, tone knobs, and volume knobs for shows!

 

[dlogreen]

It's pretty simple. I tend to use a spare battery to power it, but it can be powered by the battery on the bike.

Clip the pickup over one or the other spark plug wire and then point the light at the rotor and squeeze the trigger. The strobe light will help you see the point at which the corresponding cylinder is firing.

Mine has a dial on the back that allows you to adjust the the timing of the light itself. I suppose it could be used to determine the actual advance angle, but sometimes I accidentally bump that dial, which is annoying because it throws things off. Helps me understand why many performing guitarists put tape over pickup selectors, tone knobs, and volume knobs for shows!

it's funny you mention tape and stuff... I'm a performing guitarist, and instead of making them unchangeable on the fly (each room or song might need something different), I shove small grippy O-rings under the knobs to act as friction between the base and the body. Great for general settings retention, but i can still reach down or use my toe to spin em if I need to in a pinch. That and I use low profile small knobs on my tone and volume... or flip the control plate on teles to avoid he dreaded switch flip. big difference between a tele neck and bridge pickup.

to address the dynamic, I had one overnighted from amazon cuz by the time I get to that, chances are it'll be here, and i might not need it. but still useful to have. I watched a few vids and I understand now... I think i was thrown by some using the battery ON the vehicle while others went with a spare. induction coil to trigger makes sense, so should be cool to see even if everything is good. If that ended up being the fix...how neat to get a tool and truly use it to correct the issue.

 

[dlogreen]

I have a Harbor Freight dynamic light. Works fine and didn't break the bank.

Ethanol can clog up little jets fast if the carbs are left with fuel in the bowls.

I don't *think* a leak at the headers would cause a hang, but improper timing, air leaks, or issues with the advancer could. Carb balance also, but you've not changed the carb synch since it was running good

After some more thought, practically.... I changed the exhaust valves, but they are lapped, and should not be leaking. intake valves are sealing well.... no issues there. i did not replace the head gasket only because it did not tear or peel off with the head when I removed it....likely bc it had only been on there for a month and with minimal actual mileage.

high hanging intermittently has to be timing or a leak, and I'll triple check to make sure I didn't accidentally wiggle my pods and intake runners loose before i tear into anything else (though before when I had a whole pod pop off, it didn't hang, it just didn't wanna idle nicely). Since the bike is cold currently, I'm gonna recheck the valves and check the timing while I have the stator cover off.

I'm starting to think that protruding seal could be the issue, so again, while I'm checking the timing, I'll use my meter and light for audible and visual indication of points opening and closing in time, check the points plate to see if it rotated when I was tightening it, and then pop off the plate and the advance and see if it's dragging on the seal, at which point I'll loosen the valve cover and tap the seal into a better seated position.

I'll report back after I get thru this checklist. Shouldn't take more than an hour or so

 

[ancientdad]

i did not replace the head gasket only because it did not tear or peel off with the head when I removed it....likely bc it had only been on there for a month and with minimal actual mileage.

I realize you're on a budget, but a head gasket that had been fully torque-crushed and through heat cycles over the course of a month should have been replaced. It's obviously the fire ring that's most important.

 

[dlogreen]

I realize you're on a budget, but a head gasket that had been fully torque-crushed and through heat cycles over the course of a month should have been replaced. It's obviously the fire ring that's most important.

less on a budget and sick of replacing new parts due to silly or unfortunate events. I mean I bought a camshaft right away for $100 but repaired the first one because I didn't wanna sit here idly and wait just to figure out something else needed work.

I see head gaskets online and i don't mind the price, but shipping still takes longer than I'd expect when it can be thrown in a flat envelope and sent for $5 in two days. I'll go ahead and order one because if that's the culprit then I'll gladly replace it. My time is the biggest currency here, not my funds... i have plenty of both RIGHT now, but I would like to spend my time improving the ride not fixing it or diagnosing it.

thanks for the heads up, because I noticed this one has that ring where my FZR600 head gasket is just fiber and metal plates and no metal ring around each cylinder. New one ordered when I read your comment, and if I don't need it, no biggie until the next time.

I went for a walk to get some other stuff done digitally, so now I'm headed out to tear into the bike. fingers crossed I don't find any surprises lol

 

[ancientdad]

less on a budget and sick of replacing new parts due to silly or unfortunate events. I mean I bought a camshaft right away for $100 but repaired the first one because I didn't wanna sit here idly and wait just to figure out something else needed work.

I see head gaskets online and i don't mind the price, but shipping still takes longer than I'd expect when it can be thrown in a flat envelope and sent for $5 in two days. I'll go ahead and order one because if that's the culprit then I'll gladly replace it. My time is the biggest currency here, not my funds... i have plenty of both RIGHT now, but I would like to spend my time improving the ride not fixing it or diagnosing it.

thanks for the heads up, because I noticed this one has that ring where my FZR600 head gasket is just fiber and metal plates and no metal ring around each cylinder. New one ordered when I read your comment, and if I don't need it, no biggie until the next time.

I went for a walk to get some other stuff done digitally, so now I'm headed out to tear into the bike. fingers crossed I don't find any surprises lol

I hear you all around, I'm just thinking of you getting it truly long-term reliable and that doesn't usually happen through shortcuts.

 

[dlogreen]

I hear you all around, I'm just thinking of you getting it truly long-term reliable and that doesn't usually happen through shortcuts.

And we're back!!!

Timing light just got here but no time for that.. re set the cam shaft seal, flush and grease the face of it/rear of the advance. Timing reset, intakes were oddly both too tight after, so reset them and the exhausts were confirmed.

Points gap, mixture screws, manifolds all good.... Started right up.

Took a test ride or 5 and then when about to put her away, I noticed my headlight flickering and my right front turn signal was dead as well as my horn (rear signals both work so it's not the switch. I'll check wiring tomorrow cuz likely something wiggled loose in the bucket.

I also swapped in larger pods to see if it matters, but too soon to know. Next will be making an H-shaped plenum to possibly help intake be more consistent across the carbs.

I hafta run to the gym to lift and coach, so TBD.

Either way, at least we got a daytime rider lol

No hangs no sputtering and held low idle as well. N

 

[EzPete]

The flickering light is likely a ground.

 

[dlogreen]

The flickering light is likely a ground.

Oh yah shelf and not just flickering but it was just out after that....and it's possible the headlamp and front turn and horn share that ground.... I'd hafta look.

Since I have power going back and to the left switch but not the horn, right front blinker or headlight I prolly lost a ground routing to the leftt control.. Starter button and clutch switch work but the clutch ground was wired in afterwards so it's not routed into the bucket.

I'm not stressing it though bc typical wiring isn't that hard and bc I know what lights aren't working, I can literally trace back to them from the bulb and left switch and fork ears. 10 minute fix. And once I get that going I'll set out for a short ride while everybody else should be at work

 

[dlogreen]

Oh yah shelf and not just flickering but it was just out after that....and it's possible the headlamp and front turn and horn share that ground.... I'd hafta look.

Since I have power going back and to the left switch but not the horn, right front blinker or headlight I prolly lost a ground routing to the leftt control.. Starter button and clutch switch work but the clutch ground was wired in afterwards so it's not routed into the bucket.

I'm not stressing it though bc typical wiring isn't that hard and bc I know what lights aren't working, I can literally trace back to them from the bulb and left switch and fork ears. 10 minute fix. And once I get that going I'll set out for a short ride while everybody else should be at work

Hilariously all three issues were unrelated.... Headlight h4 connector came loose, horn positive lead was pulled while removing and replacing the head, and front right signal was just burnt out

 

[dlogreen]

Hilariously all three issues were unrelated.... Headlight h4 connector came loose, horn positive lead was pulled while removing and replacing the head, and front right signal was just burnt out

Now for the fun part with experimentation.... This is my plenum concept.... An "uninterrupted" chamber of air that feeds both carbs and thus technically would balance intake a bit more since they are pulling from the same sources. Using the small pods bc I don't wanna disrupt the other ones that are looking good and working well.

Thoughts?

 

[EzPete]

Even just the longer intake plenum does a lot to stabilize the airflow, paint that PVC black and nobody will know.

 

[dlogreen]

Even just the longer intake plenum does a lot to stabilize the airflow, paint that PVC black and nobody will know.

Kinda my thoughts too. Today it rode pretty well.... A little twitchy off throttle and when holding low rpms in 2nd n 3rd like cruising behind slow cars in residential traffic.

I'm thinking those adjustable cb160 needles might help but it's coming directly back to idle after cracking the throttle and roaming around so I think I got that part sorted. I'll try the needles this weekend, then maybe cut down the 65 primaries I got a few weeks back, and then try the plenum mod....

Or I'll throw the the plenum on there cuz I won't hafta take anything else apart and see whether it's a worthwhile adjustment before digging into the carbs.

Happy to report no hanging idles, electrical issues, overheating or oil leaks. And started right up without choke every time. It's 80 out right now, so I think that makes sense and when it gets cooler I could need a lil choke with the more dense air.

More updates tomorrow

 

[stl360+450]

@dlogreen works fast! You've been through a lot in a short amount of time. I'm glad you are rolling under power again.

 

[EzPete]

I’d go plenum mod first. No sense in trying to trick the carbs on the fuel side if you can solve for air.

 

[dlogreen]

@dlogreen works fast! You've been through a lot in a short amount of time. I'm glad you are rolling under power again.

Thanks! Yah I had a blast riding yesterday. I think before I do the plenum thing I'm gonna get a short ride in on some new plugs and do a chop to see how they're burning. Strong suspicion of some richness, but with this exhaust it's hard to tell by the sound.

I know the timing and valves are spot on, but I could prolly check the balancing and syncing this weekend since new valves could certainly affect how each cylinder is pulling.

It's also a little cooler today, so I'll also get to see what kind of impact that has on the starting and idling.

And then I have a few pinholes to close up on the exhaust that I'll can address tomorrow before cleaning, rust prevention spraying, and wrapping hopefully tame the sound a little as well.

All in all I'm stoked and glad I haven't had any truly catastrophic failures. I'll keep checking things to make sure they stay in place over the next week or so but I got an buddy I met as a mechanic at an old bike shop and he's been wanting to get it and ride the old bikes since he got his back up and running.

Thanks for all the encouragement and ideas as I've chased down these little demons lol

 

[dlogreen]

Small update on the bike. It's been a busy few weeks but I finally got some riding time in between the Florida rain and gigs.

I took it out last Sunday for a few hours and went thru a full tank with no major issues I could notice. I definitely need to add another layer of foam to the seat and swap the hard rubber grips for something a little softer to handle vibrations.

I went thru all the gears and need to check my speed with the GPS, but I feel like I maybe stuck around 70-73mph tops even though I'm certain 80 is doable. This might be where the secondary main and air factor in along with the exhaust which means more tuning.

But after I let it cool off and came back a few days ago, check out my plugs

To me that looks pretty decent. I am running a step hotter cuz I usually do it all my bikes. So these are 7s instead of 8s.

Overall it handled and played well and had plenty of thumbs up from riders and cars that pulled next to me.

Acceleration and stuff was good though, so once I sort out how to unlock more of that top end, we'll be in business.

When I finally made it home after two hours, I did notice some smoke from the exhaust and vent tube, but only when revving. Need for concern? I'm thinking I might have been burning a little oil or it was overfilled a little? Haven't been back out cuz I was dog sitting all week at my girl's house and the weather was spotty every day. But I'll get some rides in this week and check on a few things.

Hope you guys are enjoying some good rides!

 

[crazypj]

Plugs look pretty good to me as well, slightly warm but you said your running 7's.
Something very few seem to know, the ground electrode colour shows if you have correct heat range, there will be a well defined line across it when it's right, usually just before the bend where it's welded to body.
I can't tell if yours are 'perfect' for your riding style/carb set, etc, or it's shadow?

 

[dlogreen]

Plugs look pretty good to me as well, slightly warm but you said your running 7's.
Something very few seem to know, the ground electrode colour shows if you have correct heat range, there will be a well defined line across it when it's right, usually just before the bend where it's welded to body.
I can't tell if yours are 'perfect' for your riding style/carb set, etc, or it's shadow?

Here's a close up of another pic I took, and I was blocking the sun, so don't think there's a shadow.

I didn't know that about the bend reference, but that's helpful.

You think running 8s might be better? This ride was 80% US 1 and A1A up in Jax, so I wouldn't say WOT but I was over half for sure most of the time, and since I live close to the hwy, it didn't have a chance to really hang out in the low throttle range more than a few minutes out of two hours at the end.

I'm open to suggestions, and I hope to do some more tuning this week/weekend. Thanks!