A loud pop, then engine dies, then I have to push a cb350 2 miles

[cgguy09]

Hey team,
So I've been riding my bike for about 200 miles,no problem. Just got new coils and wires because i was rolling on an old set. I was riding no hesitation or issues with the bike. Then I heard a single "pop" and my engine quit, right then and there. I hit the electric start and chuck start but it felt like the engine just turned over very easily.... It normally feels like there is more resistance. I tried to put it in gear and pop start it...nothing. I could tell the engine was turning but there was no combustion. I finally got it home, and check for suck bang blow. There was gas. (Check). Battery was good (check). There was no spark on either cylinder ( fml). I could feel the exhaust when I turned th engine over ( check).

Sounds like an issue with the spark, right? There is one other concern, when I put th bike in gear I can now roll it forward, there is some slight resistance, but very little, I can't however roll it backwards. I Adjusted the clutch to ensure its not that.... Still rolls with no resistance. When I tighten up the clutch and put it in first gear and hit the starter it moves the bike forward but the engine sounds like its revving higher then it should be. The engine whenever I hit the electric start sounds like its whining.

I checked the coils, they are still intact, no wax. Clutch ( before I loosened it) still lessens whatever resistance is there. All the wires to the coils are set.

This sounds like it could be combination of problems.... But I'm at a bit at a loss. I haven't read or come across a problem like it before. I'm. Sure you wise sages have. I'll take any and all advice.

What a terrible Way to go to bed

 

[bradj]

Did you meet the nicest people?

 

[SONICJK]

Did you meet the nicest people?

BWAHAHAHAHAHAHA
douche ;D

 

[cgguy09]

Did you meet the nicest people?

I hate the entire world at this moment.... But especially you.

 

[bradj]

I hate the entire world at this moment.... But especially you.

take a number and relax 95% of the members here have pushed a bike

 

[Catbird]

Well, you've got a good start with your diagnosis of symptoms, very analytical. That's a start.

The same exact thing happened to my car a couple years back. Literally *exactly* the same symptoms. Right down to no spark.

THat can be attributed to the fact that in many cases the ignition is driven off of the camshaft in a 4-stroke, since the two functions are in-phase with one another.

I'd be inclined to suggest you broke your timing chain and your valves aren't closing to create compression, but the piston is moving well enough to create air movement and the backpressure from the carb in the intake side is preventing it from blowing out that direction.

Major props for pushing the bike though. I'm a fat, lazy arse and I would have cried to someone on the phone with a pickup truck to come get me.

Actually, the last time my bike came apart beneath me, that's almost exactly what I did. XD

 

[bradj]

^this is what happened pray you didnt bust the case

 

[Sonreir]

Yup. Cam chain is my guess. Probably need new valves, maybe new valve guides, too. Possible head damage. Hopefully nothing else.

 

[HerrDeacon]

Did you recently do any top end work on the bike? The two cam sprocket bolts don't like to be reused and can shear off or back out. The lack of resistance when starting it would scare me, doesn't sound good. Pop your tensioner off and have a peek in the hole to see if the chain is still intact and under tension. You could also rotate the engine by hand while watching through the valve adjustment ports to see if they are moving as they should. Hopefully its just something minor.

 

[TheJester]

Guaranteed timing chain issue, no compression and no spark.. Points are driven from the camshaft, and valves will not be actuated causing the lack of compression. Hopefully nothing got destroyed. Good luck.

 

[cgguy09]

Did you recently do any top end work on the bike? The two cam sprocket bolts don't like to be reused and can shear off or back out. The lack of resistance when starting it would scare me, doesn't sound good. Pop your tensioner off and have a peek in the hole to see if the chain is still intact and under tension. You could also rotate the engine by hand while watching through the valve adjustment ports to see if they are moving as they should. Hopefully its just something minor.

Hey guys,
I plan on popping the tensioner off as soon as I get home from work, I'll also do a compression test. The cam chain breaking/ coming off would make sense concerning I'm not getting any spark from the plugs despite new coils and a new battery. I did do a top end rebuild about 500 miles ago & I did reuse the same cam-sproket bolts (I didn't think to replace them). I'll also popoff the valve caps and peak and see if there is any movement.

I'll report back with my findings.
Thanks, boys.

cFogs Out
BT
NNNN


P.S. I'm glad I had a fully charged battery, because the road I pushed the bike up and down was completely dark and had tons of turns and that HID headlight was the only thing that let me see where I was going & ensured car's didn't hit me along the way.

 

[cgguy09]

Guaranteed timing chain issue, no compression and no spark.. Points are driven from the camshaft, and valves will not be actuated causing the lack of compression. Hopefully nothing got destroyed. Good luck.

^^^
My thoughts exactly.

 

[Catbird]

We all learn at some point that there's two ways to do anything in this world, do it right or do it again. I think you'll do it just fine this time around, brother!

Just take your time and be patient, and if it looks rougher than you thought, don't get discouraged.

Don't worry! You've got this.
As long as you're still breathing, there's always more time.

As long as you haven't got high-compression domed pistons or a high-lift cam with a crazy duration (and that you said there was only one pop, not a single pop followed by a cacophony of clattering), there's a good chance that you haven't damaged your pistons or your valves.

 

[GLENNWOOD55CAMEO]

The two cam sprocket bolts don't like to be reused and can shear off or back out.

^^^ +1, I'll bet thats what happened. The bolts broke. If the cam chain broke, it would lock up the engine and prevent it from turning at all. When you rebuilt the top end, were you aware that the two cam sprocket bolts are different and each goes in a specific hole??? One is all thread and the other has a shoulder on it.........

 

[Rich Ard]

Did you recently do any top end work on the bike? The two cam sprocket bolts don't like to be reused and can shear off or back out. The lack of resistance when starting it would scare me, doesn't sound good. Pop your tensioner off and have a peek in the hole to see if the chain is still intact and under tension. You could also rotate the engine by hand while watching through the valve adjustment ports to see if they are moving as they should. Hopefully its just something minor.

Threadjack - Deacon, is that a photoshop job or did you put a fairing on the MB5?

 

[HerrDeacon]

Its a photoshop that I've been playing around with, contemplating doing a half fairing over the winter. I was just about to update my thread with a picture of it. http://www.dotheton.com/forum/index.php?topic=27289.msg590499#msg590499

 

[teazer]

Remove the points cover and press the starter button. Points cam turns - not the chain but maybe the tensioner broke and chain jumped gears - ask me who I know about that one............

If the points cam does not turn the chain is either broken or popped off the sprocket.

If the chain "broke", 99% probability it was the connecting link that was re-used or not put on correctly.

Pull the top cover off to determine which .

 

[cgguy09]

^^^ +1, I'll bet thats what happened. The bolts broke. If the cam chain broke, it would lock up the engine and prevent it from turning at all. When you rebuilt the top end, were you aware that the two cam sprocket bolts are different and each goes in a specific hole??? One is all thread and the other has a shoulder on it.........

Yes, I made sure to put them in the right slot. The manual and all the build threads were very stressing on that.

That being said, when I got the bike, I spoke with the second owner, nephew of the man who orginally owned it, he said the bike had never been rebuilt, everything I've seen on the bike from the worn clutch pads to the tar that was in engine when I first got it lead me to believe he was telling the truth. So I'm willing to bet those are defintely the original bolts (or whats left of them) in there.

On that note, (not trying to get ahead of myself) it would probably be a good idea to switch out the cam-chain even if that's not what was busted, right? Being that this chain likely has 23,000+ miles on it. I'm sure the manual has something to say about that.

 

[Catbird]

It can't hurt to change the cam chain. Hate to find out later that whatever did go wrong, didn't ruin, but perhaps compromised the cam chain and caused you to lock-up at 75MPH. THat would really, really suck.

 

[mydlyfkryzis]

take a number and relax 95% of the members here have pushed a bike

The other 5% have pushed them too, but deny it... 8)