Bike running poorly after valve adjustment - CB360

Gedigedi

Gedigedi

New Member
Hi All,

So after tinkering with my bike for the last 2 years I have decided I should check my valves.
My bike has been backfiring through the carbs and exhaust prior to adjustment. At night I could even see a small blue flame shoot out once in a while or a good pop through my carbs.
I adjusted for .003 for Exhaust and .002 for Intake as recommended and did my adjustments on the compression stroke ( Left on LT and T on right).
Prior to valve adjustment, I tensioned the cam chain also ( seems to have quieted the bike a bit).
The carbs have been adjusted and modded my PJ himself and I won't be touching them or looking for problems in there. After adjusting my valves I also replaced the spark plugs but did not have a gauge to set the gaps for them ( Is this necessary?)

Once I was finished I took the bike out for a ride and noticed the bike was running way way worse than before adjustment and the backfiring through the exhaust increased x10 and way louder! One odd thing that I am now able to idle my bike at much lower RPMS.

I am assuming that I need to reset my points ignition and maybe check for sticky exhaust valves?
Can anyone suggest some other things I could check ? Exhaust Air Leak ? Did I mess up my valve adjustment?

Thank you,

- Gedi
 
Well, if the only thing you did was valves, then yes, you did that wrong.
Camshaft turns at half the speed of the crankshaft, so there are 2 times the marl on the crankshaft is lined up. Choose the one where the piston is at tdc of the compression stroke and adjust those
You will need to set valves at tdc of the piston that is on its way down from explosion.

Intake is 0.05mm, exhaust is 0.08mm. Setting them both to 0.10 will give you answer to sticky valves, as 0.10 is more then enough. Dont ride for long with valves @0.10, tappets will damage
 
Thanks for your reply. I followed the directions and did set them both at TDC when both valves were closed.
I will crack it open again once I return from a work trip in a few weeks. When both valves are closed, should my rocker arms be loose if I would try to lift them a little?
 
The tappets will be loose when at ACTUAL TDC.

The piston will be at the top TWICE per cam revolution. Once is TDC the other is 360° out.

Watch the exhaust tappets as you rotate the magneto rotor anti-clockwise (same direction as the tires driving forward). If the exhaust valve is closing as you reach TDC, you need to rotate the crank 360° to TDC again and adjust THAT cylinder's valves.

Repeat for the other cylinder.

Once you've set all of the tappets, rotate the engine three full turns and check once more.

Don't set the idle too low. You need RPM's to maintain proper oil pressure.
 
Frogman79 on Hondatwins suggested it might have been to taking the slack out of the cam-chain and effecting the timing.
I think I will set my points and time the bike before I mess with the valves again.
If that doesn't seem to improve, I will turn the bike into yard-art.

- Gedi
 
well taking the slack out of the cam chain only stabilizes the timing o the valves and ignition, it does not change it significantly enough to effect running to the poor side
it sounds to me like you may have a some gremlins working with you :-[
 
Redliner said:
The tappets will be loose when at ACTUAL TDC.

The piston will be at the top TWICE per cam revolution. Once is TDC the other is 360° out.

Watch the exhaust tappets as you rotate the magneto rotor anti-clockwise (same direction as the tires driving forward). If the exhaust valve is closing as you reach TDC, you need to rotate the crank 360° to TDC again and adjust THAT cylinder's valves.

Repeat for the other cylinder.

Once you've set all of the tappets, rotate the engine three full turns and check once more.

Don't set the idle too low. You need RPM's to maintain proper oil pressure.
Click to expand...

you are mistaken in some of this information
the crank is a 180 not 360 so there is a piston at tdc every 180 of crankshaft rotation
 
We're focusing on one side at a time.

Start with left side.

Align LT as you watch the exhaust tappet.

If the tappet doesn't move as you rotate to LT, you're at the right point.

If the tappet did move, rotate 360° to LT again.

Repeat for other side T mark.
 
So I checked my timing today with a strobe and from what I understand I should be hitting right on LF mark and T mark.
Also, I checked my compression after my valve 'adjustment' and I am up from ~120psi to ~150psi.
Take a look at the photos and let me know what you think. What little that I know, my spark is way advanced, unfortunately I'm leaving on a work trip for 2 weeks so I won't be able to report back until come back and adjust my timing.

One thing that really amazes me now is how the bike ran at all before I adjusted my valves.

Managed to take a photo while the strobe was on - at about ~2,000 RPM's

photo1-1.jpg


photo2.jpg


Thanks for your replies,

- Gedi
 
No, you want LF on the left side and F on the right side. Igniting on T will kill that cylinder at low revs.
 
Try to get your timing set at 1000 - 1200 RPM. Much more than that and you're already into the advance curve.
 
Sonreir, so I should be hitting LF and F around 1,000-1,200 rpms and see it hit full advance around 3,000 rpms?
 
1000-1200 for checking initial settings
but you should be more concerned about full advance timing,it is the one that matters because you cannot ride very much at all below 3000
and spin it up to more than 3000 more like 4000 to verify and make sure it is not over-advancing
 
Alright so I am back!

As of few days ago I managed to get my timing right, a friend of mine has a strobe and that helped quite a bit getting it dialed in.

LEFT right around 3K in between two advance marks:


RIGHT right around 3K in between two advance marks:



Unfortunately it is still backfiring but it does appear to be running better. So I have already adjusted my valves and compression has gone up.

As for timing, I made sure to set my points gaps and then rotated the plate while shooting the strobe for each side of the cylinder until both were right in between the advance marks.

Starting to think that I might just be having an exhaust leak possibly and will check that tonight when I get to the garage.

Any other ideas?


Thanks!
 
If compression and timing are both good, then it's time to look at fueling.

When was the last time you had the carbs apart for cleaning and inspection?
 
The carbs were rebuilt by PJ in January, when I got them installed the bike was not backfiring.
The backfiring began when I decided to adjust my valves and cam chain tension, I noticed immediate backfiring.
Upon further inspection I noticed my timing was way off and got that sorted out recently - still backfiring but definitely an improvement.

My next steps are to look for air leaks and then check my valves again to see if I f'ed up somewhere.
 
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