Timing tips with Strobe v Carb Setup Bike popping

[jonathanrowley]

So after fitting the new Trigger unit I needed to Time the Bike back up.
It ran roughly after a first rough twist of the new beancan - but I had no Timing light. I finally tracked one down yesterday (In Sharjah - look it up!) and eagerly went back to time it and get it running properly.

I tweaked the Can until the "S" lined up with the notch on the Engine Case and the strobe lighting it up nicely.

Believe that is how it should be but maybe someone can confirm?

I've also finally got round to upgrading the carbs to 32mm BING Carbs so had to set them up and balance too. (I was waiting until I had the ignition back up and running.)

To explain - I was previously running 28mm Carbs as it was originally an R45 until I upgraded the pots.

I've read and re-read a 100 times all the articles on Timing and I'm no stranger to getting it running but any tips on timing and setup welcome.

The picture shows the two bits of kit any Airhead owner needs!

[mrclubike]

You can set the timing as you did at low idle (less than 1500rpm)
But the most important timing is at High idle (over 3000rpm)
You should set you timing to 32deg  BTDC at 3500 rpm that will be a "Z" or a "F" mark on the flywheel  and let you base timing fall where it is after that. But it should be close to the "S" mark at low idle.  
If you get a dual plug ICU by accident  your base timing will not come back to 6 deg but will fall at about 10deg  
That is why you need to check both.

As the old mechanical advance bean cans  wore  the max would get higher  causing spark knock  and then when you would adjust it back to 32deg your base timing would get lower causing a rough idle

I added a timing pointer to mine to help in setting the timing more accurately
I did this by drilling a hole at an angle down into the flywheel housing towards the timing marks and inserting a roll pin

[Barry]

I did something similar by making a timing tool with a pointer that inserts into the timing hole. Th pointer is offset to align with the chisel mark.

I also concluded that the pointer should not be aligned perpendicular to the engine case as the casting gets thicker towards the top. I used this picture to make a more accurate alignment. The difference is approx. half a tooth or 1.6 Deg

[jonathanrowley]

OK, so I set it at low idle and got the S mark to line up with the notches. I got that spot on with the strobe.

I didn't try to do the 3,500 rpm timing - as it makes so much lovely noise from my shorty pipes it would wake the whole apartment complex up so I have to be mindful of that.

It's banging and popping away, though feels strong, I'm just wondering whether that is timing or carb related? Any thoughts?

[montmil]

Getting that timing light "square" to the flywheel can be a chore what with carbs and cables blocking a straight visual shot. Since you're there abouts, some owners will use a Q-tip saturated with carb cleaner to clean off the debossed markings, then smear some white paint on 'em. Then, when the paint is mostly dried, a thin paper shop towel, with a dab of that carb cleaner, will clean off the excess leaving clear markings for your next, and easier, timing drill.

Here's the deal. If you make two major alterations and do not feel one is perfect before making anther major change, say new carbs and ignition system for example, you really don't know where the final problems are. You'll end up chasing your tail and, eventually, find the fault.

You may want to write that down. <sarcastic humor>  [smiley=wall.gif]

[mrclubike]

OK, so I set it at low idle and got the S mark to line up with the notches. I got that spot on with the strobe.

I didn't try to do the 3,500 rpm timing - as it makes so much lovely noise from my shorty pipes it would wake the whole apartment complex up so I have to be mindful of that.

It's banging and popping away, though feels strong, I'm just wondering whether that is timing or carb related? Any thoughts?

Not sure what you mean by popping and banging

Are you talking about back firing thru the carbs or spark knock or pinging

You really need to check  it  at full advance.
Can you ride the bike out to a parking lot somewhere and check it there.  
It would be good to have it warmed up any way.

Popping back thru the carbs can be from different things.
 Most of those are not common to the Air head engine as far as I can tell
Like sticking  valves and the distributer be installed 180 deg out  

[mrclubike]

That is a good Idea Barry
With my pointer i will have to drive it out before I can remove the flywheel.
I have been wanting to check how close my pointer is to being accurate but I figured the most important thing is that you get a solid f reference point to go off of when retarding the timing  to correct a pinging issue
I know one thing if a advance the timing any further than 32 deg I get pinging.  

[jonathanrowley]

Not sure what you mean by popping and banging Are you talking about back firing thru the carbs or spark knock or pinging  

Yes, on the overrun it's backfiring - sounds great, but not sure it's right?
It's not pinging or spark knock - popping and banging.

I want to know if it's likely to be timing related or overfueling?
Any ideas.

[jonathanrowley]

You really need to checkitat full advance.Can you ride the bike out to a parking lot somewhere and check it there.It would be good to have it warmed up any way.

Thanks, and yes, but it's 115 degrees in the shade here right now and a minute in a carpark with a Hot Airhead engine doesn't really appeal!

[jonathanrowley]

Here's the deal. If you make two major alterations and do not feel one is perfect before making anther major change, say new carbs and ignition system for example, you really don't know where the final problems are. You'll end up chasing your tail and, eventually, find the fault. You may want to write that down. <sarcastic humor>

Thanks Montmil, I kinda like the challenge and the tweaking. I static timed the Bike, and it pulled like a Horse - much better power through the new Carbs.

I also balanced at Idle the Carbs with the dials and set the Mixture by ear. Bike pulls great, just backfires once I throttle off.

Chasing our tails, is what home mechanics are famous for!
It's that tradeoff between knowing a little but not enough - so I'm always striving for more understanding!

Thanks for responding and the input - appreciate having other owners experience.

[skippyc]

On my BSA it was lean and a leaky exhaust.

[mrclubike]

Some of the more experienced tuners may know better but I think leaning out of the mixture is the most likely problem
I don't think the timing is the problem.  

[montmil]

Some of the more experienced tuners may know better but I think leaning out of the mixture is the most likely problem
I don't think the timing is the problem.  

 [smiley=tekst-toppie.gif]

[Bob_W]

Could the shorty pipes contribute to the problem?

Bob

[Barry]

If by popping you mean the engine is missing or 8 stroking then usually an air leak or lean mixture.  Reduced back pressure from the exhaust might also do it.

I have been wanting to check how close my pointer is to being accurate but I figured the most important thing is that you get a solid f reference point to go off of when retarding the timing to correct a pinging issue
I know one thing if a advance the timing any further than 32 deg I get pinging.  

I agree it's about reproducibility rather than out right accuracy. Once you establish a timing that doesn't ping the pointer helps reproduce the exact same timing the next time around. When doing static timing it also enables an accurate check that both cylinders are the same.

Mine pings easy too.