Setting the timing on my 81

[01ps]

So, I have a couple of questions regarding timing. It was suggested to me in another thread that the flat spot I am getting at higher rpm under load (5-6000 rpm) could be timing related, rather than carb. So, I'd like to check my timing.

I read the manual and I guess all I can basically do with electronic ignition is confirm that it is correct at 1200 rpm. I could probably confirm that it is advancing off idle too.

I have no tachometer, but the light does, however I assume it is designed for 4-6-8 cylinder and may not read correctly? Is there a way to use the tach info anyway, like divide the reading by 2 or something?

I should be able to adjust the timing some with the cam plate, right?

Any other suggestions or tips?

 

[bcware]

What are the modifications done to the bike? Have you adjusted the valves?

 

[01ps]

Open pipes, pod filters, oversize jets. It pulls really well up to that rpm and will rev with no load just fine. In fact it runs and pulls perfect for most of my riding but the OCD in me wants to iron that last problem out.

 

[bcware]

With those mods timing is not likely the issue. What size main jets are you running? What needle clip position if applicable?

 

[01ps]

Well the mains are 155 I think. Pilots are two over. I played with several combo of jets starting with single over mains and pilot and different needle positions, but while increasing performance at low and midrange I have always had that dead spot. I'd like to check the base timing just to make sure.

 

[bcware]

With electronic ignition it would be at the very bottom of my list of things to check considering your significant mods. A mid-rpm flat spot just doesn't seem like a symptom of maladjusted timing to me.

How do the plugs look with 155 mains?

What's your float height?

Did raising the needles (lowering the clip position) move the flat spot at all?

 

[01ps]

With electronic ignition it would be at the very bottom of my list of things to check considering your significant mods. A mid-rpm flat spot just doesn't seem like a symptom of maladjusted timing to me.

How do the plugs look with 155 mains?

What's your float height?

Did raising the needles (lowering the clip position) move the flat spot at all?

bcware, I took your suggestion and played with the carbs some more. I went to a bigger main, got a way bigger flat spot, so I went back to a 150 and a slightly larger pilot than what was in it and it got better. I set the jet needle to the highest (bottom clip) and it got worse. Move it down to the lowest setting and it got better, and one more and it is all but gone. Along with these adjustments I bought a parts bike this week and stole some carb parts. One of my jet needles was in pretty poor condition when I got the bike but I never had a replacement. Comparing idle screws showed that one of mine was blunted and even bent a bit!

With these changes I seem to have lost a little bit off the bottom end but it is even all the way through now. Thanks

 

[bcware]

Pods and exhaust will tend to sacrifice some low end grunt for a greater top end; it's normal for most motors. In order to make use of this shift you'll need to pin the throttle more; if you baby it you'll actually end up with a slower bike!

A lot of intakes and exhausts with dyno sheets display this trend.