Main Jet 74 Z1 4-1 pods......

I have been playing around with my main jet on my 74 Z1. I have pods, VH 4-1 with the baffle in but removed the sound deadening, I've upgraded the whole ignition system..electic ignition, dyna coils and wires (haven't done the WG coil mod yet though).
The setup the bike has had for a long time while my dad owned it was stock pilots and 122.5 mains. Stock mains on the bike are 112.5
A couple years ago I went up to a 125 main and thought it was fine. However I felt like the bike just wasn't pulling as hard in the higher RPM as it should. I also noticed if I am cruising at say 3K rpm in 5th and go to WOT, the bike pulls, but kinda feels a bit boggy, if I back off the throttle a bit, the power comes on stronger. So I thought maybe putting the 122.5's in would help that. So I did and it did seem to pull a bit harder in the high RPM's, however the WOT bog at 3K in 5th issues still remains. I tried putting in a 117.5 tonight and again....seems to even pull slightly better in the high RPM's, but at low RPM's at WOT it falls a bit flat unless you back the throttle off a bit.
Any suggestions from you guys? Is the bog at WOT at low RPM just the nature of these carbs? Or Should I be going the other way...I have some 130's I could try....
Just looking for insight and suggestions.
Thanks.

130's are going to be too much jet. Where are the needles?

They're no powerhouse in 5th gear at 3K when you wack it full throttle. What happens at 4000 when you hit it like that?

The clips are in the middle. The mid range throttle response is really good.
I know its not going to take off at 3K in 5th, but its just the fact that is seems to pull harder at less throttle at that RPM that bugs me.
I will have to try 4K and see......

If not already done, would assure valve clearances are within specs.

Am assuming ignition timing is spot on (with strobe type timing light); and advancer is properly functioning without sticking; and visual check of plugs shows a healthy fat blue spark.

Good Luck!

Mine too is boggy like you describe. I think it might just be the relatively low air velocity with the carb wide open when the engine not drawing much air. Carbs tend to work better (fuel atomizes better) when the air velocity is higher.

Patton wrote:

If not already done, would assure valve clearances are within specs.

Am assuming ignition timing is spot on (with strobe type timing light); and advancer is properly functioning without sticking; and visual check of plugs shows a healthy fat blue spark.

Good Luck!

Yup, I just adjusted the valves this spring.
I set the timing a couple summers ago with a strobe. The advancer is nice and free. I haven't checked the spark though...only thing I haven't done ignition wise is the WG coil mod.

ArthurGoVroom wrote:

Mine too is boggy like you describe. I think it might just be the relatively low air velocity with the carb wide open when the engine not drawing much air. Carbs tend to work better (fuel atomizes better) when the air velocity is higher.

Thanks for the input. This is what I was wondering...anyone else with this experience?

but kinda feels a bit boggy, if I back off the throttle a bit, the power comes on stronger.


What kind of petcock are you using and have you checked float height? I have 29s on mine and a Pingle made a huge difference...Russ

Russ Jackson wrote:

but kinda feels a bit boggy, if I back off the throttle a bit, the power comes on stronger.


What kind of petcock are you using and have you checked float height? I have 29s on mine and a Pingle made a huge difference...Russ

Running the stock petcock as far as I know...the float heights...boy I dunno, never checked them. What is a Pingle?

Just went out. Put the 122.5's back in. Checked the float levels, adjusted a couple of them though none seemed too far off. Took it for a spin...no real difference..though I did try putting it down into 3rd to get the rpms up to 5K or so and then hit WOT...it didn't seem to do the same thing (bog down at wot a bit and pull harder if you let off the throttle). So maybe it just is the fact that the engine is just revving too low and hitting wot at that RPM is just too much for the engine to properly handle. I have to say other than that...it really does seem to be running good. Pulls really nice through the whole rev range. I don't have anything to compare it to as I have never ridden another Z1..but it feels pretty good to me overall. Thanks for all the suggestions guys.