Car will not rev past 4000 rpm

[lpraun]

Okay – a quick update!

This morning I switched the float cover from the old carburetors to the new on the car – this did little to nothing on fixing my problem. Then after a little bit of thinking and a cup of coffee I needed something else to do than messing around with the carburetors and decided to look into spark delivery and timing – even though

I cleaned the sparkplugs – that where quite black (rich mixture??) – the points in the distributer cap and the distributer pointy thing that goes round and round inside the distributer. I left the timing at 10 deg BTDC. And that helped to a degree – now it will rev to 5000-6000 rpm but it sounds sick and without a lot of power. When I started it up the idle settled on 1000 rpm even though I had tuned to around 600 before I cleaned the sparkplugs etc.

[ChrisZ]

L.P. that thingy that goes around is a rotor.

So your timing is to retarded, do you have a vacuum gauge, if so, attach it to one of the ported studs on the front carb, one of those with a rubber cap on, then rotate your dizzy to best possible vacuum at idle (clockwise i guess), if the car pings when you test drive it, back it off a few degrees.

If i remember correct, a ZX dizzy have 8.5 stampen on the shaft, that should give you 17 degrees of initial advance, so 10 degrees at idle is not enough, you should set it to 15 - 17 at 750 RPM

I run 17 degrees at 800 RPM with triples and the idle is so smooth.

Chris

[lpraun]

Okay – float level set at 14mm exactly and fuel mixture setting is set so, when I lift the piston in one of the carburetors using the little pin on the underside, the rpm goes down and the idle get rough. Sparkplugs etc. cleaned and timing set to 15 deg BTDC.

The car will rev all the way to redline when standing still – and it seems like it gets worse up through the gears – the engine sounds troubled – it’s like a deep rumbling sound while the willingness to increase the engine rpm goes down.

What does it sounds like when the car pings – I know it is difficult to describe a sound, but give it a try!

[lpraun]

In desperation and because I ran out of ideas, I changed back to the old carburetors – and it drove beautifully. It felt rock solid all the way up to 6500 – and beyond!

So this IS a carburetor issue – and I’m empty for ideas!

[ChrisZ]

L.P. you should try to contact Bruce Palmer and guide him to this topic, i was thinking fuel starvation, but after reading post #16, i can see that that is not the case, maybe you should try with a lighter weight oil, so are you bringing the car back to Copenhagen now?.

Chris

[Gary in NJ]

Well the good news is that you sorted through the problem. The bad news is that you're rebuilt carbs have an issue. I'm sure Bruce will help you out on this.

[lpraun]

Yep – I think I have to contact Bruce – I’m sure he can lead me in the right direction.

Chris,

I did not bring the car to Copenhagen – I need a place to park the car and that needs some planning!

[ChrisZ]

What a shame to here Lars Peter, so when do you think you will have the car home i CPH ?

[Zedyone_kenobi]

L.P. that thingy that goes around is a rotor.

So your timing is to retarded, do you have a vacuum gauge, if so, attach it to one of the ported studs on the front carb, one of those with a rubber cap on, then rotate your dizzy to best possible vacuum at idle (clockwise i guess), if the car pings when you test drive it, back it off a few degrees.

If i remember correct, a ZX dizzy have 8.5 stampen on the shaft, that should give you 17 degrees of initial advance, so 10 degrees at idle is not enough, you should set it to 15 - 17 at 750 RPM

I run 17 degrees at 800 RPM with triples and the idle is so smooth.

Chris

I was going to comment on how much initial advance you guys are running, but then I realized at where you were.. here in the states we are stuck running 5 degrees initial advance. Which reminds me, I need to source a european dizzy or get mine rebuilt.

[ChrisZ]

Stephen, the cars Lars Peter and i have, is both -73 brown US imports, are you looking for a points or ZX dizzy?

Chris

[lpraun]

Problems solved.

Basically it was incorrect float level setting, that was the cause of the problem. With competent guidance and advice from Bruce Palmer from ztherapy and a little time in the garage, the car now drives like a dream.

It is now again my favorite car:love: