34 replies to this topic

[petey81]

I have tested it connected and disconnected.
I checked the compression and 160 ISH across all cylinders.
So confused!
More checks today, tappet chest covers tightened up as a little loose, check float levels, manifold gaskets,tightened and inspected all fuel clips,jets checked..
As mentioned without the breathers connected to the carb it runs fine, if I block off the carb connections it drops the afr to 8...

Edited by petey81, 18 April 2025 - 11:50 AM.

[68+86auto]

That indicates that it's not a breather issue.

[petey81]

Yeah seems it. The needles were profiled around 11 years ago and I have fitted a different head (same type 12g202)but nothing else has changed apart from the usual service items.

Edited by petey81, 22 April 2025 - 06:30 PM.

[Lplus]

Yeah seems it. The needles were profiled around 11 years ago and I have fitted a different head (same type 12g202)but nothing else has changed apart from the usual service items.

One would almost think they were profiled with the pcv system open to free air.

[petey81]

Unless Ive had a poor breather system until now. I've also replaced the timing chain and tensioner plus the timing cover seal.
The needles were profiled with the breather system connected to the carbs and not changed in 12 years

[ACDodd]

Have you tried without the airfilters fitted?

Ac

[petey81]

Have you tried without the airfilters fitted?

I have yep and with them fitted

Ac

Edited by petey81, 23 April 2025 - 12:06 PM.

[ACDodd]

Then I suggest you have them looked at.

Ac

[petey81]

It's so frustrating. All I did was change the head which I've done multiple times. It was working fine before lol

[Lplus]

Unless Ive had a poor breather system until now. I've also replaced the timing chain and tensioner plus the timing cover seal.
The needles were profiled with the breather system connected to the carbs and not changed in 12 years

The breather sytem may have been connected to the carbs but open elsewhere.  That said it seems incredibly unlikely it wouldn't have been noticed but in the face of the engine's behaviour, I can't think of anything else.  Sorry.

[stuart bowes]

what are you connecting the breathers to exactly, at the other end are the ways free and unblocked.

 

i.e. are you connecting the carb breather up to what is now effectively a blocked pipe.  whereas, when tuned previously that breather way was free so it got the extra air you're trying to find

 

just a thought

[petey81]

It's always been set up with breather connected to the carbs from the tappet cover breather canister.
Now if I disconnect from the carbs it's fine but I won't leave it like that.
Breathers are clear and rocket cover cap is clear and tested with a spare.
I just can't lean out the carbs with the breather connected.

Edited by petey81, 23 April 2025 - 01:14 PM.

[stuart bowes]

ok fair do's just ruling out what was probably obvious

[miniGTS]

I know you only changed the head but is there Any chance the timing could be too retarded and causing too rich a mixture?

[petey81]

Timing hasn't been touched and I have checked it with my timing gun. I have retarded/advanced it a bit but made little difference regarding the leaning out. I was sitting at 14 on the afr but now doesn't drop below 11 after changing the head with the breathers connected