7 replies to this topic

[DClarke1954]

Recently rebored/rebuilt 1293 A+

 

I am almost finished my first 500 miles of gentle running in and am starting to make a few demands of the engine.

 

Case 1.
I am going up a steep hill and in 3rd and she takes it in her stride with a bit of welly, no issues.

Case 2.

I try to accelerate from 40MPH in top on a flat road.

It doesn't feel like it wants to go.
If I snap the throttle or try to accelerate quickly I get a loud rifle-shot "crack" from just the other side of the bulkhead.  If I back off and try again slowly it manages to pick up, but far slower than I would like.

 

I'm struggling to nail the most likely suspect.

Is it too advanced and firing before valve is closed?

Is the mixture too weak and it is pre-detonating?

Is my red spring too soft, should a 1293  with an EVO1 cam have a Yellow spring?

Is the 30W oil  in the dashpot too thin?

 

I hate the "poke & hope" approach and it is always best to change only one thing at a time and re-measure/retest.

 

I have ordered a Yellow spring, I think this old Red one is tired anyway.

 

Any suggestions, tips, techniques would be much appreciated.

 

TIA.

 

 

 

Dan.

 

 

 

[imack]

It sounds like you need to visit AC Dodd

[Shooter63]

Try heavier oil in the dashpot, my Mrs mini with a similar spec is very picky in that department. 

 

Shooter

[DClarke1954]

It sounds like you need to visit AC Dodd

 

 

Try heavier oil in the dashpot, my Mrs mini with a similar spec is very picky in that department. 

 

Shooter

 

AC Dodd had a go at tuning it last year but we had to abandon it because of all the blow-by as the engine was "past its prime".

One of the things he did do was stretch the spring that was in there as it seemed inadequate.

 

I will put a new Yellow spring in and try it, then change the oil for 20/50.

 

at 3,000 rpm it is lambda 1.0 @ 1,000 it is lambda .86 and @2000 it is .94.

 

It could do with another looking at for sure. 

Thanks both.
 

[bpirie1000]

When it flat spots try pulling out the choke. Does it get better or worse?

[DClarke1954]

When it flat spots try pulling out the choke. Does it get better or worse?

Good call, I will try that.  Thanks.

[68+86auto]

If you thoroughly test everything you will find the answer. Always start with the ignition system.

[DClarke1954]

Further progress has been made and an AC Dodd recurved dizzy was fitted yesterday.

All I can say is....    Wow! 

What a difference a decent advance curve makes.

 

So, onto my next "niggle/worry/whinge".
The EVO1 cam calls for non standard tappet clearances (14 inlet and 16 exhaust).

I have set it like this but I find it is pretty "clattery" at idle.
Have any of you using the EVO1 also found it noisy?

Some people say a "tappy engine" is a "happy engine", but it just sounds crap.
I will do a search for an EVO1 thread and ask there too.