37 replies to this topic

[Dusky]

Hi all!

In really stumped now.. I still cant get my mini over 100-110 kmh.

specs are twin hs2 with cone filters and stubstacks
needles are M with blue springs
998cc
12g295 head with 1.3 rockers
Aeg 643 camshaft (288°)
Custom AC Dodd dizzy

When getting to around 5000 rpm in 3the the car just doesnt want to go faster anymore... Any advice on this?
Maybe a mixture that gets too weak now? It doesnt sound like misfiring and timing was set with a timing light.
Am I just expecting too much from this setup? Or should it go faster?

cheers

[Tommyboy12]

Diff and wheel size matter too but it sounds like something is off timing or mixture wise. Will it pull at all in 4th gear?

[Dusky]

Diff and wheel size matter too but it sounds like something is off timing or mixture wise. Will it pull at all in 4th gear?

12 inch and 3.1 diff, bit doesnt pull in 4th, I only use that gear to cruise now..

[coopdog]

Get it on a rolling road to be set up correctly

[jaydee]

Play with timing first, but this usually happens when the needle profile is wrong. You need to set it using a CO meter, forget the spark plug colours, colourtune and other witcheries that wont take you anywhere when profiling a needle from scratch.

With a 3.1 and 12" wheels you expect lot more than 70mph top speed.

[lawrie124]

I agree. Running a 3.1 on 12" rims (165/60/12 so not 'big) gives a cruising speed over 80mph, more downhill, on those German Autobahns of course!

[Dusky]

Im giving it full throttle and it doesn't get over 100 ( just manages to get 'around' 100.

Even with that cam, there should be enough power @5K rpm to go faster?

 

I went from E3 needles to AH2 needles to M needles because I thought it was running too rich at the top end, does that make sense? Or should I try richening ?

WOuld look at the spark plugs, but it's not easy to go to a sudden stop when comming from full throttle( no roads around ehre where I can actually shut off the ignition and look to the plugs).

 

Would take it to a rolling road, but there is no rollingroad in Belgium that's able to handle our lovely SU carbs

[lawrie124]

As someone earlier suggested, can you get the CO checked at idle and say 4,000rpm.

 

.... or pop over here to get it rollered!!

[Tommyboy12]

You really need to get it on a rolling road and get the needle profiled to suit. Its very difficult to do without knowing where the flatspots are.

[nicklouse]

 there should be enough power @5K rpm to go faster?

 

 

power does not matter. revs and speed are a fixed ratio per gear. so at 5k in third you will always do the same speed.

 

but it is not clear what is happening.

 

will it rev to more than 5k in first and second?

 

what happens in 4th?

 

 

of the top of my head it sounds like fueling.

[Dusky]

It will rev over 5k in first, but the fuelling problem is probably not worse enough for that.

my local garage has a CO tester, and I have a colortune... will have a look with the colortune at 5k rpm and see what it gives me (I have twin carbs so a CO meter will only give an average I guess).

Would it be good to set the mixture at 4k rpm orso for better. performance?
Ignition is now at 14° static (adviced by AC for this dizzy)


If I knew if it is over or under fuelling 's already be happy xd

cheers, and thanks for the input

Edited by Dusky, 11 November 2014 - 04:06 PM.

[nicklouse]

you have balanced the carbs? (and checked their condition etc?).

 

and it revs freely in first and second?

 

and forth?

[jaydee]

I have no idea of the air density in belgium but M needles with that spec no doubt you wont get anywhere near to full power

I would start from E3, both carbs balanced to idle at NO MORE than 3.0-3.5 CO (ideal 2.5 with both jets sitting at the same height and equal fuel in the float bowls) and then move on and define the cruising speeds with a CO tester

[Dusky]

you have balanced the carbs? (and checked their condition etc?).

 

and it revs freely in first and second?

 

and forth?

 

Carbs are balanced at 2K rpm with a aldon carb balancer
It revs freely, but it gets 'restricted' at higher revs even in second

 

I have no idea of the air density in belgium but M needles with that spec no doubt you wont get anywhere near to full power

I would start from E3, both carbs balanced to idle at NO MORE than 3.0-3.5 CO (ideal 2.5 with both jets sitting at the same height and equal fuel in the float bowls) and then move on and define the cruising speeds with a CO tester

I'll swap back to my E3 needles then ^^

 

Maybe a stupid question :

 

Should I rebalance the carbs when changing dashpot oil?

[jaydee]

There are two things to balance

Idle

load

You set the balance with a flow meter at around 1k idle (its a lumpy camshaft you have)

The balance under load is determined by piston rise-fall time, springs, dampers and yes, dashpot oil

Bear in mind that switching to standard airbox will affect mixture to the point you'll need another pair of needles different to those you use with cones and stacks