Twin 40 Tuning

[womble sri]

mine was a bit rough at lower revs an it has a similar cam to yours it wasnt very good at 2k in a high gear. the power band on the cam is quite high and as said maybe the rr operator isnt that great with carbs its best to get a veteran to set then up who as been tuning then since they were the best thing to do to an engine

[Nick]

It was dead responsive low down, felt great... But as soon as it came onto the powerband at 3-4k, it then just flattened off and seemed to bog. It even struggled reving around 6.5k in 4th !

I had to do a 60 mile round trip to get it looked at the 2nd time. So i wouldn't have done it unless it was pretty unnacceptable.

I checked the advance after the 1st attempt myself, it was running about 20 at 1.3k rpm and pulled about 32. when the revs fell to about 600ish it was 14.


I'm not sure wether they changed this, but he said he changed the mixture for the 2nd time, and then cleaned some "crap" out of a jet.

[Dan]

You can't expect good low down driveability with a 290 cam, also the gearing can have a marked effect on the way the car responds to throttle inputs.
No offence mate, but it sounds to me that you have over-cammed the engine, for what you want out of it.

Sorry tom, i have as others have, it pulls in fifth nice and strong from as low as 16mph when i am super lazy This is the cam i have driven with for years and on an everday case for the first couple. Drivability wise its spot on whether on track as people have seen down to poodling in traffic jams.

Just saying as i have first hand exp of this cam in a similar engine

[Nick]

No, i have not overcammed the engine. I want 3k+ pull for track use, But it's clearly obvious that a good low end is also achievable with the right setup !

[Stuart]

even a piper BP300 isnt over cammed either......ok not got quite the same low down pull as an AST2 but its fricking close on a PROPERLY SETUP engine.

Gotta love old wives tales hey :D

[tom reid]

Ok, I get what your saying, but, this cam is designed to "work" from 3-7k, now you could time it in earlier to get it "on" a little earlier. Assumming that the people that set it up know their stuff, there shouldn't be too much to do to get it working better.
What advance are you seeing at 4000rpm?
What is the fuel pressure set at?

[Stuart]

shame that bike hasnt got a reverse gear huh

[tom reid]

This bike don't need a reverse gear to go up your A$$

[Nick]

Fuel pressure is set @ 3Psi, and i've adjusted it to 3.5 with no noticable differences. I was getting 32 max Advance, but this may have been altered on the 2nd attempt.

I think i've found my answer though - Take it to someone else who knows what they're doing.

May have found a Local Pinto King who's very handy with Carbs !