Tuning question, high speed drop in power?

[Phreak]

Hmmm okay, I wasn't 100% familiar with your bike's mechanics, but I think you have hit the nail on the head - sounds like you need to lift the secondary needle up a notch or two (I raised mine using small washers, has the same effect). From the sounds of things you still have your original carbs handy? Have a look at those and see if the jetting / needles are any different...

Just remember, once you drill something out, you can't go back!

[geoffm]

Rather than drilling the jets, buy new ones. they are cheap enough, and drilled jets don't flow consistnatly, and the sizes are limited. Check the jet sizes from yours (with pods) vs the new ones - has the jetting been altered due to the pods? Might be worth trying a larger main and seeing if it makes a difference.

Pods also do funny things to engines - eg in Yam RDs, the reflection from the solid endcap is well known for causing flat spots, unless they are spaced out 25mm or so rather than just on the end of the carbs.

Must get the dyno controller fixed, then you could dyno it which would help find the prrblem.

[nzspokes]

Rather than drilling the jets, buy new ones. they are cheap enough, and drilled jets don't flow consistnatly, and the sizes are limited. Check the jet sizes from yours (with pods) vs the new ones - has the jetting been altered due to the pods? Might be worth trying a larger main and seeing if it makes a difference.

Pods also do funny things to engines - eg in Yam RDs, the reflection from the solid endcap is well known for causing flat spots, unless they are spaced out 25mm or so rather than just on the end of the carbs.

Must get the dyno controller fixed, then you could dyno it which would help find the prrblem.

Jets went up 2 sizes when the pods went on. I drill jets as I have the drills and not lots of spare jets.

[ducatilover]

Jets went up 2 sizes when the pods went on. I drill jets as I have the drills and not lots of spare jets.

I've never had any luck with drilled jets.
I reckon to CVK-32's would look grouse on it

[nzspokes]

Well today I drilled a jet and the world didnt end. Took the primary carb main jet from 112 to 118. Seems to have made a big difference.

Either its in my head or she has picked up power right through the range and spins up to top speed faster.

Thinking about lifting the needle 1 notch on the secondry or going to bigger jet.

[ducatilover]

Good stuff mate!

[nzspokes]

Just got to get my head around what lifting the needle will do. I know it makes it richer but not sure how it effects the whole range.

[ducatilover]

Makes it richer until the slide has lifted, so around mid way up the rev range, maybe a little lower in higher gears. It shouldn't have any effect on your top end.
If it's flat in the middle (like Keira Kinghtley) then raise the needle one clip

[nzspokes]

Makes it richer until the slide has lifted, so around mid way up the rev range, maybe a little lower in higher gears. It shouldn't have any effect on your top end.
If it's flat in the middle (like Keira Kinghtley) then raise the needle one clip

Cheers, good explanation. Its a bitch to do but have done it on the new carbs on the secondry. You have to pull the carbs to do it.

But jebus what a difference tonight. I seem to be able to stay in 6th more and hold higher speed. Very happy with it. Cant wait for a longer blast.

[ducatilover]

Good stuff! Remember to run it and thrash the fuck off it before re-tuning. You want to see how it performs at all temps. Good excuse to have that needle in the red lots too

[nzspokes]

Well working on the time honored theory of if some is good then more is better ive go up in main size on the secondry carb. Seems to rev harder....

Cant ride it untill tonight after kid dutys....

[mossy1200]

I was looking at some info does your bike have direct pull primary and cv secondary card
If so you need a airbox rather than pods or your secondary carb wont want to open at top end.

Yamaha circumnavigated this difficulty first on its XT5 50 trail thumper by the simple solution of having two carburettors, one to feed each inlet valve, and linked so that one of 'em does the business at low and mid-range revs and the other comes in to join it when serious grip-twisting and 'go for it' situations occur. The Yam system uses a slide carb primary and constant velocity carb secondary set-up, but when Honda gratefully thieved the idea, it found that a pair of Throttle response is instant and smooth from tickover to the ten-and-a-half-grand red line


http://www.motorcyclespecs.co.za/mod...bx250%2087.htm

[nzspokes]

I was looking at some info does your bike have direct pull primary and cv secondary card
If so you need a airbox rather than pods or your secondary carb wont want to open at top end.

Yamaha circumnavigated this difficulty first on its XT5 50 trail thumper by the simple solution of having two carburettors, one to feed each inlet valve, and linked so that one of 'em does the business at low and mid-range revs and the other comes in to join it when serious grip-twisting and 'go for it' situations occur. The Yam system uses a slide carb primary and constant velocity carb secondary set-up, but when Honda gratefully thieved the idea, it found that a pair of Throttle response is instant and smooth from tickover to the ten-and-a-half-grand red line


http://www.motorcyclespecs.co.za/mod...bx250%2087.htm

The secondry carb is mechanically operated. So it starts to open at 1/4 throttle.

[ducatilover]

I would have smacked a CVK on there by now

[nzspokes]

I would have smacked a CVK on there by now

To be honest, I dont know what a CVK carb is.

So the bike has beter top end and speed but seems a bit flat mid range. So Im gunna try either staying with this jet size and dropping the needle one notch or going back to the original jet and lifting the needle one notch.