Carb Tuning guide (setting up a Dynojet or Factory Pro kit)

[mik_str]

FYI, here are the components included in the HRC jet kit :

2@ vacuum slides (with single lift hole)
2@ pairs of needles (one "lean", one rich - the latter meant, apparently, for ram-air set-up)
13@ pairs of different size main jets (2 each ranging from 140 to 170)
2@ pilot jets (#48)
2@ main air jet blocks
4@ needle clips
6 washers

cheers

[lloydie]

Ive read this now a few times but found no info on it .
"Large v2 should be set up for torque and not bhp "

How would one go about doing this ?

[VTRDark]

Thanks Mik, are the mains in steps of 3 like Keihin?

Lloyd I have not heard of that. I would set up for most efficient power and A/f ratio. I guess torque = power to a degree so it's all relevant.

(:-})

[mik_str]

yes, they are Keihin jets.... (140, 143, 145, 148,....)

[tony.mon]

Ive read this now a few times but found no info on it .
"Large v2 should be set up for torque and not bhp "

How would one go about doing this ?

Increase intake stack length, leave ignition timing wheel as std, fit high-comp pistons, over-fuel slightly through the rev range, gas flow heads to suit, consider oversize valves although these may not work well at very low revs. Cams would benefit from a regrind. Maybe worth trying a set of XL1000 cams to see what difference that cam profile makes, but they have less lift so you'd definitely lose top end power.
Lastly you might prefer to use carbs from an early (carbed) XL1000, they'll boost torque. Or even fit an engine form a later fi model, but with Storm cams, gearbox and heads. Not sure if heads are different but it wouldn't surprise me.
All these mods will detract from top end BHP and willingness to rev, you can't get something for nothing and it's usually one or the other.

If you want to get radical, separate the airbox into two separate halves and reset the valve timing to 180 degrees out.

I'll have bhp and torque figures for mine end Jan, as I'm doing some extra work over Xmas to raise a few hundred for dyno time. Still got variable stacks to sort out, no time atm though.
I need a lathe for Xmas.....

[motostorm]

great thread , good info and links , thanks

[VTRDark]

That reminds me, I must gather some more info on the HRC set up. I also want to add some high altitude info as the affects of altitude have not been mentioned.

(:-})

[sirch345]

Good job Guys

Chris.

[8541Hawk]

That reminds me, I must gather some more info on the HRC set up. I also want to add some high altitude info as the affects of altitude have not been mentioned.

(:-})

What do you need to know about the HRC kit? I've had mine in for a long time and am pretty up on their set up.

[Roger Ditchfield]

Once again Tony has posted comprehensive and accurate info. In this area which is full of "B******t and robotic Dyno operators it is so refreshing to find knowledgeable guys willing to share the truth. Congratulations!!

[Griff1977]

Once again Tony has posted comprehensive and accurate info. In this area which is full of "B******t and robotic Dyno operators it is so refreshing to find knowledgeable guys willing to share the truth. Congratulations!!

Roger. Agreed. As you know I've been stung with a hint of a dyno man being more of a power commander specialist but since that episode I've learnt from this thread and talking to other guys on the forum. Regards. Griff.

[ptynan]

So helpful I know where I went wrong now a big thank you Paul

[tony.mon]

If you want to buy genuine Keihin main jets you need to get jet type: KEIHIN 99101-393

The Pilot jet type is KEIHIN N424-21 although there are two fine side hole positions, the rear carb one is much nearer the outlet than the front carb one, Factory Pro supplied ones are different front and rear, and so are Keihin standard ones. Don't know about Dynojet kits.
Only one is shown in the ID chart below, and I don't know how you would specify the different hole position ones when ordering.

This identification chart is useful:
http://jetsrus.com/FAQs/FAQ_identify_that_jet.htm
Although jetrus's shipping to the UK is 20 dollars, so only really worth it if you want to order a range and swap them about yourself.

Be careful about using charts on the internet; I had a look today and found several charts, some of which were mis-labelled and would lead you astray.
I hesitate from saying there is a "right" one to follow, but a good check is to multiply the Kehin size, if given in thousands of an inch, by 25.4- this will give you a number that should correspond with the hole diameter. This way of defining a jet hole diameter is shared by Keihin and Factory Pro, but Dynojet do their own thing, and the sizes are different. If this check doesn't give you a very close conversion, ignore the chart.

Mikuni seem to want to use flow rates, and so that's problematic, and the threads are different, too, so just don't, basically, unless you are using Mikuni flat slides, you flash git.

Basically I'd suggest using just one range- if you are going to try to tune carbs and have to keep converting from one range to another it'll drive you mad.

[Phil_H]

If you want to buy genuine Keihin main jets you need to get jet type: KEIHIN 99101-393

The Pilot jet type is KEIHIN N424-21 although there are two fine side hole positions, the rear carb one is much nearer the outlet than the front carb one, Factory Pro supplied ones are different front and rear, and so are Keihin standard ones. Don't know about Dynojet kits.
Only one is shown in the ID chart below, and I don't know how you would specify the different hole position ones when ordering.

This identification chart is useful:
http://jetsrus.com/FAQs/FAQ_identify_that_jet.htm
Although jetrus's shipping to the UK is 20 dollars, so only really worth it if you want to order a range and swap them about yourself.

Be careful about using charts on the internet; I had a look today and found several charts, some of which were mis-labelled and would lead you astray.
I hesitate from saying there is a "right" one to follow, but a good check is to multiply the Kehin size, if given in thousands of an inch, by 25.4- this will give you a number that should correspond with the hole diameter. This way of defining a jet hole diameter is shared by Keihin and Factory Pro, but Dynojet do their own thing, and the sizes are different. If this check doesn't give you a very close conversion, ignore the chart.

Mikuni seem to want to use flow rates, and so that's problematic, and the threads are different, too, so just don't, basically, unless you are using Mikuni flat slides, you flash git.

Basically I'd suggest using just one range- if you are going to try to tune carbs and have to keep converting from one range to another it'll drive you mad.

Just to add to this, I can't stipulate how important it is to use jets from the same supplier, ie, Keihin copies from ebay/China are unlikely to flow the same as oe Keihin. Been there, done that, it WILL drive you mad.

A great UK source for genuine carb parts is Allens Performance, great service & cheaper than ebay copies ;)
Just be sure to use the correct jet part No listed above before ordering.

Phil

[TravisZack]

For anyone that ends up here, Allens Performance are great but just phone them.

I was emailing back and forth for a couple of days but they got my email address wrong trying to PayPal an invoice and were slow to respond.
Rang them yesterday and sorted it in 5 mins, jets arrived this morning happy days