Carb slide holes - which diameter

[Chris.R.]

Help, I've been trying to find out the right size to drill the holes bigger that are in the carburettor slides? Is it 2.5mm as I read somewhere?

Apparently there are certain holes you ought not to drill, so which ones are the right ones then?

I've tried to find and download a DynoJet manual to no avail...thankyouthankyouthankyou...

[Chris.R.]

No one? I might need to reply directly to the thread I found here on the site...

[AIRWOLF]

Have'nt heard about this before

I presume it performance related as you mention dyno-jet.

Hopefully someone will be along to shed some light on the subject.

[anton88]

Chris,

I re-jetted my @ carbs - bought jets from wemoto. And used some small washers from a radio control model shop to fit on the needles to lift them in the slides.

Heres some pics of the slides with holes enlarged (sorry theyre a bit out of focus):

Its the 2 TOP holes NOT the middle one - this is where the needle sits.


View inside - middle hole is where needle goes:


The dynojet kit comes with different slide springs, which are designed to quicken the throttle response. As i didnt get a dynojet kit, i'd also read about drilling the 2 slide holes - its supposed to quicken throttle response by increasing air flow.

Make sure you double check, but i think i drilled mine with a 4mm bit not 2.5 - they are probably about 2.5 as standard i think. Make sure you get rid of all the swarf from around the holes - i used a small file to finish the edges of the holes, and cleaned out with carb cleaner - but i think you have to make sure you dont get it on the diapraghms as it might damage them - i cant remember

Hope this helps.

Ant.

[anton88]

Chris, this will help you more from 4strokes.com - its the info i used to help me do my mods :

http://www.4strokes.com/tech/honda/xr650lcarbmods/

[Chris.R.]

Have'nt heard about this before

I presume it performance related as you mention dyno-jet.

Hopefully someone will be along to shed some light on the subject.

Have a look here, that's what I was referring to, just check the whole article Poor throttle response?

[Chris.R.]

Thanks heaps Anton,

This is what I was looking for!!

Ok, I've got an RD07, but how did you determine that you needed to change the jets? Did you do the plug-chop method?

I haven't managed yet to do this tedious job...but I read that the RD07 doesn't necessarily need bigger jets when putting an aftermarket pipe on and a K&N filter!?

I have a local aftermarket stainless steel pipe on, which is pretty much a "pipe" only (no baffle plates or what they are called), I would guess 30-40mm outlet. I never had the original pipe on it but would wish a bit more torque in the mid range...

[anton88]

Hi Chris,

I went up one size on each jet - it was just a guess (NOTE the rear cylinder jet is larger than the front cylinder jet as standard to allow for reduced airflow to keep it from overheating). Ive fitted a k&n filter, drilled airbox and straight thru exhaust with removable baffle, and every time ive checked the plugs theyve been the right colour.

[Chris.R.]

Go for it!! What a response! First time round i failed to drill the hole fully through. Only the other day I took the needles out and saw that this things that keeps the needle down actually blocks the hole that I enlarged (have a look here for the RD07a) www.dynojet.com/pdf/European/Honda/E1165.001.pdf

So, I took the noses/corners off that thing (Fig.B on the right in the above link) and voila, here she awakes. No more this odd hesitation from going off the throttle to open up again etc.