Drilling Slides - good idea opinions?

[salty_monk]

I'm rallying to my 2nd round of carb playing... Hopefully this weekend if all goes well (might even get an early start tomorrow if I'm lucky, you never know \\/ )

I now have a parts set thanks to a very nice man in Canada (thanks Richard) & both sets seem to have good slides.

My original set was supposedly drilled by a mechanic used be TPO for "increased throttle response" but I don't know what drill size he used.

My questions are:

1. What part of the slide gets drilled (so I can measure the difference)...
2. Any problems with swapping slides & needles over from one set to the other (my original diaphragms are in better shape I believe so they'd need transfering). Do slides and bodies wear as sets or anything? I can't see how....

3. I understand you would ordinarily drill the slides so that they would move faster when you open the throttle to compensate from increased air flow from pods etc. What effect does this have on a stock bike, it doesn't seem to have affected mine but I have nothing to compare it against... does it mean it would go rich when you open the throttle (as it's opening too fast) & then lean out as slide stabilises? I guess I'm asking if it would flow too much fuel too quickly... (My bike seems to be fast better when throttle opening is increased slowly than quickly so I wonder if this is the effect).

Anyway, any thoughts appreciated as ever!

Dan

 

[Steve]

Please don't consider me an "expert", I am merely the first responder. 8-[

As I understand the carb slides, vacuum from the intake tube is routed to the top of the diaphragm to pull it up. Since this would tend to raise them all the way any time the engine is running, there is a bleed hole in the bottom of the slide, near the needle. Not sure what the stock size is, but the Stage One kit I helped install a few weeks ago called for a 7/64" bit to enlarge the hole. Different engines might call for different-sized holes. It is my impression that because of better air flow with pods and headers, there might be too much vacuum, so a larger bleed hole is necessary.

Hopefully someone that knows better will step in and either confirm or correct this.


Can you switch your diaphragms over? Sure, if you don't see any wear marks on the sides of the slide or the bore. Check to make sure they move freely and you should be good to go.

.

 

[Guest]

The diaphragms are pressed on the slide so you can't switch them out. If the new diaphragms don't have pinholes in them (check by looking through the diaphragm into a bright light) I would try using them with the stock needles. I don't know why the PO drilled the slides. It was not necessary. With the stock air box and the K&N filter I would bump the main jet up a step and that's it.

 

[salty_monk]

Thanks Bill. That's that then. Richard told me the diaphragms were past their best... Not checked myself yet.

The stock jet seems to be ok, I may raise the float levels a little towards the richer end of spec to compensate for the K&N but I can't see it's making that much difference.

Running quite good now, surgey on the needles & can't setup the pilots properly but generally ok.


I guess if the slides do cause a prob i'll have to JB weld them & re-drill.


Cheers,

Dan

 

[Jd Powell]

Salty,
I also ride an '80 1000G. I have Installed a dynojet stage one kit. The bike has the stock air box. PO installed MAC? 4-1. Dynojet supplied a 5/32 bit to drill the slides. All you are doing is redrilling the slide hole to make it slightly larger. This is actualy to allow the slide to close faster when you shut the throttle. I have had good results, but be prepared to do some adjustments/tuning with the kit. As a side note I accidentily driled my original slides to large. (D.J. supplies a larger bit for removing the caps over the mixture screws.) So I had to swap the slides from my 1100GK parts bike. I advise not making that mistake. Anyway, I am currently in Phoenix Az (location always subject to change) 1800 ft ele. running 125 mains from the 1100. 45 pilots also from the 1100. 1 1/2 turns out on the screws. Needle at D.J. reccomended 3rd setting. Hope this helps.

 

[salty_monk]

Wow, that's loads different from me... I've just come down from 122.5 to 115 stock & it's running better already. I have a K&N inbox but stock exhaust.

I have measured the holes in a stock set of slides off a parts set I've got... 2.3mm. Will be measuring mine when I open it up tomorrow.

I can't use the parts ones as a couple of the diaphragms are shot.

5/32 is a lot bigger... that's 3.97mm

Chef told me he JB welded his & re-drilled from memory when he went too big....

It seems that the standard Needles for the 1000G have notches for the E clip, stock position is 3 (up I think).

The spare set has one jetting spacer under the clip. Mine is supposedly up two notches but that will be going back to stock 3rd setting tomorrow as well.

Dan

 

[Jd Powell]

Screwed up again. The 5/32 bit is the wrong one Do Not drill the slide with it. 7/64 is the correct one which I belive is 2.75 mm. Also forgot to mention I am running the K&N filter in the stock airbox. As for needles my stock ones didn't have adjusments. They are mikuni 5D50's. Needle jets are mikuni 318 X-6. what do you have?

 

[salty_monk]

Ha.... now this is interesting! I got a spec on here (on the spec sticky) that said the needles should be 5D57's - 3rd notch.

The Canadian ones had these needles with 4 notches so I used them.

My carbs had 5D50's in them but the plastic pacer had been moved to under the eclip instead of on top of it.... I guess either set of needles would have done.

Anyway it now seems to run much better....... I have the 115 mains in it. No hint of surgey stuff so far but I haven't done a proper shakedown run, just around the block a couple of times & it was very good.

Needs a proper synch I think (it's only bench synched & I had it completely apart) to mix & match (I used bodies 1 & 2 from the Canadian set & 3 & 4 from my set plus a mix of parts & new o rings...)

Interestingly I measured the holes in my slides at 4.1mm!! Anyway, despite this it doesn't seem to be having any ill effect so far....

The jets in both sets of carbs (under the rubber plug) were labeled "780".

I set the floats to 22.4mm (stock) measured at the step down where the metal ends & meets the float to the aluminium body face (where the gasket sits).

Dan