Need tech information Gen1

Need some help.
I want to know what size the drill bit is for the carb slide on a stage one carb kit VF1000R carbs.

Fractional size or thousandths.

 

Looked for it Don but didn't see anything on it .I would thik it should be in thous.

 

Some one must know. Thanks.

 

AAAAHHHHHH!!!!!!!

Donald - please do not drill those slides. That would be a terrible mistake. It sounds like you are using a Dynojunk jet kit, I've never been able to get one of those to dial in properly. My suspicion is that it's because of the band-aid approach with the slide drilling. My suggestion would be to keep the stock springs and undrilled slides along with the adjustable needle from the Dynojunk kit. Better yet, get a Factory Pro kit and all will be good with the world.

Good luck!

 

Not using a Dyno junk kit.

I agree with you but I got one of the kits for my Kawasaki 1500 I used to have and the Dynojet needles did not work at all. I did drill the slides and it helped a LOT. The idle would come down instantly.
I ended up having to use the stock unadjustable needles.
I got the jetting dialed in but it was not perfect at idle.
It would get loaded up if you did not use the choke just right.
Probably just needed adjustable needles.


I was thinking that on the VF1000R that if I drilled the slides the idle would come down faster. Right now I am using # 38 idle jets and 2 shims under the needles and #128 mainjets. I am thinking about going to # 136 or #140 mainjets.
It is running very good though. Stock slide springs. No hesitation at all.

The factory specs show a top speed of 156 mph but I start getting worried at 100 MPH.

My front sprocket is 17 teeth. and the rear is 40T.
I can cruise comfortably at 65. With a 45 tooth rear sprocket it was really wound up at 65.
The H-D's blow by me at 85 mph all the time.


BTW all the money you pay for the kit is mostly for the coupon you get for a dyno run but when i went to the dyno place I was told that if they dyno'd it and had to make ANY adjustments it could cost $300 or more.. and so the coupon would only pay 1/3.

Also the place was just set up for sport bikes, and I would not let kids work on my chopper. Sorry but that is how i felt. Idid not get a good feeling from them at all. They mostly just did sport bikes and the same ones all the time.

 

I really don't think that I would dictate the rest of the carburation just on the way the engine returns to idle. Those bikes always have a slow time to return to idle. I've never liked it either, but it's more of a nuisance than anything else. It really sounds like you have a decent jetting setup now, my suggestion would be to leave it alone.

Please please, do not drill those slides. They are NLA and I think you'll find that the engine will run poorly after you do that. My experiences are that you cannot dial the jetting back in again either. Thus the name - Dynojunk.

 

do the vf1000 carbs not have butterflies like the 500 and 750? if they do the slides have very little to do with the speed the engine returns to idle since when the butterflies close they cut the vacume signal that the slides see and they are controlling the air the engine receives at that point, not the slides. sounds more like rotating mass/ compression (ratio) slowing the drop (or not).

If half asleep so if I misunderstood the point I apologise.

 

Of coarse the vf1000 has a butterfly. ALL carbs have butterfly valves.
Older carbs had the throttle cable go directly to the slide.
The butterfly was used as a CHOKE only.

Now the throttle cable controls the butterfly which controls the vacuum which controls the slide.
The reason for that was so that motorcycles at lower and higher altitudes would have the right mixture and would not all have to be tuned for a particular altitude. But the older carbs worked VERY WELL !! I know because I worked on them. They were crisp and great throttle response.
Most places that people live do not have great differences in altitude.

The vacuum operated carbs have a small hole in the slide to let the air escape as the piston falls and the spring helps push it down. By drilling the hole larger it drops faster. The emissions testers want the slide to drop slowly
so that more air has time to enter the cylinder on the exhaust stroke and burn p more of the unburned gases.
But that is not necessary if they had better exhausts on it that flow better.

The manufacturers whole program is to cover the exhaust ,clog the intake, and make the engine run real hot and quiet to meet the emissions and sound level. Of coarse the engine won't last long running that hot.
They will be completely happy when all motorcycles are electric and you cannot hear them, (kills more motorcyclists), and no emissions except for the monster power plant that they own to supply all the electricity to charge up your vehicle, and they get ALL THE MONEY. So it will be one big fight between the fuel companies and the electric plants to gain market share.

 

The larger whole takes care of that slow return to idle.
IF it did not work you could just epoxy in a small brass tube to get the hole back to original size.
No reason to throw away the slides. Matter of fact if any members have slides like that you can easily fix them.

 

Not trying to be rude but no, not all carbs have butterflies, I currently own a Honda and a Yamaha that never had a butterfly. The both use an enrichment circuit like the VF engines as a choke and the slide is connected to the throttle cable.

 

I also forgot to mention that the hole is not there for air to escape when you close the throttle, it's the exact opposite. As air rushes past the slide it speeds up and per the Venturi principal the pressure drops, this is when the air escapses the hole in the slide creating vacume inside the chamber, collapsing the diaphram and raising the slide and needle. When the throttle is closed (not the slide) the air slows down and the pressure rises allowing air to re enter the chamber at which point the spring over comes the force of the diaphram and the slide closes. As for air entering on the exhaust stroke that's controlled by the valve overlap (intake and exhaust valve open at the same time) and rpm. More duration and overlap generally speaking favors higher rpm where lower duration and less or no over lap favor low rpm high torque (ie cricle track/drag race v rv towing cam). Rpm comes into play due to velocity, objects in motion tend to stay in motion ect (basic physics), at low rpm valve overlap allows exhaust gas to enter the intake (this is what causes that wonderful rough idle in muscle cars and most things fast most of us love). At higher rpm the incoming air charge does have mass and once set in motion by the vacume created by the intake stroke tries to continue even though the valve closes and creates a pressure spike in the intake that the next next over lap bleed over would have to over come as well as being reduced by the scavenging effect of the spent gasses leaving through the exhaust at high speed (how a sand blaster and some paint guns work). I may be wrong but a golf buddy who is an engine builder for a notable nascar team seems to be under the same impression.

 

Auto carbs work differently that motorcycle carbs.
Car carbs do NOT have slides.
They have butterflies and venturis different sizes.

Apples and oranges.

I HAVE drilled the hole in the slide and gotten good results.
The slide dropped much quicker.

 

Hate to break it to you but no, they do not "work" differently. The carbs on VF bikes work identical to the secondaries on a Quadrajet or Edelbrock. The difference being the auto carbs use an "airdam" (Edelbock term) instead of a slide to control airflow. Drilling the slides is the same as reducing the weight (Edelbrock) or spring pressure (Quadrajet) on the airdam over the secondaries. Yes both those auto carbs use needles (metering rods) they just are not located in the throttle bore. Auto carbs don't contain "Venturi" that may be what we call them but Venturi is a person and a principal, what we commonly refer to as Venturi in an auto carb are, by definition and design an airfoil or simply an airplane wing wrapped into a circular shape. They are hardly apples and oranges. different types of apples? yes I never said that drilling the slide would not make the slides close faster, I said that closing the slides faster has no effect on how fast the engine returns from redline to idle, that is controlled by the butterflies. I too, on certain bikes have drilled the slides. My current 500 has the slides drilled to get rid of a flat spot in the midrange from running after market exhaust and a K&N filter. as for "veturis different size" I'm not exactly what your referring to. If it's variable venturi such as those on a Predator carb I'm not even going to attempt to explain that since it has absolutely nothing to do with motorcycles in general especially VF bikes. If your referring to just being different sizes, well yeah, the carbs from a 84 and an 86 vf500 have different venturi sizes (bore). If you want the bike to rev down faster 1. reduce rotating mass 2. increase compression ratio go out, start your bike and use your fingers or a screw driver to open the slides (not the butterflies) and you'll see they don't do much of anything when the throttle is closed, you can also try it on the secondaries of a Qudrajet or Edelbrock and get the same results.

 

BTW if you want the drill bit size just go to dynojets website, download the instructions (pdf file) and look at the list of included parts. It tells you what size bit is included.

Went and looked. #19 .1660" in between 5/32 and 11/64 or 4.21mm